Camouflage treatment guided by facial improvement in hyperdivergent skeletal class II malocclusion

Expert consensus on orthodontic treatment of protrusive facial deformities

Protrusive facial deformities, characterized by the forward displacement of the teeth and/or jaws beyond the normal range, affect a considerable portion of the population. The manifestations and morphological mechanisms of protrusive facial deformities are complex and diverse, requiring orthodontists to possess a high level of theoretical knowledge and practical experience in the relevant orthodontic field. To further optimize the correction of protrusive facial deformities, this consensus proposes that the morphological mechanisms and diagnosis of protrusive facial deformities should be analyzed and judged from multiple dimensions and factors to accurately formulate treatment plans. It emphasizes the use of orthodontic strategies, including jaw growth modification, tooth extraction or non-extraction for anterior teeth retraction, and maxillofacial vertical control. These strategies aim to reduce anterior teeth and lip protrusion, increase chin prominence, harmonize nasolabial and chin-lip relationships, and improve the facial profile of patients with protrusive facial deformities. For severe skeletal protrusive facial deformities, orthodontic-orthognathic combined treatment may be suggested. This consensus summarizes the theoretical knowledge and clinical experience of numerous renowned oral experts nationwide, offering reference strategies for the correction of protrusive facial deformities.

Associations between condylar height relative to occlusal plane and condylar osseous condition and TMJ loading based on 3D measurements and finite element analysis

To investigate the relationship between condylar height relative to occlusal plane (CHO) and condylar osseous condition and the changes of condylar stress loading before and after CHO modifications. The condylar osseous conditions of 434 temporomandibular joints (TMJ) were assessed and grouped. Measurements of anatomical parameters were performed on CT-based reconstructed 3D stomatognathic models. Differences in anatomical parameters of the jaws in the different groups were compared, and the correlation between the Angle α (representing the CHO ratio) and related parameters was investigated. A finite element model (FEM) was constructed using 3D finite element analysis (FEA). The Angle α was altered by modifying condylar position and the inclination of mandibular plane (MP) and occlusal plane (OP) based on the FEM to analyze condylar stress loading under different working conditions. There were differences in anatomical parameters among the different groups, with the smaller Angle α in the osseous destruction group. Angle α was negatively correlated with the inclination of MP and OP. The FEA illustrated condylar stress loading changed after modifying the Angle α by both two modalities. After modifying condylar position, the stress increased with the proximal movement of the condyle toward the OP. After changing the inclination of MP and OP, the stress increased with increasing inclinations. Changes in CHO correlate with condylar osseous condition, and distal movement of the condyle to the OP and reduction of MP and OP inclination may reduce TMJ stress overload. In clinical practice, it is advisable to assess patients for sufficient CHO ratio, as insufficiency in CHO may elevate the risk of TMJ stress overload. The CHO ratio could be modulated by changing the inclination of the OP.

Facial profile evaluation and prediction of skeletal class II patients during camouflage extraction treatment: a pilot study

BACKGROUND

The evaluation of the facial profile of skeletal Class II patients with camouflage treatment is of great importance for patients and orthodontists. The aim of this study is to explore the key factors in evaluating the facial profile esthetics and to predict the posttreatment facial profile esthetics of skeletal Class II extraction patients.

METHODS

124 skeletal Class II extraction patients were included. The pretreatment and posttreatment cephalograms were analyzed by a trained expert orthodontist. The facial profile esthetics of pretreatment and posttreatment lateral photographs were evaluated by 10 expert orthodontists using the visual analog scale (VAS). The correlation between subjective facial profile esthetics and objective cephalometric measurements was assessed. Three machine-learning methods were used to predict posttreatment facial profile esthetics.

RESULTS

The distances from lower and upper lip to the E plane and U1-APo showed the stronger correlation with profile esthetics. The changes in lower lip to the E plane and U1-APo during extraction exhibited the stronger correlation with changes in VAS score (r = - 0.551 and r = - 0.469). The random forest prediction model had the lowest mean absolute error and root mean square error, demonstrating a better prediction accuracy and fitting effect. In this model, pretreatment upper lip to E plane, pretreatment Pog-NB and the change of U1-GAll were the most important variables in predicting the posttreatment score of facial profile esthetics.

CONCLUSIONS

The maxillary incisor protrusion and lower lip protrusion are key objective indicators for evaluating and predicting facial profile esthetics of skeletal Class II extraction patients. An artificial intelligence prediction model could be a new method for predicting the posttreatment esthetics of facial profiles.

Differences in the effects of orthodontic treatment on airway-craniocervical functional environment in adult and adolescent patients with skeletal class II high-angle: a retrospective pilot study

INTRODUCTION

This retrospective cohort study aimed to compare the change in upper airway and craniocervical posture after orthodontic treatment between adolescent and adult patients with Class II high-angle malocclusion.

METHODS

A total of 12 adolescent (mean ± standard deviation age = 13.0 ± 2.0 years) and 12 adult patients with Class II high-angle malocclusion (mean ± standard deviation age = 23.7 ± 6.4 years) were selected in this study. The lateral cephalograms and cone beam computed tomography images of adolescent and adult patients were taken before and after treatment, which can be employed to evaluate the variables of craniofacial morphology, upper airway, and craniocervical posture through paired t tests, respectively. An independent sample t test was performed to observe the differences between two groups after orthodontic intervention. For adults and adolescents, the correlation between craniofacial morphology, upper airway, and craniocervical posture was determined through Pearson correlation analysis.

RESULTS

In all subjects, the improvements in vertical and sagittal facial morphology after treatment were observed. Anterior and inferior movements of the hyoid bone, an increase of upper airway dimension, posterior tipping of the head and a reduction of cervical inclination in the lower and middle segments post-treatment were identified in adolescence (P < 0.05). Adults displayed anterior movements of the hyoid bone, whereas no significant difference was observed in upper airway dimension and craniocervical posture (P < 0.05). Notable differences were identified in the change of hyoid position and airway volume between two groups (P > 0.05). Mandibular plane inclination, growth pattern, occlusal plane inclination, and chin position were all significantly correlated with craniocervical posture in adolescent patients. Besides, the mandibular growth pattern and chin position in adult patients were significantly correlated with craniocervical posture (P < 0.05).

CONCLUSIONS

Orthodontic treatment is capable of enhancing the facial profile of patients with skeletal class II high-angle while improving their upper airway morphology and craniocervical posture, where adolescents and adults differ substantially in that the former exhibit a more favorable alteration in the airway-craniocervical functional environment.

Treatment outcome of class II malocclusion therapy including extraction of maxillary first molars: a cephalometric comparison between normodivergent and hyperdivergent facial types

Background

The dentoalveolar component of a Class II division 1 malocclusion can be orthodontically treated either with extractions or by distalization of the molars. This study aimed to compare skeletal, dentoalveolar and profile changes in normodivergent and hyperdivergent Class II Division I growing patients orthodontically treated with fixed appliances including maxillary first molar extraction.

Methods

Sixty-four patients treated orthodontically with full fixed appliances including maxillary first molar extractions were retrospectively analyzed. Patients were divided into a normodivergent group (Group N; 30° ≤ SN^GoGn < 36°) consisting of 38 patients (17M, 21F; mean age 13.2 ± 1.3 years) and a hyperdivergent (Group H; SN^GoGn ≥ 36°) including 26 patients (12M, 14F; mean age 13.7 ± 1.1 years). Lateral cephalograms were available before (T0) and after treatment (T1) and cephalometric changes were calculated for 10 linear and 13 angular variables. The Shapiro-Wilk test confirmed a normal distribution of data, hence parametric tests were employed. The Student t-test was used to compare groups at baseline. The paired t-test was used to analyze intragroup changes between timepoints, and the Student t-test for intergroup comparisons. The level of significance was set at 0.05.

Results

The Class II division 1 malocclusion was successfully corrected, and the facial profile improved both in normodivergent and hyperdivergent patients. Divergency increased by 0.76 ± 1.99° in Group N (p = 0.02) while it decreased -0.23 ± 2.25° (p = 0.60); These changes were not significant between groups after treatment (p = 0.680). Most dentoskeletal measurements changed significantly within groups but none of them showed statistically significant differences between groups after treatment. Dental and soft tissue changes were in accordance with the biomechanics used for this Class II orthodontic therapy.

Discussion

The effect of orthodontic treatment of Class II division 1 malocclusion including extraction of the maxillary first molars in growing patients can be considered clinically equivalent in normodivergent and hyperdivergent patients. For this reason, this orthodontic treatment can be considered a viable option in the armamentarium of the Class II Division I therapy for both facial types.