[초벌원고]

By now, I assume that you have heard of the foot in the shoe theory of class Ⅱ treatment. This theory suggests that for class Ⅱ patients if you expand the maxillary arch i.e widening the shoe that will allow the foot, the mandible, to spontaneously slip further forward, thereby achieving the class Ⅱ correction of the occlusion. Is this theory true? Can you achieve class Ⅱ correction by simply expanding the maxillary arch? A study title “Rapid Palatal Expansion for Spontaneous Class Ⅱ Correction” By Tonya Volk et al which appeared in the March, 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics addressed this question.

[수정원고]

In this study, the authors evaluated the sample of thirteen patients with the mean age of 10 years 3 months. All of the patients have rapid palatal expanders in place for 6 months. The authors used the articulated models to equal centric relation, centric occlusion that is the occlusion of the opposing teeth of the mandible is in centric relation and maximum intercuspation prior to expansion and after expansion was complete at 6 months. They used models to measure the changes in the occlusal relationship of the molars.

When the authors evaluated the changes that had occurred after expansion what do you think that they found? The results are interesting. In at the only measurements with statistically significant changes from pre-treatment to post-expansion or the maxillary inter-molar width, which would you hope will be wider after rapid palatal expansion. Because the class Ⅱ relationship improved in only 7 patients and actually got worse in 5 subjects with 1 subject staying the same, the authors concluded that their study did not support the foot in shoe theory. I should also know that the maximum improvement for any patient was 2 millimeters.

The bottom line of this study is that changes that occurred could be directly related to growth. Hugo Larger noted as early as the 1960s that if a patient has anterior mandibular growth and the class Ⅱ malocclusion that all you have to do is somehow interfere with occlusion and anterior growth of the mandible with change the occlusion from class Ⅱ to class I. Wow! The sample for the study is small. It seems to me that the fact that as many as 5 patient actually developed worse class Ⅱ malocclusion should put the foot in the shoe theory to rest once for all. You can find this article in the March 2010 issue of the American Journal of Orthodontic and Dentofacial Orthopedics.

20-Year Follow-Up Study of Disc Repositioning Surgery for Temporomandibular Joint Internal Derangement.

Abramowicz S, Dolwick MF.
J Oral Maxillofac Surg 2010;68:239-242
                                                                                    

                                                            March 11, 2011
                                                            Dr. Sang-Mi Lee

[초벌원고]

Has this ever happened to you? You completed orthodontic treatment on an adult female about a year ago. Her treatment was uneventful and the end result was nearly perfect. She has a beautiful Class I occlusion with good functional excursions and she was very happy with the result. In fact you’ve seen her today for a retainer check appointment. When you look in the mouth for the occlusion, everything looks great. So you ask the patient how everything’s been going. And then she tells you her story. She was in an automobile accident about six months ago. Ever since that time, she’s had popping of her right TMJ. When you ask her to open and close, you note the joint sounds on the right side. You are suspicious of an anteriorly displaced disc. So you ask her if it causes her any problems. And she says yes. She has a limited opening and moderate pain on the right side. Her occlusion is perfect. So what would you recommend for her? Is there any way of repairing the anteriorly displaced disc? Is repositioning surgery a possibility? Would it be predictable? Would it be long lasting? As orthodontists, we run across patients like this from time to time. How do you advise them regarding the potential for disc repositioning surgery?

[수정원고]

I found an article published in the February 2010 issue of the Journal of Oral and Maxillofacial Surgery that could help you provide your patients with some answers to these important questions. The title of the article is "20-Year Follow Up of Disc Repositioning Surgery for Temporomandibular Joint Internal Derangement." The study was co-authored by Shelly Abramowicz and Frank Dolwick from the University of Florida in Gainesville. The purpose of this study was to report the 20-year outcome of the temporomandibular joint disc repositioning surgery as a treatment for TMJ internal derangement. Frank Dolwick is chair of the department of Oral and Maxillofacial Surgery at the University of Florida.

For a six-year period from 1984 to 1990, he and his colleagues completed disc repositioning surgery on over 150 adults. In fact, they reported their success rates in the early 90s at about 70 to 80 percent. But this was only short term. What had happened to these patients long term? That was the purpose of this article.

As many patients as possible were sought out to determine the outcome after 20 years. After exhaustive search for these patients, the authors successfully found 20 patients who had a total of 40 TMJs that had been operated. Now remember, this was an operation that was surgically to reposition the disc back into its proper relationship. Although it was impossible to re-examine the patients, they were sent a questionnaire to determine if they had any pain and how the surgery had worked out for them over the long term.

Let me explain what these researchers found. First of all, although only about 12 percent of the patients have been located and since the discs were operated on both sides, the authors did have 40 joints on which to report.

Let’s look at joint pain. On average, these individuals had pre-operative TMJ pain of 9 on a range of 1 to 10 with 10 being the worst. Twenty years later, the average joint pain was little over 1 on a scale of 1 to 10 with 10 being the worst. So there was a significant reduction in TMJ pain in this group 20 years later.

How about their overall quality of life? Nearly 95 percent of the respondents reported an improvement in over all quality of life which included improvement in their ability to eat foods, a reduction in pain, and an improvement in their previous functional limitations. Only one patient reported that the quality of life was unchanged.

So, in conclusion, it seems that the vast majority of these individuals who had had disc repositioning surgery have a much better quality of life, a reduced pain level, and improvement in their TMJ function 20 years after the surgical procedure had been performed. Now the authors do state that this type of surgery is probably our last resort surgery. In other words, if the patients can live with the disc displacement and has no pain or limited opening, then that’s probably the advisable course of treatment: do nothing. But for those patients who do have severe pain and do have limited mouth opening and function, then perhaps disc repositioning surgery is a reasonable option over the long term.

If you’d like to review this study that evaluates the long term benefits of disc repositioning surgery of the TMJ, you can find it in the February 2010 issue of the Journal of Oral and Maxillofacial Surgery.

Root Shortening in Patients Treated with Two-step and En Masse Space Closure Procedures with Sliding Mechanics

Yan Huang, Xu-Xia Wang, Jun Zhang, Chao Liu.
Angle Orthod 2010;80:492-497   
                                                                                    

March 18, 2011
Dr. Mi-Soon Lee

[초벌원고]

Have you ever altered your extraction space closing mechanics when you’re concerned about the potential for root resorption? Suppose you’re planning orthodontic treatment for 15 year old female with a crowded and protrusive dentition. She has a class I molar relationship but because of the amount of the arch length deficiency and the degree of dental proclination, you must extract teeth. When you view her panoramic and periapical radiographs, you notice that the maxillary anterior roots are a bit short. You’re concerned because there could be a potential for root resorption. So how would you close the extraction spaces? There’s two possibilities. One would be to first retract the canines, then close the remaining extraction space. The other option would be to simply close the space by moving all six anterior teeth at the same time. Which of these techniques would result in less root resorption for your patient. The answer to that question can be found in the study that was published in the May 2010 issue of the Angle Orthodontist.

[수정원고]

I’ve often wondered about this question, so I was delighted to find this article to review on this month’s issue of practical reviews on orthodontics. The title of this article is “Root Shortening in Patients Treated with Two-step and En Masse Space Closure Procedures with Sliding Mechanics”. This study comes out of the orthodontic department at Shandong University in China. The study is co-authored by Dr. Huang and three other colleagues from that same orthodontic department.

The purpose of their study was to comparatively assess the severity of root shortening in patients treated with two-step as opposed to en masse procedures with sliding mechanics to close extraction spaces. In order to accomplish the subject the authors gathered 50 adolescent patients. They averaged about 15 years of age. None of these individuals had any evidence of previous treatment or root resorption. And none had history of trauma to their anterior teeth. All subjects had either class I or class II malocclusions and they all required extraction of four first premolars along with space closure using moderate anchorage. The sample was arbitrarily devided into two groups. In half the sample the extraction’s bases were closed using en masse techniques. With NiTi springs attached across the extraction space to gradually close the space and move all 6 teeth palatally. In the second group the canines were initially moved across the extraction space and then ligated. Then the four incisors were moved using this two-step approach. In this group NiTi coil springs were also used and sliding mechanics were incorporated. Then the authors evaluated the radiographs to determine if any root shortening had occurred.

I was pleased that the authors used vertical orientation wires that were attached to the brackets whenever they took radiographs so they could resolve any problems with magnification on the radiographs that could have occurred. Okay, I think you get the idea of methodology. So what happened? Remember the initial and main question. If you use a two-step approach, or a one-step approach during extraction space closure, are there any varings on the amount of root resorption that occurs in the maxillary incisor region? And the answer to that question is, No.

When the authors carefully compared the root lengths of both samples, they found no statistically significant differences in the amount of root resorption between the two treatment groups. So there you have it. When you’re closing anterior spaces created by the extraction of teeth and you may be concerned about the potential for the root resorption using different types of space closing techniques, this study has clearly shown that it really doesn’t make any difference. If you retract the canines first, or simple close the extraction space with all six teeth moving distally, the amount of root resorption, which was minimal in the sample, was equivalent between the two groups.

If you’d like to review the study that evaluates the differences in the amount of root resorption with anterior space closing techniques, you can find it in the May 2010 issue of the Angle Orthodontist.

Part II：Managing orthodontic Treatment for the Adult Patient with Periodontal Problems


                                                                                    

March 25, 2011
Dr. Sun-Young Lim

[초벌원고]

The third situation where orthodontics can be of significant benefit is in the patient who requires forced eruption or controlled extraction. Occasionally children and adolescence will fall and accidentally injured their anterior teeth. If the injuries are minor and result in small fracture of enamel, these could be restored with light cured composites or porcelain veneers. But in some situations the fracture may extend beneath the level of the gingival margin and terminate at the level of the alveolar ridge. In these situation, restoration of the fractured crown is impossible because the tooth preparation would extend to the level of the bone. This over extension could results in an invasion of the biologic width of the tooth and cause persistent inflammation of the marginal gingiva. In these situations, it may be beneficial to erupt the fractured root out of the mold and move the fracture margin coronally, so they can be restored without creating gingival inflammation.

[수정원고]

The orthodontist, restorative dentist and periodontist should evaluate six criteria to determine if the root should be forcedly erupted or extracted. These include root length, root form, location of the fracture, lip level of the patient during smiling, relative importance of the tooth and the endo-perio prognosis. If the six are favorable, then forced eruption and restoration may be appropriate. But in some situations, if the fracture is too severe, it may be better to extract the tooth and replace it with an implant or bridge. If the decision is made to extract the tooth or teeth and replace them with implants, it's often beneficial to extract the roots orthodontically by gradually erupting them out of the bone to create a better implant site. The eruption should be performed at about the rate of one half millimeter per month to permit the gingiva bone to follow the tooth and undergo adequate remodeling during the eruption process.

There are three indications for performing controlled extraction.: gingival level discrepancy, bone level defect or discrepancy and upright inclination of the tooth root. This last criterion will ensure that the alveolar bone will follow the erupting tooth. If the tooth were inclined or proclined labially, the bone typically does not follow the root as it's erupted. The crown of the tooth to be erupted should be perpendicular to the occlusal plane. If so the bone and tissue will follow the tooth and enhance the bone and tissue levels in the implant site.

A 4th situation where the orthodontist can aid the restorative dentist is in the patients with significant anterior tooth abrasion and compensatory eruption of the abraded tooth. Occasionally patients will have destructive dental habits such as protrusive bruxing habit that can result in significant wear of the maxillary and mandibular incisors. Tooth wear typically result in compensatory over-eruption of these teeth. When the restorative dentist contemplates restoration of these abraded teeth, it's often impossible because of the lack of crown length to achieve adequate retention and resistance form for the crown preparations.

Two options are typically available. One would be extensive crown lengthening by elevating a flap, removing sufficient bone and apically positioning of the flap to expose adequate tooth length for crown preparation. But this type of procedure is contraindicated in the patient with short, tapered roots because it could adversely effect the final root to crown ratio and it could potentially open up black triangles or open embrasures between the anterior teeth.

The other option for improving the restorability of the short abraded teeth is to orthodontically intrude the teeth and move the gigival margins apically. It's possible for the orthodontist to intrude up to four maxillary incisors by using the posterior teeth as anchorage during the intrusion process. This process is accomplish by placing the orthodontic brackets as close to the incisal edges of the abraded maxillary incisors as possible. The brackets are placed in their normal position on the canines and remaining posterior teeth. The patients posterior occlusion will resist eruption of the posterior teeth and the incisors will gradually intrude and move the gingival margin and crowns apically. This creates the restorative space necessary to temporary restore the incisor edges of these teeth and then eventually to place the final porcelain veneers or crowns on these teeth.

When abraded teeth are intruded significantly it's necessary to hold these teeth in position for at least 6 months with the orthodontic brackets and/or arch wires or some sort of bonded retainer. The principal fibers of the periodontium must accommodate to the new intrude position and this process could take a minimum of 6 months in most adult patients. Orthodontic intrusion of severely abraded and overerupted teeth is usually a distinct advantage over periodontal crown lengthening, unless the patients has extensively long and broad roots or has had extensive horizontal periodontal bone loss.

The 5th and last advantage that I'd like to talk about for orthodontics in the perio-restorative patients is to aid in the elimination of open gingival embrasures or black triangles between the maxillary and mandibular anterior teeth that develop during orthodontic treatment. The presence of a papilla between the maxillary central incisors is a key esthetic factor for any smile. Occasionally adults may have open gingival embrasures or black triangles between their central incisors. These unsightly areas are often difficult to resolve with periodontal therapy. But orthodontic treatment can correct many of these open gigival embrasures, even in the difficult adult periodontal patient. This space is usually due to one of three causes.: root angulation, tooth shape, or periodontal bone loss.

The interproximal contact between the maxillary central incisors usually consists of two parts. One portion is the tooth contact, and the other portion is the papilla. The ratio of papilla to contact has been shown in previous studies to be about one to one. In other words, half the space is typically occupied by the papilla and the other half is formed by the tooth contact. If the patient has an open embrasure, the first aspect that the clinician should evaluate is weather the problem is due to the papilla or the tooth contact.

If the papilla is the problem, then the likely cause is lack of bone support due to an underlying periodontal problem. In some situations a deficient papilla can be accentuated with orthodontic treatment by closing open contacts the orthodontists can squeeze the interproximal gingiva and move it incisally. This type of movement can help to create a more esthetic papilla between two teeth in spite of alveolar bone loss. Another possibility is to erupt adjacent teeth when the interproximal bone level is positioned apically. Most open embrasures between central incisors are due to problems with the tooth contact.

The first step in the proper diagnosis of this problem is to evaluate an periapical radiograph of the central incisors. If the root angulation is divergent then the brackets should be repositioned so the root position can be corrected in these situations. Now, the incisal edges may be uneven and that will require restoration with either composite or porcelain restoration. If the periapical radiograph shows the root are in the correct relationship, then the open gingival embrasures is due to triangular root or tooth shape. If the shape of the tooth is the problem, two solutions are possible. One possibility is to restored the open gingival embrasures, the other option is to reshape the tooth by flattening the interproximal contact and closing the space. This will result in lengthening of the contact until it meets the papilla. In addition if the embrasure space is large, closing the space will squeeze the papilla between the central incisors. This will help to create a one to one relationship between the contact and the papilla, and restore uniformity to the heights between the midline and the adjacent papillae.

But there is a limit as to how much interproximal reduction should be performed. The limiting factor is typically the eventual size and shape of the resulting central incisor crown. Typically the width to length proportion of a maxillary central incisor should be somewhere between 75 and 80%. If the interproximal reduction of the central incisor result in excessive narrowing of the tooth it could look too long and too narrow. In these situations, it's better to have the restoration dentist restore the open gingival embrasure which helps to maintain an esthetically pleasing width to length proportion of the central incisor but closing the gingival embrasure.

In summary, this discussion has hopefully illustrated some of the benefits of integrating orthodontics and periodontics in the management of adult patients with underlying periodontal defects. The key to treating these type of patients is communication and proper diagnosis before orthodontic therapy as well as continued dialogue with the restorative dentists and periodontists during orthodontic treatment. Not all periodontal problems are treated in the same way. Hopefully this discussion of hemiseptal defects, uneven gingival levels, open gingival embrasures and periodontally hopeless teeth provides you with the framework that will be helpful in treating these situations in the future.

Dental Effects of Interceptive Orthodontic Treatment in a Medicaid Population: Interim Results From a Randomized Clinical Trial

Jolley CJ, Huang GJ, et al.
Am J Orthod Dentofacial Orthop 2010;137:324-33
                                                                                    

April 1, 2011
Dr. Kyung-Min Lee

[초벌원고]

If you took a group of medicaid patients and divided into two subgroups one of which received interceptive orthodontic treatment and the other which did not, how much of it difference would you expect to see after 2 years? This question was addressed in the study titled “Dental Effects of Interceptive Orthodontic Treatment in a Medicaid Population: Interim Results From a Randomized Clinical Trial” by Cameron J. Jolley et al which appeared in the March 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

[수정원고]

In this study 170 Medicaid-eligible children were randomized into two groups one of which received interceptive orthodontic treatment and the second acted as a control and received only observation for 2 years. The Peer Assessment Rating or PAR score was used to evaluate the severity of malocclusion initially and after the completion of interceptive treatment or at 2 years. When the two groups were compared what do you think happened? Was there a significant improvement in PAR scores for the interceptive group versus the observational group? The answer to this question is a definite yes. The interceptive group showed a mean improvement of almost 50% whereas the observational group had a mean worsening of almost 6%. Fifty-five of the 72 interceptive patients showed greater than 30% PAR score improvement but only 3 of the 74 observational patients showed a greater than 30% improvement. Seventeen of the 72 patients in the interceptive group had a greater than 70% PAR improvement whereas none of the 74 observational group patients had a 70% improvement. Based on these results it might be easy to conclude that it was a good choice for the Medicaid patients to receive interceptive orthodontic treatment.

However there is a second aspect of this study that is very interesting. And it is that of the original 67 patients in the interceptive group was treatment needs at baseline, 53 no longer had medically handicapping malocclusion at the end of interceptive treatment and therefore did not qualify for comprehensive treatment in the Medicaid program. In the observational group, only 6% of those with a medically handicapping malocclusion at baseline were not qualified for comprehensive treatment. The bottom line is that for 81% of the patients who were randomly assigned to the interceptive group, further orthodontic treatment would no longer be considered “medically necessary” compared with only 6% of the observational group. Although 81% of interceptive orthodontic patients were no longer considered “medically necessary”, only 24% of them had a 70% reduction in PAR score, the level required to be considered greatly improved.

This is very interesting finding because I believe it is generally accepted that interceptive orthodontic treatment does not preclude the need for a second phase of treatment in the permanent dentition. After reading this study big question that I had was whether or not the Medicaid patients who received interceptive treatment were better off in the long run then those who did not and therefore qualified for comprehensive treatment. If I had to advise a patient in this situation, I would suggest that they would forego the interceptive treatment if it would result in them not being eligible for comprehensive treatment. I should know that little more than 80% of the interceptive treatment consisted of two molar bands and four anterior brackets, and that patients who had posterior cross bite with functional shift were not include in this study because the authors felt it would be unethical not to treat them.

The bottom line is that two ways you can look at the results of this study. From the view point of Medicaid ministries, interceptive orthodontic treatment can be in an effective way to reduce cost and reduce the number of patients who require medically necessary treatment with the understanding that this option will not provide adequate treatment as measured by the PAR index. The other view point is that of the patients who can qualify for more comprehensive orthodontic treatment by avoiding interceptive treatment.

You can find this very interesting study in the March 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Clinical Outcomes of 0.018-Inch and 0.022-Inch Bracket Slot Using the ABO Objective Grading System

David A. Detterline, Serkis C. Isikbay, Edward J. Brizendine, Katherine S. Kula.
Angle Orthod 2010;80:528-532
                                                                                   

April 8, 2011
Dr. Hoon Noh

[초벌원고]

What size of orthodontic brackets do you use? Do you prefer 018 or 022 sized bracket slots? I would guess that most orthodontist today would use 018 rather than 022. I'm probably in the minority because I still use a bracket with an 022 slot. But here's my question. Does the size of the slot have any effect on the quality of treatment or the length of treatment? Now the length of treatment could be measured between 2 groups. But how about the quality of treatment? One would have to use some sort of occlusal grading system and compare the quality of treatment between a sample of 022 and 018 subjects.

[수정원고]

That has now been accomplished. The study was published in May 2010 issue of the Angle orthodontist evaluated over 800 subjects who had been treated at Indiana University. The title of the study is "Clinical outcomes of 018 and 022 bracket slots using the ABO objective grading system". This study is co-authored by David A. Detterline and 3 other faculty from the Orthodontic Department at Indiana University. Now the purpose of their study was to quantitatively compare the clinical outcomes of orthodontic subjects who'd been treated in the university graduated orthodontic clinic with either 018 or 022 bracket slots. 25% of the 800 subjects had been treated with the larger bracket slot, well 75% had been treated with the 018 inch brackets. All cases had both the discrepancy index performed as well as the ABO objective grading system calculated at the end of treatment using plaster dental casts. Treatment time was also calculated in both groups.

OK, what did these researchers find? Remember the main questions. Question No.1. Was there a significant difference in treatment time when comparing 018 and 022 bracket slots? The answer of that question is yes. There was statistically significant time difference of 4 months between the 018 brackets and the 022 brackets. That is, it took an average 4 months longer to finish those cases that had been treated with 022 brackets. Now you may ask, "Were those cases perhaps more difficult?" So the authors compared the discrepancy index prior to treatment in both groups. The discrepancy index was almost equivocal between the two groups. So based upon that analysis the severity or difficulty of the malocclusions was probably about the same.

Second question. Which bracket produced a better finished result? Based upon the American Board of Orthodontics Objective Grading System, the authors found that those subjects treated with an 018 bracket slot scored about 2.5 points less on the objective grading system. In other words, there were about 2.5 points better than those subjects treated with the 022 slot. Now the authors were careful to point out that although the differences between the groups were statistically significant, they were probably clinically insignificant. The difference of 2.5 points on the objective grading system could be the result of measurement error. In addition when I looked over the table that was published in the article, the differences for each of the 8 categories that were assessed on the objective grading system were not that the similar.

So what's the bottom line? Well If you use an 018 bracket slot, you should feel pretty good. Statistically in this large study, there was a difference that was significant between the treatment time and the finished result in favor of the 018 bracket slot. But if you are on the group of practitioners who uses 022 bracket slots, don't feel so badly because the statistically significant difference is probably not clinically significant.

If you'd like to review the study, you'll find it in the May 2010 issue of the Angle Orthodontist.

The accuracy of 2-dimentional planning for routine orthognathic surgery

Rustemeyer J, Groddeck A, Zwerger S, Bremerich A
British Journal of Oral and Maxillofacial Surgery 2010;48:271-275
                                                                                 

April, 15, 2011
Dr.Nabha Wael

[초벌원고]

Most studies examing the usefulness of cephalomtric planning for orthognathic surgery have focused on soft tissue and looked at the ability of the cephlometric planning software to predict the soft tissue outcome when the hard tissue was changed exactly as planned. A new study published in the June 2010 issue of the British journal of oral and maxillofacial surgery looked at the usefulness of 2-dimentional planning a bit differently. The study is called the accuracy of 2-dimentional planning for routine orthognathic surgery and was published by Rustemeyer and colleges from Germany.

[수정원고]

The question asked by this study was a pit different because they wanted to know if a certain movement of the mandible and or maxilla was planned after a combination of cephalometric planning on model surgery, how close to the actual bony structures end up compared to that planned ideal, in order to answer this question a retrospective group of 54 subjects was studied who all had mandibular surgery for advancement or set back, a little more than half the subjects also had maxillary surgery to address vertical issues and the subjects were relatively evenly divided between advancements and setbacks, the predictions were done on a pre-surgical cephalometric tracing using the soft ware tools provided, six cephalometric measurements where then recorded from the prediction tracing and compared to the actual surgical outcome derived from a post surgical cephalogram taken 2 weeks after surgery when the splint was removed, the assessment included the sagittal measurements SNA, SNB, and ANB and the vertical measurements of mandibular plane angle, palatal plane angle, and gonial angle, the comparison of these six measurements between prediction and actual were used to access the accuracy of the planning process for everyday use, in general the mean difference between prediction and outcome was found to be about 1 to 2 degrees, this sounds pretty good until you examine the range of differences which had extremes of 6 to 8 degrees, I think we would all agree that being within a degree or two is reasonable but being eight and a half degrees different on the mandibular plane angle which's ones extremeness the sample is probably not acceptable.

The general conclusion would be: that 2-dimentional cephalometric predictions are a useful every day tool and generally represent how the hard tissues will be poisoned after surgery, it's important to realize however that some relatively significant differences from the predictions are possible due to a number of issues ranging from transferring the plan to three dimensions to executing the plan during the operation, the general trance found in the study showed that the maxilla tended to be less advanced and more impacted in the anterior then planned and that the amount of mandibular change either advancement or set back was greater than predicted, my recommendation would be that you continue to use proven 2-dimensional prediction tools for orthognathic surgery until something better comes along, the ad generally accurate but can have incenses of large error.

For more information about this study of orthognathic surgery planning, see the June 2010 issue of the British journal of oral and maxillofacial surgery.

Early Headgear Effect on the Eruption Pattern of Maxillary Second Molars

Yossi Abed, Ilana Brin
Angle Orthod 2010;80:642–48
                                                                                  

April 22, 2011
Dr. Biao Yan

[초벌원고]

Do you still utilize early treatment for the correction of Class II malocclusion during the mixed dentition? With all of the negative comments that have been made about two-phase treatment over the past two years, many clinicians have reduced the amount of early treatment in their practices. But for the significant Class II malocclusion in a 9-year-old, some orthodontists still try to improve the skeletal and dental relationships as much as possible during the mixed dentition. So if you were to utilize early treatment, do you ever use a headgear to affect a skeletal change? Some orthodontists still use headgear for Class II correction. That leads to my final question: when you apply the headgear force for the maxillary first molars, what happens to the erupting maxillary second molars? Do you attempt to cause the impaction of these teeth? Do you slow down the eruption potentials? What are the long term effects of headgear therapy on the maxillary first and second molars? Those are important clinical issues for orthodontists who are to utilize a headgear. A study published in the July 2010 issue of the Angle Orthodontist answers these questions.

[수정원고]

The title of this study is ??Early Headgear Effect on the Eruption Pattern of Maxillary Second Molars.?? This study comes out of the department of orthodontics at Hadassah School of Dental Medicine in Jerusalem, Israel. This study was co-authored by Yossi Abed, and Ilana Brin. The purpose of their research project was to investigate the possible effect of combination headgear treatment during the first phase of orthodontics on the eruption pattern of the maxillary second molars in a random population of Class II subjects. These authors utilized the clinical records from the University of North Carolina: A two-phased randomized clinical trial of early Class II treatment. The nice thing about using this sample is that there was a built-in control sample as well. So these authors identified fifty patients who had utilized a combination headgear for fifteen months. They compared this to a sample of fifty subjects who didn’t receive any phase I treatment. The average age of both groups was around 9 years. Pre- and post-treatment supplementary radiographs were made on the treated group and radiographs were also available on the controls taken around the same time intervals. The authors devised this system where they could measure the linear changes that occurred in the maxillary first and second molars in the headgear group and compared that for the control group. What did they find?

In the headgear group, the maxillary first molars showed an average distal displacement at about two and a half millimeters, and those molars erupted about one and a half millimeters. On the other hand, in the control group, the maxillary molars moved mesially about one and a half millimeters and erupted about two and a half millimeters. So when we compared the two groups, there was a significant distal displacement of the first molar in the headgear group and its eruption was retarded by about one half during the treatment.

What about the maxillary second molar? Remember: this tooth is still unerupted at 9 years of age. The authors showed that the maxillary second molar erupted toward the occlusal plane in both groups. But in the headgear group, the eruption was significantly slower compared to the control group. In fact the amount of eruption of the second molar in the control group was about five millimeters. But in the headgear group, it was about two and a half millimeters. In addition, the maxillary second molars moved distally nearly three millimeters in the headgear group. Well, there was obviously no displacement of this tooth in the control group.

Final question: what effect did this have on the outcome of the second molars and first molars after the second phase of treatment? These authors were able to look forward following the second phase of treatment in the sample and found that there was no long-term effect of this distalization of the first and second molars. In all subjects, in both control and headgear groups, the maxillary second molars erupted into occlusion without problems. So in other words, the change in second molar position to the headgear effect was simply temporary. These teeth eventually erupted without a problem.

If you’d like to read this study and look at some of the examples, you can find it in the July 2010 issue of the Angle Orthodontist.

Modifications of midpalatal sutural density induced by rapid maxillary expansion: a low-dose computed-tomography evaluation

Lorenzo Franchi et al
Am J Orthod Dentofacial Orthop 2010;137:486-8
                                                                                  

April 29, 2011
Dr. Da-Nal Moon

[초벌원고]

When you do rapid maxillary expansion on a prepubertal patient, what changes will you expect to see in the density of the suture from pre-treatment to after the completion of active expansion. How does the density of the midpalatal suture compare with the density of the maxillary bone? How does the density of the anterior part of the midpalatal suture compare with the density posteriorly. When rapid maxillary expansion is completed, how long does it take for the midpalatal suture to return to normal? These questions are all addressed in an article titled “Modifications of midpalatal sutural density induced by rapid maxillary expansion: a low-dose computed-tomography evaluation”, by the Lorenzo Franchi et al.

[수정원고]

In this study the authors used the sample of 17 white prepubertal patients who required rapid maxillary expansion. The maxillary expansions for all the patients were activated 2 turns a day for 14 days for total of 7 mm of expansion. Multi-slice low-dose CT scans were taken before rapid palatal expansion, at the end of active expansion, and after a retention period of 6 months to evaluate changes in bone density. The authors specifically evaluated 4 different areas: 1) at the anterior area of the suture, 2) at the posterior area of the suture, 3) in the anterior maxillary bone, and 4) in the posterior maxillary bone. What they found was very interesting. First, they confirmed that the density of the midpalatal suture was less than the density measured at the maxillary bone. Second, the density of the anterior part of the suture was significantly less when compared with the posterior. This difference would help to explain why there is a greater opening in the anterior versus the posterior of the suture after the active phase of expansion. As might be expected, there was a significant decrease in the density of the midpalatal suture after the completion of active expansion. However, after 6 months of retention, the density of the midpalatal suture was similar to what it was prior to the initiation of treatment. This last finding would confirm that 6 months of post-active retention should be sufficient.

Obviously, based on the protocol used in this study, it is impossible to say whether a shorter period of retention would also be satisfactory. Low-dose computed-tomography has previously been used to measure bone density in areas being considered for the placement of implants, but not for measuring midpalatal bone density. I expect we will see greater and more widespread use of low-dose computed-tomography to study bone density in the future. You can find this article in the 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Classification of midpalatal suture opening after surgically assisted rapid maxillary expansion using computed tomography

Max Domingues Pereira et al
Oral Surg Oral Med Oral Pathol Oral Radiol Endod  2010;110:41-5
                                                                                  

May 6, 2011
Dr. Hyun-Ran Jeon

[초벌원고]

Surgically assisted maxillary expansion is an important tool for treatment of transverse problems in none growing patients. There’s continued disagreement among surgeons regarding which bone cuts are critical and whether the pterygoid plates need to be separated. CT imaging is a tool that allows better examination and classification of the changes that occur with surgically assisted expansion. And it can potentially improve our evidence-base for decision-making. One study that may provide some objective information was recently published in the July 2010 issue of the tripleo. The study is from Brazil and is titled "Classification of mid-palatal suture opening after surgically assisted rapid maxillary expansion using computed tomography". This was a retrospective study of 70 patients over the age of 18 that had undergone a surgically assisted procedure.

[수정원고]

The actual expansion appliance was either a Hass or a Hyrax type of expander attached to first premolars and first molars. The unique thing about this group is that they had a medical CT image of the palate taken just before expansion and then again right at the completion of activation. The surgical procedure was the same for all patients and consisted of sub-total Le Fort I with separation of the pterygoid plates. The post-expansion CT images were examined to classify the expansion is either type 1, which was expansion all the way from ANS to PNS or type 2, which was expansion from ANS to the transverse palate in suture but limited or no expansion from their back to PNS. What would be your guess about how the expansion takes place? Remember the surgeon in this case made a distinct attempt to separate pterygoid plates during surgery. Well, in spite of this attempt, only 1/3 of the subjects had separation of the mid-palatal suture from ANS to PNS, what the authors classified as type 1. The other 2/3 had the type 2 expansion with separation from ANS back to the transverse palatine suture, and little or no expansion posterior to the transverse suture. At this point we don’t know the clinical ramifications of getting type 1 versus type 2 expansion. We could theorize that perhaps the long term stability would be better if there was clear separation from ANS to PNS. But it’s just speculation at present. What we do know is that with surgically assisted expansion, sutural separation posterior to the transverse suture is not predictable, with only 1/3 of the subjects getting clear separation in that area. We also know that the expander design does not seem to be a critical factor at least when comparing a Hass versus Hyrax device. For more information about the sutural outcome of surgically assisted maxillary expansion, look for this article in the July 2010 issue of Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology.   

Accuracy of Cephalometric Landmarks on Monitor-Displayed Radiographs with and without Image Emboss Enhancement.

Leonardi RM, Giordano D, Maiorana F, Greco M.
Eur J Orthod 2010;32:242-247
                                                                                  

                                                             June 3, 2011 
Dr. Min-Hee Oh

[초벌원고]

I was walking by a computer recently when one of my staff members was digitizing a lateral cephalometric film for me. I noticed that she was using an embossed filter while locating some points and asked her why she was viewing the film in that way. She replied that to her, it appeared sharper that way and for certain landmarks, it seemed to be easier to decide the best location. This experience is what drew me to an article published in the June 2010 issue of the European Journal of Orthodontics called "Accuracy of cephalometric landmarks on monitor-displayed radiographs with and without image emboss enhancement." I will briefly review this article with you and discuss whether it supports the use of the embossing filters when digitizing.

[수정원고]

The study design was relatively straight-forward. Forty lateral cephalometric radiographs were selected randomly from the archives from the university clinic. These radiographs were scanned in high-resolution for viewing on a computer monitor. Five members of the university teaching staffs were recruited to participate in identifying 22 common cephalometric landmarks on the images. Each panel member digitized all forty radiographs in two modes: with and without an embossing filter. The digitizing was spread over several sessions to avoid fatigue. The best landmark location was determined to be the average location identified by the five panel members. Once this best location was determined, then the difference from this location could be measured for each panel member using either the normal image or the embossed image.

The results were somewhat surprising. Although the embossed image gives a perception of improved sharpness and ease of identification, the landmark identification was superior in most landmarks using the normal unfiltered image. The error was significantly greater for the embossed image for sixteen of the twenty two landmarks. It appears that in the process of manipulating the image to give it that three-dimensional look, the embossed filter may actually distort the landmark location giving a false sense of accuracy.

For now, the general recommendation would be to minimize the use of filters when digitizing and to focus on acquiring on an excellent image in the first place that requires little manipulation. I've already had a discussion with the assistant I saw digitizing with the embossed filter and reviewed the findings of this article with her. You may want to do the same with your staff.

If you want the entire article as a resource for the upcoming staff meeting, to explain why you prefer to avoid using the embossed filter when digitizing, you can find it in the June 2010 issue of the European Journal of Orthodontics.

Patient attitudes toward retention and perceptions of treatment success

Nikolay D. Mollova Steven J. et al.
Angle Orthod 2010;80:656-661
                                                                     

June 10, 2011
Dr. Young-Min Hong

[초벌원고]

Let me ask you a question. Are your patients generally satisfied with their orthodontic result at the end of treatment? Do your patients wear their retainers well after orthodontic treatment? Is there any association between wearing of an orthodontic retainer on a regular basis and perceived satisfaction with orthodontic treatment long-term? Would your patients be happier or more satisfied if you used a clear retainer compared to a Hawley retainer? You know as orthodontists we don't generally have the opportunity to survey our patients after treatment. But it's interesting to understand what their feelings might be about their treatment long-term. These questions were addressed in a study that was published on the July 2010 issue of The Angle Orthodontist.

[수정원고]

I thought this was an interesting study and would be of value to orthodontists. The title of this article is Patient's Attitudes toward Retention and Perceptions of Treatment Success. This study was co-authored by Nikolay Mollov and several other colleagues from the department of orthodontics at Virginia Commonwealth University. The purpose of this study was to determine patients' opinions regarding responsibility for orthodontic retention and to ascertain the association between patient's attitudes toward retention and perceptions of treatment success. This study involved a survey. This survey was constructed for distribution to former orthodontic patients with questions regarding their retention experiences.

Now the initial survey was distributed to over 500 individuals. About 425 individuals responded to the survey so the response rate was actually quite good. Patients were asked questions about the types of retainers they wore and how long they wore them and also whether or not they were satisfied with the results of their treatment. What did these researchers find? Let me take these questions one at a time. First of all, when the authors asked whether or not the previous orthodontic patients were satisfied, most of those surveyed indicated that they were either satisfied or very satisfied with the alignment and fit of their teeth. Well over 90% were satisfied at the end of the treatment and about 85% were satisfied at the time of the survey. It was interesting that about 40% those surveyed reported a decrease in satisfaction since the end of their orthodontic treatment. Then the researchers asked respondents how they felt and who they felt was responsible for orthodontic retention. Nearly 90% of the individuals surveyed perceived that they themselves were responsible for maintaining the alignment of their teeth after treatment. When asked about the types of retainers, most patients said that they received the removable retainer after treatment. Interestingly, only about 15% said that they had a bonded or banded mandibular retainer.

Now here's the unique association. Patients with invisible or clear retainers were more likely to report that they were very satisfied compared to those individuals with Hawley or permanent bonded retainers. Finally, discontinuation of retainer use was significantly related to the type of retainer prescribed. Only about 45% of those who had been given Hawley retainers were still wearing their retainer. But about 65% of those who had invisible or clear retainers were still wearing them. And nearly 70% of those with bonded retainers reported that they were still in place. So what did these authors conclude? Generally, most post-orthodontic patients are satisfied or very satisfied with their orthodontic treatment. In addition, there was a strong relationship between the perception of stability of tooth position after treatment and current satisfaction. The more stable the alignment, the greater the satisfaction. Now this makes sense.

Finally, what we really want to hear is that individuals themselves perceived that they were primarily responsible for maintaining the alignment of their teeth. This response was in 90% of those people that were surveyed. So if you'd like to review the results of this study regarding the perception of satisfaction after orthodontic treatment and the wearing of orthodontic retainers, you can find it in the July 2010 issue of The Angle Orthodontist.

Frequency of Intrusive Luxation in Deciduous Teeth and its Effects

Vivian C, Diana RJ, Vera C
Dent Traumatol 2010;26:304-307
                                                                      

June 17, 2011
Dr. Nam-Soon Park

[초벌원고]

As orthodontists, we arn't often involved in the management of trumatic injuries to primary teeth but, these injuries in the primary dentition can impact the treatment at a later date if the injury has an effect on the prominent successor tooth. The most likely type of injury to risk the developing permanent tooth is some sort of intrusive injury. To clarify the prevalence of intrusive injuries in children and to study the impact these injuries on the permanent teeth, researchers in Brazil conducted the study of traumatic injuries in children over a period of 8 years. A fortune of the results were published recently in the August 2010 issue of the Journal of Dental Traumatology in an article called "Frequency of Intrusive Luxation in Deciduous Teeth and its effects". The data used for this analysis was collected from the Pediatric Dental Trauma Center of Rio de Janeiro State University from 1996 to 2004. For each individual the type of injury was recorded along with age, gender, and cause of the injury. These individuals received follow-up in the clinic in the consequence of the injury on the primary tooth was determined. Ultimately the successor permanent tooth was examined after eruption for any signs of any impacts secondary to the primary tooth trauma.

[수정원고]

The study examined 3 main questions. The first was what is the prevalence of an intrusive injury among children treated for dental truma of the primary incisors. The answer to this question is about 30%, the most frequent type of injury seen. Of the approximately 750 injuries seen during the study period, 221 were either partial or total intrusions. The second question was what were the effects of the intrusive trauma on the primary tooth and its permanent successor. The most common effect on the primary tooth was pulp necrosis and tooth loss which occurred nearly 80% of the totally intruded teeth and about 25% of the partial intrusions. The permanent succesor suffered for enamel discoloration or hypoplasia in 20% of the total intrusion cases and 30% of the partial intrusion. The third question was whether the consequences to the primary or permanent teeth were influenced by the child's age at the time of the injury. In this population, researchers found no correlation between the effects on the teeth and the age at the time of the injury.

What we know from this study is that intrusive injuries are common and they happen to children one to four years of age most commonly in a fall at home. We also know that 20 to 30% of these injuries were result in some enamel disturbance of the permanent incisor with other consequence such as root/crown dilacerations or eruption disturbaces also possibility.

More information about traumatic intrusive injuries to the primary teeth can be found in the August 2010 issue of the Journal of Dental Traumatology.

Long-Term Follow-Up of Dental Single Implants Under Immediate Orthodontic Load. 답 mistaken positional diagnosis, poor anchorage, ankylosis

Palagi LM, Sabrosa CE, et al.
Angle Orthod 2010;80:807-811
                                                                      

June 24, 2011
Dr. Sang-Mi Lee

[초벌원고]

Suppose you are creating an interdisciplinary treatment plan with one of your best referring restorative dentist. This adult male is about 45 years of age and has missing posterior teeth in both maxillary and mandibular dental arches. In fact, there are long spans of missing teeth in the mandibular arch. He has a complicated malocclusion that requires significant anchorage to move the remaining teeth. But with so many missing teeth, your anchorage requirements will be challenging at best. Now the patient will eventually be restored with implants and restorations in all four quadrants. So the restorative dentist suggests that these restorative implants could be placed during the orthodontics and that you as the orthodontist could use the implants to move the adjacent teeth. Great idea! But here is the question. How long do you wait before you load these types of implants? If these were mini screws or mini implants, you'd probably load them immediately. But these particular implants will eventually be restored with crowns. Should you wait 2 months, 3 months, 4 months or perhaps 6 months? The answer to that last question can be found in an article that was published in the September 2010 issue of the Angle Orthodontist. Although not every orthodontist will treat this type of patient, this article provides excellent information on when to begin orthodontic loading of conventional, restorative implants.

[수정원고]

The purpose of this investigation was to evaluate the long-term success of implants that were loaded immediately. The sample for this study included 20 titanium implants that were placed in a total of 13 patients. These implants were restored immediately after placement with provisional crowns. Then the implants were divided randomly into two groups. In the control group, a period of 4 months was allowed before the implants were loaded with an orthodontic load. In the immediate loading group, a 200 gram load was placed on the implant immediately after it was inserted and restored with a provisional. After 6 months of orthodontic movement, clinical and radiographic evaluations were obtained and the implants were considered successful when favorable results were obtained for all of evaluations. Finally, the implants were evaluated 2 years after placement to determine the success rate.

What do you think these authors found? Now, remember the question. Can you load conventional restorative implants immediately or would it be better to wait 4 months before loading? Based upon the results of the study the authors found no difference. In those implants that received immediate loading, 90% were successful. In the group where the implant crown was placed but not loaded for 4 months, the success rate was exactly the same. In fact, one implant failed in each of those groups. So the authors determined that the failure was not due to the loading, but do to a problem with a surgical technique. So what's the bottom line? If a conventional restorative implant will be used as an orthodontic anchor, it can be loaded immediately after placement and restoration. The success rate is identical to that of implants where a 4-month waiting period was allowed.

If you'd like review this information, you can find it in the September 2010 issue of the Angle Orthodontist.

Efficacy of a Filled-Resin Sealant in Preventing Decalcification During Orthodontic Treatment.

Leizer C, Weinstein M, et al.
Am J Orthod Dentofacial Orthop 2010;137:796-800
                                                                                  

July 1, 2011
Dr. Min-Hee Oh

[초벌원고]

Enamel decalcification during treatment is a problem that all orthodontist worry about. In an attempt to reduce decalcification during orthodontic treatment, manufacturers have attempted to increase the strength and resistance to abrasion by adding filler materials to resin-based sealants. To further minimize decalcification during treatment, fluoride- containing particles have been included in resin sealants. Are fluoride-releasing filled enamel sealants any more effective in preventing decalcification than unfilled non-fluoride sealants?

[수정원고]

This question was addressed in a study titled “Efficacy of a filled-resin sealant in preventing decalcification during orthodontic treatment” by Cary Leizer et al. which appeared in the 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics. In this study, the authors evaluated 22 consecutively treated patients who were initiating 1-phase orthodontic treatment. Of the sample of the 22 patients, 18 were included in the final evaluation because 4 patients were lost to follow up treatment. A split-mouth design was used to apply “Pro Seal” which is a fluoride releasing filled resin sealant to half the teeth and “Transbond MIP” to the other half of the teeth which served as an unfilled non-fluoride control. Individual teeth from canine to canine in each arch were alternatively treated with either Pro Seal or Transbond MIP. Photographic evaluation was then used to determine the levels of decalcification over a 12 to 18 month period which roughly simulated the duration of orthodontic treatment. Twelve orthodontic professionals then evaluated all photographs and scored them on a 3-point scale related to the degree of decalcification.

What do you think happened when the results for two groups were compared? The bottom line is that there was no statistical or clinical significant difference in decalcification when the two different products were evaluated.

Although the sample for the study was small, I thought it was a well-conducted study that had the advantage of being an in-vivo study which closely mimicked the actual conditioned under which sealants would be clinically used. It also had the advantage of using within-patient comparisons over a reasonable length of time. Considering all the different factors that go into creating decalcification such as hygiene and sealant wear from brushing, I am not surprised at the results of this study. The bottom line is that the additional time and expense required to use a fluoride releasing filled enamel sealant to prevent enamel decalcification during orthodontic treatment do not appear to be justified.

You can find this article in the June 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Prognosis of the Implants Replaced After Removal of Failed Dental Implants

Kim YK, Park JY, Kim SG, Lee HJ
Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:281-286
                                                                                   

September 2, 2011
Dr. Mi-Soon Lee

[초벌원고]

Dental implants are an integral part of many orthodontic treatment plans for patients with missing teeth. As such, we need to know something about the success or failure rates as we help patients with making appropriate treatment decisions. Of specific interests is whether a failed implant can be replaced with reasonable success. This may be a particular interest in a younger patient that has many years to live with an implant in place.

[수정원고]

An article called ‘prognosis of the implants replaced after removal of failed dental implants’ appears in the September 2010 issue of the triple O. It gives us some valuable information about the success of failed implant replacement. Let me briefly review with you a few details of the study design and the results that were found. To start with, the study was done retrospectively, meaning the data may not be as reliable or complete. However, the study subjects were all treated by the same clinician, which can reduce some variability. 49 subjects with the total of 60 failed implants were included. This was a subset of nearly 600 subjects with implants placed over 3.5-year period.

The implant failure rate during initial placement was 3.2%. The 60 replaced implants were examined for success and periodontal health during an average 2 year follow-up time. Information was also gathered about whether the replacement implant was placed immediately or whether it was delayed until after a healing period. The results showed that the failure rate of the replacement implants was just over 10% or about 3 times initial placement failure rate. So replacement implants have nearly a 90-percent success rate, but are not quite as successful as initial placement. Another interesting finding was that many of the failed implants were upper first molars. The authors had some suggestions as to why this may be the case. But as an orthodontist, this knowledge may lead you to more aggressively suggest orthodontic space closure for missing teeth in this location. When comparing the success of replacement implants placed immediately versus after healing period, no difference in success rate was found.

What we learned from this report is that replacement implants have a high success rate, nearly 90%, but not quite as high as initial placement. We also learned that, at least in this group of subjects, delaying placement of new implant until after healing did not seem to impact the success rate. And lastly, upper first molar implants show the greatest number of failures. So missing teeth in those areas may be considered for orthodontic space closure. Remember to keep in mind that this study is limited by its retrospective design, but it still provides useful information when considered in that light. The article itself can be found in the September 2010 issue of the journal, Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology.

Effects of Surface Conditioning on the Shear Bond Strength of Orthodontic Brackets Bonded to Temporary Polycarbonate Crowns

Blakey R, Mah J.
Am J Orthod Dentofacial Orthop 2010;138:72-78
                                                                                  

September 9, 2011
Dr. Sun-Young Lim

[초벌원고]

If you have a patient present to your office who has a maxillary anterior temporary polycarbonate crown, how do you bond to this crown? A number of articles have been written about bonding to porcelain crowns but none that I am aware of about bonding to polycarbonate temporary crowns, which I seem to be seeing more and more in practice. I think when most orthodontists think about preparing artificial crowns for bonding, they usually think one of three ways to prepare the crown surface; namely sandblasting, roughening with diamond bur and etching with strong acid. When you have to bond to polycarbonate temporary crowns how do you prepare the surface? Does it make any difference if you use any of the three method that I just mentioned? And furthermore, does it make any difference if you are bonding a metal or ceramic crown?

[수정원고]

An article title “Effects of surface conditioning on the shear bond strength of orthodontic brackets bonded to temporary polycarbonate crowns” Rondell Blakey and James Mah which appeared in the July 2010 issue of the American Journal of Orthodontics and Dentofacial Othopedics addresses these questions. In this study the authors used 80 maxillary right central incisal polycarbonate crowns and devided them into four groups of 20 each. One group received no treatment and served as a control. The second group was sandblasted. The third group at the glazed surface removed with diamond bur and the fourth group was etched with 9.6% hydrofluoric acid. Half of the teeth in each group were bonded with metal brackets and the other half with ceramic brackets.

An instron testing machine was then used to test shear strength of each bonded bracket and adhesive remnants index (ARI) was also used to document site of bond failure. When the shear strength were recorded and statistically analyzed what do you think that authors found? Was one of the three methods surface prepare better than any of the others? And did it make any differences if metal or ceramic brackets were used?

There is also interesting. The authors found that sandblasting was the only surface treatment to significantly affect adhesion of metal and ceramic brackets to polycarbonate crowns. When the adhesive remnants index was evaluated the groups that had surface roughening with diamond or etching with 9.6% hydrofluorid acid had an adhesive remnants index of 0, meaning that no adhesive was left on the polycarbonate crown. The only group that showed still attached adhesive to crown was group which has surface prepared with sandblasting.

Bottom line of this study is that only the sandblasting treatment was statistically significant difference compared with the control. I thought it is interesting to know scanning electromicroscope and photomicrographs show that etching polycarbonate crowns with hydrofluoric acid produce minimal changes and did not appear to altered surface. This is because polycarbonate is resistant to strong acid. When the metal and ceramic brackets in the sandblasting group were evaluated, the ceramic brackets demonstrated higher shear bonding strength, although the results were still lower and the value were generally considered to be clinically acceptable. The message from this study is that if you have to bond a bracket to polycarbonate crown you will achieve the highest shear bond strength by sandblasting the surface and using ceramic brackets. You can find this article in the July 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Comparison of Two Protocols for Maxillary Protraction: Bone Anchors Versus Face Mask with Rapid Maxillary Expansion

Cevidanes L, Baccetti T, et al.
Angle Orthod 2010;80:799-806
                                                                                  

September 16, 2011
Dr. Hoon Noh

[초벌원고]

Suppose you are planning treatment for a 10 year old boy. He has a class III malocclusion with an anterior crossbite. When you perform your cephalometric analysis, you realized that the mandible is normal but the maxilla is underdeveloped or hypoplastic. Neither of the patient's parents had a crossbite or any previous orthodontic treatment. Your plan is to place a maxillary palatal expander and utilize the face mask to protract maxilla forward and correct the anterior crossbite as well as the maxillary hypoplasia. Sounds like a great plan. Here's the only problem. During the consultation, this young boy says he will never ever wear a face mask in public. So there is a limited amount of time that he can utilize this appliance. Is there any other option for correcting the maxillary hypoplasia? Could you perhaps use bone anchors to correct this problem? If you could place some sort of bone anchor in the zygomatic region on both sides of maxilla and similar bone anchors in the area of the mandibular canines, could you use intermaxillary Cl III elastics to pull the maxilla forward? That question was addressed in the study was published in the september 2010 issue of the Angle orthodontist. This unique type of treatment could be a great alternative to avoid the use of the face mask.

[수정원고]

Let me explain what was found in the study. The title of the article is "Comparison of two protocols of maxillary protraction: bone anchors versus face mask with rapid maxillary expansion". This study was co-authored by Lucia Cevidanes and several other researchers from the departments of orthodontics at university of North carolina, the university of Michigan and the university of florence in Italy. Now the purpose of this study was to compare active treatment effects in the skeletal maxillary and mandibular structures when bone anchors were used for maxillary protraction compared to face mask therapy and rapid maxillary expansion. In order to accomplish this goal, the authors gathered 2 separate samples. One sample had been treated in Belgium by a single operator. It was a group of 20 Cl III subjects with an average age over around 12 years. The sample was but evenly between boys and girls. In the sample, miniplates were placed bilateral in the maxilla in the zygomatic arch area and on either side of anterior of mandible in the canine region. These miniplates were secured with two or three small screws underneath the tissue. A hook protruded through the attached gingiva. 3 weeks after placement of these plates, Cl III intermaxillary elastics were used to correct the anterior crossbite by protracting the maxilla forward. The procedure continued until a positive overjet was achieved and in some cases overcorrection was produced. This sample was compared to a sample that had been treated at the university of Michigan using face mask and rapid maxillary expansion. That particular group consisted of over 30 subjects with an average age over about 8 years at the start of procedure. These patients were also treated to achieve a positive overjet and in some cases overcorrection. Then the authors evaluated cephalometric radiograghs taken on each of the samples before the protraction and then within 1 month after, the protraction was discontinued. What the authors wanted to determine was the impact or side effects of each of these techniques.

OK, What are they find? First of all, most orthodontist utilized a face mask to protracting maxilla at least some point of time. So you know what the problems are. There was typically a clockwise rotation of the mandible downward. So as the maxilla is brought forward since the expander attaches to teeth, it produces mostly dental movement with proclination of the maxillary incisors, some retroclination of the mandibular incisors and clockwise rotation of the mandible. What happened in the sample that had bone anchors in Cl III intermaxillary elastics? There were significant differences in that group compared to face mask group. In the bone anchor group, there was actually a slight closer of the mandibular plane. In addition in the bone anchor group, there was a reduction in lower anterior facial height and the molar relationship improved significantly more than the face mask group. Finally there was no proclination of the maxillary incisors or retroclination of the mandibular incisors in the bone anchor group.

So what have we learned from the study? The bone anchor protocol was able to induce significantly greater maxillary advancement than face mask and palatal expander therapy. In addition there were more controled vertical changes in the mandible with the bone anchor group and there was a lack of clockwise rotation of the mandible in that group as well. So back to your patient. Remember the 10 year old who won't wear a face mask? Now you have an alternative. You could consider placing bone anchors with the elastic hooks protruding through the gingiva. This study showed that this technique can produce maxillary protraction and avoid dental changes as well as unwanted skeletal changes. If you'd like to review the study and look at the photographs of the bone anchors yourself, you will find it in the september 2010 issue of the Angle orthodontist.

Condylar Displacement Between Centric Relation and Maximum Intercuspation in Symptomatic and Asymptomatic Individuals

Weffort SYK, de Fantini SM.
Angle Orthod 2010;80:835-842
                                                                                 

September 23, 2011
Dr. Hyun-Jung Lee

[초벌원고]

Do you check a patient’s centric relation during an initial orthodontic examination appointment? I think most orthodontists check to make certain that there are no significant differences between maximum intercuspation and centric relation. Now, I’m defining centric relation as the midmost, uppermost relationship of the condyle in the fossa. So, if you do check this relationship, do you typically find any significant differences? I think the answer to that in the minds of most orthodontists would be ‘yes’. The differences may not be great, but there is typically some sort of slide between CR and CO.

[수정원고]

Now for my last question, would this slide be greater in patients who have temporomandibular joint symptoms or perhaps less? That’s a little bit more difficult question to answer. But the answer to that question can be found in the September 2010 issue of the angle orthodontist. The title of that article is ‘Condylar displacement between centric relation and maximum intercuspation in symptomatic and asymptomatic individuals’. This study comes out of the department of orthodontics at university of Sao Paulo in Brazil. The senior author is doctor Weffort.

Now, the purpose of this study was to perform a cross-sectional investigation to measure condylar displacement between centric relation and maximum intercuspation in a group of symptomatic compared to asymptomatic individuals. Now, when I say symptomatic and asymptomatic I’m talking about patients with TMD. There are specific research diagnostic criteria that have been established for TMD. And so the definition of symptomatic in this paper was defined by these specific criteria.

The overall sample consisted of 70 subjects. They were divided into half asymptomatic and half symptomatic individuals. Females and males were represented in both samples. Then in each group, all of the dental casts of these individuals were mounted on a fully adjustable articulator. These articulators could record differences between CR and CO. The authors evaluated the amount of change in three dimensions; vertically, anteroposteriorly, and transversely. The authors then compared the amount of shift between CR and CO between symptomatic and asymptomatic subjects and also took into consideration the patients’ gender.

OK, what did the authors find? Is there any difference between symptomatic and asymptomatic subjects? And the answer to that question is ‘yes,’ sort of. Let me explain, first of all, in the symptomatic group, the authors found that the difference in amount of shift was greater on the right side than on the left side in the vertical plane. This was compared to those subjects who were asymptomatic who had much less of a shift in these directions. What about in the transverse plane? The authors found that the asymptomatic subjects had a greater transverse shift predominantly in the mesial direction compared to the symptomatic group. In addition, the presence of bilateral condylar displacements, in other words, both right and left sides in an inferior and distal direction were significantly greater in symptomatic individuals. OK, last question. What about differences between males and females? Based upon this study, the authors found no significant difference in the amount of shift between symptomatic and asymptomatic individuals when it came to comparing genders.

So in conclusions the authors did find some differences between the genders. Now you have to trust the authors’ methods. They did mount these dental casts on articulators and they made transfer recordings using centric relation records and maximum intercuspation records. But we all know there’s some error in doing this. It seems to me that this type of study might perhaps be more accurate if performed in other ways. But at least this is a good start in answering a question such as this. So if you’d like to read this study for yourself, you’ll find it in the September 2010 issue of the angle orthodontist.

Pulpal Blood Flow Changes Due to Rapid Maxillary Expansion

Babacan H, Doruk C, Bicakci AA.
Angle Orthod 2010;80:1136-1140
                                                                                

September 30, 2011
Wael Nabha

[초벌원고]

When you perform palatal expansion on your patients what happens to the pulp of those teeth that are been used to anchor the expansion devise, let me be more specific: Is there any trauma that occurs within the pulp of these teeth that are been used to perform sutural whelming, farther more are the changes that occur in the pulp reversible or does this force produce a permanent alteration in the dynamics of the pulp within the anchor teeth, personally I think that these are interesting questions, but how would one measure the effect on the pulp, pulpal changes are typically determined in one way by measuring the blood flow within the pulp, this could be accomplished with a Doppler specifically laser Doppler flowmetry is it although could be used to measure pulp blood flow, during or after some sort of orthodontic treatment, that’s the mechanism that was used in an evaluation that appeared in the November 2010 angle orthodontist, the title of the study utilized that methodology was: Pulpal blood flow changes due to rapid maxillary expansion. This study comes out of the department of orthodontics at Cumhuriyet University in turkey. The seiner author is Dr.Hasan Babacan who is an associate professor in that department.

[수정원고]

The purpose of this study was to evacuate pulpal blood changes in human dental pulp with the Laser Doppler flow-meter form the beginning of rapid maxillary expansion all the way to the end of retention, in order to accomplish this project the author utilized 21 patients, now let me explain the expander that was used, this was full coverage light acrylic appliance similar to aligner, in another words it covered all of the teeth, an expansion device was anchored to the palatal portion of this appliance, so when it was delivering its expansive force, it delivered the force to all of the teeth, in addition it opened the vertical dimension because of all the teeth that were being covered ,expansion was performed at the rate of one turn of the expansion screw per day, all subjects were expanded until the expansion was complete for the correction of the cross bite, now incorporated into the aligner was the ability for the authors to accurately measure pulpal blood flow of the maxillary central incisors, canine, and first molar, these teeth had had their blood flow measured before expansion, after the first week, then after the second week which also indicated the end of the expansion, and then at the third, seventh, and twelfth weeks of retention, what did these researches find when they compared the blood flow measurements during these time intervals, let me answer that as succinctly as possible.

First of all; the blood flow changes significantly during the first week of expansion, in fact the laser Doppler flow-meter showed that the blood flow was doubled in each of the three teeth after the first week of expansion. Where there any differences between the central incisor, canine, or molar?, the answer to that question is: No, all teeth responded similarly, how long did the increased blood flow last?, good question, actually after the second week which was the end of the expansion the laser Doppler flow-meter showed that the blood flow had reversed its strand and approached a more normal value, what happened within increase time, actually there was a decrease in blood flow gradually until the twelfth week at which point the blood flow was nearly identical to what it was at the outset of the expansion, so what’s the point of this study.

Well, since expansion has been around for a long time, i think we all realize that there is probably no an tour defects on pulps of teeth when we expand the maxilla and use teeth as anchors, but it is important to know that there are physiologic changes that do occur within the pulp, the blood flow within the pulp doubles within the first week of expansion, but these authors have clearly shown that this apparent problem at the beginning is completely reversible, so that blood flow returns to its normal rate after about three months, if you are interested in reviewing this study on changes in pulpal blood flow during palatal expansion, you can find it in the November 2010 issue of the Angle Orthodontist.

Psychosocial Reward of Orthodontic Treatment in Adult Patients

Gazit-Rappaport T, Haisraeli-Shalish M, Gazit E.
Eur J Orthod 2010;32:441-446
                                                                                

October 7, 2011
Dr. Sang-Mi Lee

[초벌원고]

We all see many adults seeking orthodontic treatment for esthetic reasons. They may have crowding or spacing or other dental irregularities that they wish to have corrected. Does treating these alignment issues really benefit the patients in terms of their self-confidence, social impact, or other psychosocial measures of well-being? We have some new information recently published in the August 2010 European Journal of Orthodontics that may help our understanding about the impact of orthodontic treatment on adult patients. The study I am referring to was done in Israel and published with the title ‘Psychosocial Reward of Orthodontic Treatment in Adult Patientsʼ.

[수정원고]

In order to make the study result applicable to routine practice, the subjects for this project were recruited from a single orthodontic private practice. Subjects were only included in the study if they presented for treatment to improve their dental esthetics. All patients underwent fixed orthodontic treatment for a period of six to fourteen months to correct alignment, spacing, or other irregularities. In order to measure the psychosocial changes as a result of treatment, each subject was asked to complete the psychosocial impact of dental esthetics questionnaire. This questionnaire was completed prior to treatment, and then again once treatment was complete. These assessments lead to specific scores in the areas of dental self-confidence, social impact, psychosocial impact, and esthetic concerns. The change in scores for each area was compared for each subject. Information was also collected regarding age, gender, marital status, and education.

The results were very positive for the orthodontic profession. There was a significant positive improvement in the average score for each of the four areas. There was no correlation between score improvement and the subjects, age, gender, educational, marital status indicating that the benefit was seen evenly across all subgroups.

So, is this the definitive evidence that orthodontic treatments benefit adult patients? Well, it’s certainly positive but far from definitive. This is one study done in one practice. The details of patient selection were not well-defined and there was no true control group that was monitored for psychosocial changes over time without having the orthodontic treatment. The follow-up assessment time was also vaguely defined “shortly after the treatment was completed”. Also, it would be nice to know whether the positive changes observed lasted over subsequent years. But, for now we can say that there was additional evidence of the psychosocial benefits to adults that have orthodontic treatment to improve esthetics at least in the short term.

For more information about this project, see the August 2010 issue of the European Journal of Orthodontics.

Modified fluoride toothpaste technique reduces caries in orthodontic patients: A longitudinal, randomized clinical trial

Anas H. Al Mulla, Saad Al Kharsa, and Dowen Birkhed
Am J Orthod Dentofacial Orthop 2010;138:285-91
                                                                                

October 14, 2011
Dr. Da-Nal Moon

[초벌원고]

All orthodontists work hard to improve the oral hygiene of their patients during treatment and to try to reduce the number of teeth that develop decay and require restorations. To do this, most orthodontic offices have specific tooth brushing instructions which are routinely given to their patients. What type of tooth brushing instructions do you give to your patients? If you are like most orthodontists, you have your staff show the patients how to brush around their brackets, how to evaluate if their teeth are clean and encourage them to brush at least twice a day. Is there a better way to have your patients brush their teeth that will result in a decrease in caries and the need for restorations?

[수정원고]

An article titled 'Modified fluoride toothpaste technique reduces caries in orthodontic patients: a longitudinal, randomized clinical trial' by Anas Al Mulla et al which appeared in the September 2010 issue of the 'American Journal of Orthodontist and Dentofacial Orthopedics' suggests that there might be. In this study, the authors randomly devided 100 orthodontic patients into two groups. A test group and a control group. The control group which consisted of 49 patients was given a fluoridated toothpaste and routine clinical oral hygiene instructions which consisted of brushing twice a day after breakfast and after dinner before going to bed and rinsing with the fluoridated mouthwash. The test group which consisted of 51 orthodontic patients was also given toothpastes containing fluoride but received a completely different set of instructions for brushing. This group was instructed to use 1g of toothpaste on a wet toothbrush, spread the toothpaste evenly between both arches, brush all surfaces for 2 minutes, use a small amount of water with a toothpaste remaining in the mouth and, swish the toothpaste slurry between the teeth by active cheek movements for 30 seconds before expectorating. They were also told to avoid further rinsing with water, avoid drinking or eating for 2 hours and to brush teeth twice a day after breakfast and at night before going to bed and finally, to abstain from all other types of toothpaste during treatment until its completion. Each patient was examined before starting orthodontic treatment and shortly after debonding in a 2-year study period. At the beginning and debond visits each patients underwent an intraoral clinical examination and a radiographic examination. At both examination, the DFS index was used, which evaluated the number of decayed and filled tooth surfaces. At the end of the study, plaque index scores were also compared between the two groups. When the DFS index and plaque indices was statistically compared between the test and control groups at the end of treatment. What do you think the authors found? The bottom line of this study is that the test group patients have significantly better plaque index scores compared with the control group. The control group patients also had more than 7 times the clinical DFS more than 4 times the radiographic DFS, and more than 5 times the combined clinical and radiographic DFS scores. All of these differences were highly significant.

Based on the results of this study, it appears that it would be well worth it to modify your office instructions on brushing to include the regimen discussed in this article which appeared in the September 2010 issue of the 'American Journal of Orthodontics and Dentofacial Orthopedics'.

Treatment and Posttreatment Skeletal Effects of Rapid Maxillary Expansion Investigated with Low-Dose Computed Tomography in Growing Subjects

Ballanti F, Lione R, et al
Am J Orthod Dentofacial Orthop 2010;138:311-317
                                                                                

October 28, 2011
Dr. Min-Hee Oh

[초벌원고]

I’m sure you have used rapid maxillary expansion on many of your patients. When you do successfully expand maxilla with RME, what dental and skeletal changes do you think occur? When the midpalatal suture opens, does it expand more inferiorly than superiorly? And does it expand more anteriorly than posteriorly? What happens to the maxillary central incisors during rapid maxillary expansion? Do they expand more coronally than apically at the end of active expansion? How you answer these questions is probably based on information from studies using two dimensional posterior-anterior cephalometric radiographs. Would the results of these studies change if they were repeated utilizing three dimensional multisliced CT scans?

[수정원고]

This question was addressed in a study titled “Treatment and post-treatment skeletal effects of rapid maxillary expansion investigated with low dose computed tomography in growing patients” by Fabiana Ballanti et al., which appeared in the September 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

In this study, the authors used a sample of seventeen healthy white children with a mean age of slightly over eleven years who sought orthodontic treatment. All of the subjects in this study required rapid maxillary expansion and were treated with the rapid maxillary expander that was activated two turns per day for fourteen days for total amount of expansion of seven millimeters at which time the screw was tied up with the ligature wire. Multisliced coronal CT scans were taken before RME, at the end of active expansion, and after the retention period of six months when the expander was removed. At each of these measurement periods, three coronal scans perpendicular to the occlusal plane were taken, passing through the anterior nasal spine, the mid-point between the anterior nasal spine and posterior nasal spine and through posterior nasal spine. Basically, three coronal scans were taken at three different locations anteroposteriorly.

When the authors evaluated the dental and skeletal changes at the three different time periods, some of the results were very interesting. As you might have predicted, anteroposteriorly the maxillary suture opening was greatest in the anterior tapering to less of an opening posteriorly. A finding that you might not have predicted and which was surprising to me was that vertically the maxillary halves were separated in an almost parallel manner – that is there was this much opening superiorly as there was inferiorly. I would not have predicted this because I think most previous studies using two dimensional radiography suggest that the amount of midpalatal suture opening decreases as you move superiorly, a finding contradicted by this study.

This study also found that there was the significant amount of expansion of the nasal cavity in all three coronal scans indicating that the transverse increase of the nasal cavity was not limited to the anterior region. The authors also found that at the end of active expansion, the roots of the maxillary central incisors were more divergent than the crowns. However, between the end of active expansion and the six months stabilization period, the crowns tip toward the midline while the roots remained divergent. Also, at the end of the six-month retention period, the midpalatal suture appeared reorganized in all the subjects, and the expansion of the nasal cavity was stable.

I believe this study is an example of the better research data we will be able to obtain when using three dimensional vs. two dimensional radiographic techniques. The bottom line of this study is that the midpalatal sutures open in a parallel manner; there is a stable increase in the width of the nasal cavity; and the midpalatal suture is reorganized after six months.

You can find this article in the September 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Long-Term Success and Survival Rates of Autogenously Transplanted Canines

Gonnissen H, Politis C, et al.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod
2010;110:570-578
                                                                                

November 11, 2011
Dr. Biao Yan

[초벌원고]

Consider the clinical situation where you have a sixteen-year-old patient with a severely impacted upper right canine. You are relatively confident that you can move the tooth into position orthodontically after surgical uncovering but are also realistic that the treatment time might be longer than you would like because of the canine position. When discussing treatment options with the family, the sixteen-year old said that she did some searching on the internet and learned that autotransplantation of the tooth could be a much faster way to get the canine into the arch. Is this a reasonable treatment option?

[수정원고]

I have some data for you that may help you answer this clinical question. The data comes from a recent publication in the triple O called “Long–term success and survival rates of autogenously transplanted canines.” In order to collect the information for this paper, the authors made an effort to recall patients that had autotransplanted canines in the years 1995 to 2002. They were able to locate 59 subjects that have 73 transplanted teeth. These patients were then subjected to a clinical and radiographic examination to see which teeth had survived and to evaluate the success of those that remained. The tooth was judged to be unsuccessful even if present when there was evidence of progressive root resorption, significant periodontal involvement, or apical inflammation. The average follow-up time was 11 years, which makes these results more valuable than some other studies with more limited follow-up.

Here are some of the important findings. 18 of the 73 transplanted canines were lost by the time of follow-up. So, 75 percent survived. The most common reason for loss was progressive root resorption. Using the criteria I mentioned a minute ago for success, 42 of the transplanted canines about 58 % were judged to be successful with no indication of progressive resorption, periodontal issues, or apical inflammation.

There were two factors found to be related to success: age and initial ankylosis. This means that autotransplantation tended to be more successful, the younger the subject was at the time of procedure. And if the tooth was initially judged to be ankylosed prior to transplataion, the success rate was reduced.

So we now know the long-term success rate of autotransplanted canines is just under the sixty percent. The survival rate was somewhat higher but some of those teeth demonstrate progressive resorption or periodontal issues that that will lead to loss. This success rate is lower than orthodontic movement, so when ideally be reserved for teeth or orthodontic movement is not feasible or not successful.

Getting back to our initial discussion of the 16 year-old with the severely impacted canine who asks about the transplantation option? My response would be that the orthodontic alignment with the canine would be a more predictable long-term treatment. And that the long-term success of the transplantation option would only be about 60 percent.

If you have an interest in more detailed information from this study, look for this paper by Gonnissen and colleagues in the November 2010 issue of the Oral Surgery, oral medicine, oral pathology, oral radiology and endodontology.

Effective Radiation Dose of ProMax 3D Cone-Beam Computerized Tomography Scanner with Different Dental Protocols

Qu XM, Li G, et al.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:770-776
                                                                               

November 18, 2011
Dr. Hyun-Ran Jeon

[초벌원고]

A recent New York Times article highlighted public concerns about radiation doses from dental in orthodontic imaging. The report specifically questioned the use of cone-beam imaging in orthodontics. In order to good make good decisions about imaging in orthodontics, we need accurate information regarding the effective radiation dose of the imaging systems we use. The December 2010 issue of the Triple O included an article giving us more objective information to use. It's called, “Effective radiation dose of ProMax 3D cone-beam computerized tomography scanner with different dental protocols.” I want to review a few of the highlights with you so you have more information to make good imaging decisions.

[수정원고]

The study used a standard adult head phantom with a series of thermoluminescent dosimeter chips placed in the areas of radiation sensitive tissues. The phantom was exposed using 12 different available scanning protocols for the ProMax machine. The adjustable settings included 5 different patient size settings, adjustments for different fields of view, and 3 resolution settings. The dosimeter chips were read and the calculation of effective dose was carried out using the 1990 and 2007 versions of the International Commission on Radiation Protection Protocols. The ProMax 3D has a maximum field of view which is just large enough to include the maxilla and mandible. It requires some software stitching to get a larger view. Some of the more important results are that the effective radiation doses are two to three times higher when using the 2007 protocol for calculation which reflects the increased weighting for salivary glands and other tissues. Using these 2007 calculations which best reflect our current understanding, the ProMax machine had effective doses ranging from 30 μSv to just over 300 μSv. The lowest dose was from the low resolution setting and the highest dose from the normal resolution setting and the largest patient size setting. In general, reducing the field of view to either the maxilla or mandible alone reduced radiation dose 40 to 50 percent. The machine also has a mode that stitches together 3 low resolution views to give a larger field of view and that protocol resulted in a dose of 87 μSv. A normal resolution setting for a middle size patient in a full field of view had a dose of about 200 μSv.

Here are a few general conclusions to remember. First, on a machine such as this with different patient size, field of view, and resolution settings, the radiation dose can vary up to about 10 times depending on the scanning protocol selected. This means it's very important to give specific directions to the person performing the scan, so that the diagnostic information that is needed is obtained with the lowest possible radiation burden. The second important point is that using the 2007 ICRP calculations results in radiation doses that are 2 to 3 times greater than the same machine using the 1990 calculations. This is incredibly important to know when comparing study data or when comparison shopping for a machine.

More information about the study of effective radiation dose for the Planmeca ProMax 3D scanner can be found in the December 2010 issue of Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology.

Influence of enamel sandblasting prior to etching on shear bond strength of indirectly bonded lingual appliances

Cal-Neto JP, Castro S, Moura PM, Ribeiro D, Miguel JA.
Angle Orthod 2011;81:151-154
                                                                               

November 25, 2011
Dr. Nam-Soon Park

[초벌원고]

How many of you listening to this issue of practical reviews and orthodontics do some sort of lingual bonding? Today with the increased numbers of adults seeking orthodontics, there are many practitioners that at least offer lingual appliances to their options for adult patients. If you do place lingual brackets, you obviously do indirect bonding. But with indirect bonding, especially on the lingual surfaces, there can be a problem of bracket debonding. So how do you increase your ability to retain the bracket on the tooth, in other words, improve the shear bond strength of lingual bracket?

[수정원고]

One possibility would be to sandblast the enamel surface prior to using your indirect bonding technique. But does that really help? That question was addressed in the study that was published in the January 2010 issue of the Angle orthodontist. The title of that article is ‘Influence of Eenamel Sandblasting Prior to Etching on Shear Bond Strength of Indirectly Bonded Lingual Appliances’. The study is co-authored by Julio P. Cal-Neto and four other research associates from the department orthodontics at the Federal University in Rio de Janeiro, Brazil.

The purpose of this study was to evaluate the influence of enamel sandblasting prior to etching of the shear bond strength of lingual appliances that were indirectly bonded. In order to accomplish this subjective the authors performed this experiment in the laboratory. For the human maxillary premolars that had been extracted for orthodontic purposes were used in this experiment. The sample was divided in two groups. In group I, the teeth were etched with phosphoric acid and an indirect bonding technique using a Reliance Product was used to bond brackets to the tooth. In group II, the teeth were sandblasted for 3 seconds using 65-70 psi with the distance of 5 mm using 50μm aluminium oxide powder and a micro etcher. After the sandblasting, the acid etching and bonding were performed. Then all of these teeth were debonded using a device to test the shear bond strength. In addition to testing shear bond strength the authors also evaluated the enamel surface to see how much composite remained on the teeth.

OK, I think you get the idea of the experiment the big question is ‘Will sandblasting prior to indirect bonding using lingual appliances give a better shear bond strength?’ The answer that question is ‘Yes’, absolutely. There was statistically significant increase in the shear bond strength when the 3 seconds sandblasting was performed with a micro etcher.

Second question, what happens to the adhesive remnant index (ARI)? Or in other words, the amount of composite that remains on the teeth. Unfortunately, the answer to that question is that it was increased. When the brackets were removed, there was more composite remaining on the teeth. Therefore the clean up time would obviously be increased. Since this bonding material remains on the lingual surfaces of the teeth. It could be more difficult to remove.

So there are favorable and unfavorable aspects to the results of this experiment. The Microetcher increases the bond strength but the clean up after the bracket removal would take more time. If you are interested in reviewing the study that utilizes of Microetcher prior to indirect bonding of lingual brackets, you can review it in the January 2011 issue of the Angle orthodontist.

Interleukin-1β levels, pain intensity, and tooth movement using two different magnitudes of continuous orthodontic force

Suwannee Luppanapornlarp, Takashi S. Kajii, Rudee Surarit, Junichiro Iida
Eur J Orthod 2010;32:596-601
                                                                                

December 2, 2011
Dr. Young-Min Hong

[초벌원고]

It seems amazing to me that after all this time, we still have no real evidence of what optimal tooth moving force levels are. I'd like to use the lowest force levels that moves teeth at optimal rates, hopefully reducing patient's discomfort and the risk of resorption. But I don’t risk using forces so light that treatment takes forever. This ongoing question of optimal tooth moving forces is what drew to read an article of Bangkok published in the October 2010 issue of European Journal of Orthodontics.

[수정원고]

The article is titled interleukin-1β levels, pain intensity, and tooth movement using two different magnitudes of continuous orthodontic force. One appealing thing to me about this study is that it was done in humans, tough to do but much more applicable. The sixteen subjects were classⅠby maxillary protrusion patients who were planned to have four premolars removed and canines retracted to correct their malocclusion. After premolars were extracted, posterior segmental appliances were placed in the maxilla with a TPA helping to create a relatively non-moving large posterior anchorage segment. The canines were than retracted along segmental wires with either a 50g or 150g force.

Each subject served his or her own control by having the 50g force on one side, and 150g force on the other. The levels of interleukin were sampled in the gingival crevicular fluid at the observation times and the patients rated the level of discomfort on a Visual Analogue Scale at those same times. The amount of tooth movement was measured from stone casts over the 2 month study period. Here the important results for you to know, there were increased levels of interleukin-1β measured in the 150g sides at 24 hours. And then again at 2 month. The level of pain reported by the patients was generally higher in the 150g sides, and this difference was significant at the 24 hour mark. Over the 2 months, the rate of tooth movement was no different when using 50g vs. 150g. Both groups moved between 1 and 1½ mm.

Like all clinical studies, this one had some weaknesses. It was a small study with only 16 subjects and they were mostly female. The observation time was relatively short with only 60 days of tooth movement. And it appears that mechanical force system used was a sliding retraction system that makes it hard to precisely control force levels. However, it appears at the findings with support the use of lower force levels for tooth movement since the same rate of movement was seen with less patient pain. Clinically this tells me when I'm debating in my own mind about force levels for tooth movement, I should err on the side of light forces rather than heavier forces. To see if you reached the same conclusion when examining all the data, take a look at this article in its entirety in the October 2010 issue of the European Journal of Orthodontics.

The Long-Term Effects of Water Fluoridation on the Human Skeleton

Chachra D, Limaback H, et al.
J Dent Res 2010;89:1219-1223
                                                                                

December 9, 2011
Dr. Sang-Mi Lee

[초벌원고]

Is your community water supply fluoridated? If so, or if not, you’ve probably participated in the debate over water fluoridation with either dentist, patients, or orthodontic colleagues over the years. There’s no doubt based upon available research that water fluoridation has notably reduced the incidence of dental caries. In fact, water fluoridation is considered a huge public health success. But the opponents of water fluoridation suggest that ingestion of fluoride in the water supply also means that fluoride is deposited in the bones of the body. Is this true? And if it is true, does increased fluoride in bone create a problem for an individual? That particular question was addressed in a study that was published in the November 2010 issue of the Journal of Dental Research. Since many of us participate in the fluoride debate from time to time, I thought this would be good information for us to review. The title of the study is “The Long Term Effects of Water Fluoridation on the Human Skeleton.” The study comes out of the University of Toronto and the senior author is Dr. Chachra from the Institute of Biomaterials at the University of Toronto.

[수정원고]

The purpose of this study was to compare the fluoride content in bone specimens from a fluoridated region and a non-fluoridated region. The author selected two major cities in Canada; Toronto has had its water fluoridation in effect for more than four decades. Montreal has never had fluoridated water. In order to compare the effect of decades of fluoridation with non-fluoridation, the authors gathered bone samples from adults subjects in their 60s who were having hip replacement. When the femoral heads were removed, there were analyzed and compared between those subjects who had lived in a fluoridated community and those that had lived in a non-fluoridated community. The authors evaluated compression test, fluoride content, the amount of mineralization, and micro-hardness of the bones in both groups to determine if there were any differences that could be attributed to fluoride in the skeleton.

Okay, what did these authors find? First of all, let’s look at fluoride content. Is there any difference? The answer to that question is yes. The fluoride content of bone from individuals residing in Toronto was significantly higher than those in Montreal. Was there any effect on the compressive strength on the bones in these groups? The answer to that question is no. The density of the cancellous cores of bones in this study did not correlate closely with either the fluoride content or the age of the patients. Question number three: Is there any difference in the amount of mineralization between those subjects that received fluoride in the water supply and those that did not. The answer to that question is no. There were no statistically significant differences observed in the degree of mineralization between the two regions. Now here is the caveat. The authors found that there were analyses of the samples at the tissue level rather than at the population level reveals high levels of variability in response to water fluoridation. Why is there variability? Because of the differences in genetic response and the disease background in each individual that could render a subject unusually susceptible to fluoride.

So what’s the bottom line? The authors conclude that any possible effect of municipal fluoride ingestion is too small in municipal water fluoridation to be a significant determinant of bone health within the general public. In other words, the effect of fluoride on a skeleton from the water supply is minimal or insignificant. If you like to review this study, you can find it in the November 2010 issue of the Journal of Dental Research

The Effect of Rotation Moment on the Stability of Immediately Loaded Orthodontic Miniscrews: A Pilot Study

Cho YM, Cha JY, Hwang CJ.
Eur J Orthod 2010;32:614-619
                                                                              

December 16, 2011
Dr. Min-Hee Oh

[초벌원고]

If you're planning to use miniscrew anchorage to intrude lower second molars, by placing a lever arm into the miniscrew slot, does the rotational moment that you applied to the screw risk the stability? If you think about it, the arm on the patient’s lower right would tend to rotate the miniscrew clockwise or tighten it, and a similar arm on the left would tend to rotate the miniscrew counter-clockwise or loosen it. To investigate whether this rotational loading moment may impact miniscrew failure, researchers in Korea conducted a study reported in the December 2010 European Journal of Orthodontics.

[수정원고]2.16

This study was done using beagle dogs and is called “The effective rotation moment on the stability of the immediately loaded orthodontic miniscrews: a pilot study”. Here is how the study was done: six dogs were used and six miniscrew implants were placed in each dog, three on the lower left and three on the lower right. In each quadrant, one miniscrew was an unloaded control. The other two miniscrews had 7 mm lever arms attached to the screwhead and the lever arms were connected to generate opposite moments of 1 or 2 Ncm. So half the experimental screws were loaded in a clockwise or tightening direction, and the other half in a counter-clockwise direction. The dogs were sacrificed after either 3 or 12 weeks and the screws examined histologically to measure the bone in contact area. The more bone in contact, the better the stability. In addition any screws that failed prior to the end of the experiment were recorded.

Here's what the researchers found. First, three of the 36 screws failed. And all three were the 2 Ncm screws loaded in the counter-clockwise direction. When the histology was examined, there was a trend for the counter-clockwise group to have lower bone in contact scores, and this difference was significant at 12 weeks.

The question we asked in the beginning is whether placing a rotational moment on a miniscrew might impact its stability. The evidence from this study would suggest that it does for counter-clockwise rotations. The clinical ramifications of this would be to design your mechanics to minimize counter-clockwise rotational moments. If you do need to load miniscrews with a counter-clockwise moment, keep it light. And if you need to produce a larger counter-clockwise moment, you should consider reinforcing the screw with a second screw tied together or resisting the rotational moment by tying the screwhead to a tooth.

As always with animal studies, keep in mind that this may might not translate directly to humans, but the concepts make sense. Find more details of this investigation in the December 2010 issue of the European Journal of orthodontics.

Randomized Clinical Trial of Treatment for TMJ Disc Displacement.

T. Haketa, K. Kino, M. Sugisaki, M. Takaoka, T. Ohta.
J Dent Res 89(11): 1259-1263, 2010
                                                                              

December 23, 2011
Dr. Nam-Soon Park

[초벌원고]

Has this ever happened to you? Suppose you are in the middle of orthodontic treatment on a 16 year old female. In between her orthodontic appointments, while she is eating a chewy bagel, she notices that her condyle on the right side all of a sudden pops. As result, she now has limited opening of the mandible on that side. When she comes in for her orthodontic appointment, she wonders what happened. You have her opening closed, but she still has limited opening on the one side. You suspect that she has an anterior displacement of the temporomandibular disc on the right side. Now what do you do? She is in some pain. She has limited opening. So what are your options? Actually there are three options.

[수정원고]

One would be to do nothing and hope that it gets better. Is there any evidence to suggest that could occur? Actually, a study published in the late 1990s showed that after two and a half year follow-up about 40% of patients with anterior disc displacement became asymptomatic. But this patient is concerned in appearance don’t like the option of doing nothing. So, there are two other options. One would be to place maxillary occlusal splint that is equally equilibrated on the mandibular teeth. A third option would be to provide an exercise regimen for the patient to stretch the mouth opening over a period of time to gradually increase it. Do either of these options work? Is one better than the other? Those issues were addressed in a study that was published in the November 2010 issue of the Journal of Dental research. I found this to be an excellent article. It’s a randomized clinical trial and it’s considered one of the highest levels of evidence based research. So I like to review it for you on this month’s issue of practical reviews in Orthodontics.

The title of this study is ‘Randomized Clinical Trial of Treatment for TMJ Disc Displacement’. This study is co-authored by Dr. Haketa and four other research colleagues from the department of dentistry at Tokyo medical & dental University in Japan. The purpose of this study was to evaluate the therapeutic efficacy between two treatment options for anterior disc displacement, either an occlusal splint or joint mobilization and self exercise. In order to accomplish this objective the authors began a randomized clinical trial in January 2006. From a consecutive series of over 800 new patients with TMD, the authors identified 50 who had anterior disc displacement. All were over eighteen years of age, they all had mouth opening pain on the TMJ affected side. And they all were over two weeks after the onset of disc displacement and had mouth opening at less than 40 millimeters.

Finally an MRI confirmed anterior disc displacement for all subjects. Then this patients were randomly allocated to one of two treatment groups. In one group, patients were given a maxillary occlusal splint that evenly contacted all mandibular teeth with canine guidance in lateral excursion. The patients were asked to wear the appliance for 24 hours a day for 8 weeks. In the second group, the subjects were asked to perform mouth stretching exercises four times a day. These exercises were conducted for about 3 minutes at each of this session and occured after meals and while bathing. Then the entire group was examined after four weeks and eight weeks to determine their level of pain, maximum mouth opening, and limitation of daily functions. Ok, I think you get the idea of this experiment. What did these authors find? Remember the question, “Which is better, an occlusal splint or mouth stretching exercises for anterior disc displacement?” The answer is both are effective. After 8 weeks, both groups of individuals had improvement in the amount of mouth opening, reduction of pain, and reduction of limitation in the daily functions. Second question, “Was one of the techniques better than the other?” And the answer of that question is “Yes, and it was statically significant.” The authors found that the mouth opening range increased more in the exercised group than in the splint group. As a result, the authors suggested that their study demonstrated that therapeutic exercise ranged earlier recovery of jaw function compared with splints. So there you have it.

Now back to your 16 year old female with anterioriorly displaced disc. What would you recommend? Actually either of the choices, splint therapy or exercise will work but the one that works the best is mouth exercise. If you are interested in reading the study, you can find it in the November 2010 issue of the Journal of Dental Research