Long-term Observation of Autotransplanted Teeth with Complete
Root Formation in Orthodontic Patients

Watanabe Y, Mohri T, et al.
Am J Orthod Dentofacial Orthop 2010;138:720-726
                                                                                   

March 2, 2012
Dr. Min-Hee Oh

[초벌원고]

In Scandinavia, autotransplantation of teeth have been done for well over 20 years. Studies in Scandinavia of the survival rate of autotransplanted teeth have ranged between 90 and 100% which are very impressive results. The autotransplanted teeth that were used in the studies in Scandinavia had incomplete root formation which is considered the ideal time to autotransplant teeth. The Japanese however, have generally performed autotransplantation after the complete of root formation. How does the success of autotransplantation of teeth with complete root formation compare with the autotransplantation of teeth with incomplete root formation as is done in Scandinavia? A study titled, "Long-term Observation of Autotransplanted Teeth with Complete Root Formation in Orthodontic Patients" by Yohei Watanabe et al. which appeared in the December 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics address this question.

[수정원고]

In this study, the authors who are from Japan, evaluated the long-term success of 38 teeth that were autotransplanted in 32 patients who were examined more than 6 years after transplantation with the mean observation time of 9.2 years. For these teeth, the authors recorded both the survival rate and the success rate. The survival rate was calculated as the percentage of transplanted teeth that were still present at the long-term examination relative to the total number of transplanted teeth. The success rate was represented as the percentage of transplanted teeth that showed no abnormal findings, such as progressive root resorption or periodontal problems. When the authors evaluated the long-term results in these two areas, what do you think they found?

The bottom line is that at a mean observation time of 9.2 years, the survival rate was 86.8% and the success rate was 63.1%, both of which were lower than the success rate reported in the Scandinavian studies which evaluated autotransplanted teeth with incomplete root resorption. When the authors further evaluated the autotransplanted teeth, they noted that the plaque in gingival indices tended to be higher for these teeth and they tended to show slightly increased pocket depths compared with the controlled teeth. Of the 38 teeth that had been autotransplanted, they also noted that 21 required full restoration that is crowns or bridges and 12 teeth required partial restoration which consisted of composite fillings or inlays. Root canal treatment and temporary root filling with calcium hydroxide of the transplanted teeth was done within 3 weeks after transplantation and the authors noted that the quality of root filling significantly affected the success of autotransplantation of teeth with complete root formation. They also noted that the survival rates of bridges have been reported to be 80% at 10 years and 70% at 20 years and that the survival rates of implants were 96% at 5 years and 90% at 10 years. They concluded that from the point of view of maintaining compatibility between adjacent teeth and maintaining or restoring alveolar bone volume of the missing tooth, transplantation appeared to be more desirable than implants.

The bottom line of this study however is that if you plan to use autotransplantation for one of your patients, it should be performed before the completion of root formation if possible. You can find this study in the December 2010 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Prevalence of White Spot Lesions During Orthodontic Treatment With Fixed Appliances

Tufekci E, Dixon JS, et al.
Angle Orthod 2011;81:206-210
                                                                                   

March 9, 2012
Dr. Hyun-Jeong Lee

[초벌원고]

Suppose you’re having a patient conference in your office. You are consulting with a 13-year-old adolescent male, and his mother is present at the consultation. Now this is a new patient to your practice but not a new family to orthodontics. This family recently moved from a different state, and this boy’s older brother had orthodontic treatment. Therein lies the problem. At the consultation the mother asks you an interesting question. She wants to know if this son will have spots on his teeth like his older brother after the braces come off. What she’s talking about is white spot lesions. Apparently, her brother had several on these on his upper anterior teeth and the parents were extremely dissatisfied. How you would answer her question? What’s the percentage of white spot lesions that occur in the general population? Let me give you some information in this next review that will help you if you ever have to answer that question. This study comes out of Virginia Commonwealth University, and is published in the March 2011 of the Angle Orthodontist. The title of this article is “Prevalence of white spot lesions during orthodontic treatment with fixed appliances”.

[수정원고]

This study is coauthored by Dr. Tufekci and 3 other researchers from that same institution. The purpose of this study was to determine the prevalence of white spot lesions using visual examination in orthodontic patients before treatment began and then at 6 and 12 months into orthodontic treatment. In order to accomplish this, the authors established 3 groups of patients. The first group was a group of orthodontic patients with had had orthodontic appliances in place for about 6 months. There were about 35 patients in that group with equal representation of males and females. The second group, had had orthodontic appliances in place for 12 months and also consisted of about the same number of patients equally divided between the genders. The third group consisted of about 30 subjects who had never had any orthodontic treatment. The author dried the surfaces of the maxillary teeth and evaluated the teeth to determine if any white spot lesions were present on the labial surfaces of the maxillary teeth from second premolar to second premolar. This was done for the control group, the 6-month group, and finally those that had had appliances in place for 12 months. Then the author compared these to see of there were any differences in the prevalence of white spot lesions among these individuals. What do they find? Do individuals with orthodontic appliances actually have detectable greater prevalence of white spot lesions? And second question, does this prevalence increase with time? Let’s take question No.1. The answer of that question is ‘yes’. There is a greater prevalence of white spot lesions in individuals who have appliances in place for 6 months. The percentage of the total was about 38%. But what about the control group? Only about 10% of the control group had at least one white spot lesion. What happens with increased time? Does the number of white spot lesions increase? And the answer to that question is ‘also, yes’. Although it was not statistically significantly different about 45% of the individuals who had orthodontic appliances in place for 12 months showed white spot lesions. Next question, was there are difference between males and females. And, as you might have guessed, the answer to that question is ‘yes, definitely’. In fact, overall, 76% of the subjects in the study who had at least one visible white spot were males. And only 25% were females. So there are the answers to your questions. There’s a higher prevalence of white spot lesions in individuals who are wearing orthodontic appliances. And it was greater for males.

So now back to your patients who’s in your office and you’re doing a consultation. How would you answer the mother’s question? Yes, this son is at risk for having white spot lesions. So at least you know ahead of time that you must take precautions and warn the parents about that possibility happening to this son. Now the use of sealants, other oral hygiene measures, fluoride rinses and frequent checks by the general dentist will possibly help to reduce this prevalence. If you’re interested in reading this study about the prevalence of white spot lesions of orthodontic patients, you’ll find it in the March 2011 issue of the Angle orthodontist.

A Comparison of Hand-tracing and Cephalometric Analysis Computer Programs With and Without Advanced Features
- Accuracy and Time Demands. 

Tsorovas G, Karsten AL.
Eur J Orthod 2010;32:721-728
                                                                                   

March 16, 2012
Dr. Sun-young Lim

[초벌원고]

There have been many studies published that indicate using computer generated cephalometric analysis generally give you the same information as a traditional manual tracing and measurement. But does it really save time? And what about all those fancy advanced features available when digitizing on the computer like zoom, brightness and contrast, sharpening. Do they improve the reliability of the analysis? These questions and several others are answered by study done in Sweden published in the December 2010 issue of European Journal of Orthodontics.

The study is called ‘A comparison of hand-tracing and cephalometric analysis computer programs with and without advanced features-accuracy and time demands’.

[수정원고]

The Author started by soliciting many different software venders to allow testing of their products under controlled conditions. Five companies from Europe and Japan donated software for testing. The names are available in the article.

Then thirty random the identified digital lateral cephalograms were selected from subjects that had undergone orthodontic treatment. And these images were also printed on film so that a traditional film image was available.

A single investigator then traced and measured all thirty films on a conventional way using tracing acetate and a protractor. The measurements from the hand tracing acted as the controls or the gold standard. These same thirty images were then analyzed using the five different software programs. Once using the basic feature set and a second time using advanced feature set such as zoom, brightness and contrast adjustment, and sharpness control. The computer analysis were repeated at second time. At least a month later to check reproducibility the time required to make all the measurements was recorded.

A comparison was made between the gold standard and tracing measurements and the measurements from the computer programs. Of the 23 common cephalometric measurements studied, 20 showed good agreement with the manual tracing measurements with either the basic or advanced feature set. The lower incisor to NB (Ii to NB) measurements showed better agreement when using the advanced features. Two measurements the Wits analysis and lower incisor to A/Pog (Ii to A/Pog) showed poor agreement with either basic or advanced features. There was little difference between any of the software products.

From a time stand point, it took about 2.5 minutes to complete a computer analysis using the basic features, about 5 minutes if advanced features were used and about 15 minutes to do a manual tracing and measurement.

I think the important take home messages from this study were: (1) computer cephalometric analysis generally gives the same results as manual tracing in much less time, (2) The advanced features like zoom, brightness and contrast adjustment, and sharpening add to the time required but generally don’t add to the reliability, and (3) be careful of the Wits analysis done on a computer, as it is difficult to locate functional occlusal plane properly. There are huge number of details that appear on the paper that I didn't have time to review with you. You can find these along with the entire text in the December 2010 European Journal of Orthodontics.

Efficacy of a Fluoride Varnish in Preventing White-Spot Lesions
as Measured with Laser Fluorescence

Demito CF, Rodrigues GV, Ramos AL, Bowman SJ.
J Clin Ortho 2011;45(1):25-29
                                                                                   

March 23, 2012
Dr. Mi-soon Lee

[초벌원고]

Orthodontic patients that struggle with brushing also generally don’t comply well with protective fluoride rinses to help protect calcification. Fluoride varnishes have demonstrated some potential for delivering the protection of fluoride without the same level of the cooperation. How effective are these varnishes if applied in your orthodontic office every 12 weeks? To study this question, a group of researcher from Brazil recruited a group of 15 adolescent patients willing to participate in the clinical trial. The results of this trial are published in January 2011 Journal of Clinical Orthodontics.

[수정원고]

And I wanna share the findings with you. This trial was designed as split mouth study which means that the fluoride varnish was applied to the upper arch on one side, and the lower arch on the opposite side. The contralateral quadrants served as controls. Fluoride varnish was applied to the study quadrants, one week after the start of treatment then every 12 weeks. The degree of demineralization of the enamel was measured at 4 locations of the each tooth with laser fluorescence tool designed for early caries detection. This tool allows the user to get a numeric readout of enamel fluorescence which directly corresponds to the degree of mineralization. This measurement was done at the beginning and then repeated 3, 6 months into orthodontic treatment.

The results show no difference in demineralization between groups of teeth at the beginning of treatment. This would be expected. At 3 months, there was a trend towards less demineralization of in the fluoride varnish group but not enough to be statistically different. At sixth month, there was about one third of less demineralization in the fluoride varnish group. But when analyzed with all the tooth sites together, this was not significant. But when the area gingival to the bracket was examined specifically, there was a significant reduction of demineralization on those teeth receiving varnish.

I wonder about the wisdom of using a split mouth design with fluoride varnish application. Because although it obviously has local effect, it may also increase salivary fluoride content, and therefore affect the control teeth as well. It’s a great design to control for differences in hygiene, but it may have been possible to demonstrate even greater advantages of varnish with alternate design.

But take all messages. It’s that fluoride varnish appears to have a protective benefit to the tooth enamel gingival to the bracket when applied in the office every 12 weeks. This would seem to be relatively cost effective way of reducing decalcification in orthodontic patients. Yet surveys indicate very modest hues among orthodontists. Perhaps you might consider trying in your office at least in those patients most susceptible. For more information on the study of fluoride application, see the article titled ‘Efficacy of a fluoride varnish preventing white spot lesions as measured with laser fluorescence’ that appears in the January 2011 issue of JCO.

Effect of Chitosan Containing Dentifrice on Demineralization Around Brackets

Uysal T, Akkurt DM, et al.
Angle Orthod 2011;81(3):319-325
                                                                                   

March 30, 2012
Dr. Nabha Wael

[초벌원고]

How do you reduce or prevent demineralization around orthodontic brackets in your patients. This is always a challenge to orthodontist who treat adolescents. Some patients have great oral hygiene, but others were not so good. Although many different types of oral hygiene aids have been recommended, are there any new items on the market that could show promise? In recent years researches have been experimenting with the chemical called chitosan. This is derived from chitin which is a glucosamine and is mainly contained in the shells of craps and shrimp. After the chitosan is produced from the chitin, it has a PH of 6.3 which is suitable to buffer the oral environment which could then prevent the deleterious action of organic acids on enamel surfaces. In addition the chitosan is bio-combatable and biodegradable. In past studies the chitosan has been shown to exhibit bactericidal action against streptococcus mutants. What if chitosans were incorporated into a tooth paste? Would that toothpaste have greater tendency to reduce demineralization than conventional non-fluoridated tooth paste? That particular question was studied and published in the march 2011 issue of the Angle Orthodontist.

[수정원고]

The title of that article is: Does a chitosan containing dentifrice prevent demineralization around orthodontic brackets? This study comes out of Erciyes university in Kayseri Turkey. The senior author of this paper is doctor Uysal. He was joined in this project by several other investigators from that same Orthodontic Department. Now the purpose of their study was to determine if there are any differences between a chitosan containing dentifrice compared to a conventional non-fluoridated toothpaste in inhibiting enamel demineralization around orthodontic brackets. In order to accomplish this project, the authors performed a study in 16 orthodontic patients were going to have four first premolars extracted for orthodontic purposes, two months prior to extraction the authors examined the surfaces of the premolars to make certain there were no areas of demineralization on the labial surface. Then orthodontic brackets were bonded to all four premolars. They were bonded with conventional technique using light cured composite. Then one group of individuals received a dentifrice containing chitosan, the other group received a tooth paste that was non-fluoridated. The patients were asked to use this dentifrice daily. Sixty days later the premolars were extracted and after extraction the teeth were sectioned so that the crown and roots were separated. Then the crown of each premolar was hemisected into mesial and distal half. The authors then used a special technique that tested the micro-hardness of the enamel to determine if there were any differences which would reflect a deference in the amount of enamel demineralization between the chitosan group and the non-fluoridated toothpaste.

What do you think they found? Does a chitosan containing dentifrice reduce the demineralization around orthodontic brackets? The answer to that question is yes. The authors showed with the micro hardness test that the use of chitosan containing dentifrice during the sixty days prior to extraction was able to prevent demineralization of enamel around those teeth that had the orthodontic brackets. There was a statistically significant difference between this group and the group that used the conventional non-fluoridated toothpaste. So there you have it: Chitosan containing tooth paste can be a benefit to patients who are wearing orthodontic brackets.

Now the only problem is that the patient first must place the dentifrice on the toothbrush and second must use it daily to clean their teeth. As with many of these improved oral hygiene aids that have been manufactured in recent years much of the effect depends upon the patient actually using then. If you are interested in reading this article that highlights the benefits of a chitosan containing dentifrice, you will find it in the march 2011 issue of the Angle Orthodontist.

Maxillary canine retraction with self-ligating and conventional brackets

Mezomo M, de Lima ES, et al.
Angle Orthod 2011;81:292-29
                                                                                   

April 6, 2012
Dr. Park Won Young

[초벌원고]

Do you use self ligating brackets? Although ten years ago, the answer to that question would most likely be “no”. Many orthodontists today use self ligating brackets. One of the reasons that’s given by those who choose self ligating brackets says that there’s less friction between the arch wire and the bracket with the self ligiating appliance. So if you are treating a patient who you had extracted maxillary first premolars and were retracting maxillary canines along the arch wire, could you retract the canines faster with self ligating brackets, or conventional brackets? It would make sense, that if there’s less friction that the self ligating brackets would be able to produce more rapid movement then conventional brackets with ligature ties.

[수정원고]

But is that really true? In order to answer that question, one would actually have to perform a clinical trial. That’s been accomplished. An article published in the March 2011 issue of the Angle Orthodontist tests that question. The title of the article is, “Maxillary canine retraction with self ligating unconventional brackets”. This study comes out of the department of orthodontics at Central University Franciscano in Santa Maria, Brazil. The senior author of this article is Mauricio Mesomo.

The purpose of this study was to measure space closure during the retraction of maxillary canines comparing self ligating appliances with conventional brackets. In order to accomplish this project, the author identified 15 patients who required premolar extraction and canine retraction. The patients were randomly allocated to one or the other side, since this was a split mouth design. Each patient then acted as its own control. On one side, self ligating brackets were placed and on the other side, conventional brackets were used. Elastic chains were used to retract just the canine distally over a period of time. Dental casts were used to determine the amount of canine movement as well as the amount of molar movement mesially during the process. The dental cast was taken and measured initally, then at 4 weeks, 8 weeks, and 12 weeks. In addition the authors measured the amount of rotation of the canines between self ligating and conventional bracket groups.

Okay, I think you get the idea of the experiment, what happened? Do canines with self ligating brackets move faster during retraction? And the answer to that question is, no. The authors found no statistical difference in the rate of canine retraction when compared conventional or self ligating brackets in the same patient. The only difference that they found was that there was less rotation of the canine using self ligating bracket compared to the conventional bracket.

So there you have it. Although some may claim that there’s faster tooth movement with sliding mechanics using a self ligating bracket. This study would contradict those claims. And the patients have clinically shown that there’s no significant difference. If you like to review the study comparing self ligating and conventional brackets during canine retraction, you can find it in the March 2011 issue of the Angle Orthodontist.

Comparison of Two Cone Beam Computed Tomographic Systems Versus Panoramic Imaging for Localization of Impacted Maxillary Canines and Detection of Root Resorption

Alqerban A, Jacobs R, et al.
Eur J Orthod 2011;33:93-102
                                                                            

April 13, 2012
Dr. Sang-Mi Lee

[초벌원고]

Consider the situation where you strongly suspect an impacted maxillary canine in a thirteen year old patient referred to you for treatment. Should you take a conventional panoramic image? Or should a cone-beam CT image be taken? I am going to review a study with you that suggests that the cone-beam image will provide you with improved localization and better assessment of any associated incisor root resorption. The study was published in the February 2011 issue of the European Journal of Orthodontics and the article is titled “Comparison of two cone beam computed tomographic systems versus panoramic imaging for localization of impacted maxillary canines and detection of root resorption.”

[수정원고]

The images included in this investigation were from 60 consecutive patients presenting for orthodontic treatment in which a screening panoramic film identified at least one impacted maxillary canine. These patients were then referred to an imaging center for a CBCT image; 30 at a scan with a Accuitomo machine and 30 were scanned with Scanora. I am going to limit my review largely to the differences between the panoramic and CBCT images rather than any comparison of the two CBCT machines. Each patient therefore had a panoramic image and a CBCT image taken within two weeks of one another. These 120 images were reviewed by a group of experienced clinicians and a group of orthodontic residents. Various measurements and assessments were completed by each observer including canine localization and assessment of root resorption.

The result showed some important differences between 2D and 3D imaging. The width of the canine and the angulation of the canine compared to the occlusal plane were both statistically different between 2D and 3D imaging, so these measurements made from panoramic images must be considered accordingly. Root resorption of adjacent incisors was more frequently detected and was found to be more severe when using CBCT imaging. One of the more surprising findings was that buccal canine impactions were diagnosed with almost twice as often using CBCT imaging compared to 2D imaging. This could cause significant orthodontic complications if the buccal-lingual localization is not clear. I am not suggesting that this study alone supports CBCT imaging for all impacted canines but it clearly suggests that localization and root resorption are better assessed in 3D. I’ve personally seen two cases in the last six months where the canine was palatal to the central incisor but buccal to the lateral incisor root when assessed by CBCT, a difficult diagnosis to make with 2D imaging.

If you want more details regarding the comparison of the two CBCT machines used in this study or would like to read the relatively extensive literature review included in this paper, you can find the full text published in the February 2011 issue of the European Journal of Orthodontics.

Altered Sensation after Orthognatic Surgery

Kim Y-K, Kim S-G, Kim J-H
J Oral Maxillofac Surg 2011；69:893-898
                                                                             

April 20, 2012
Dr. Sun Li Jun

[초벌원고]

Suppose you are doing a consultation with a 35-year-old adult female. This woman has a ClassⅡ division 1 malocclusion with no crowding in either dental arch. She has a retrognathic mandible. Now her treatment will involve a combination of orthodontics and mandibular advancement surgery. The surgeon is also recommending a genioplasty in addition to the mandibular advancement. Here is the patient’s concern. A friend of hers had a jaw surgery and had altered sensation of the lip and chin after the surgery. Your patient is concerned about the potential for altered sensation in her situation. Her question is whether or not the altered sensation will be worse if she has the genioplasty performed along with the mandibular advancement. So how would you answer that question?

[수정원고]

A study published in the March 2011 issue of the Journal Oral Maxillofacial Surgery will help you with the answer to that question. The title of this article is “Altered Sensation after Orthognathic Surgery.” This study comes out of Soul National University in Korea, and the lead author of this paper is Dr. Young Kim. The purpose of the study was to perform a subjective evaluation of altered sensation that occurs following and upto 6 months after different types of orthognathic surgical procedures.

The overall sample consisted of 50 subjects. All subjects had a sagittal osteotomy performed. In some either a genioplasty or maxillary Lefort surgery were also performed. Following the surgery, the authors asked the subjects to comment subjectively on altered sensation in the area of the chin, lip, cheek, teeth and tongue. These subjective evaluations were made 1 month after surgery and then at 3 and 6 months following the surgery.

What the authors wanted to determine was first of all whether altered sensation was greater with a genioplasty compared to a simple sagittal osteotomy, and whether or not any altered sensation improved or got worse with time. What did they find? First of all, the patients who underwent orthognathic surgery experienced a diverse set of altered sensations immediately after the surgery.

Which area was the most prone to altered sensation? That was easy. It was always the chin. What were the next most common areas of altered sensation? After the chin, in descending order it was the lip, cheek and finally the teeth. What was the most frequent discomfort mentioned by the patient? Consistently lip biting was the most frequent consequence of altered sensation.

How did altered sensation affect these patients in their day to day activities? The two most common remarks of the patients were : 1) difficulty in chewing, and 2) difficulty in speaking immediately after the surgery. Did these altered sensations improve? The answer to that question is ‘Yes’. In all cases, the altered sensation was reduced with time. Now here is the last question: Did the addition of genioplasty create any difference in the altered sensation in these patients? The answer to that question is definitely ‘Yes’. The extent of altered sensation was always greater in patients who underwent a genioplasty. So let’s get back to your patient. Now you have an answer for her question. If there’s ever a choice between the sagittal split osteotomy only, and that same surgery combined with a genioplasty, at least you can advice the patient that altered sensation will be more common if the genioplasty is added to the surgical procedure. But in most of these cases the altered sensation improves with time.

If you'd like to read this study that evaluates the currents of altered sensation after jaw surgery, you’ll find it in March 2011 issue of the Journal of Oral and Maxillofacial Surgery.

Are Temporomandibular Joint Disk Displacements without Reduction and Osteoarthrosis Important Determinants of Mandibular Backward Positioning and Clockwise Rotation?

Emshoff R, Moriggi A, et al.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:435-441
                                                                                   

April 27, 2012
Dr. Kamran Davami

[초벌원고]

I recently saw a young lady that had been out of orthodontic treatment for a year or two and she was concerned because her anterior teeth could no longer incise properly. She had developed a slight anterior openbite. Although she didn't have significant pain, she did have a lateral deviation of the mandible when opening suggesting a possible disk displacement. This patient made me think about the relationship between disk displacement, joint osteoarthrosis and the down and back rotation of the mandible. Shortly after seeing her I read an article published in the April 2011 issue of the Triple O that addresses this topic and I would like to share those findings with you. The article is called “Are Temporomandibular Joint Disk Displacements without reduction and Osteoarthrosis important determinants of mandibular backward positioning and clockwise rotation?”

[수정원고]

The fifty subjects in this study were a part of investigation at Innsbrook Medical University originally designed to look at nonsurgical management of TMD pain.

They were consecutive subjects that presented with pain and who were 18 to 50 year old Caucasion and had first molars present. As a part of study all fifty had open and close mouth MRI's of the TM joints and had a lateral cephalogram in the centric occlusion position. A radiologist unaware of clinical findings made a diagnosis of disk position and joint osteoarthrosis. The cephalometric tracings were done independently by a different investigator. The MRI findings and the cephalometric measurements were then compared to look for a significant relationship between disk displacement without reduction and/or osteoarthrosis and certain cephalometric characteristics of backward mandibular rotation or mandibular posture positioning.

What the investigators found is that a diagnosis of disk displacement without reduction or osteoarthrosis alone, did not increase the risk of seeing an associated backward mandibular rotation or postural positioning. But two together was associated with 7-10 times increased risk of backward mandibular rotation and/or postural positioning. So it appears that someone with disk displacement and some evidence of bony degeneration is more likely to have skeletal changes thatt could result in an openbite. But the study did not realy look at disease progression that is to see if the cephalometric characteristics got worse as the joint disease appeared. It would be interesting to see if the additional. follow up of these patient would improve our understanding. Also these were patients who would present to TMD clinic with joint pain. How do they compare to the patient of mine who I described to you that was more concerned about her slight openbite. So we are still searching for a better understanding of a cause and effect relationship if any between joint degeneration and skeletal relationship. But the study is one step in right direction.

For more information about the association of MRI joint findings and cephalometric charastaristics of down and back mandibular rotation this entire article can be found in the April 2011 issue of Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology.

Effect of Maxillary Incisor Labiolingual Inclination and Anteroposterior Position on Smiling Profile Esthetics.

Cao L, Zhang K, et al.
Angle Orthod 2011;81:123-129
                                                                                    

May 11, 2012
Dr. Hou Yanan

[초벌원고]

Does the inclination of the maxillary incisors have any impact on smile attractiveness? Now let me clarify that question, I am not referring to viewing a smile from the front. I think it’s difficult to ascertain minor differences in maxillary incisor proclination when viewing an individual from the front. What am I talking about is when you view a person smile in profile, since we often view people from the side when they speaking or smiling, it would be interesting to know whether or not proclined, upright or retroclined incisors are regarded as more or less attractive. This question was addressed in a study that was published in the January 2011 issue of the Angle Orthodontics. I thought this would be an interesting study for us to review. The title of the article is “Effect of maxillary incisor labiolingual inclination and anteroposterior position on smiling profile esthetics”. This article was co-authored by Doctor Cao and several other research colleagues from the Department of Orthodontics at Sichuan University in China.

[수정원고]

The purpose of this study was to evaluate the effect of maxillary incisor labiolingual inclination on smile profile esthetics in young adult females. In order to accomplish this study, the authors chose one lateral smiling photograph of a Chinese female with a normal profile, a Class I occlusion, and a Class I skeletal pattern. This photograph was digitized and then the tooth inclination of the maxillary incisors was altered. The incisors were retroclined in 5-degree increments or proclined in 5-degree increments to alter the smile esthetics, then these altered images were shown to a group of orthodontics as well as a group of young undergraduate university students who had no dental training.

They were asked to score the attractiveness of the smile using a visual analogue scale; this methodology is typical of many experiments that have used a computer to alter smiling images. What did these researchers find? Question No. 1: Was there any difference between the assessments of orthodontists and the undergraduate university students? The answer that question is “no”. The assessments were similar. Question No. 2: Were proclined maxillary incisors regarded as attractive? The answer to that question is also “no”. The more proclined the incisors the greater was the negative impact on smile esthetics. Question No. 3: Were the retruded maxillary incisors regarded as attractive? The answer to that question again is “no”. The two groups of panelists were similar in their assessment. Last question: What degree of inclination of maxillary incisors was regarded as most attractive? The answer to that question is upright; the authors showed in their study that upright or very very slightly retroclined incisors were regarded as the most attractive inclination when viewed in lateral prospective. So there you have it: proclined maxillary incisors simply do not look attractive in lateral profile view and neither do significantly retroclined incisors. It's best to lead the teeth in the upright position.

If you like to review this study you can find it in the January 2011 issue of the Angle Orthodontics.

A Retrospective Randomized Double-Blind Comparison Study of the Effectiveness of Hawley vs Vacuum-Formed Retainers

Barlin S, Smith R, et al.
Angle orthod 2011;81:404-409
                                                                                  

June 1, 2012
Dr. Nam-Soon Park

[초벌원고]

What type of retainer do you typically use for your orthodontic patients? Whereas conventional Hawley retainers were a standard form for many years, recently vacuum-formed retainers had become more popular. There are several reasons. First of all, it’s believed that patients would wear the vacuum-formed retainers more consistently because they’re less obvious. In addition, laboratory fees for these types of retainers is typically less expensive compared to Hawley retainer. But is one retainer better than the other in maintaining the orthodontic correction?

[수정원고]

A recent study published in May 2011 issue of the Angle Orthodontist has made that assessment. The title of the article is ‘A retrospective randomized double-blind comparison study of the effectiveness of Hawley vs vacuum-formed retainers’. This study is co-authored by Steven Barlin and several other research colleagues from several different orthodontic departments throughout the United Kingdom. The purpose of this study was to compare the effectiveness of vacuum-formed and Hawley retainers in maintaining arch width as well as incisor alignment.

This was prospective randomized clinical trial. Sample of eighty-two patients who had received complete orthodontic treatment was randomly assigned to either Hawley or vacuum-formed retainer on the day of appliance removal. They were asked to wear this retainers full time for a year. At the time of appliance removal, dental casts were made of each patient. Then, similar dental casts were made at 2 months, 6 months, and finally one year after appliance removal. The authors’ then evaluated maxillary and mandibular inter-molar width, inter-canine width, arch length, and mandibular incisal alignments over this time intervals. What do you think the author has found? Which of these retainers provides the best retention for those aforementioned variables?

The authors found that there was no differences between either of the two retainer designs. Here is my concern. The authors didn’t evaluate occlusion. It’s been my experience that of patients wearing both the maxillary and the mandibular vacuumed-formed retainers that there is a little opportunity the teeth come into contact. And therefore, little opportunity for orthodontic saddling after treatment. Hawley retainers, on the other hand, that do not cover the occlusal surface give this opportunity for saddling. So, in terms of what was measured alignment, arch length, and arch dimensions, there are no differences between these retainers. Perhaps, these authors will evaluate other parameters in future studies. In the mean time, if you like to review this comparison of Hawley and vacuum-formed retainers, you can find it in the May 2011 issue of the Angle Orthodontist.

Comparison of Actual Surgical Outcomes and Thress-Dimensional Surgical Simulations

Scott Tucker, Lucia Helena Soares Cevidanes, et al.
J Oral Maxillofac Surg 68:2412-2421, 2010
                                                                                  

June 8, 2012
Dr. Young-Min Hong

[초벌원고]

When planning double-jaw surgery for an adult patient, how do you determine how much of each jaw should be moved during the surgical procedure? In the past, the ability to predict how much skeletal movement should be performed was typically accomplished using a combination of cephalometric radiographs with predicted tracing and mounted dental casts. But with advent of cone-beam imaging, it's possible to capture the skeletal image and the dental image and perhaps plan the surgery virtually using the three-dimensional radiographic image without the mounted dental casts. But would this be accurate? That question was addressed in the study that was published in the Oct. 2010 issue of the Journal of Oral and Maxillofacial Surgery.

[수정원고]

The purpose of the study was to determine whether virtual surgery performed on cone-beam segmentations could correctly simulate the actual surgical outcome and validate the ability of this technology to recreate orthognathic surgery, hard tissue movements in all 3 planes of space. In order to evaluate this concept, the authors retrospectively investigated cone-beam images of 20 patients. 14 of these individuals had a combination of maxillary advancement and mandibular setback surgery to correct a class III malocclusion. The other 6 patients simply had maxillary advancement to correct the malocclusion. These individuals had been operated on about 5-6 years previously. However, each of these patients had a cone-beam scan made just prior to surgery and at 6 weeks after surgery. So the authors were then able to take the scans prior to surgery, create, and segment the scan, alter the scans so that they simulated the surgery and then capture that image. In addition, because the surgical procedures had been performed on these individuals, the authors could compare the virtual scan and construction with the actual surgery that was accomplished.

They could compare these to determine the accuracy of virtual treatment planning using cone-beam imaging techniques. I think you get the idea of the experiment wasn't accurate. When the authors compared the virtual scan with the actual surgical correction, they found that for all anatomic regions of interest, there were no statistically significant differences between the simulated and the actual surgical models. The only area where there were some slight difference was the right lateral ramus, which was a relatively small difference when comparing two-, and one-jaw surgeries.

So there you have it! If you routinely take cone-beam images of your surgical orthodontic patients, especially those that are going to have double-jaw surgery to correct the class III relationship, you may want to consider virtual projection of the potential surgery for your patient. This gives one the opportunity to simulate movements of the maxilla and mandible, so that the most ideal correction can be accomplished during the surgical procedure. If you would like more information on this possibility as well as the specific technique that was used by these authors, you can find it on the Oct. 2010 issue of the Journal of Oral and Maxillofacial Surgery.

Effects of fluorosis on the shear bond strength of orthodontic brackets bonded with a self-etching primer

Isci D, Saglam AMS, et al. Eur J Orthod 2011;33:161-166
                                                                                 

June 15, 2012
Dr. Tae-Woo Kim

[초벌원고]

It’s common these days to see orthodontic patients that have mild enamel fluorosis. This may be due to natural fluoride content in certain areas or due to fluoride exposure from supplements and beverages. Do you change your bonding procedure when constructing patients with mild fluorosis?

[수정원고]

What about if you typically use a self etching primer for bonding? To determine the impact of fluorosis on orthodontic bond strength using conventional acid etching and self-etching primers, researchers in turkey conducted an in-vitro test that was published in the April 2011 issue of European journal of Orthodontics. The article is called “Effects of fluorosis on the shear bond strength of orthodontic brackets bonded with a self-etching primer”. The study designed straight forward. The Arthurs obtained 40 premolars that displayed mild fluorosis that were extracted for orthodontic purposes in an area of turkey with endemic fluorosis. They had an additional 40 extracted premolars from a different area that had no evidence of fluorosis. 20 teeth from each group were bonded using a conventional acid etching technique and the remaining 20 from each group were bonded using a self-etching primer. All brackets were attached using Transbond XD as the composite adehesive, after bonding the samples were stored 24 hours thermo-cycled and then tested for shear bond strength. The result showed no difference in shear bond strength between the fluorosed teeth and the non-fluorosed teeth when conventional phosphoric etching was used. The non-fluorosed teeth bonded with self-etching primer also demonstrated bond strength equivalent to the conventional etching groups. But, the fluorosed teeth bonded with self-etching primer showed a significant reduction in bond strength compared to the other groups. In addition, very little adhesive remained on enamel surface after failure with these teeth, which again indicates a less than optimal attachment to the enamel. Although the fluorosed teeth bonded with self etching primer had lower bond strength, it was still in the neighborhood of 9 mega-pascals, still clinically adequate according to most recommendations. But the Weibull survival analysis indicated a 10% chance of failure at 4.8 mega-pascals not an ideal clinical situation. Based on results of this study I would recommend that if you have a patient with mild enamel fluorosis, you consider bonding with a conventional phosphoric acid etching technique even if you normally use self-etching primer. To get a first-hand look at the evidence for this recommendation this article is found in the april 2011 issue of the European journal of Orthodontics

Efficiency of Serial Extraction and Late Premolar Extraction Cases Treated with Fixed Appliances

O'Shaughnessy KW, Karakul LD, et al.
Am J Orthod Dentofacial Orthop 2011;139:510-516

June 22, 2012
Dr. Min-Hee Oh

[초벌원고]

I believe most orthodontists incorporates serial extraction as one of the procedures that they use for early interceptive or phase 1 treatment. Effectiveness of serial extraction has been well documented. I assume that you also have treated patients in a fully developed dentition with four premolar extractions. How do patients who are treated in a mixed dentition with serial extraction compare with patients who have four first premolar extractions after the permanent dentition has erupted? Are the overall results of treatments any better with one method or the other? Is one method more efficient than the other? These questions were addressed in the study titled “Efficiency of Serial Extraction and Late Premolar Extraction Cases Treated with Fixed Appliances” by Kevin O’Shaughnessy et al which appeared in the April 2011 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.”

[수정원고]

In this retrospective study, the authors compared two groups of patients; one consisted of 51 patients who have undergone serial extraction and the other 49 patients were treated with premolar extractions in the full dentition. The PAR index was used to evaluate the severity of crowding initially and after completion of comprehensive orthodontic treatment in the two groups. Additionally, records were taken prior to extractions in the serial extraction group, prior to the initiation of fixed orthodontic treatment for both groups and after completion of fixed orthodontic treatment for both groups. Treatment record for each of the patients was reviewed and the estimated chair time for each orthodontic visit was documented based on the office computer scheduling system. When these data were statistically analyzed, what do you think they showed? Was one method or the other more efficient? And was there difference in the quality of final treatment after comprehensive orthodontics?

The data indicated that there was no difference in the quality of treatment when the two groups were compared after completion of comprehensive treatment which all of the serial extraction patients received after the completion of the serial extraction procedure. When treatment efficiency was evaluated, the serial extraction group had much longer total treatment time. However, the patients in this group had a shorter active treatment time of four months when compared with the late premolar extraction group. The serial extraction group also had more total visits but fewer visits while in active treatment. Based on these data, you can conclude that waiting for the development of the permanent dentition, to extract four first premolars was more efficient.

However, based on my experience, I don’t believe that this is so. First of all, I found the difference of only four months in active treatment to be a surprisingly small difference. I have treated some patients after serial extraction in six months to basically just parallel the canine and first premolar roots and I assume that you would agree with me that it would take much longer to do four first premolar extraction treatment in the permanent dentition. Also, while it makes sense to me that the serial extraction group had a greater overall treatment time with more total visits, I don’t think that visits during serial extraction are comparable with visits during active treatment. This is because the serial extraction treatment visits are usually very short observation visits to evaluate progress of the serial extraction procedure or prescribe extractions. I believe there is one additional consideration that is important and that is: to separate decisions that are in the best interest of the patients VS those that may lead to better office efficiency which often are not necessarily the same.

I thought this was an interesting article with a good sample and I am not sure I understand why there was such a small difference in the length of active treatment for the two groups which differs from previous studies and my own experience. You can find this article in the April 2011 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Anatomical Guidelines for Miniscrew Insertion: Vestibular Interradicular Sites

Ludwig B, Glasi B, et al.
J Clin Orthod 2011;45:165-173

June 29, 2012
Dr. Won-young Park

[초벌원고]

Due to biomechanical considerations, it’s often convenient to place miniscrews between adjacent teeth for anchorage. But which of these interradicular sites commonly have the combination of adequate bone width and the necessary attached gingival tissue to allow predictable success? To provide a guideline for miniscrew placement, Dr. Bjorn Ludwig and colleagues conducted a research project that combined 3d radiographic information and attached tissue measurements. These findings are published in the March 2011 issue of the “Journal of Clinical Orthodontics.”

[수정원고]

This project begins with assumption that the minimal bone width that is desired between tooth roots for predictable miniscrew stability would be at least 2.6 to 3.1 millimeters. This was calculated using a 1.6 mm screw, 0.5 mm of bone on each side, and 0.25 mm per side for the periodontal ligament. The authors then obtained the sample of 39 CBCT scans that included the desired interradicular regions and measured them very carefully using vertical image slices. The bone width between tooth roots was determined every half millimeter vertically for 15 millimeters as measured from the contact area. They had some additional data on the separate population of subjects that provided information on the mean distance from the interproximal contact points to the mucogingival junction. These two sets of data were combined to give a picture of those areas most likely to have both adequate bone and adequate attached tissue. Here’s what they found.

There are very few interradicular spaces that can be considered ideal. Many had either inadequate bone width or inadequate attached tissue. Those areas that were found to be the most ideal were between the 2nd premolars and 1st molars both upper and lower, between lower first and second molars and, with caution according to the authors, between the first and second premolars in either arch. You may know it that anterior areas did not fare well in this analysis. Obviously these ideal areas are only guides. Individual patient assessment is needed, using CBCT if already available, or other appropriate radiographs. It does mean, however, that if an anterior screw is needed, it’s likely that some root diversions will be required prior to placement to enhance screw stability. I do like the idea of using the interproximal contact point as a vertical reference, since it’s available to measure both on the radiographs, and on the patient clinically. The article provides many useful graphics that help to present their data in an easy-to-use way. And if place interdental miniscrews, you’ll want to keep some of these information handy. To find these graphics and additional data, look for the article called “Anatomical guidelines for miniscrew insertions vestibular, interradicular sites” in the March 2011 issue of the “journal of clinical orthodintics.”

Skeletal Stability After Mandibular Setback Surgery: Comparisons Among Unsintered Hydroxyapatite/Poly-L-Lactic Acid Plate, Poly-L-Lactic Acid Plate, and Titanium Plate

Ueki K, Okabe K, et al.
J Oral Maxillofac Surg 2011;69:1464-8
                                                                                 

August 31, 2012
Dr. Min-Hee Oh

[초벌원고]

How would you react to this question from one of your patients? You're planning combined orthodontics and orthognathic surgery for one of your patients. This is an adult with a significant class III malocclusion due to mandibular prognathism. The plan for surgery is a sagittal osteotomy and mandibular set-back. The patient has already agreed to the surgery. But here's the problem. The patient doesn't want to have any metal remaining in her jaws after the surgery. As a result, the surgeon suggests that perhaps, resorbable plates and screws could be used. This could either consist of poly-L-lactic acid plates or a combination of hydroxyapatite and poly-L-lactic acid plates. The patient wonders if there would be any difference in the potential for relapse or change using the resorbable plates compared to the typical titanium plates. So how would you answer that question? Is there any data or research upon this topic? Let me give you some data.

[수정원고]

A study published in the May 2011 issue of the Journal of Oral Maxillofacial Surgery evaluated this question. The title of the article is㰡’Skeletal stability after mandibular set-back surgery: comparison of resorbable plates and titanium plates.㰡“ This study has co-authored by Dr. Ueki and several other researchers from Kanazawa university in Japan. The purpose of this study was to determine the time-course changes in skeletal stability after sagittal split osteotomy using either hydroxyapatite in combination with poly-L-latic acid plates, a poly-L-lactic acid plate system alone, or conventional titanium plates for securing the proximal and distal fragments of the mandible after mandibular set-back surgery. The sample for this study consisted of 60 subjects. They were equally divided into 3 groups. All subjects had class III malocclusions with mandibular prognathism. All subjects had mandibular set-back surgery. But in 20 subjects, hydroxyapatite combined with poly-L-lactic acid plates were used to secure the bones. In a second group, poly-L-lactic acid plates alone were used for fixation. In the third group of 20 subjects, traditional titanium plates were used to secure the bony fragments. Lateral, frontal, and axial cephalograms were taken before the surgery and then at 1, 3, and 12 months after surgery to determine whether or not any changes had occurred in the bony fragments. Okay, what do you think these authors found? The results of this study showed that although there were some minor changes in the condylar axis following surgery, that there were no statistically significant changes in any of the cephalometric parameters when comparing the two by absorbable plates with the traditional titanium plates used for fixation.

So there you have it. If your patient is concerned about having rigid fixation with titanium plates that must remain in the mandible, there is other alternatives. Either poly-L-lactic acid plates, or the same plates combined with hydroxyapatite could be reasonable alternatives for fixation following mandibular set-back surgery. If you'd like to read this study, you'll find it in the May 2011 issue of the Journal of Oral Maxillofacial Surgery.

Changes in Intraoral Pressure and Molar Position Associated With Facial Asymmetry

Takada J, et al.
Eur J Orthod. 2011 Jun;33(3):243-9
                                                                                 

September 07, 2012
Dr. Won-young Park

[초벌원고]

I think that all orthodontists understand that soft tissue pressures can impact tooth position. Understanding what exactly constitutes or determines the equilibrium zone has been difficult however. Our body of knowledge in this area hasn't increased much in recent years, but in the June 2011 issue of the European Journal of Orthodontics, a paper which published by Takada and colleagues from Japan, that tries to provide us with more evidence. The paper is called,㰡’Association between intraoral pressure and molar position and inclination in subjects with facial asymmetry.㰡“

[수정원고]

Before I tell you about the results, let me describe how the study was done. First, the authors recruited 12 subjects that had facial asymmetry, meaning the lower midline was deviated at least 4mm to one side of the mid-sagittal plane. In addition, the subjects had the unilateral crossbite on the side to which the mandible was shifted, what the authors called,㰡’the shifted side.㰡“Data was collected from two sources. The first source was a PA cephalogram, that was used to determine the position and buccolingual inclination of the lower 1st molars. The second source was pressure readings from four sensors - the buccal and lingual surfaces of the same lower 1st molars. These pressure sensors were placed in the thin plastic carrier. The molar position and pressure readings were then compared between the shifted and non-shifted side.

Let's move on to the results. The molars on the shifted, or crossbite side, were more lingually inclined and further from the mid-sagittal plane. This makes sense what we commonly see. The pressure readings were interesting. The cheek pressure was much higher on the shifted side and the tongue pressure lower. The imbalance of pressures from side to side correlates with the tooth position change, that is, the higher cheek pressure on the shifted side is where the lower molar is tipped lingually.

The challenge with these equilibrium studies is that you can't really measure the intraoral pressure without placing something in the mouth that may alter the pressure. In this case, the authors tried to make the plastic carriers thin to minimize any alteration. The other problem is that the variation in pressures is so high, that it's very difficult to determine differences. But the fact that the pressure results correlated well to the tooth position data, suggests that the authors may be measuring some real pressure differences. Further miniaturization of the pressure sensors and better wireless monitoring may make it possible for us to do a better job with measuring pressures in the future and possibly lead to breakthroughs in our understanding. But for now, to learn about intraoral pressure measurement as it exists today, take a look at this article from Japan, in the June 2011 issue of the European Journal of Orthodontics.

An In-Office Wire-Bending Robot for Lingual Orthodontics

Gilbert A.
J Clin Orthod 2011;45:230-234
                                                                                 

September 14, 2012
Dr. Sun-Young, Lim

[초벌원고]

Contemporary pre-adjusted labial orthodontic bracket systems had been very successful because most patients can be treated with small adjustments from a so- called straight wire. This development has been possible in part because well aligned arch has labial surfaces aligned with only slight in-out variation that can be built into the brackets. This system doesn't work so well with lingual appliances because there are very large in-out differences on the lingual surfaces and therefore these differences can't be built into the brackets and first-order arch wire bends are needed. In order to bring lingual treatment to more useful level, an article in the April, 2011 JCO describes relatively simple, in-office robot that can bend the first-order lingual adjustments for the orthodontists.

[수정원고]

This system known as LAMDA (Lingual Archwire Manufacturing and Design Aid) allows quick digitalization of photographs and fabrication of custom lingual arch wires. Photographs can be taken of the study cast or an intra oral occlusal photo can be used, as long as calibration points are included. Once loaded into the LAMDA software, points are digitized on the photograph where bends should be created. The x and y coordinates of these points are converted by the software to distances and angles between bends. A small wire-bending robot that is only able to create first-order bends can take this information and fabricate a lingual arch wire in 5 minutes. The robot also includes a heater that can raise nickel titanium arch wires to 600℉ in order to permanently set bends. This heating process increases the time required to fabricate a nickel titanium arch wire to 6 minutes.

In order to test the capability of the LAMDA system, fifteen lingual orthodontic specialists were asked to manually bend an arch wire and then create an arch wire using the LAMDA system. A separate orthodontist rated the adaptation of all the arch wires on a 10-point scale. The result was that the arch wires were bent by experienced clinicians averaged 6.9 out of 10 for adaptation. The wires produced by the LAMDA system averaged 9 out of 10. Obviously we must be a little skeptical of these results since they come from the product developer, but it is some indication that the device may have potential. Technology continues to impact on orthodontics in a dramatic way. In this LAMDA software and a robot are just another addition. Further development and independent evaluation will be needed to determine it's true usefulness and obviously cost will be a factor. But I am interested in seeing where this leads.

If you would like to see color images of the robot and screen shot of the software controls it, I would suggest you find out the copy of this complete article, the title is ‘An In-Office Wire Bending Robot for Lingual Orthodontics’ and it's found in April, 2011 issue of the Journal of the clinical orthodontics.

Risk Factors for Anterior Disc Displacement with Reduction and Intermittent Locking in Adolescents

Stanimira I. K
J Orofac pain 2011;25:153-160
                                                                                 

September 21, 2012
Dr. Nam-Soon Park

[초벌원고]

Let me begin this next review by asking your question. Do any of your adolescent patients between the ages of 12 and 16 ever complained of intermittent locking or popping of their temporomandibular joints? As orthodontists I think all of us would have to answer yes to these questions. It's not common but some adolescents can't develop locking or popping of the TMJ during orthodontics. If that's the case, are there any risk factors that one can assist during pretreatment examination that would increase the likelihood of locking or popping of the joint. That question was answered in a study that was published in the May 2011 issue of the Journal of Orofacial Pain. I thought this would be an excellent study for us to review. The title of the article is “Risk Factors for Anterior Disc Displacement with Reduction and Intermittent Locking in Adolescents”.

[수정원고]

This study is co-authored by Dr. Kalaykova and two other researchers from the department of oral kinesiology at the University of Amsterdam in Holland. The purpose of this study was to determine if parafunction in the oral cavity or TMJ hypermobility are risk factors in adolescents for either anterior disc displacement or intermittent locking. In order to accomplish this objective the authors evaluated over 250 adolescents between the ages of 12 and 16 about half of female and half male. Now the presence of disc displacement and TMJ hypermobility was diagnosed during the clinical examination.

The authors also assessed whether or not joint locking had occurred, then they evaluated parafunctional habits such as tooth grinding or jaw clenching and also identified whether or not the patients performed nail biting or lip and cheek biting. In addition the authors examined the opposing dentition to see if they could find matching tooth wear facets. Using a logistic regression analysis the authors determine whether or not any of these parafunctional habits had a correlation with disc displacement or intermittent locking.

What are these researchers find? Question number one. Was there any association of disc displacement to any of the factors evaluated. The answer is yes. There was a weak association between disc displacement and increasing age. In other words, as adolescents became older, there was higher incidence of disc displacement. Question number two. Was there an association between intermittent locking of the joints and any of the factors assessed? The answer that question is yes. There was a weak correlation between intermittent locking and jaw clenching. Question number three. Was TMJ hypermobility related to either disc displacement or intermittent locking? The answer to that question is no. There was no relationship between hypermobility of the joint and either disc displacement or TMJ locking. So what's the bottom line? The authors concluded that during adolescence clenching is a possible risk factor for intermittent locking while increased age is a risk factor for disc displacement. If you'd like to review the study that assesses the risk factors for anterior disc displacement and locking in an adolescent subject population you'll find it in the May 2011 issue of the Journal of Orofacial Pain.

Comparative bond strength of new and reconditioned brackets and assessment of residual adhesive by light and electron microscopy

Wendl B, Muchitsch P, et al.
Eur J Orthod 2011;33:288-292
                                                                                

September 28, 2012
Dr. Lee Mi-soon

[초벌원고]

What is your routine procedure when rebonding a loose bracket? Do you use a new bracket? Or do you remove the adhesive and sandblast the original bracket, and rebond it? One of the considerations when making this decision is cost. Does the new bracket cost more than the additional staff time to sandblast the old bracket? This may be an individual practice decision. Another consideration is bond strength. Does a reconditioned bracket have the same bond strength as a new bracket? I am going to review an article with you from the June 2011 issue of the European Journal of Orthodontics that will provide bond strength comparisons for you.

[수정원고]

The article is called ‘comparative bond strength of new and reconditioned brackets and assessment of residual adhesive by light and electron microscopy'. This study was done in the laboratory on extracted human molar teeth. Molar brackets were bonded to teeth using a light-cured resin and a chemically cured resin. They were bonded to previously bonded surfaces as well as to intact enamel surfaces. In addition, the brackets were bonded new and reconditioned by in-office sandblasting as well as with two commercial reconditioning techniques. All brackets were bonded using a traditional etching technique. And all were tested to failure in a universal testing machine. The end result was comparison of light-cured and chemically cured resin, intact and previously bonded enamel, and among new sandblasted and reconditioned brackets.

The results showed bond strengths were the highest with the new brackets, 10.8 MPa, followed by laser-reconditioning, 10.3 MPa, solvent-reconditioning, 9.8 MPa, and in-office sandblasting 9.3 MPa. The average bond strength in each group remained above the published minimum recommended value of 5 to 8 MPa. On average, bond strengths with a chemically cured adhesive were approximately 1.5 MPa higher than with a light-cured resin. Additionally, rebonding to previously bonded enamel caused a decrease in bond strength of 1 to 2 MPa. So it appears that most combinations of rebonding will likely be adequate for clinical use. But there are some bond strength differences that may be up to 10 to 20%. Most of us don't use chemically cured adhesives for rebonding because of the clinical ease of light-cured adhesives. But this study would suggest that since you give up a little bond strength with light-cure, you may consider using a new bracket rather than the sandblasted one in a susceptible location.

If you would like more information about the comparative results when rebonding brackets so that you can make good business and patient-care decisions, I would suggest digging up it deeper into the results of this laboratory study. Again, it can be found in the June 2011 issue of the European Journal of Orthodontics.

A Simple Method for Twin Block Reactivation.

Doshi UH, Bhad Wa.
J Clin Orthod 2011;45:328-331
                                                                                 

October 5, 2012
Dr. Lee Sang-Mi

[초벌원고]

If I am gonna use a removable functional appliance for class 2 correction, my choice is usually a twin block. I find that patients generally adapt quickly to the appliance and that the two piece design makes it easier for them to talk with in it and therefore they wear it better. One frustration I have with the appliance is the difficulty in adding further incremental advancement if I find the initial advancement isn’t adequate. A recent article in JCO describes possible solution to the frustration by illustrating a method of modifying the twin block to allow easy adjustment.

[수정원고]

The article is aptly titled “A simple method for twin block reactivation". The key to this technique is two simple readily available jack screws like the ones used in variety of appliances. One end of each jack screw is covered with acrylic to form a 70 degree inclined plane. This surface will engage the incline plane of the lower part of the appliance. The other end of jack screw is then incorporated into the maxillary occlusal blocks in the position desired for the initial advancement. Once installed this screws will allow up to 7 mm of additional advancement that can be obtained just by turning the screw on each side.

The usefulness of this appliances demonstrated in the case report of a 13-year-old female with a class 2 division 1 malocclusion and 10 mm of overjet. Due to limited protrusive movement of mandible the initial bite advancement was only 3 mm. Each 8 weeks an additional 2 mm of activation was added until a class 1 molar relationship was achieved. Overall treatment time was 20 months. The twin-block appliance was worn for 9 month, our removable incline plane was worn for 2 month and full fixed appliances were used 9 month to finish the case.

The twin block appliance allowed for the gradual correction of the class 2 malocclusion with accurate measurement of the incremental advancement and no need for special screws, free monomer cements or additional laboratory work. Next time I have the need for the twin block appliance I’ll likely give this modification a try. I am a bit nervous that the screw may weaken the acrylic blocks and cause breakage. But the ability to easily prescribe additional advancement makes it worth to try. Because it may be difficult for you to visualize this modification just from my verbal description, it may be wise for you to view the photographs in the article to make it clear. A copy of the article would also be good to give to your lab tech as it gives specific part numbers of jack screws that are used. This will help ensure to get what you want the first time.

The source for this article, should you be interested, is the June 2011 issue of the Journal of Clinical Orthodontics.

Two-Versus Three-dimensional Imaging in Subjects With Unerupted Maxillary Canines

Botticelli S, Verna C, et al.
Eur J Orthod 2011;33:344-349
                                                                                  

October 19, 2012
Dr. Won-Young Park

[초벌원고]

Do you think your treatment decisions would differ if you had access to 3 dimensional imaging for assessment of ectopic maxillary canines compared to traditional 2 dimensional imaging? This is certainly an important question to ask if you are deciding whether to use 3D imaging. After all, there would be no good reason to add the cost of 3D imaging if it didn’t change the treatment decisions that were made. Researchers from Denmark published a paper in the August 2011 issue of the European Journal of Orthodontics that provides some data whether decisions change with the use of 3D imaging. Their paper is called ‘2 versus 3 dimensional imaging in subjects with unerupted maxillary canines', and I’d like to share a few of the highlights of this article with you.

[수정원고]

The researchers obtained a series of 27 patients with at least one unerupted maxillary canine that had both conventional 2D images consisting of a Ceph and Pan, and multiple periapical views, as well as a 3D CBCT scan. 8 Orthodontists or residents ranging from inexperienced to very experienced were recruited to participate in the diagnosis and treatment planning exercise. They never had access to both the 2D and 3D views at the same time but rather made independent judgements from the individual record sets. Each judge was asked to make assessments of the unerupted canine position, its angulation, and whether there was any associated root resorption. They were than asked to indicate their treatment choice and to judge the difficulty of the case. The result showed some distinct differences between the localization and the treatment recommendations when using 3D images compared to 2D imaging. The canine was judged to be displaced more vertically, and more palatally when using 2D imaging. The 3D imaging resulted in more perceived lateral incisor overlap and more associated root resorption. The judgement of case difficulty was greater when using 3D imaging. And more importantly, the 3D imaging changed the treatment recommendations in many instances. The 3D imaging resulted in fewer observational recommendations and more surgical exposure with traction and more recommendations for extraction of permanent canine.

So it’s becoming clear that 3D imaging provides additional information for diagnosis of impacted canines. And now we have results to suggest that this information changes treatment recommendations as well. In the future, we’ll hopefully have information about whether the treatment recommendations delivered using 3D imaging lead to better patient outcomes. You can find more information about this study that suggests 3D imaging leads to more active treatment recommendations for ectopic maxillary canines, by looking in the August 2011 issue of European Journal of Orthodontics.

Evidence-Based Considerations for Determining  Appointment Intervals

Jerrold L, Naghavi N. J Clin Orthod 2011;45:379-383
                                                                                 

October 26, 2012
Dr. Davami, Kamran

[초벌원고]

In spite of all the discussion in recent years of increase the appointment intervals I have to admit that I still see most of my patients every four to six weeks. I don’t do this because I need to reactivate the appliance necessarily but because I want to keep my patients on track in other ways with hygiene, elastics and to make sure there aren’t some unwanted side effects creating problems. It was because of this feeling that I was not keeping up with contemporary practices that I was drawn to an article in the July 2011 JCO. The article is called evidence-based considerations for determining the appointment intervals and although it isn’t really evidence-based in the contemporary sense it does try to bring some rationale to making decisions about appointment intervals by referring to the meager literature that is available on this subject .

[수정원고]

The major point made in the article is that one appointment interval is not appropriate for all patients that patients should be individualized based on at least nine factors. Let me tell you what those factors are and how the authors conclude the issue effects scheduling the intervals. Number one: Patient age, adult patients should be seen no longer than every four to six weeks based on slower cellular response and an increased risk for periodontal diseases. Number two: Type of arch wires, nickel titanium arch wires have a very long range of actions and can support longer intervals of six weeks to ten weeks. Number three: Periodontal status, patients with periodontal diseases or poor oral hygiene should be seen at least every four weeks to monitor the cleaning and periodontal health. Number four: Extraction versus none-extraction, patients with extractions should be seen more frequently due to the increased risk of side effects during space closure. Number five: Surgical and impaction cases, the authors suggest this difficult cases often need to be scheduled at least every four weeks to keep them on the schedule. Number six: Compliance versus none compliance mechanics, appliances that require compliance such as head gear or elastics should be seen more frequently to measure treatment progress. Number seven: Decalcification, patients with decalcification and poor oral hygiene must be seen every four weeks for oral hygiene management. Number eight: Root resorption, severe root resorption should be closely monitored every four weeks. Number nine: Family schedule considerations, when it’s very difficult for parents or children to make frequent appointment, they may require longer intervals.

These are some very specific recommendation for scheduling intervals that you may want the list considering your office. You may have different thoughts or experiences that leads you to different conclusions, but an open discussion about intervals may lead to improvements in your practice. If nothing else, you may get your staff to understand why not all patients need the same intervals. I really like the fact that considerations discussed in this article were patient-driven not consultant-driven. If you want to find the full article to stimulate the discussion of the appointment intervals in your office take a look at the overview section of the July 2011 Journal of Clinical Orthodontics.

Temporomandibular joint and normal occlusion: Is there anything singular about it? A computed tomographic evaluation

Vitral RWF, da Silva Campos MJ, et al.
Am J Orthod Dentofacial Orthop 2011;140:18-24
                                                                                 

November 9, 2012
Dr. Da-Nal Moon

[초벌원고]

Where the mandibular condyle should I deal with be positioned in the temporomandibular fossa? Has long been a subject of controversy in both dentistry and orthodontics, the development of computed tomography scans has provided researchers an excellent tool to more accurately evaluate 3D anatomic relationships. CT scans of the temporaomandibular joint provide the significant advancement in the research of the morphology of these joint structures and the diagnosis of pathologies that are difficult to identify using conventional radiographs. CT scans are the method of choice for obtaining images of bone structures. Also, CT scans enable researchers to make real and precise measurements of structures such as the temporomandibular joint. Because the most traditional CT scanners are large and expensive systems, they have not been used very much by orthodontist.

[수정원고]

However, the advent of cone beme computed tomography has made these examinations more accessible to orthodontist because of the more compact nature of this equipment which is more affordable and requires less radiation than conventional CT scans. If you are to take advantage of cone-beam computed tomography to precisely measure the position of the mandibular condyle, in a sample of non-symptomatic patients with Class I occlusions, what would you expect to see. This is exactly what was done in a study titled ‘Temporomandibular joint and normal occlusion: Is there anything singular about it? A computed tomographic evaluation’ by Robert, Willer, Farinazzo, Vitral et al which appeared in the July 2011 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

In this study, the authors evaluated 30 persons with normal occlusion, ranging in age from 15 to 32, who had CT scans of their TMJs. The participants all had their permanent teeth erupted except third molars, no functional mandibular deviations, no evidence of facial asymmetry, first molars and canines in Class I relationship, canine guidance with no working or nonworking side interferences on lateral excursions, anterior guidance with no posterior interferences, normal overbite and overjet, and no crossbite. When the authors precisely measured the relationship of the mandibular condyles to the fossa in these patients what do you think they found? The bottom line is they found no singular characteristic of the TMJs of the normal occlusion group. The largest mediolateral diameter of the mandibular condyle process and the posterior joint spaces showed the statistically significant difference between the right and the left sides. They also found that noncentralized position of the condyles with the condyles anteriorly positioned.

I must say that the results of this study did not surprise me. I think as orthodontist, we have been taught for a long time to treat to ideal numbers and relationships and have failed to fully appreciate, then the most of the things that we deal with there is a wide range of normal variation and fortunately nature in most incidences appears to be able to adapt to this variation. What surprises me after same results of this study and others, is that there are still practitioners trying to jam the mandibualr condyle upward and backward to some ideal position. Rather than worry about some theoretical ideal position of the mandibular condyle, I believe it is much more important to evaluate patient's symptoms. And as Dr. Frager points out in his guest lecture in this month program, even if some symptoms are present, they should be treated very conservatively giving nature chance to correct things without intervention. One other area that I would like to comment on is the philosophy of some orthodontists that it is necessary to use articulator mounted models to avoid missing a large functional shift or what has been commonly referred to as a ‘Sunday bite’. I think it is important to understand that any articulator can only mount models in the position in which you put the mandible and if you can’t detect the functional shift clinically the articulator is not going to do it for you. You can find this article in the July 2011 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

Effects of Face Mask Treatment Anchored With Miniplates After Alternate Rapid Maxillary Expansions and Constrictions: A Pilot Study

Kaya D, Kocadereli I, et al.
Angle Orthod 2011;81:639-646
                                                                                  

November 16, 2012
Dr. Sun Lijun

[초벌원고]

How would you treat this situation? You were enduring recurrent planning treatment for an 11-year-old male who has a Class III malocclusion. Now the problem is not the mandible. It is the maxilla retrognathic. There’s an adequate space for all maxillary teeth to erupt. This boy is in the transitional dentition and has nearly erupted most of the teeth. So your plan is to consider maxillary protraction using a facemask. But his maxillary incisors are already proclined. Your concern is that if you use the teeth as an anchor to attach the facemask you are likely procline maxillary incisors even more.

[수정원고]

What will you do? Would you consider using miniplates in the maxilla to attach a facemask? Would this work? Is this an effective way of providing and anchor to the maxilla, and avoiding maxillary incisor proclination? Those questions were addressed in study that was published in the July 2011 issue of the Angle Orthodontist. The title of this study is “Effects of a facemask treatment anchored with miniplates”. This study was co-authored by Dr. Kaya and three other researchers from the faculty of Dentistry Hacettepe University in Ankara, Turkey.

The purpose of this study was to evaluate the dental skeletal and soft tissue effects of Delaire-type facemask treatment anchored with miniplates in patients with maxillary retrusion. In order to accomplish this goal, the author gathered 15 patients who required maxillary protraction. All subjects had a Class III malocclusion. Now as an additional part of the experiment, the authors placed a palatal expander, and over 8-week period they alternately expanded and constricted the expander in order to simulate osteoblastic and osteoclastic activity in the circummaxillary sutures. After 8 weeks of the expansion technique, 2 miniplates were attached to the maxilla and the patients were asked to wear a Delaire-type facemask. The force on the facemask began at 100 grams, and eventually was increased to about 400 grams during the second week. The patients were advised to wear the facemask full time and they were seen about every 3 weeks in order to control the force. Now the amount of protraction was based upon the amount of negative overjet. All subjects were asked to wear the appliance until the anterior crossbite was corrected. The total time in of all involved in this experiment was about 9 months which included the time for the expansion protocol. Cephalometric created graphs were taken before and after treatment in order to determine the impact of the miniplates.

What do you think happened? Remember the original question: Will miniplates allow maxillary protraction without secondary dental effects on the maxilla? The answer of that question is “Yes” definitely. In none of the cases, did authors find the maxillary incisors changed their inclination. In fact, on average the maxilla move forward 2 to 3 mm in these subjects. So the treatment was successful. The miniplates were removed in all cases and did not cause any problems for these patients.

Now, on my mind there were a couple of questions that I would still like to have an answer. The first one is: “What happened over the long term?” We know maxillary protraction can work. But in a patient with Class III malocclusion, what happened after one or two years in this sample? I hope the authors will follow these patients and provide us with that answer. My second question relates to the use of alternate expansion and constriction prior to protraction. It would be interesting to know it in these patients to respond more rapidly than the group of patients without the expansion protocol. Hopefully again these authors were provided that information in a future study. In the meantime, if you like to read this study the highlight effectiveness of miniplates for anchoring the maxilla during protraction facemask therapy, you will find it in July 2011 issue of the Angle Orthodontist.

Tooth Movement and Root Resorption: The Effect of Ovariectomy on Orthodontic Force Application In Rats

Sirisoontorn I, Hotokezaka H, et al.
Angle Orthod 2011;81:570-577
                                                                                  

November 23, 2012
Dr. Hyun-Ran Jeon

[초벌원고]

Suppose you're about to begin treatment on a 65-year-old female. She has a Class I malocclusion with severe crowding and anterior dental protrusion. Your plan is to extract 4 premolars to unravel the crowding and then treat her with conventional routine

full bracketed orthodontics. But when you're reviewing the health history, you notice that this woman is postmenopausal. She also noted that she has been diagnosed with osteoporosis. What effect will these 2 factors have on your orthodontic tooth movement? Will her teeth move faster or slower? Will she have greater or lesser chance for root resorption? Are there any studies that with substantiate your answer? These questions, these answers, and these issues, will be discussed in an animal experimental study that was published in the July 2011 issue of the Angle Orthodontist. Although this is translational research and an anmial sample, I believe that it does have some bearing on the questions that I posed, for this hypothetical patient. The title of this article is “Tooth movement and root resorption: The effect of ovariectomy and orthodontic force application”.

[수정원고]

This study comes out of the department of orthodontics at Nagasaki university in Japan. The lead author of this paper is Dr. Sirisoontorn. Now the purpose of this study was to evaluate the interrelationship between the effect of ovariectomy on tooth movement as well as its effect on root resorption. First of all, why would ovariectomy be assist in a sample of an experimental animals? Actually, osteoporosis can occur as a result of menopause or can be induced by removing the ovaries. The principle here is that there's an increase in bone turnover caused by a reduced level of estrogen during the postmenopausal period which can be simulated by performing ovariectomy in an experimental animal. You see the authors wanted to determine the effect of osteoporosis on the rate of tooth movement and the degree of root resorption. In order to accomplish this study the authors used 10 female Wistar rats. 5 of the animals had their ovaries removed and the other 5 were non-operated controls. 4 weeks after the surgery, a coil spring was placed on the right maxillary first molar and a mesial force was placed on that tooth. After 1, 3, 7, 14, 21 and 28 days micro-computerized tomography was used to assess the impact of the force on the molar, comparing the controls to animals whose ovaries had been removed. Finally after 28 days, the teeth were removed and the amount of root resorption was assessed. I think you get the idea of the experiment. The question is, what happened? Remember the original question. Does ovariectomy or osteoporosis have an impact on the rate of tooth movement or the amount of root resorption? And the answer to that question is, yes in both situations. In the ovariectomized animals, the authors found that the rate of tooth movement was significantly faster one day after the orthodontic force was applied and that this more rapid tooth movement occurred throughout all of the experimental period. Second question, is there an impact on the amount of root resorption? The answer to that question is, yes. In the ovariectomized animals the root resorption craters were deeper and more severe than in the control animals that did not have the ovaries removed.

So back to the original clinical question. When you're treating an adult female who has osteoporosis, would you find similar reactions when moving the teeth? As I said at the outset, it is not easy to translate from an animal study to a human. But it would be interesting to anaylze a large group of adult female subjects who had orthodontic treatment to determine if similar responses would occur in those women with a diagnosis of osteoporosis. In the meantime if you're interested in reading this animal study, you'll find it in the July 2011 issue of the Angle orthodontist.

Longitudinal Growth Changes in Subjects With Deepbite

Baccetii T, Franchi L, McNamara JA Jr.
Am J Orthod Dentofacial Orthop 2011;140:202-209
                                                                                  

November 30, 2012
Dr. Yanan Hou

[초벌원고]

I suspect you have had many patients come in to your office with deep overbite in the early mixed dentition. While I am not sure what your philosophy of treatment would be for patients like this? I would like to ask one question, the question is what would happen to that deepbite if you didn’t do anything? Would it likely to get worst, stayed the same or possibly improve? A study titled “Longitudinal growth changes in subjects with deepbite” by Tiziano Baccetti et al. which appeared in the August 2011 issue of the Am J Orthod Dentofacial Orthop addressed this question.

[수정원고]

In this study, the author evaluated 29 subjects with deepbite which was to find as an overbite greater than 4.5 mm. The subjects were from Michigan Growth study and the Denver Child Growth study were followed longitudinally from approximately 9 through 18 years of age. Cephalometric radiographs were used to measure the overbite for reach subject at 4 different periods: prepubertal, pubertal, post-pubertal, and the fourth at last observation which correspond to young adulthood.

After evaluating the subjects at 4 different time periods, what do you think the author found? The bottom line is that overbite worsened in 62% of the subjects during the prepubertal period which correspond to the mixed dentition and improved in 79% of the subjects at puberty and from the transition from the late mixed or early permanent dentition to the permanent dentition. From prepuberty through young adulthood, overbite showed improvement in 83% of the subjects and self-corrected in 62% of the subjects. During the prepubertal period, overbite worsened significantly. However, it improved significantly during pubertal growth spurt and continued to improve to adulthood. When the author related the changes in overbite the other dental and skeletal cephalometric perimeter, he was interesting to note that skeletal vertical relationships were not a good predictor of overbite correction or worsening. The only thing, that seems to have some predict value was initial angulation of maxillary incisors which subjects with more protrusive maxillary incisors having a greater likelihood of overbite improvement while subjects with retro-inclined maxillary incisors had a poor prognosis for self correction.

The authors found that significant improvement in overbite during adolescence growth spur appear to be related to the amount of vertical growth of the mandibular ramus and the eruption of the mandibular molars. The overall messages of this study is that patients with deep overbite are likely to see that overbite worsen during the prepuberty growth period but significant improved from there on.

If you are treating a patient with deep overbite, you are likely to have more effective correction of the deepbite if the treatment is delayed until the late mixed dentition the pubertal growth spurt. You are also likely to have great success in overbite correction in ClassⅡ division 1 patients versus ClassⅡ division 2 patients.

I thought it was an excellent study and provide some guideline for the timing of treatment in patient with deep overbite. You can find this study in the August 2011 issue of the Am J Orthod Dentofacial Orthop.

Shear Bond Strength After Multiple Bracket Bonding With or Without Repeated Etching.

Rϋger D, Harzer W, et al.
Eur J Orthod 2011;33:521-527
                                                                                  

December 7, 2012
Dr. Young-Min Hong

[초벌원고]

Imagine an afternoon in your office and your suction fails. You reschedule your banding and bonding appointments, but proceed to see your routine adjustments. One of your patients comes in with a loose upper central incisor bracket and you hate to let her go without rebonding. Since most of the bonding material remains on the tooth you decide you will just carefully smooth the composite and rebond without etching and rinsing, something you can do without suction. Can you expect the bond strength to be adequate with this procedure? Or should the patient come back immediately after the suction is fixed to rebond the bracket properly?

[수정원고]

After I review this article "Sure Bond Strength after Multiple Bracket Bonding With or Without Repeated Etching", you will have an answer to that question. The auther set out to investigate whether reapplying the etchant was necessary when rebonding a bracket. After all we know that there are adhesive tags that remain in the enamel. So they used extracted human premolars and bonded metal brackets to all 120 teeth in a conventional manner including an acid etch step. After bond-strength testing, they then rebonded all the brackets two more times and compared the bond strength. Forty of the premolars had all composite removed, the surface re-etched and the bracket rebonded. This acted as a control. The second group of 40 teeth had the composite removed and the bracket rebonded without etching. This group relied on the existing adhesive tags for strength. The third group had the composite on the tooth leveled but not removed and the bracket rebonded without etching. The bond strength was compared amongst these various rebonding procedures. 

Here's what was discovered. The first group, that had all composite removed and was re-etched, had bond strength equal to the original. This is what most of us do routinely. The second group, that had the composite removed and was rebonded without etching, had a dramatic drop in bond strength to a value that would not be clinically adequate. So we know the adhesive tags alone are not enough.  The third group, where the composite was levelled but not removed, then was bonded without etching, showed bond strength values nearly equal to the original. This indicates that the original enamel bond is still intact and adequate. 

So the answer to my question regarding your patient on whom you rebonded a bracket without suction is that if you just level the composite, the bond strength could be expected to be adequate and the patient does not need to be immediately reappointed. The question then arises whether I should use this as a routine rebonding technique when most composite remains on the tooth. It would save time and supplies. For me, I'm not sure the time saved would be worth the uncertainty. This study was a bench-top study and not done in the presence of plaque and saliva. Although the results look promising, I'll probably stick with routinely re-etching for now. If you want to consider changing your procedures based on these findings I reported, you may want to read the article in detail. You can find it published in the October 2011 issue of the European Journal of Orthodontics. 

Immediate Effects of Rapid Maxillary Expansion With Haas-Type and Hyrax-Type Expanders: A Randomized Clinical Trial.

Weissheimer A, de Menezes LM, et al.
Am J Orthod Dentofacial Orthop 2011;140:366-376
                                                                                  

December 14, 2012
Dr. Tae-Woo Kim

[초벌원고]

When you do rapid maxillary expansion in your practice, what type of expander do you use? I suspect that most likely you will be using either hass type or hyrax type of expander. I know some excellent orthodontist who use hass type of expander and other excellent orthodontist who use the hyrax expander. Depending on who you ask, you will get different opinions as to which type of these expanders is more effective and which produces greater skeletal expansion.

One of the reasons that there has been a different opinion about the effectiveness of these two expanders is that upto recently research tools that were being used to evaluate or differentiate skeletal and dental expansion has significant limitations. Most studies are evaluating rapid maxillary expansion used either models or anteroposterior cephalometric radiographs to evaluate these changes both of which has significant limitations. The development of cone-beam computed tomography has gven reserchers a much more effective tool to measure both skeletal and dental changes.

[수정원고]

A recent study titled ‘Immediate effects of rapid maxillary expansion with Haas-type and hyrax-type expanders: A randomized clinical trial’ by Andre Weissheimer et al. used cone-beam computed tomography to compare the dental and skeletal changes created by Haas-type and hyrax-type expanders. In this study the author used sample of 33 subjects with mean age of 10.7 years who had transverse maxillary deficiency. The subjects were randomly devided into two groups. One of which was treated with Hass expander and others with Hyrax expander. For both groups, the expansion of appliances were activated by 4 quarter turns initially, followed by 2 quarter turns per day until the expansion of 8 mm was achieved. Cone-beam computed tomography scans were taken before expansion and at the end of the active expansion phase. When the researchers compared the anteroposterior and vertical skeletal changes that occurred between the two appliances, there wasn’t any difference. The bottom line is that both appliances acheived significant skeletal expansion. Anteroposteiorly, the expansion was triangular, with the greater expansion in the anterior part of the maxilla. The pure skeletal expansion was greater than actual dental expansion. The hyrax group had greater statistically significant orthopedic effects, and less tipping tendency of the maxillary first molar when compared with Hass group.

I’m sure the results of this study may surprise some orthodontist who use the Hass expanders in the belief that it creates greater skeletal expansion due to the cooperation will occur fast. I should point out, however, that the changes in this study were evaluated at the end of appliacen activation and significant skeletal differences were very minimal, and probably not clinically significant. It would be interesting to see if there are any differences between two appliances at a longer post treatment observation time.

You can find this study in the September 2011 issue of the American Journal of orthodontic and Dentofacial orthopedics.

Prevalence and Risk Factors of Sleep Bruxism and Wake-Time Tooth Clenching in a 7 to 17-Year-Old Population

Carra MC, Huynh N, et al.
Eur J Oral Sci 2011;119:386-394
                                                                                   

December 21, 2012
Dr. Min-Hee Oh

[초벌원고]

As part of your initial patient visit for children and adolescents, do you ask parents about observed sleep bruxism or daytime clenching? These may be important parafunctions to assess, since they have been related to TMD symptoms, headaches and toothwear. If you did assess your patients, what percentage of this group would you expect to report clenching or bruxism? Since I didn't know the answer to this question, I decided to review an article called "Prevalence and risk factors of sleep bruxism and wake-time tooth clenching in a 7 to 17-year-old population". This article appears in the October 2011 issue of the European journal of oral sciences. This paper appealed to me because it assessed children and adolescents that presented for orthodontic evaluation: just the group that steps in my office door.

[수정원고]

A total of 604 subjects were recruited to participate in this study that consisted of a clinical examination and a completion of a questionnaire. The questionnaire consisted of 4 sections and assessed medical and dental history along with bruxism, sleep disorders, clenching and other behaviors. The parents were asked to complete the questionnaire along with their child on their behalf. The clinical examination was done by an experienced orthodontist who is blinded to the answers in the questionnaire. In other words, the examiner did not know if the subject reported bruxism or clenching when the exam was done. The examination assessed a variety of dental, skeletal and esthetic factors as well as an assessment of malocclusion.

So what percentage of these children and adolescents reported sleep bruxism? 5 percent? 10 percent? 30 percent? The answer is 15 percent. Just about 1 in 6 reported this sleep time parafunctional activity. What about daytime clenching? Just slightly less about 1 in 8 reported this behavior. Interestingly, more sleep bruxers were under the age of 12 and more daytime clenchers were over age of 12. Also, there were some interesting relationships between these activities and facial pattern. Sleep bruxers were almost 3 times as likely to be classified as brachycephalic compared to non-bruxers, and also were more often class II.

The take-home message is that sleep bruxers and daytime clenchers are very common among the group of children and adolescents we see presenting for orthodontic treatment. If you don't presently ask questions about these activities on your history form, you may want to consider adding them. For more details about bruxers and clenchers in our orthodontic population, refer to this article from Montreal, Canada, that appears in the October 2011 issue of the European journal of oral sciences.