Nonsurgical treatment of a hyperdivergent skeletal Class III patient with mini-screw-assisted mandibular dentition distalization and flattening of the occlusal plane

Identification of key determinant for predicting feasible mandibular molars distalization

Background/purpose

The distal movement of mandibular molar is effective treatment strategy, while it is still difficult to determine if the posterior available space is sufficient or not for mandibular molar distalization before treatment. Thus, this study aimed to identify the measurement items of lateral cephalograms with the potential to accurately predict the posterior anatomical limit of mandibular molar distalization.

Materials and methods

Cephalometric images of 26 patients were used. We establish five landmarks: the distal contact point (D7), the distal root apex (R7), the distal tooth cervix (TC) of the mandibular second molar, the anterior border of the ramus (ABR) and the external oblique line of the mandible (E). The D7-ABR and the vertical height between TC and E (TC-V), the distal movements of D7 and R7 during treatment (D7D, R7D) were measured. The subjects were divided into bodily-like and tipping movement group, according to the ratio D7D/R7D.

Results

Significant differences in D7D and R7D were found between the bodily-like movement and tipping movement groups (P < 0.01). Moreover, TC-V was significantly larger in the bodily-like movement group (P < 0.01). A positive correlation was found between TC-V and D7D (r = 0.68) and between TC-V and R7D (r = 0.69), indicating that TC-V has the potential to make accurate predictions for D7D and R7D. D7-ABR did not show a positive correlation with R7D.

Conclusion

Using TC-V can strengthen the prediction of available posterior space for mandibular molar distalization.

Current situation, trends, and challenges navigating temporary anchorage devices usage among orthodontists in China: a comprehensive multi-center survey

BACKGROUND

The temporary anchorage devices (TADs) are presently a viable and popular treatment option for orthodontics all over the world. However, there is a lack of investigation and research on its application among orthodontists in China. This study aims to explore factors influencing temporary anchorage devices usage and compare current perspectives and usage patterns between orthodontic specialists and general dentists, thereby establishing new consensus and guiding future improvements.

METHODS

A cross-sectional study using a multi-center structured questionnaire was designed. The Chi-square test, Mann-Whitney U test, and logistic regression were performed.

RESULTS

Respondents were from 30 provincial-level regions. Most doctors had relatively rich clinical experience in orthodontics, with 65.70% working for over 10 years. Respondents reported a relatively high usage rate (87.54%) and satisfaction with TADs (93.85%). The analysis result showed Chinese orthodontists who received more TADs training (P < 0.01), had higher educational attainment (P < 0.01), and used more clear aligners (P < 0.01) tended to use TADs more frequently. About 95.90% of respondents believed TADs helped achieve higher treatment goals, 68.23% agreed they could shorten treatment duration, and 51.82% believed they reduced the probability of orthodontic-orthognathic treatment. Differences in the understanding of indications for TADs, improvement method of TADs can be observed between orthodontic specialists and general dentists (P < 0.05).

CONCLUSIONS

Chinese orthodontists were relatively active in using TADs. The factors most closely associated with TAD usage included related training, the type of orthodontic appliances used and the highest educational attainment. Orthodontic specialists and general dentists might had differing perspectives regarding TADs, but they tended to follow similar management procedures.

Feasibility of occlusal plane in predicting the changes in anteroposterior mandibular position: a comprehensive analysis using deep learning-based three-dimensional models

BACKGROUND

A comprehensive analysis of the occlusal plane (OP) inclination in predicting anteroposterior mandibular position (APMP) changes is still lacking. This study aimed to analyse the relationships between inclinations of different OPs and APMP metrics and explore the feasibility of OP inclination in predicting changes in APMP.

METHODS

Overall, 115 three-dimensional (3D) models were reconstructed using deep learning-based cone-beam computed tomography (CBCT) segmentation, and their accuracy in supporting cusps was compared with that of intraoral scanning models. The anatomical landmarks of seven OPs and three APMP metrics were identified, and their values were measured on the sagittal reference plane. The receiver operating characteristic curves of inclinations of seven OPs in distinguishing different anteroposterior skeletal patterns and correlations between inclinations of these OPs and APMP metrics were calculated and compared. For the OP inclination with the highest area under the curve (AUC) values and correlation coefficients, the regression models between this OP inclination and APMP metrics were further calculated.

RESULTS

The deviations in supporting cusps between deep learning-based and intraoral scanning models were < 0.300 mm. The improved functional OP (IFOP) inclination could distinguish different skeletal classification determinations (AUC Class I VS Class II = 0.693, AUC Class I VS Class III = 0.763, AUC Class II VS Class III = 0.899, all P values < 0.01) and the AUC value in skeletal Classes II and III determination was statistically higher than the inclinations of other OPs (all P values < 0.01). Moreover, the IFOP inclination showed statistical correlations with APMP metrics (rAPDI = -0.557, rANB = 0.543, rAF-BF = 0.731, all P values < 0.001) and had the highest correlation coefficients among all OP inclinations (all P values < 0.05). The regression analysis models of IFOP inclination and APMP metrics were yAPDI = -0.917x + 91.144, yANB = 0.395x + 0.292, and yAF-BF = 0.738x - 2.331.

CONCLUSIONS

Constructing the OP using deep learning-based 3D models from CBCT data is feasible. IFOP inclination could be used in predicting the APMP changes. A steeper IFOP inclination corresponded to a more retrognathic mandibular posture.

Boundary of mandibular molar distalization in orthodontic treatment: A systematic review and meta-analysis

To explore the mandibular retromolar space length (MRSL), initial root-inner cortex contact percentage (IRCCP), and the various factors that influence mandibular molar distalization. Searches were undertaken in PubMed, EMBASE, Web of Science, Cochrane Library, Scopus, and grey literature (Google Scholar and OpenGrey) for eligible cross-sectional observational studies measuring the MRSL and IRCCP in healthy adult patients. The risk of bias and evidence quality were evaluated using the Joanna Briggs Institute's checklist and GRADE framework. Thirteen studies involving 1169 patients were included for qualitative synthesis. Seven of these studies were eligible for quantitative analysis. Meta-analysis showed that the mean MRSL at the subfurcation-6 mm plane in Asian normodivergent cases was 3.78 mm (95% confidence interval [CI]: 2.81-4.35; I2 = 79.7%) for skeletal Class-I malocclusions, 3.02 mm (95% CI: 2.10-3.94; I2 = 62.5%) for Class-II, and 4.43 mm (95% CI: 3.14-5.73; I2 = 75.1%) for Class-III. The mean MRSL at the sub-cementoenamel junction (CEJ)-10 mm plane for Asian, Class-I, normodivergent cases was 3.28 mm (95% CI: 2.44-4.12; I2 = 68.9%). The mean IRCCP for Asian, Class-I, normodivergent cases was 27.2% (95% CI: 0.22-0.32; I2 = 0%). In Asian normodivergent cases, MRSL ranges from 3.28 to 4.43 mm with a 27.2% IRCCP for Class-I. Cone-beam computed tomography imaging is recommended for measuring the MRSL in the apex region particularly before molar distalization. Factors influencing MRSL and IRCCP include different races, skeletal patterns, facial types, and third-molar status.

Evaluation of the facial profile of skeletal Class III patients undergoing camouflage orthodontic treatment: a retrospective study

Objective

To identify objective metrics for evaluating the esthetics of facial profiles in skeletal Class III patients undergoing camouflage orthodontic treatment.

Methods

Eighty Asian-Chinese patients classified as skeletal Class III were included. Thirty cephalometric measurements of pre- and posttreatment cephalograms were analyzed. Ten orthodontists assigned visual analog scale (VAS) scores to the pre- and posttreatment profiles based on standardized lateral photographs. Correlations between subjective VAS scores and objective measurements were assessed using Pearson correlation and stepwise multiple linear regression analysis.

Results

Lower incisor (L1) protrusion, nasolabial angle, lower lip-E line distance, SNB angle, and L1 to AP plane were significantly correlated with VAS scores of pretreatment profiles of skeletal Class III patients. Factors such as retraction of the lower incisor, increased interincisal angle and overjet, reduction of lower lip-E line distance, as well as augmentation of the Z angle and nasolabial angle were significantly correlated with the changes in VAS scores post-camouflage orthodontic treatment. Stepwise multiple linear regression analysis revealed that pretreatment nasolabial angle, changes in the lower lip-E line distance, and pretreatment Pog-NB distance were the key factors influencing the posttreatment facial profile esthetics of skeletal Class III patients with camouflage orthodontic treatment.

Conclusion

Several cephalometric measurements correlate with subjective facial esthetic evaluations of skeletal Class III patients. Changes in lower lip prominence, the pretreatment nasolabial angle, and Pog-NB distance are the main factors related to facial esthetics in skeletal Class III patients after camouflage orthodontic treatment.

Implications of occlusal plane in diagnosis and treatment of malocclusion

Occlusal plane (OP) is one of the essential factors affecting craniofacial morphology and function. The OP not only assists in diagnosing malocclusion but also serves as an important reference for making treatment plans. Patients with different types of malocclusions have different forms of OP. Compared with patients with standard skeletal facial type, the occlusal plane of patients with skeletal class Ⅱ and high angle is steeper, while that of patients with skeletal class Ⅲ and low angle is more even. In orthodontic treatment, adjusting and controlling the OP can promote the normal growth and development of the mandible in most patients with malocclusion during the early stage of growth, while causing favorable rotation of the mandible in some adults with mild-to-moderate malocclusion. For moderate-to-severe malocclusion, the OP rotation by orthodontic-orthognathic treatment can achieve better long-term stability. This article reviews the evolution of the definition of OP and its implications for diagnosing and the guiding treatment of malocclusion.

Evaluation of stress distribution values at the temporomandibular joint and distalization of teeth during en-masse retraction of the mandibular dentition using buccal shelf bone screws: A FEM study

INTRODUCTION

Present Finite-element-method (FEM) study evaluates the stress distribution values at the Temporomandibular-Joint (TMJ) during en-masse retraction of the mandibular dentition using buccal shelf bone screws with varying magnitudes of forces.

MATERIAL AND METHODS

Nine replicas of a pre-existing three-dimensional finite element model of the craniofacial skeleton and articular disc from Cone-Beam-Computed-Tomography (CBCT) data and Magnetic-Resonance-Imaging (MRI) data of a patient were used. Buccal shelf (BS) bone screws were inserted buccal to the mandibular second molar region. Forces of magnitudes 250 gm, 350 gm and 450 gm were applied through NiTi coil springs along with stainless-steel archwires of sizes 0.016 × 0.022-inch, 0.017 × 0.025-inch and 0.019 × 0.025-inch.

RESULTS

On the articular disc, the maximum stress was observed at the inferior region and the inferior part of the anterior and posterior zone at all force levels. The stress on the articular disc and displacement of teeth increased with increase in force levels in all the 3 archwires. The maximum stress at the articular disc and displacement of teeth was observed for 450 gm force and the least for 250 gm force. No significant difference in the amount of displacement of teeth or the stresses produced at the articular disc was seen with increasing the size of the archwire.

CONCLUSION

With the present FEM study, we can deduce that it is better to use forces of lower levels on patients with temporomandibular-disorders (TMD) so as to reduce the stresses produced at the TMJ to avoid worsening of the TMD condition.

Analysis for Predictors of Failure of Orthodontic Mini-implant Using Patient-Specific Finite Element Models

In this study, we analyzed the clinical factors and mechanical parameters for predicting orthodontic mini-implant (OMI) failure in the mandible, which has different properties from the maxilla. A patient-specific finite element analysis was applied to 32 OMIs (6 failures and 26 successes) implanted between the mandibular second premolars and first molars used for anchorage. The peak stress and strain parameters were calculated for each sample. A logistic regression of the failure (vs. success) of OMIs on the mechanical parameters in the models was conducted. In addition, the influence of clinical factors on the mechanical parameters considered to be related to OMI failure was examined by a regression analysis. The mechanical parameter which best predicts OMI failure in the mandible was found to be a minimum principal strain of between 0.5 to 1.0 mm from the OMI surface (R² = 0.8033). The results indicate the patient's bone density, distance between the OMIs and adjacent root, and vertical implantation angle of the OMIs are potential clinical predictors of OMI failure in the mandible.