The Orthodontics Professors
the latest in contemporary & evidence-based orthodontics
BY DAVID M. SARVER, DMD, MS
An eye-tracking study from The Ohio State University published in the AJO-DO provides clinicians new data to help them understand how smile esthetics interact with overall facial esthetics.
In the study, faces of varying attractiveness (“attractive”, “average”, or “unattractive”) were paired with dentitions that reflected malocclusions with a dental attractiveness ranging from 3-7 on the IOTN-AC scale. In this way, attractive faces could be paired with unattractive teeth, for example.
66 lay persons viewed 15 different combinations of faces with the teeth visible only within the framework of the smile. All of the faces were those of Caucasian women, and all participants were 18 - 30 year old Caucasians, in an effort to control for any possible other-race or age effects in terms of perception.
Objective eye-tracking hardware and software was used to evaluate what parts of the face participants spent the most time viewing during a 3 second exposure to each face. Interestingly, participants were not told that the purpose of the study was to evaluate dental or facial esthetics until after their participation.
Both eye fixation duration (time spent looking at one part of the face) and eye fixation density (how many times one part of the face was viewed) differed depending on the attractiveness of the face, the attractiveness of the dentition, the region of the face, and the gender of the participant.
For all the participants, more attention was focused on the mouth as the dentition became more unattractive.
For female participants, a significantly greater density and duration of gaze was focused on the mouth with the combination of an attractive face paired with an unattractive smile.
WHAT THE PROFESSOR THINKS
The study design is appropriate and used validated techniques that generate objective data for the very subjective field of facial esthetics. Using a specific age and ethnicity demographic, as well as an age, gender, and race restricted set of faces as stimuli is appropriate since it helps to control for some well-established potential confounders of judging facial attractiveness.
Finally, deceiving participants as to the nature of the eye-tracking task was clever. In this way, participants were not biased. Instead, these eye tracking data represent the “unconscious” judgement of facial attractiveness, which is ultimately the way most of our patients are judged most often after treatment.
This study has some interesting implications for the clinician who is interested in the very best communication with patients when it comes to the complicated topic of facial and dental esthetics:
Article Reviewed: Johnson EK et al. Role of facial attractiveness in patients with slight-to-borderline treatment need according to the Aesthetic Component of the Index of Orthodontic Treatment Need as judged by eye tracking. Am J Orthod Dentofacial Orthop. 2017; 151 (2) 297-310.
Reference: Sarver DM. Enameloplasty and Esthetic Finishing in Orthodontics—Identification and Treatment of Microesthetic Features in Orthodontics Part 1. J Esthet Restor Dent. 2011; 23 296-302.
Risky Business: Is Root Resorption More Likely with Fixed or Removable Appliances? The Latest Evidence Might Surprise You. . .
BY SYLVIA A. FRAZIER-BOWERS , DDS, PhD
The authors of Orthodontically-induced external apical root resorption in patients treated with fixed appliances vs. removable aligners, present a thoughtful and relevant clinical study that investigates the relationship of orthodontically induced external root resorption (OIERR) with the use of two different orthodontic treatment modalities (fixed appliances versus Invisalign®).
The objective of this case-control study was to determine if an association exists between OIEARR, appliance type, radiographic, clinical, and genetic factors using a backward stepwise conditional logistic regression analysis. OIEARR Cases and controls were selected in a non-random fashion from a private practice and a university clinic. OIEARR was defined as >2mm resorption of at least one incisor after completion of treatment, as judged using panoramic and lateral radiographs.
For each of the 372 participants, 12 clinical variables were assessed as well as polymorphisms in 3 genes, Interleukin 1B (IL1B), Interleukin 1 receptor agonist gene (IL1RN), and the osteopontin gene (SPP1).
The findings were as follows: of the 12 factors, two were associated with an increase of OIEARR, when controlling for the influence of all of the clinical and genetic factors recorded: 1) clinical case complexity (ABO discrepancy index) and 2) extent of incisor displacement in the sagittal plane. The results also showed that when subjects were homozygous for the T allele of the IL1RN gene (rs419598) they were 3 times as likely (or 2 times more likely) to experience root resorption.
Perhaps more importantly, the predisposition for OIEARR was similar whether using removable or fixed appliances. The odds ratio of 1.66 for predisposition of OIEARR in fixed versus removable appliances, in fact, indicates a modest but not statistically-confirmed increase in OIEARR associated with the use of removable versus fixed appliances.
WHAT THE PROFESSOR THINKS
The development of root resorption is a topic of growing interest to orthodontists; based on a nationwide survey conducted by the AAO, root resorption was considered a very important clinical issue by 60% of participating orthodontists. Accordingly, the study is timely and presents a unique view of an interesting question: Is root resorption more likely in a cohort with specific genetic factors and treatment modalities?
The authors, therefore, conduct a study that may translate into the clinical/practical orthodontic setting as follows:
“Would I advise my patients that one appliance type carries less risk than another in the development of root resorption?”
Based on the authors’ analyses, it is clear that the patients studied developed OIEARR at comparable rates with fixed or removable appliances. This finding is quite illuminating since anecdotally the assumption is that removable appliances may be gentler in terms of orthodontic tooth movement and lead to less root resorption.
This study ranks modestly in the hierarchy of study effectiveness. Given the retrospective design, systematic (non-random) factors may have determined treatment choice with removable versus fixed appliances. Also, the analysis considers a high number of variables that may be inter-correlated. In other words, it is likely that several of these factors actually cluster together and they are not independent, which could possibly change the relationship of clinical outcome and etiology.
The bottom line is that this study provides an important contribution to our ever-changing understanding of the relationship between specific clinical, genetic, and treatment factors on adverse treatment outcomes, such as root resorption (see the Figure above).
The take-home message when you go into the office on Monday morning is that orthodontically-induced root resorption happens more often than we may imagine, regardless of appliance type.
The simple notion that changing orthodontic treatment modality may decrease the risk of root resorption is not supported, based on the evidence here. Given advances in genomic studies, we can speculate that a combination of factors lead to the development of root resorption, with the problem being a defect in the repair mechanism of those who develop moderate or severe root resorption. The promise of more refined genotype-phenotype correlations that provide a practical tool to predict the risk of root resorption is foreseeable.
Article Reviewed: Iglesias-Linares et al. Orthodontically induced external apical root resorption in patients treated with fixed appliances vs removable aligners. The Angle Orthodontist. January 2017.
BY TATE H. JACKSON AND CLARKE STEVENS
A study just published in the Angle Orthodontist has analyzed 419,363 tweets, shared publicly regarding the patient experience with either traditional fixed appliances or Invisalign®. The data were collected over a period of five months from April to September in 2015 and analyzed by sentiment analysis using Naïve Bayes classifiers.
Tweets were identified by the use of the keywords “braces” or “Invisalign” and filtered using software so that content irrelevant to orthodontics (braces as a term for suspenders in fashion, for example) was excluded. All tweets relevant to orthodontics with either keyword were then classified in sentiment as positive, negative, neutral, or as an advertisement.
Overall, more tweets about orthodontic treatment were positive (62%) than negative (38%). There was no statistically significant difference in the proportion of positive tweets when comparing traditional braces to Invisalign®. More individuals tweeted about braces than Invisalign®, and 1/3 of all the tweets involving Invisalign® were classified as advertisements. Generally, positive tweets most often focused on gratitude while negative tweets most often focused on pain.
WHAT THE PROFESSORS THINK
The topic and methodology of this study are certainly relevant to those practicing in the era of social media. The use of a simplified sentiment analysis was evidence-based, and the authors used adequate search terms and a human-defined pool of categorized terms of adequate size to train the software for the larger analysis that took place.
The authors did not analyze if tweets originated from individuals associated with an orthodontics practice. Although that may be impossible to do effectively, it is important to interpret the data with that fact in mind.
Although this study only presents data from one form of social media, it does have some interesting ramifications for practicing orthodontists.
First, the fact that more than 400,000 tweets published over a five month period involved orthodontic treatment reinforces the power of social media in the public discourse relative to orthodontics.
Second, the majority of tweets were positive in nature, a point that might reassure orthodontists that the profession is viewed favorably. The magnitude of positive sentiment reported (62%) can serve as a sort of evidence-based benchmark for individual practices. If an analysis of a practices’ social media references shows a lower proportion of positive comments, it might be an objective reason for concern on the part of the practice.
Third, it is also interesting to note that despite the fact that there were more tweets related to traditional braces overall, there was a much higher proportion of advertising related to Invisalign®.
33% of all tweets related to Invisalign® were advertisements, compared to only 7% for braces. Again, for clinicians in practice who want some sort of evidence-based benchmark related to the density of advertising for either traditional braces or Invisalign® using social media, these data give some insight.
Article Reviewed: Noll et. al. Twitter analysis of the orthodontic patient experience with braces vs. Invisalign. The Angle Orthodontist. Online Early, Jan 2017.
BY TATE H. JACKSON AND WILLIAM V. GIERIE
A study in the Angle Orthodontist has surveyed 1,000 General Dentists and 1,000 Orthodontists – drawn from a list of Invisalign® providers on the company’s website. Those surveyed were asked to rate their confidence using Invisalign® to treat six different cases for which intra-oral photographs were provided: a Deep Bite case, a Posterior Crossbite case, a Anterior Open Bite case, Mild Crowding case, a Severe Crowding case, and a Class II case. Additionally, both Orthodontists and General Dentists were asked about their various treatment planning (e.g. time spent with ClinChecks) and mechanics (e.g. use of Class II elastics or auxiliaries) tendencies with Invisalign®. Finally, demographic and training information, as well as experience in treating cases with Invisalign® was reported.
Overall, both Orthodontists and General Dentists were relatively confident in treating the four cases presented with Invisalign®. Interestingly, General Dentists were significantly more confident when it came to more complex cases: deep bite, severe crowding, and Class II. Orthodontists reported higher confidence in treating mild crowding than General Dentists.
Orthodontists were significantly more likely to spend more time reviewing ClinCheck set-ups and were more likely to use refinements and elastics as a part of treatment. Not surprisingly, Orthodontists reported more training and experience using Invisalign® and were more likely than General Dentists to tell patients that their malocclusion was too complex for Invisalign®.
WHAT THE PROFESSORS THINK
This article provides some data for practicing Orthodontists that might be of great use in discussing with patients why orthodontic care is specialized treatment – not just the appliance used to straighten teeth.
The use of a specific case records in conjunction with confidence ratings, and not just a survey self-report, gives these data some greater credibility. The use of intra-oral photographs alone had good rationale, since it provided a realistic version of the information that a General Dentist might consider when planning an Invisalign® case. The structure of the survey, asking respondents to give demographic and training information after completing the confidence ratings is helpful since it aids in avoiding bias when reporting confidence.
The fact that the response rate to the survey is not clearly reported is an unfortunate shortcoming of the study – one that, if clarified, would significantly improve the reliability of the results.
There are two pieces of information from this study that are most interesting and clinically relevant:
Article Reviewed: Best et al. Treatment management between orthodontist and general practitioners performing clear aligner therapy. Angle Orthodontist. Online Early Nov 2016.
BY TATE H. JACKSON
An Italian group has published a systematic review and meta-analysis that holds some practical clinical information for orthodontists or dentists using mandibular repositioning appliances to treat obstructive sleep apnea.
The authors followed PRISMA guidelines and reviewed publications from 1990 – 2015. Only randomized controlled trials were included in the analysis of the association between reduction in apnea-hypopnea index (AHI) and therapy with a mandibular repositioning device in adults. Importantly, all changes in sleep-disordered breathing were measured by polysomnography (PSG) – both at baseline and after treatment. 13 studies were included in the analysis.
Successful reduction in AHI (reduction of sleep apnea) was found in studies where the mandible was advanced as little as 25% of the maximum protrusion possible. Advancement of 50% showed equivalent results to advancements of a greater magnitude.
Although the treatment modality was effective in significantly reducing AHI, no clear association between advancing the mandible further and a greater reduction in AHI could be made.
Since variability in individual response was reported, the authors suggested a conservative and personalized approach to treatment by initially posturing the mandible forward only “the minimum effective” distance.
WHAT THE PROFESSOR THINKS
Although the authors conclude that the 13 RCT’s included in this meta-analysis represent a relatively small body of evidence of moderate quality, the data presented have some strengths.
Only randomized controlled trials where the outcome of interest was clearly defined were included. The “gold standard” of polysomnography was used to assess changes in sleep apnea in each study. Further, only studies that accounted for changes in BMI and considered patients over 18 were included.
From an orthodontic perspective, posturing the mandible forward in a non-growing adult with a fixed or removable appliance could certainly have ramifications, both for the patient’s occlusion / alignment and for the patient's comfort / ability to tolerate the appliance. If protruding the mandible 50% of the maximum possible works, then tooth-movement side effects, as well as pain and discomfort, might be limited.
Not posturing the mandible forward fully at baseline might also allow for future increases over time as needed.
This article provides two key pieces of information for the clinician treating sleep apnea in adults with appliances that protrude the mandible:
As the enthusiasm for treating sleep apnea with mandible-posturing oral devices continues, these data may become more and more relevant for orthodontists – either as we provide treatment for sleep apnea, or as we address the potential changes in occlusion and alignment caused by such treatment.
Article Reviewed: Bartolucci, et. al. The effectiveness of different mandibular advancement amounts
in OSA patients: a systematic review and meta-regression analysis. Sleep Breath. Jan 2016