Occlusal contact changes in patients treated with clear aligners: A retrospective evaluation using digital dental models.

INTRODUCTION: This study used digital intraoral scans to evaluate how clear aligner treatment affects occlusal contacts and to determine the influence of sex and age on contact changes. Results were compared with contact changes that occur during fixed appliance therapy. METHODS: Patients included in this study were treated in a University setting and private practice. Inclusion criteria were a Class I malocclusion treated nonextraction with clear aligners and the presence of pretreatment and posttreatment digital intraoral scans. Scans were imported into specialized software, and occlusal contacts were analyzed. The effects of age and sex on contact changes during clear aligner treatment were determined. Changes in occlusal contacts were compared with changes that occur during nonextraction treatment of patients with a Class I relationship using fixed edgewise appliances. RESULTS: A total of 45 clear aligner patients fit the eligibility criteria. Clear aligner treatment reduced the percentage of tight, near, and approximating contacts, whereas the percentage of open and no contacts increased. These changes in occlusal contacts were greater for the older age group studied. Genderinfluenced occlusal contact changes in the anterior dentition only where the decrease in near contacts and increase in open contacts were greater for males. These results for patients treated with clear aligners were similar to those for patients treated with fixed appliances; both treatment modalities reduced close occlusal contacts at the time active treatment was completed. CONCLUSIONS: These results indicated that when clear aligners or fixed appliances are used to treat a Class I malocclusion, the resulting occlusion immediately after debonding is not as "tight" as it was at pretreatment.

Association between crowding estimation and extraction recommendations in orthodontics.

INTRODUCTION: Little is known about how precisely orthodontists in the United States (US) assess crowding or at what range of crowding they recommend extraction. This study aimed to assess the relationship between estimated crowding in patients with a Class I relationship and extraction recommendation by orthodontists in the US. The secondary aims were to evaluate the accuracy and precision of clinician estimations and determine if clinician background traits play a role in extraction decision-making. METHODS: An electronic survey was prepared using 4 patients with a Class I relationship with anterior crowding selected from a University Orthodontics Clinic and was sent to approximately 10,400 subjects through Facebook and the American Association of Orthodontists Partners in Research program. RESULTS: From the 297 responses received, most clinicians recommended extraction once crowding reached 9-10 mm in either the maxilla or the mandible. The data from 2 patients suggest this decision was more strongly correlated with mandibular crowding. Clinician estimations varied widely but, on average, were precise within approximately 2 mm of objective measurements. There was a tendency to overestimate crowding, especially by Northeastern practitioners. Clinicians who reported routinely measuring crowding or who reported that they recommended extractions to >10% of their patients were 1.2-2.0 and 1.4-1.6 times more likely, respectively, to recommend extraction in the patients. CONCLUSIONS: Crowding estimation was highly subjective and varied widely among clinicians. Most clinicians recommended extraction once maxillary or mandibular crowding approximated 9-10 mm. Some clinician demographics were correlated with the precision and accuracy of estimations and the likelihood of extraction in the patients.

Effect of birth season on anthropometrics and diseases of bone mineralization in the US population.

OBJECTIVES: Birth season has been inconsistently associated with anthropometrics, bone fractures, and malocclusion. Our aim was to assess the association between birth season and anthropometrics (height, weight, birth weight), bone fractures and dental malocclusion in the United States. METHODS: US surveys conducted between 1963-1973 assessed 16 152 6-to-21-year-old participants. Prevalence ratios and mean differences were estimated using linear models using fall as reference. RESULTS: Participants born in spring, when compared to fall, were of similar height (mean difference (MD) in height-adjusted Z score 0.03, 95% Confidence Interval (CI): -0.01 to 0.08; P-value = .17), weight (MD for weight-adjusted Z-score 0.00, 95% CI: -0.05 to 0.04; P-value =0.83), had similar rates of bone fractures (Prevalence Rate [PR] 1.07; 95% CI: 0.94 to 1.22; P-value = .28) and similar rates of dental malocclusion (MD of malocclusion index HLD -0.16; 95% confidence interval - 0.39 to 0.07; P = .18). CONCLUSION: We did not find an impact of birth season on anthropometrics, bone fractures, and dental malocclusions.

The influence of labiolingual and mesiodistal anterior tooth dimensions on interarch relationships: A modified anterior Bolton analysis.

INTRODUCTION: Tooth size and morphology of anterior teeth influence interarch relationships. The Bolton analysis uses tooth width to calculate a sum of mandibular to maxillary tooth width ratios necessary for proper occlusion. Several parameters not factored in the Bolton analysis influence occlusion, such as tooth thickness. This study sought to use 3D modeling to develop and assess a tooth size analysis that encompasses labioligual thickness as well as mesiodistal width of anterior teeth. METHODS: The role of tooth thickness in interarch relationships was studied using simulations in a 3D modeling software (Suresmile). To develop a new chart of interarch ratios based on tooth thickness, a series of simulations were produced with varying tooth thicknesses and widths. The new ratios were evaluated on records from 50 patients. RESULTS: Findings from the simulations suggest that the ideal tooth thickness remains approximately 2 mm if the overall tooth width of the dentition increases and the interarch anterior ratio is maintained. The thickness-adjusted anterior mandibular to maxillary tooth ratio ranges from 0.70-0.79 depending on the tooth thickness. This thickness-adjusted ratio provides a superior prediction for the sum of anterior tooth width compared with the Bolton analysis. CONCLUSION: Tooth thickness affects interarch tooth width ratios and anterior occlusion. A thickness-adjusted ratio can be used to more accurately predict anterior tooth dimensions necessary to achieve proper occlusion.

Influence of clinicians' experience and gender on extraction decision in orthodontics.

OBJECTIVE: To determine whether, in Class I borderline cases, experienced orthodontists choose nonextraction treatment more frequently than do orthodontists with less experience. A secondary aim was to evaluate whether clinicians' gender and place of education play a role in extraction decision making. MATERIALS AND METHODS: An online survey was developed using three Class I borderline patient cases. The survey included questions about clinicians' demographics as well as questions about the selected cases. The survey was distributed to approximately 2000 clinicians through the American Association of Orthodontics. RESULTS: Of the 253 responses collected, a trend was observed wherein clinicians with more than 15 years of experience preferred an extraction treatment option more frequently than did clinicians with less than 5 years of experience. There was no association between gender and place of education and the decision to extract in the selected borderline cases. Crowding, patient's profile, and mandibular incisor inclination were among the top three reasons chosen by clinicians for both the extraction and nonextraction treatment decisions. CONCLUSIONS: A trend was observed in which clinicians with more experience chose an extraction treatment option more frequently in borderline cases than did those with less experience. Clinicians' gender did not play a role in extraction decision making.

Assessing the feasibility of yttria-stabilized zirconia in novel designs as mandibular anterior fixed lingual retention after orthodontic treatment.

INTRODUCTION: The purpose of this study is to explore the feasibility of yttria-stabilized zirconia (Y-TZP) in fixed lingual retention as an alternative to stainless steel. METHODS: Exploratory Y-TZP specimens were milled to establish design parameters. Next, the specimens were milled according to ASTM standard C1161-13 and subjected to 4-point flexural tests to determine material properties. Finite element analysis was used to evaluate 9 novel cross-sectional designs, which were compared with stainless steel wire. Each design was analyzed under loading conditions to determine von Mises and bond stresses. The most promising design was fabricated to assess the accuracy and precision of current CAD/CAM milling technology. RESULTS: The superior design had a 1.0 × 0.5 mm semielliptical cross-section and was shown to be fabricated reliably. Overall, the milling indicated a maximum percent standard deviation of 9.3 and maximum percent error of 13.5 with a cost of $30 per specimen. CONCLUSIONS: Y-TZP can be reliably milled to dimensions comparable with currently available metallic retainer wires. Further research is necessary to determine the success of the bonding protocol and the clinical longevity of Y-TZP fixed retainers. Advanced technology is necessary to connect the intraoral scan to an esthetic and patient-specific Y-TZP fixed retainer.

Racial disparities in orthodontic service use for Medicaid-enrolled children: An evaluation of the Washington Medicaid program.

INTRODUCTION: We assessed the relationship between race and orthodontic service use for Medicaid-enrolled children. METHODS: This cross-sectional study focused on 570,364 Medicaid-enrolled children in Washington state, ages 6 to 19 years. The main predictor variable was self-reported race (white vs nonwhite). The outcome variable was orthodontic service use, defined as children who were preauthorized for orthodontic treatment by Medicaid in 2012 and subsequently received orthodontic records and initiated treatment. Logistic regression models were used to test the hypothesis that nonwhites are less likely to use orthodontic care than are whites. RESULTS: A total of 8223 children were approved by Medicaid for orthodontic treatment, and 7313 received records and began treatment. Nonwhites were significantly more likely to use orthodontic care than were whites (odds ratio [OR] = 1.18; 95% confidence interval [CI] = 1.02, 1.36; P = 0.031). Hispanic nonwhite children were more likely to use orthodontic care than were non-Hispanic white children (OR = 1.42; 95% CI = 1.18, 1.70; P <0.001). CONCLUSIONS: In 2012, nonwhite children in the Washington Medicaid program were significantly more likely to use orthodontic care than were white children. The Washington Medicaid program demonstrates a potential model for addressing racial disparities in orthodontic service use. Future research should identify mechanisms underlying these findings and continue to monitor orthodontic service use for minority children in Medicaid.

Stability of deep-bite correction: A systematic review.

OBJECTIVES: Deep bite occurs in about 15% to 20% of the US population. Currently, it is unknown which types of correction are most efficient or stable. The purpose of this systematic review was to investigate factors related to stability of deep-bite correction. MATERIALS AND METHODS: An electronic search of 4 databases was performed from January 1, 1966 to June 27, 2012. Studies were considered for inclusion if they reported on deep bite samples that underwent orthodontic treatment in the permanent dentition. Records were required at the initial, posttreatment, and 1-year posttreatment times. Hand searching of reference lists of the included studies was performed. Data were abstracted using custom forms, and risk of bias was assessed using a modified Newcastle-Ottawa Scale. RESULTS: Twenty-six studies met the inclusion criteria. Most were case series, with considerable potential for bias. The significant heterogeneity of the studies precluded meta-analyses, and only descriptive statistics and stratified comparisons were reported. On average, patients underwent significant overbite improvement during treatment, and most of the correction was maintained long-term. Across all studies, the mean initial overbite, posttreatment overbite, and long-term overbite were 5.3, 2.6, and 3.4 mm, respectively. Initial severity appeared to be related to long-term stability. However, this relationship was difficult to isolate from other factors. The length of follow-up did not appear to be related to the amount of relapse. CONCLUSIONS: Although the quality of the current evidence is not high, patients with deep-bite malocclusion appear to undergo relatively successful treatment, and most of the correction appears to be stable.

External apical root resorption in patients treated by serial extractions followed by mechanotherapy.

INTRODUCTION: In the course of orthodontic treatment with serial extractions (SE), spontaneous unraveling of crowded incisors occurs. It was hypothesized that SE followed by mechanotherapy will cause less external apical root resorption (EARR) than orthodontic treatment with late extractions (LE). METHODS: The records of 24 patients who underwent SE and mechanotherapy and 24 control patients who underwent LE and mechanotherapy were examined. The groups were matched for sex, central incisor root development and morphology, malocclusion class, ANB angle, and overjet. Lateral cephalograms taken before mechanotherapy (T1) and after mechanotherapy (T2) were traced and superimposed on the palatal plane with registration on the osseous details superior to the maxillary incisors and on the palatal curve. The T1 and T2 central incisor lengths, changes in the axial inclination, and horizontal and vertical apical movements were measured. RESULTS: The tooth lengths in both groups were reduced: the EARR values were 1.8 mm (± 1.1) in the SE group and 2.1 mm (± 1.4) in the LE group, and the difference between the groups was not significant. The movements of the teeth in both groups were similar in absolute values. CONCLUSIONS: The spontaneous unraveling of incisor crowding with SE treatment does not prevent the common EARR seen in patients treated with LE, when the patients are treated by mechanotherapy after the SE.

Bone volume, tooth volume, and incisor relapse: a 3-dimensional analysis of orthodontic stability.

INTRODUCTION: Orthodontic relapse is a common and significant problem. Few risk factors have been identified, and the role of bone has only recently been investigated. The purpose of this study was to examine the influence of alveolar bone volume and tooth volume on dental relapse. METHODS: The sample was chosen from the postretention database at the Department of Orthodontics of the University of Washington in Seattle. Based on the 10-year postretention (T3) irregularity index (II), 40 relapse subjects (T3 II > 6 mm) and the 40 most stable subjects (lowest T3 II < 1.5 mm) were identified for the study. Cone-beam computed tomography (CBCT) scans were taken of the posttreatment (T2) models. Total volume (V) was defined laterally by the distal contact points of the canines and vertically by the cusp tips of the canines to a depth 7 mm below the most inferior gingival margin. Alveolar volume (AV) was defined as the region below a vertical line at the most inferior gingival margin and tooth volume (TV) as the region above that line. The ratio TV:AV was calculated. Logistic regression analysis was used to determine the association between relapse and AV, and to adjust for potentially confounding variables (TV, initial II, sex, age, retention time, and postretention time). Mandibular cortical thickness (CT) measured on T2 lateral cephalograms was used as another measure of bone quantity. Nine patients from the graduate orthodontic clinic who had pretreatment CBCT scans were identified. V, AV, and TV were measured on both the in-vivo scans and the scans of their dental casts to verify the method. RESULTS: The relapse group had significantly greater V and AV and significantly lower CT. TV:AV was not different between the groups. T2 II was found to be a significant predictor of relapse based on logistic regression analysis, whereas AV was not. CT was poorly correlated with AV. V and AV were highly correlated between in-vivo scans and dental cast scans, whereas TV approached significance. CONCLUSIONS: Although postretention relapse was associated with increased V and AV, when other variables were controlled, bone volume was not a significant predictor of relapse.

Interceptive orthodontic treatment improves malocclusions over no treatment, but does not produce finished-quality results.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Effectiveness of interceptive orthodontic treatment in reducing malocclusions. King GJ, Brudvik P. Am J Orthod Dentofacial Orthop 2010;137:18-25. REVIEWER: Anne-Marie Bollen, DDS, MS, PhD. PURPOSE/QUESTION: The purpose of this study was to investigate the effectiveness of interceptive treatment. SOURCE OF FUNDING: National Institute of Dental and Craniofacial Research (NIDCR grant #U54DE14254). TYPE OF STUDY/DESIGN: A retrospective cohort study. LEVEL OF EVIDENCE: Level 2: Limited-quality, patient-oriented evidence. STRENGTH OF RECOMMENDATION GRADE: Not applicable.

Relapse of mandibular incisor alignment is not associated with the total posttreatment mandibular rotation.

INTRODUCTION: Our objective was to determine whether total posttreatment mandibular rotation is associated with mandibular incisor crowding after retention. METHODS: Mandibular incisor irregularity (II) at least 10 years out of retention (T3) measured on dental casts from the postretention database at the University of Washington in Seattle was used to define subjects (II ≥6 mm, relapse group) and controls (II ≤3.5 mm, stable group). After matching patients and controls for the pretreatment II, the relapse group consisted of 33 subjects (17 boys, 16 girls; age at the end of treatment [T2], 15.0 years; follow-up, 16.8 years), and the stable group comprised 36 subjects (11 boys, 25 girls; age at T2, 16.0 years; follow-up, 15.1 years). On cephalograms taken at T2 and T3, facial morphology was evaluated, and total posttreatment mandibular rotation was measured with a structural method. Logistic regression analyses were used to determine the association between relapse and amount of total mandibular rotation. The models were adjusted for potentially confounding variables (age at T2, sex, length of follow-up, and intercanine width change during treatment). RESULTS: No association between total posttreatment mandibular rotation and relapse was found (P = 0.515). Total mandibular rotations were comparable in the relapse and stable groups (P = 0.386). Age at T2 was found to be correlated with long-term incisor stability (P = 0.030). Sex and intercanine width change during treatment were not related to relapse (P = 0.225 and P = 0.264, respectively). CONCLUSIONS: Total mandibular rotation is not associated with relapse of the mandibular incisors. Posttreatment skeletal and dental growth changes were comparable in the relapse and stable groups.

Effectiveness of the cervical vertebral maturation method to predict postpeak circumpubertal growth of craniofacial structures.

INTRODUCTION: Our aim was to assess effectiveness of the cervical vertebral maturation (CVM) method to predict circumpubertal craniofacial growth in the postpeak period. METHODS: The CVM stage was determined in 176 subjects (51 adolescent boys and 125 adolescent girls) on cephalograms taken at the end of treatment (T2; mean ages, 15.75 years [boys] and 15.23 years [girls]) in subjects from the postretention database at the University of Washington in Seattle. Craniofacial growth was evaluated from the following measurements on cephalograms at T2 and end of follow-up (T3) (mean ages, 29.01 years [men] and 28.08 years [women]): condylion to gnathion, condylion to gonion, gonion to gnathion, sella to gnathion, nasion to menton, anterior nasal spine to menton, and sella to gonion. The change of each variable from T2 to T3 was assessed with paired t tests. Parametric (t tests or analysis of variance [ANOVA]) or nonparametric (Mann-Whitney or Kruskal-Wallis) tests were used to detect intergroup differences. RESULTS: One hundred eight subjects (35 boys, 73 girls) demonstrated CVM stage 3, 56 (16 boys, 40 girls) were in CVM stage 4, and 12 (all girls) were in CVM stage 5 at T2. Intrasex comparisons showed that boys in CVM stages 3 and 4 could be differentiated regarding changes of all variables. In the girls, only those in CVM stages 3 and 4 could be differentiated based on the amount of changes of 2 measurements: condylion to gonion and sella to gonion. Intersex comparisons showed that boys in CVM stage 3 had significantly more changes than girls (P <0.01). Boys in CVM stage 4 showed significant differences compared with girls in CVM stage 4 for only 2 variables (sella to gonion and condylion to gonion; P <0.001 and P = 0.012, respectively). CONCLUSIONS: The CVM method was modestly effective in determining the amount of postpeak circumpubertal craniofacial growth.

Treatment response and stability of slow maxillary expansion using Haas, hyrax, and quad-helix appliances: a retrospective study.

INTRODUCTION: In this retrospective study, we evaluated the short- and long-term effects of slow maxillary expansion with Haas, hyrax, and quad-helix appliances on posterior crossbite (PXB) correction stability, and maxillary intermolar width and angulation, in the deciduous or early mixed dentition. METHODS: The inclusion criteria were models and treatment notes of patients with PXB at the start of treatment (T1), after PXB correction (T2), and at least 2 years posttreatment (T3). Exclusion criteria were craniofacial anomalies, fixed appliance use, or more than 1 expander type. From 312 consecutive expansion patients, 74 Haas, 41 hyrax, and 45 quad-helix subjects were evaluated regarding PXB correction, intermolar width, and angulation and compared with published norms to separate treatment effects from growth. The mean ages at T1, T2, and T3 were 8, 9, and 13 years. RESULTS: There were no significant differences in PXB correction stability or treatment response at T2 and T3 among the 3 expanders. Expansion increased intermolar width by 5 mm and tipped each molar by 2.3 degrees. At least 2 years after expander removal, molar width decreased by 1.3 mm, and the molars uprighted by 6 degrees. Compared with noncrossbite norms, PXB subjects had narrower intermolar width before treatment and greater width after expansion, and were slightly wider at least 2 years posttreatment. Both younger age at T1 and retainer use resulted in statistically greater intermolar width at T3. CONCLUSIONS: Eighty-four percent of PXB correction remained with about one third of the initial expansion lost; retainer use and early treatment provided increased intermolar width. Haas, hyrax, and quad-helix appliances were equally effective. Slow maxillary expansion altered the PXB patients' maxillary widths from narrower to slightly wider than the widths of the noncrossbite norms.

Effects of malocclusions and orthodontics on periodontal health: evidence from a systematic review.

Many patients seek orthodontic treatment for esthetic improvement. These patients mostly present with mal-alignment of the anterior teeth. The positive effects of orthodontic treatment on their appearance and self-esteem are easy to envision. However, does orthodontic treatment provide dental health benefits in addition to the esthetic benefits? Do malocclusions harm the periodontium? Is correcting malocclusions with orthodontic treatment beneficial for periodontal health? The purpose of this study is to present evidence available on this topic. Two systematic reviews were conducted to address these questions: does a malocclusion affect periodontal health, and does orthodontic treatment affect periodontal health? Inclusion and exclusion criteria were established for both reviews, and an electronic search and a hand search were conducted. Several papers were included in both reviews, but the overall quality of the studies was weak. The first review found a correlation between the presence of a malocclusion and periodontal disease. Subjects with greater malocclusion have more severe periodontal disease. This may be dependent on oral health status. One should keep in mind that an association does not necessarily mean causation. The second review identified an absence of reliable evidence on the effects of orthodontic treatment on periodontal health. The existing low-quality evidence suggests that orthodontic therapy results in small detrimental effects to the periodontium. The results of both reviews do not warrant recommendation for orthodontic treatment to prevent future periodontal problems, except for specific unusual malocclusions.

Effects of posttreatment skeletal maturity measured with the cervical vertebral maturation method on incisor alignment relapse.

INTRODUCTION: Our aim was to test the hypothesis that relapse of incisor alignment is associated with skeletal maturity at the end of treatment, as assessed with the cervical vertebral maturation (CVM) method. METHODS: This was a case-control study with information from the postretention database at the University of Washington. Mandibular incisor irregularity (II) at least 10 years out of retention (T3) was used to define the subjects (II >6 mm, relapse group) and the controls (II <3.5 mm, stable group). The following model measurements were made: II at pretreatment (T1), II at posttreatment (T2), and intercanine width at T1 and T2. On cephalograms taken T2, the CVM status was determined. Logistic regression analyses were used to determine the association between relapse and CVM status after treatment. The models were adjusted for potentially confounding variables (II at pretreatment and posttreatment, intercanine width change during treatment, sex, age at T2, and treatment alternatives). RESULTS: No association between CVM stage at T2 and relapse was found (P = 0.89). Both groups had similar distributions of the CVM stages (P >0.05). Pretreatment II and postretention time were found to be correlated with long-term incisor stability (P = 0.007 and 0.034, respectively). Sex was not related to relapse (P = 0.33). CONCLUSIONS: Maturity of craniofacial structures at the end of treatment evaluated with the CVM method is not associated with long-term stability of incisor alignment.