Long-term effects produced by early treatment of Class III malocclusion with rapid maxillary expansion and facemask followed by fixed appliances: A multicentre retro-prospective controlled study.

OBJECTIVE: To assess the short- and long-term dentoskeletal effects of early Class III treatment with rapid maxillary expansion and facemask (RME/FM) followed by fixed appliances. MATERIALS AND METHODS: A total of 44 patients (27 females, 17 males) treated consecutively with RME/FM were included from the archives of 3 centres. Three lateral cephalograms were available: T0 (before the start of RME/FM therapy, mean age 8.1 ± 1.8 years), T1 (immediately after RME/FM, mean age 9.8 ± 1.6 years), and T2 (long-term observation, mean age 19.5 ± 1.6 years). A control group of 17 untreated Class III subjects (12 females and 5 males) also was selected. Between-group statistical comparisons were performed with ANCOVA. RESULTS: No statistically significant differences for any of the cephalometric variables were found at T0. In the short term, the treated group showed significant improvements in ANB (+2.9°), Wits appraisal (+2.7 mm), SNA (+1.8°) and SNB (-1.1°). A significant closure of CoGoMe angle (-1.3°) associated with smaller increments along Co-Gn (-2.4 mm) also was found together with a significant increase in intermaxillary divergence (+1.3°). In the long-term, significant improvements in ANB (+2.6°), Wits appraisal (+2.7 mm) and SNB (-1.7°) were recorded together with a significant closure of the CoGoMe angle (-2.9°). No significant long-term changes in vertical skeletal relationships were found. CONCLUSIONS: RME/FM therapy was effective in improving Class III dentoskeletal relationships in the short term. These changes remained stable in the long-term due mainly to favourable mandibular changes.

Three-dimensional comparison of bone-borne and tooth-bone-borne maxillary expansion in young adults with maxillary skeletal deficiency.

OBJECTIVE: To compare the transverse dental and skeletal changes in patients treated with bone-anchored palatal expander (bone-borne, BB) compared to patients treated with tooth and bone-anchored palatal expanders (tooth-bone-borne, TBB) using cone-beam computer tomography (CBCT) and 3D image analysis. METHODS: The sample comprised 30 patients with transverse maxillary discrepancy treated with two different types of appliances: bone-borne (Group BB) and tooth-bone-borne (Group TBB) expanders. CBCT scans were acquired before (T1) and after completion of maxillary expansion (T2); the interval was 5.4 ± 3.4 and 6.2 ± 2.1 months between the T1 and the T2 scans of Group TBB (tooth-bone-borne) and Group BB (bone-borne), respectively. Transverse, anteroposterior and vertical linear and angular three-dimensional dentoskeletal changes were assessed after cranial base superimposition. RESULTS: Both groups displayed marked transverse skeletal expansion with a greater ratio of skeletal to dental changes. Greater changes at the nasal cavity, zygoma and orbital levels were found in Group BB. A relatively parallel sutural opening in an anterior-posterior direction was observed in Group TBB; however, the Group BB presented a somewhat triangular (V-shaped) opening of the suture that was wider anteriorly. Small downward-forward displacements were observed in both groups. Asymmetric expansion occurred in approximately 50% of the patients in both groups. CONCLUSION: Greater skeletal vs dental expansion ratio and expansion of the circummaxillary regions were found in Group BB, the group in which a bone-borne expander was used. Both groups presented skeletal and dental changes, with a similar amount of posterior palate expansion. Asymmetric expansion was observed in both groups.

Three-dimensional Evaluation of the Carriere Motion 3D Appliance in the treatment of Class II malocclusion.

INTRODUCTION: This study aimed to quantify the outcomes of adolescent patients with Class II malocclusion treated with the Carriere Motion 3D Appliance (CMA) combined with full fixed appliances. METHODS: Cone-beam computed tomography scans of 22 patients were available before orthodontic treatment (T1), at removal of the CMA (T2), and posttreatment (T3). The average age of the patients was 13.5 ± 1.6 years at T1, 14.1 ± 0.2 years at T2, and 15.6 ± 0.5 years at T3. The 3-dimensional image analysis procedures were performed using ITK-SNAP (version 3.6.0; www.itksnap.org, Hatfield, Pa) and SlicerCMF (version 4.11.0; http://www.slicer.org, Cambridge, Mass); skeletal and dentoalveolar changes relative to cranial base, maxillary, and mandibular regional superimpositions were evaluated. RESULTS: Changes were analyzed with 1 sample t tests using the mean differences during the CMA phase (T1 to T2) and total treatment time (T1 to T3). Significant skeletal changes included a slight reduction of ANB from T1 to T3, mandibular growth (Co-Gn increment of 1.2 mm and 3.3 mm from T1 to T2 and T1 to T3, respectively), inferior displacement of point A, and anterior and inferior displacement of point B. The mandibular plane did not change significantly during treatment. During the CMA treatment, posterior tipping and distal rotation of the maxillary molars, tip back and inferior displacement of the maxillary canines, significant mesial rotation, and superior displacement of the mandibular molars were observed. These movements rebounded during the full fixed appliance phase except for the molar and canine vertical displacements. Clinically significant dental changes during treatment included a reduction in overjet and overbite, Class II correction of the molar and canine relationship, and proclination of the mandibular incisors. CONCLUSIONS: The CMA is an effective treatment modality for Class II correction in growing patients because of a combination of mesial movement of the mandibular molar, distal rotation of the maxillary molar, and anterior displacement of the mandible.

Variations in maxillary second molar position of untreated subjects with normal occlusions: A long-term observational study.

INTRODUCTION: The purpose of the present study was to evaluate the long-term variations in maxillary second molar position in untreated subjects with normal occlusion. SETTING AND SAMPLE POPULATION: A sample of 39 subjects (18 females and 21 males) selected from the University of Michigan Growth Study (UMGS) was followed longitudinally with digital dental casts at 3 observation times: T1, when the maxillary permanent second molars were fully erupted, T2, last observation available in the longitudinal series (38 subjects), and T3, at least 20 years after T2 (12 subjects). MATERIALS AND METHODS: Digital measurements were recorded with an open-source software. Outcome variables were sagittal and transverse inclinations of the upper second molars. Two mixed-effect models were performed. RESULTS: The maxillary second molars had a distolingual inclination at T1, T2 and T3. Sagittal and transverse inclination showed progressive significant uprighting from T1 through T3 (P < .001). From T1 to T2, the adjusted difference in sagittal crown inclination was 8.0° (95% CI from 6.5° to 9.6°; P < .001). From T2 to T3, the adjusted difference was 5.5° (95% CI from 3.0° to 8.1°; P < .001). From T1 to T2, the adjusted difference in transverse crown inclination was 1.9° (95% CI from 0.4° to 3.5°; P = .011). From T2 to T3, the adjusted difference was 6.0° (95% CI from 3.4° to 8.5°; P < .001). CONCLUSIONS: Along with age, maxillary second molars showed a progressive significant uprighting with a decrease in the distal and lingual inclinations.

Three-dimensional evaluation of skeletal and dental effects of treatment with maxillary skeletal expansion.

INTRODUCTION: The objective was to determine the skeletal and dental changes with microimplant assisted rapid palatal expansion (MARPE) appliances in growing (GR) and nongrowing (NG) patients using cone-beam computed tomography and 3-dimensional imaging analysis. METHODS: The sample consisted of 25 patients with transverse maxillary discrepancy treated with a maxillary skeletal expander, a type of MARPE appliance. Cone-beam computed tomography scans were taken before and after maxillary expansion; the interval was 6.0 ± 4.3 months. The sample was divided into GR and NG groups using cervical vertebral and midpalatal suture maturation. Linear and angular 3-dimensional dentoskeletal changes were assessed after cranial base superimposition. Groups were compared with independent-samples t test (P <0.05). RESULTS: Both groups displayed marked transverse changes with a similar ratio of skeletal to dental transverse changes and parallel sutural opening from the posterior nasal spine-anterior nasal spine; a similar amount of expansion occurred in the anterior and the posterior regions of the maxilla. The maxilla expanded skeletally without rotational displacements in both groups. The small downward-forward displacements were similar in both groups, except that the GR group had a significantly greater vertical displacement of the canines (GR, 1.7 ±1.0 mm; NG, 0.6 ± 0.8 mm; P = 0.02) and anterior nasal spine (GR, 1.1 ± 0.6 mm; NG, 0.5 ± 0.5 mm; P = 0.004). CONCLUSIONS: Treatment of patients with MARPE appliance is effective in GR and NG patients. Although greater skeletal and dental changes were observed in GR patients, a similar ratio of skeletal to dental transverse changes was observed in both groups.

Predicting mandibular growth based on CVM stage and gender and with chronological age as a curvilinear variable.

OBJECTIVE: The aim of this study was to develop a prediction model that combines the information derived from chronological age (analysed as a curvilinear variable), gender and the CVM method to predict mandibular growth. SETTINGS AND SAMPLE POPULATION: 50 participants (29 females, 21 males) were selected from the AAOF Craniofacial Growth Legacy Collection, the Michigan Growth Study and the Denver Child Growth study. MATERIALS AND METHODS: In this investigation, 456 lateral cephalograms were analysed by applying a mixed effect model. The outcome variable was the annualized increment in total mandibular length (Co-Gn) during the year following the lateral cephalogram on which the cervical stage and chronological age were evaluated. The predictive variables were chronological age up to the fifth order, gender, stage of cervical vertebral maturation, as well as interactions between age and gender, age and cervical stage, and gender and cervical stage. RESULTS: Cervical stage, chronological age up to the fourth order, gender, and the interaction between age and gender were significant predictors of annualized increments in mandibular length. The annualized increment in Co-Gn was significantly greater for CS 3 when compared to all other cervical stages. Further, annualized increments in Co-Gn for CS 1 and CS 2 were significantly greater when compared to CS 5. CONCLUSIONS: Cervical stage, chronological age and gender can be used jointly to predict the annualized increment in mandibular growth. Cervical stage 3 exhibited the greatest annualized increase in mandibular length.

Prognostic approach to Class III malocclusion through case-based reasoning.

OBJECTIVE: This investigation evaluates the evidence of case-based reasoning (CBR) in providing additional information on the prediction of future Class III craniofacial growth. SETTINGS AND SAMPLE POPULATION: The craniofacial characteristics of 104 untreated Class III subjects (7-17 years of age), monitored with two lateral cephalograms obtained during the growth process, were evaluated. MATERIALS AND METHODS: Data were compared with the skeletal characteristics of subjects who showed a high degree of skeletal imbalance ('prototypes') obtained from a large data set of 1263 Class III cross-sectional subjects (7-17 years of age). RESULTS: The degree of similarity of longitudinal subjects with the most unbalanced prototypes allowed the identification of subjects who would develop a subsequent unfavourable skeletal growth (accuracy: 81%). The angle between the palatal plane and the sella-nasion line (PP-SN angle) and the Wits appraisal were two additional craniofacial features involved in the early prediction of the adverse progression of the Class III skeletal imbalance. CONCLUSIONS: Case-based reasoning methodology, which uses a personalized inference method, may bring additional information to approximate the skeletal progression of Class III malocclusion.

Three-dimensional mandibular dental changes with aging.

INTRODUCTION: This study aimed to evaluate the 3-dimensional (3D) mandibular dental changes over 42 years using the registration of digital models. METHODS: The sample comprised digital dental models of 8 untreated subjects (4 males and 4 females) with normal occlusion measured longitudinally at ages 17 years (T1) and 60 years (T2). Using 13 landmarks placed on the mucogingival junction, we registered the T2 model on the T1 model. Three-dimensional changes in the position of the landmarks on the buccal cusp tip of the posterior teeth and incisal edge of the central incisors were measured by 2 examiners. Registration and measurements were performed using SlicerCMF (version 3.1; http://www.slicer.org) software. Intra- and interrater agreements were evaluated using intraclass correlation coefficients and the Bland-Altman method. One-sample t tests were used for evaluating interphase 3D dental changes (P <0.05). RESULTS: Adequate intra- and interrater reproducibility was found. From T1 to T2, the mandibular teeth showed significant 3D positional changes. A significant dental eruption relative to the mucogingival junction was observed for the anterior and posterior teeth. Anteroposterior movements of mandibular teeth were not significant except for the right molar that drifted mesially. Transverse movements included slight lingual tipping at canines and premolars regions. CONCLUSIONS: Dental changes in untreated normal occlusion were very slight from early to mature adulthood. The eruption of the mandibular teeth was the most consistent finding. A tendency for mesial movement of molars and lingual movement of first premolars and canines was observed in the mandible during the aging process.

A multilevel analysis of craniofacial growth in subjects with untreated Class III malocclusion.

OBJECTIVE: To analyse the craniofacial growth of a long-term semi-longitudinal sample of Caucasian subjects with untreated Class III malocclusion. SETTING AND SAMPLE POPULATION: A total of 144 Caucasian subjects (of North American and Italian origin) with untreated Class III malocclusion. MATERIALS AND METHODS: Subjects aged 2 years and 9 months up to 21 years and 7 months were selected. A multilevel model was used to calculate growth curves for ten variables for both each individual subject and for the whole sample. RESULTS: There was a statistically significant increase for total mandibular length (Co-Gn. T2-T1 = 8.4 mm), midfacial length (Co-A. T2-T1 = 3.4 mm) and lower anterior facial height (ANS-Me. T2-T1 = 3.8 mm). The multilevel analysis showed two points of acceleration of growth (about 3-5 years of age and 11-15 years of age) for seven out of ten variables. For Co-Gn and Co-A variables, males presented points of maximum growth delayed by 1 year in comparison with females, with a greater duration (1 year longer) and a greater total growth of about 5 mm. Active mandibular growth continued for a long time after the pubertal spurt: increases in mandibular length ended at about 17 years of age in females and at 21 years and 7 months in males. CONCLUSIONS: Untreated Class III malocclusion showed a specific growth curve, especially for the mandible, whose excesses added up over time. In males, the amounts of mandibular and midfacial growth during the whole observation time were greater and lasted longer than in females.

Computer-aided heuristics in orthodontics.

INTRODUCTION: During the decision-making process, physicians rely on heuristics that consist of simple, useful procedures for solving problems, intuitive shortcuts that produce reliable decisions based on limited information. In clinical situations characterized by a high degree of uncertainty such as those encountered in orthodontics, cognitive biases and judgment errors related to heuristics are not uncommon. This study aimed at promoting trust in the effective interface between the intuitive reasoning of the orthodontic practitioner and the computational heuristics emerging from simple statistical models. METHODS: We propose an integrative model based on the interaction between clinical reasoning and 2 computational tools, cluster analysis and fast-and-frugal trees, to extract a structured craniofacial representation of untreated subjects with Class III malocclusion and to forecast the worsening of the malocclusion over time. RESULTS: Cluster analysis of cephalometric values from 144 growing subjects with Class III malocclusion followed longitudinally (T1: mean age, 10.2 ± 1.9 years; T2: mean age, 13.8 ± 2.7 years) produced 3 morphologic subgroups with predominant sagittal, vertical, and slight maxillomandibular imbalances. Fast-and-frugal trees applied to different subgroups extracted heuristics that improved the prediction of key features associated with adverse craniofacial growth. CONCLUSIONS: Provided that cephalometric values are placed in the appropriate framework, the matching between simple and fast computational approaches and clinical reasoning could help the intuitive logic, perception, and cognitive inferences of orthodontic practitioners on the outcome of patients affected by Class III disharmony, decreasing errors associated with flawed judgments and improving the accuracy of decision making.

Maxillary expander with differential opening vs Hyrax expander: A randomized clinical trial.

INTRODUCTION: The aim of this 2-arm parallel trial was to compare the dentoskeletal effects of the expander with differential opening (EDO) and the Hyrax expander in the mixed dentition. METHODS: Patients aged 7-11 years with maxillary dental arch constriction and Class I or Class II sagittal relationships were randomly allocated into 2 study groups. The experimental group comprised 22 patients (10 males, 12 females) with a mean age of 8.46 years treated with the EDO. The comparison group was composed of 24 patients (6 males, 18 females), mean age of 8.92 years treated with the conventional Hyrax expander. One complete turn per day for 6 days was performed for the posterior screw of the EDO and for the Hyrax expander. The anterior screw of the EDO was activated 1 complete turn per day for 10 days. The primary outcomes were the anterior opening of the midpalatal suture, changes on the interincisal diastema width, maxillary dental arch widths, arch perimeter, arch length, palatal depth, inclination of maxillary posterior teeth and on dental arch shape, and the amount of differential expansion in the anterior region compared with the posterior region of the maxillary dental arch. Computer-generated randomization was used. Allocation was concealed with sequentially, numbered, sealed, and opaque envelopes. Blinding was applicable for outcome assessment only. Occlusal radiographs of the maxilla were obtained at the end of the active expansion phase (T2). Intraoral photographs were obtained immediately pre-expansion (T1) and at T2. Digital dental models were obtained at T1 and 6 months after the active expansion period (T3). Intergroup comparisons of T1-T2 changes were performed using multiple linear regression analysis (P < 0.05). The independent variables were both treatment and the starting forms. Bonferroni correction for multiple tests was applied. RESULTS: The experimental group showed a significantly greater opening of the anterior region of the midpalatal suture, a greater increase of the interincisal diastema width, and greater increases of the intercanine distance and inter-first deciduous molar distance than the Hyrax expander. The experimental group showed a significant differential expansion between the anterior and posterior regions, whereas the Hyrax group produced a similar expansion in the canine and molar regions. Serious harm was not observed. CONCLUSIONS: The EDO was capable of promoting greater orthopedic and dental changes in the anterior region of the maxilla than the conventional Hyrax expander. Similarity between the 2 expanders was observed for changes in the posterior region width, arch perimeter, arch length, palatal depth, and posterior teeth inclination.

Three-dimensional changes of the upper airway in patients with Class II malocclusion treated with the Herbst appliance: A cone-beam computed tomography study.

INTRODUCTION: This study aimed to determine the volumetric effects on the upper airways of growing patients with Class II malocclusion treated with the Herbst appliance (HA). METHODS: Volumetric measurements of the upper airways of 42 skeletal Class II malocclusion patients (mean age: 13.8 ± 1.2 years; ranging from 12.0 to 16.9 years) were assessed using cone-beam computed tomography scans acquired before treatment (T0) and approximately 1 year later (T1). The sample comprised a Herbst appliance group (HA group [HAG]; n = 24), and a comparison group (comparison group [CG]; n = 18) of orthodontic patients who had received dental treatments other than mandibular advancement with dentofacial orthopedics. RESULTS: In CG, nasopharynx and oropharynx volumes decreased slightly during the observation period (9% and 3%, respectively), whereas the nasal cavity volume increased significantly (12%; P = 0.046). In HAG, there was an increase in the volume of all regions (nasal cavity, 5.5%; nasopharynx, 11.7%; and oropharynx, 29.7%). However, only the oropharynx showed a statistically significant increase (P = 0.003), presenting significant volumetric changes along the time (T1-T0) in HAG. CONCLUSION: Mandibular advancement with the HA significantly increased the volume of the oropharynx, but no significant volumetric modifications were observed in the nasal cavity and nasopharynx.

Condyle-glenoid fossa relationship after Herbst appliance treatment during two stages of craniofacial skeletal maturation: A retrospective study.

OBJECTIVES: To perform a three-dimensional evaluation of the position of the condyles in patients treated with Herbst appliance (HA) in two stages of cervical vertebral maturation. SETTING AND SAMPLE POPULATION: Retrospective case-control study. Pubertal Herbst group (PHG; n = 24, mean age 14.5 years, CS 3 and CS 4) and pre-pubertal Herbst group (PPHG; n = 17, mean age 9.9 years, CS 1 and CS 2) were contrasted with comparison groups of non-orthopaedically treated Class II patients in pubertal (PCG; n = 17, mean age 13.9 years) and pre-pubertal maturational stages (PPCG; n = 18, mean age 10.6 years). MATERIALS AND METHODS: Cone-beam computer tomography scans were taken before treatment (T0) and at T1 after 8 to 12 months. Point-to-point measurements of the displacement of the condyles between T0 and T1, relative to the glenoid fossae, were performed in the X, Y, Z and 3D perspectives. Qualitative assessments using semi-transparent overlays and colour mapping also were produced. RESULTS: The displacement of the condyles within the glenoid fossae in the treated groups was small (<0.75 mm; P > .05). Relative to the glenoid fossa, condylar position at T1 was similar to T0 in pre-pubertal and pubertal groups (P > .05). Similar condylar rotations from T0 to T1 were observed in Herbst and comparison groups, and no significant difference was found between pre-pubertal and pubertal patients. CONCLUSIONS: Regardless the stage of skeletal maturation, HA treatment did not change the condyle-glenoid fossa relationship.

Superimposition of maxillary digital models using the palatal rugae: Does ageing affect the reliability?

OBJECTIVES: The aim of this study was to evaluate the reliability of 3-dimensional maxillary dental changes using two methods of digital model superimposition. SETTING AND SAMPLE POPULATION: The Department of Orthodontics of Bauru Dental School, University of São Paulo and University of Michigan Craniofacial Growth Center. Fifteen subjects with normal occlusion. MATERIAL & METHODS: The sample was composed of digital study models of 15 normal occlusion subjects taken at 13 (T1), 18 (T2) and 60 years of age (T3). Using the software SlicerCMF 3.1, superimposition (registration) was conducted using 9 landmarks placed on the incisive papilla, second and third palatal rugae and 10 mm distal to the third palatal rugae. Two registration methods were compared: landmarks (LA) and regions of interest (ROI). Three-dimensional changes of landmarks on the buccal cusp tip of posterior teeth bilaterally and the incisal edge of the right central incisor were measured by three examiners. Intraclass correlation coefficients and Bland-Altman method evaluated intra- and inter-examiner agreements. RESULTS: Good or excellent intra-examiner agreement was found for T1-T2 and T2-T3 measurements using both registration methods. Inter-examiner agreements were good to excellent for T1-T2 measurements and poor to fair for most T2-T3 measurements. Mean T1-T2 differences were less than 0.5 mm for most measurements. CONCLUSION: Maxillary digital dental models of patients with normal occlusion superimposed on palatal rugae showed an adequate reliability for a 5-year interval comparison using landmarks or regions of interest. Lower than acceptable reproducibility using both superimposition methods was found for a 40-year interval comparison.

Obstructive sleep apnea and orthodontics: An American Association of Orthodontists White Paper.

The Board of Trustees of the American Association of Orthodontists asked a panel of medical and dental experts in sleep medicine and dental sleep medicine to create a document designed to offer guidance to practicing orthodontists on the suggested role of the specialty of orthodontics in the management of obstructive sleep apnea. This White Paper presents a summary of the Task Force's findings and recommendations.

Three-dimensional evaluation of the maxillary effects of two orthopaedic protocols for the treatment of Class III malocclusion: A prospective study.

OBJECTIVES: To compare the three-dimensional maxillary dentoskeletal effects of a modified alternate rapid maxillary expansion and constriction facemask protocol (Alt-RAMEC/FM) with the traditional rapid maxillary expansion facemask protocol (RME/FM) performed in deciduous or early mixed dentition Class III patients. SETTING AND SAMPLE POPULATION: Orthodontic Clinic of the Section of Dentistry of the Department of Surgery and Translational Medicine of the University of Florence. Thirty-four Class III patients were enrolled and allocated by alternating assignment to either Alt-RAMEC/FM or RME/FM therapy. MATERIALS AND METHODS: Prior to treatment, all patients were evaluated, and a cone beam computed tomography (CBCT) scan was acquired. After completion of the orthopaedic therapy (average interval 1.2 years), a follow-up CBCT scan was obtained. Anatomic landmark identification on the CBCTs and subsequent quantification of the changes were performed. The primary outcome variable was the anteroposterior displacement of the anterior nasal spine (ANS AP). The treatment groups were compared with independent samples t tests. RESULTS: The patients in the two treatment groups showed a similar degree of compliance. No statistically significant differences were recorded for any variable when comparing the Alt-RAMEC/FM and RME/FM groups. In particular, the between-group difference for ANS AP was 0.0 mm (95%CI: -0.6;0.7, P = 0.933). CONCLUSIONS: Both Alt-RAMEC/FM and RME/FM produced favourable orthopaedic changes in Class III growing patients. Neither protocol was superior to the other in terms of maxillary protraction effectiveness.

Treatment timing for functional jaw orthopaedics followed by fixed appliances: a controlled long-term study.

Objective: To evaluate the role of treatment timing on long-term dentoskeletal effects of Class II treatment with removable functional appliances followed by full-fixed appliance therapy. Materials and methods: A group of 46 patients (23 females and 23 males) with Class II malocclusion treated consecutively with either Bionator or Activator, followed by fixed appliances was compared with a matched control group of 31 subjects (16 females and 15 males) with untreated Class II malocclusion. The treated sample was evaluated at T1, start of treatment (mean age: 9.9 ± 1.3 years); T2, end of functional treatment and prior to fixed appliances (mean age: 11.9 ± 1.3 years); and T3, long-term observation (mean age: 18.3 ± 2.1 years). The treated and the control samples were divided into pre-pubertal and pubertal groups according to skeletal maturity observed at the start of treatment. Statistical comparisons were performed with independent sample t-tests. Results: When treatment was initiated before puberty, Class II correction was mostly confined to the dentoalveolar changes, with significant improvements of both overjet and molar relationships. On the other hand, treatment with the outset at puberty produced significant long-term improvement of sagittal skeletal relationships, which were mainly sustained by mandibular changes. Conclusions: Treatment with removable functional appliances (Bionator or Activator) followed by full-fixed appliances produced significant skeletal long-term changes when it begins at puberty. Prepubertal Class II treatment results primarily in dentoalveolar changes.

Understanding interactions among cephalometrics variables during growth in untreated Class III subjects.

OBJECTIVE: The aim of the present study was to apply a computational method commonly used in data mining discipline, classification trees (CTs), to evaluate the growth features in untreated Class III subjects. MATERIALS AND METHODS: CT was applied to data from 91 untreated Class III subjects (48 females and 43 males) and compared with the results of discriminant analysis (DA). For all subjects, lateral cephalograms were available at T1 (mean age 10.4 ± 2.0 years) and at T2 (mean age 15.4 ± 1.9 years). A cephalometric analysis comprising 11 variables was performed. The subjects were divided into two subgroups, unfavourable ('Bad') and favourable ('Good') growers, according to the quality of the skeletal growth rate in comparison with the normal craniofacial growth. RESULTS: CTs showed that the most informative attribute for the prediction of favourable/unfavourable skeletal growth was the SNA angle. Subjects with SNA values lower than 79.1 degrees showed a risk of 94 per cent of growing unfavourably. DA was able to select palatal plane to mandibular plane angle as predictors. DA, however, showed a statistically significant higher rate of misclassification when compared with CTs (40.7 per cent versus 12.1 per cent, binomial exact test: odds ratio = 6.20; P < 0.0001). CONCLUSIONS: CTs provided a valid measure of elucidating the effective contribution of craniofacial characteristics in predicting favourable/unfavourable growth in untreated Class III subjects.