Three-Dimensional Quantitative Assessment of Condylar Displacement and Adaptive Remodeling in Asymmetrical Mandibular Prognathism Patients After Sagittal Split Ramus Osteotomy.

This study was performed to evaluate the condylar displacement and associated condylar remodeling in class III patients following mandibular setback surgery via sagittal split ramus osteotomy (SSRO). The sample comprised of 26 condyles of 13 subjects (mean age of 21.2±2.6 y). We evaluated patients with mandibular prognathism and facial asymmetry who had undergone SSRO for mandibular setback at Korea University Hospital between January 2016 and December 2018. Three-dimensional segmentation of the mandibular condyles was done using the initial cone-beam computed tomography scan and scan taken 12 months postoperatively or later. Quantitative assessments of the 3-dimensional condylar displacement from T0 to T1 and bony remodeling of 8 regions of the condylar head were performed. The correlation between the condylar displacement and condylar head remodeling on the deviated (D) and nondeviated (ND) sides was analyzed. Significant correlations between condylar displacement and surface remodeling were observed in both D and ND condyles. The anteroposterior condylar displacement was significantly different between the D and ND sides (P=0.007). There was no significant difference in condylar remodeling between the 2 sides. Condylar displacement and adaptive remodeling after SSRO varied greatly among individuals. Compared with displacement in the ND condyle, displacement in the D condyle has a greater association with condylar remodeling in both D and ND condyles. There is no significant difference in condylar head remodeling between D and ND condyles.

Soft tissue assessment before and after mandibular advancement or setback surgery using three-dimensional images: systematic review and meta-analysis.

The aim of this systematic review was to evaluate the effects of mandibular advancement or setback surgery on the facial soft tissue assessed using three-dimensional images. An electronic search was performed in the MEDLINE, Cochrane Library, Scopus, Virtual Health Library (VHL), Web of Science, and OpenGrey databases. Inclusion criteria comprised studies that evaluated the soft tissues of adult patients before and after mandibular advancement or setback surgery using computed tomography or magnetic resonance imaging. The risk of bias was analyzed. A total of 3501 studies were retrieved. The titles and abstracts of 2071 studies were read and 2040 of them were excluded. Thirty-one articles were read in full and six fulfilled the eligibility criteria and were included. A meta-analysis was performed using three of these articles. The correlation was significant and strong in the chin area (r=0.876 and r=0.868) and moderate for the lower lip/lower incisor (r=0.690). The ratio for lower lip/infradentale was 78% and for Pog'/Pog was 98%. Due to the limited number of articles included, there is weak evidence to infer that changes in the facial soft tissue due to mandibular advancement or setback are significant, but changes in the lower lip tend to be smaller than changes in the chin area.

Three-Dimensional Computed Tomographic Assessment of Temporomandibular Joint Stability After Orthognathic Surgery.

PURPOSE: Ensuring that the condyle is appropriately positioned and that positional changes are minimal is considered crucial for the temporomandibular joint (TMJ) to function without symptoms after orthognathic surgery. The purposes of this study were to evaluate condylar changes after surgery and to examine the association between these changes and TMJ symptoms. PATIENTS AND METHODS: A retrospective cohort study was conducted in patients with mandibular prognathism who underwent orthognathic surgery. Linear and angular changes in the positioning of the condyle were measured by superimposing 3-dimensional computed tomograms taken before surgery and 3 months after surgery. Clinical symptoms of TMJ pain and sound were recorded at 3, 6, 9, and 12 months after surgery. Possible associations between TMJ symptoms and clinical variables, such as postoperative condylar changes, were investigated using multiple logistic regression analysis. RESULTS: Linear condylar displacement after orthognathic surgery occurred predominantly in the anterior, medial, and inferior directions, with minimal changes (<1 mm) observed. Most angular condylar changes were smaller than 4° and occurred in the inward direction in the axial plane and the posterior direction in the sagittal plane. The best predictor of postoperative TMJ signs and symptoms was the preoperative status of TMJ signs and symptoms. Neither linear nor angular condylar displacement showed a relevant influence on postoperative pain and sound. CONCLUSIONS: Within the ranges of linear (<1 mm) and angular (<4°) condylar displacement noted in this study, displacement was not associated with postoperative TMJ pain and sound.

Radiographic assessment of lower third molar eruption in different anteroposterior skeletal patterns and age-related groups.

OBJECTIVE: To analyze radiographic predictors for lower third molar eruption among subjects with different anteroposterior skeletal relations and of different age groups. MATERIALS AND METHODS: In total, 300 lower third molars were recorded on diagnostic digital orthopantomograms (DPTs) and lateral cephalograms (LCs). The radiographs were grouped according to sagittal intermaxillary angle (ANB), subject age, and level of lower third molar eruption. The DPT was used to analyze retromolar space, mesiodistal crown width, space/width ratio, third and second molar angulation (α, γ), third molar inclination (ß), and gonion angle. The LC was used to determine ANB, angles of maxillar and mandibular prognathism (SNA, SNB), mandibular plane angle (SN/MP), and mandibular lengths. A logistic regression model was created using the statistically significant predictors. RESULTS: The logistic regression analysis revealed a statistically significant impact of ß angle and distance between gonion and gnathion (Go-Gn) on the level of lower third molar eruption (P < .001 and P < .015, respectively). The retromolar space was significantly increased in the adult subgroup for all skeletal classes. The lower third molar impaction rate was significantly higher in the adult subgroup with the Class II (62.3%) compared with Class III subjects (31.7%; P < .013). CONCLUSION: The most favorable values of linear and angular predictors of mandibular third molar eruption were measured in Class III subjects. For valid estimation of mandibular third molar eruption, certain linear and angular measures (ß angle, Go-Gn), as well as the size of the retromolar space, need to be considered.

Cephalometric and three-dimensional assessment of the posterior airway space and imaging software reliability analysis before and after orthognathic surgery.

PURPOSE: This study aimed to compare the reliability of three different imaging software programs for measuring the PAS and concurrently to investigate the morphological changes in oropharyngeal structures in mandibular prognathic patients before and after orthognathic surgery by using 2D and 3D analyzing technique. MATERIAL AND METHODS: The study consists of 11 randomly chosen patients (8 females and 3 males) who underwent maxillomandibular treatment for correction of Class III anteroposterior mandibular prognathism at the University Hospital in Zurich. A set of standardized LCR and CBCT-scans were obtained from each subject preoperatively (T0), 3 months after surgery (T1) and 3 months to 2 years postoperatively (T2). Morphological changes in the posterior airway space (PAS) were evaluated longitudinally by two different observers with three different imaging software programs (OsiriX(®) 64-bit, Switzerland; Mimics(®), Belgium; BrainLab(®), Germany) and manually by analyzing cephalometric X-rays. RESULTS: A significant increase in the upper airway dimensions before and after surgery occurred in all measured cases. All other cephalometric distances showed no statistically significant alterations. Measuring the volume of the PAS showed no significant changes in all cases. All three software programs showed similar outputs in both cephalometric analysis and 3D measuring technique. CONCLUSION: A 3D design of the posterior airway seems to be far more reliable and precise phrasing of a statement of postoperative gradients than conventional radiography and is additionally higher compared to the corresponding manual method. In case of Class III mandibular prognathism treatment with bilateral split osteotomy of the mandible and simultaneous maxillary advancement, the negative effects of PAS volume decrease may be reduced and might prevent a developing OSAS.

Assessment of ramus, condyle, masseter muscle, and occlusal force before and after sagittal split ramus osteotomy in patients with mandibular prognathism.

PURPOSE: The purpose of this study was to examine the relationship between the morphologies of the masseter muscle and the ramus and occlusal force before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. PATIENTS AND METHODS: The study group consisted of 26 patients with mandibular prognathism. All patients underwent bilateral SSRO as well as 3-dimensional computed tomography on which the masseter muscle, ramus, and condyle were measured preoperatively and at 1 year postoperation. Occlusal force and contact area were also recorded with pressure-sensitive sheets. RESULTS: In the cross-sectional area of the masseter muscle, there were no significant differences between the pre- and postoperative status. However, postoperative ramus width and area were significantly larger than preoperative values (P < .0001). Postoperative right condylar area was significantly larger than the preoperative value (P = .0120). Occlusal force and contact area 1 year after surgery were significantly larger than the preoperative values (P = .0016, P = .0190). CONCLUSION: This study suggested that the masseter muscle area did not significantly differ from preoperative status 1 year after SSRO, although occlusal force, contact area, and ramus area and width increased significantly 1 year after SSRO.