Three-dimensional virtual planning in mandibular advancement surgery: Soft tissue prediction based on deep learning.

The study aimed at developing a deep-learning (DL)-based algorithm to predict the virtual soft tissue profile after mandibular advancement surgery, and to compare its accuracy with the mass tensor model (MTM). Subjects who underwent mandibular advancement surgery were enrolled and divided into a training group and a test group. The DL model was trained using 3D photographs and CBCT data based on surgically achieved mandibular displacements (training group). Soft tissue simulations generated by DL and MTM based on the actual surgical jaw movements (test group) were compared with soft-tissue profiles on postoperative 3D photographs using distance mapping in terms of mean absolute error in the lower face, lower lip, and chin regions. 133 subjects were included - 119 in the training group and 14 in the test group. The mean absolute error for DL-based simulations of the lower face region was 1.0 ± 0.6 mm and was significantly lower (p = 0.02) compared with MTM-based simulations (1.5 ± 0.5 mm). CONCLUSION: The DL-based algorithm can predict 3D soft tissue profiles following mandibular advancement surgery. With a clinically acceptable mean absolute error. Therefore, it seems to be a relevant option for soft tissue prediction in orthognathic surgery. Therefore, it seems to be a relevant options.

Predictability of pharyngeal airway space dimension changes after orthognathic surgery in class II patients: A mathematical approach.

INTRODUCTION: Angle Class II malocclusion due to mandibular retrognathia is a common dentofacial deformity. It is well known that mandibular advancement increases pharyngeal airway dimensions. The aim of this study was to evolve a mathematical method for predicting posterior pharyngeal airway space (PAS) changes based on 2D lateral cephalographic radiographs (LCRs) and expected extent of mandibular advancement prior to BSSO. MATERIALS AND METHODS: Linear regression analyses were performed in order to investigate the relation between the posterior airway space and mandibular advancement. LCRs where carried out to assess skeletal landmarks and pharyngeal airway space pre- (T0) and postoperatively (T1). To detect changes postoperatively, the posterior airway space was divided into three units: nasopharyngeal airway space (superior airway space - SPAS), oropharyngeal airway space (mid airway space - MAS) and hypopharyngeal airway space (inferior airway space - IAS). The differences between the distances of distinct measurement points (DIFF) were measured pre- and postoperatively. DOA referred to the distance of mandibular advancement and DP to the distance between the measurement points preoperatively. The parameters a, b1 and b2 were the regression coefficients that were determined separately for each unit (SPAS, MAS, and IAS). RESULTS: 49 patients (16 male and 33 female) with a mean age of 27.2 years (SD: 10.09), ranging from 18 to 51 years, who underwent mandibular advancement surgery (BSSO) were enrolled in this study. The mean distance of mandibular advancement was 5.05 mm (SD: 1.63). Regarding SPAS and IAS, mandibular advancement did not affect dimensions significantly: SPAS DIFF, 0.33 mm ± 1.13 mm (b1, p = 0.0881; b2, p = 0.087); IAS DIFF, 0.66 mm ± 2.45 mm (b1, p = 0.342; b2, p = 0.765). DOA and DP did not influence DIFF significantly in both sections. Regarding MAS, the mean effect of mandibular advancement was an expansion of 2.47 mm ± 2.24. The linear regression model showed a statistically significant (b1, p = 0.0064; b2, p = 0.0240) influence of DOA and DP on DIFF in posterior airway dimensions pre- and postoperatively. DISCUSSION: Based on preoperative LCR imaging data, a linear regression model was developed as a mathematical approach to allow prediction of PAS development in patients with Angle Class II malocclusions of different degrees. Increasing mandibular advancement was shown to be linked to increasing PAS, while a greater distance between the measuring points preoperatively led to smaller predicted PAS increases postoperatively. CONCLUSION: Predicting pharyngeal airway space (PAS) development after mandibular advancement by analysing lateral cephalometric radiographs (LCR) may be useful in the screening and treatment of obstructive sleep apnea syndrome (OSAS) patients. Our mathematical approach is a simple and sustainable prediction tool based on LTR data for patients with Class II malocclusions.

Short-term pharyngeal airway space changes after mandibular advancement surgery in Class II patients-a two-dimensional retrospective study.

INTRODUCTION: Planning successful treatment for the correction of anatomic abnormalities of the upper airways, by surgical advancement of the mandible, depends on extensive knowledge of the pharyngeal airway space (PAS). However, there is limited scientific evidence about changes in PAS after mandibular advancement surgery. AIM: To evaluate the immediate changes in superior posterior airway space (SPAS) in Class II patients, after mandibular advancement surgery. MATERIALS AND METHODS: A cephalometric evaluation of 37 patients with skeletal Class II deformity was performed at 2 distinct time intervals: Pre-operative (T0) and immediate post-operative (T1), using Dolphin Image & Management Solutions, version 11.9, according to the method of Arnett/Gunson FAB Surgery. The differences due to the surgical intervention were assessed with Student's t test, and a Principal Component Analysis was used to evaluate the relationship between mandibular advancement and SPAS variables. Anticlockwise and clockwise rotation groups were also evaluated with Mann-Whitney tests. The statistical analysis was conducted in SPSS and R assuming a 0.05 level of significance. RESULTS: As an effect of mandibular advancement, an anteroposterior statistically significant increase in SPAS (P < 0.001) was perceived at all points measured. CONCLUSION: Our findings indicate that mandibular advancement surgery is a viable option to achieve widening of the SPAS in patients with Class II skeletal morphology.

Short- and long-term changes of the pharyngeal airway after surgical mandibular advancement in Class II patients-a three-dimensional retrospective study.

PURPOSE: To evaluate the short- and long-term impact of mandibular-only advancement on pharyngeal airway space (PAS) changes by using cone-beam computed tomography (CBCT) and a new segmentation software. Furthermore, to determine whether a correlation exists between forward movement and PAS gain. MATERIALS AND METHODS: A retrospective evaluation of a homogeneous cohort of Class II patients who had undergone mandibular-only advancement was performed. Pre- (T0), post- (T1), and 1-year post-operative (T2) CBCT scans were obtained in each case, and the changes in PAS parameters (volume and smallest cross-sectional area) were compared with new segmentation software. Mandibular advancement was measured and correlated with PAS parameters. RESULTS: A significant postoperative gain in all airway parameters compared with baseline was shown for T1 (p = 0.02), with an additional increase for T2 (p < 0.001). No significant linear association between the movement of the measurement points and any other PAS parameters could be discerned (p > 0.05). CONCLUSION: Our findings indicate that bilateral mandibular-only advancement surgery results in a significant widening of the PAS in Class II patients. Long-term adaption of the PAS also occurs after surgery implying an additional gain of PAS over time. Sicat Air® software seems to be a sufficient and promising tool for PAS evaluation.

Effects of mandibular advancement surgery on the temporomandibular joint and muscular and articular adaptive changes--a systematic review.

The objective of this study was to assess the anatomical changes to the condyle and articular disc following mandibular advancement surgery, the adaptation of the masticatory muscles, and the improvement or worsening of temporomandibular disorders (TMD) in patients with pre-existing disorders and those who developed them following surgery. Four databases were searched systematically: PubMed, Scopus, Embase, and Cochrane Library. Of the 544 articles initially selected, 219 were duplicates and a further 165 were excluded on the basis of their titles and abstracts. On reading the full text, 89 were excluded because they were of no interest and 43 because they did not meet the inclusion criteria. Of the remaining 28 articles, six were excluded because they were considered of low quality and 22 articles were reviewed. Mandibular advancement surgery with condyle repositioning is associated with less TMD. Condylar resorption is a physiological process with a multifactorial aetiology. It is accelerated following mandibular advancement surgery but is not a contraindication to this procedure. Despite the large number of studies on the effects of mandibular advancement surgery on the temporomandibular joint (TMJ), this surgery can neither be said to improve nor to worsen TMJ health.