Volumetric changes in temporomandibular joint space following trans-oral vertical ramus osteotomy in patients with mandibular prognathism: a one-year follow-up study.

This study measured and analyzed chronological changes in temporomandibular joint space volume by compartment following transoral vertical ramus osteotomy (TOVRO) using reconstructed 3-dimensional (3D) images of patients with mandibular prognathism. It included 70 joints of 35 patients who underwent TOVRO between January 2018 and December 2021. Computed tomography (CT) or cone-beam CT (CBCT) was performed before surgery (T0) and at 3 days (T1), 6 months (T2), and 12 months postoperatively (T3). These scans were then analyzed using 3D software. The volumes of the overall (Vjs), anterior (Vajs), posterior (Vpjs), medial (Vmjs), and lateral (Vljs) joint spaces were calculated at each time point. A linear mixed model and repeated-measures covariance pattern with unstructured covariance were used to evaluate significant changes in joint space volume over time. Vjs significantly increased to 134.54 ± 34.28 mm3 at T3 compared to T0 (p < 0.001). Vpjas and Vljs increased by 130.72 ± 10.07 mm3 and 109.98 ± 7.52 mm3 at T3 compared to T0, respectively (p < 0.001). However, no significant difference was observed between T0 and T2 in Vajs and Vmjs (p = 0.9999). The observed volume increases in Vpjs and Vljs appeared to contribute to the overall Vjs increase.

Machine Learning Effectively Diagnoses Mandibular Deformity Using Three-Dimensional Landmarks.

BACKGROUND: Jaw deformity diagnosis requires objective tests. Current methods, like cephalometry, have limitations. However, recent studies have shown that machine learning can diagnose jaw deformities in two dimensions. Therefore, we hypothesized that a multilayer perceptron (MLP) could accurately diagnose jaw deformities in three dimensions (3D). PURPOSE: Examine the hypothesis by focusing on anomalous mandibular position. We aimed to: (1) create a machine learning model to diagnose mandibular retrognathism and prognathism; and (2) compare its performance with traditional cephalometric methods. STUDY DESIGN, SETTING, SAMPLE: An in-silico experiment on deidentified retrospective data. The study was conducted at the Houston Methodist Research Institute and Rensselaer Polytechnic Institute. Included were patient records with jaw deformities and preoperative 3D facial models. Patients with significant jaw asymmetry were excluded. PREDICTOR VARIABLES: The tests used to diagnose mandibular anteroposterior position are: (1) SNB angle; (2) facial angle; (3) mandibular unit length (MdUL); and (4) MLP model. MAIN OUTCOME VARIABLE: The resultant diagnoses: normal, prognathic, or retrognathic. COVARIATES: None. ANALYSES: A senior surgeon labeled the patients' mandibles as prognathic, normal, or retrognathic, creating a gold standard. Scientists at Rensselaer Polytechnic Institute developed an MLP model to diagnose mandibular prognathism and retrognathism using the 3D coordinates of 50 landmarks. The performance of the MLP model was compared with three traditional cephalometric measurements: (1) SNB, (2) facial angle, and (3) MdUL. The primary metric used to assess the performance was diagnostic accuracy. McNemar's exact test tested the difference between traditional cephalometric measurement and MLP. Cohen's Kappa measured inter-rater agreement between each method and the gold standard. RESULTS: The sample included 101 patients. The diagnostic accuracy of SNB, facial angle, MdUL, and MLP were 74.3, 74.3, 75.3, and 85.2%, respectively. McNemar's test shows that our MLP performs significantly better than the SNB (P = .027), facial angle (P = .019), and MdUL (P = .031). The agreement between the traditional cephalometric measurements and the surgeon's diagnosis was fair. In contrast, the agreement between the MLP and the surgeon was moderate. CONCLUSION AND RELEVANCE: The performance of the MLP is significantly better than that of the traditional cephalometric measurements.

Does Articular Disc Position Change Following Mandibular Setback Surgery?

BACKGROUND: Maintaining condyle position following bilateral sagittal split ramus osteotomy (BSSO) is crucial to minimizing postoperative relapse. However, the impact of BSSO on the articular disc position remains inconclusive. PURPOSE: This study aimed to investigate the changes in articular disc position following setback BSSO surgery. STUDY DESIGN, SETTING, AND SAMPLING: In this prospective cohort study, subjects with mandibular prognathism requiring setback BSSO were enrolled between August 2021 and June 2022 at the Oral and Maxillofacial Surgery Clinic, Faculty of Dentistry, Chiang Mai University, Thailand. Patients with surgical complications, loss of follow-up, or significant artifacts in their MR images were excluded. PREDICTOR/EXPOSURE/INDEPENDENT VARIABLES: The predictor variable was time. The articular disc position was assessed at 3 time points, preoperatively (T0), 3 months postsurgery (T1), and 6 months postsurgery (T2). MAIN OUTCOME: The primary and secondary outcome variables were the changes in articular disc position between T0-T2 and T0-T1, respectively. Articular disc position was coded as normal, anterior disc displacement with reduction (ADDwR), anterior disc displacement without reduction (ADDwoR), and anterior disc displacement without reduction and degenerative joint disease (ADDwoR + DJD). COVARIATES: Covariate variables collected included age (years), sex (male or female), asymmetry (present or absent), surgical procedure (single jaw (BSSO) or bimaxillary surgery), and setback distance (millimeters). ANALYSES: Friedman's test with 80% power and a significance level of 0.05 was employed. Pairwise comparisons were performed using the Dunn-Bonferroni posthoc test to identify statistically significant differences. RESULTS: The study included 16 subjects, 6 females and 10 males, with a total of 32 TMJs. Subjects had a mean age of 23.75 (4.57) years. The proportion of TMJs with normal disc position postoperatively increased from 3 (9.4%) to 19 (59.4%). Statistically significant differences were found in the changes in disc position over time (P < .001). CONCLUSIONS: Following setback BSSO, the articular discs underwent changes, with a majority of ADDwR cases transitioning to a normal position. Cases with ADDwoR also demonstrated disc reduction capability after surgery. The combined orthodontic treatment and setback BSSO appear to have an effect on articular disc position in skeleton class III patients.

Comparison of three-dimensional soft tissue changes according to the split pattern after sagittal split osteotomy in patients with skeletal class III malocclusion.

OBJECTIVES: This study aimed to analyse the changes in soft tissue and hard tissue stability associated with the split pattern, i.e. long split (LS) or short split (SS), after sagittal split osteotomy. MATERIALS AND METHODS: Patients who underwent sagittal split ramus osteotomy were classified into LS or SS groups according to postoperative computed tomography images. They were examined via lateral cephalography and three-dimensional (3D) optical scanning before surgery (T0) and 1 (T1), 3 (T2), and 12 (T3) months after surgery. Six standard angles (SNA, SNB, ANB, FMA, FMIA, and IMPA) were used as measures of hard tissue change. The two sets of 3D data were superimposed, and the volumetric differences were calculated as the soft tissue change. The areas evaluated were delimited by 10 × 20-mm rectangles in the frontal aspect and a 25 × 25-mm square in the lateral aspect. RESULTS: A total of 42 sides (26 patients) were analysed, including 20 (16 patients) in the SS group and 22 (16 patients) in the LS group. We found no significant differences in cephalographic angle or soft tissue changes in the frontal aspect between the SS and LS groups. We found significant differences in the subauricular region from T0-T1 (p = 0.02), T0-T2 (p = 0.03), and T0-T3 (p = 0.037) in terms of soft tissue changes in the lateral aspect. The volume increase associated with posterior mandibular movement was greater in the LS group. CONCLUSIONS: We found that LS patients with mandibular prognathism exhibited increased subauricular volumes following mandibular setback. CLINICAL RELEVANCE: It is essential to predict the postoperative facial profile before surgery. The split pattern after sagittal split osteotomy affects the postoperative profile of patients with mandibular prognathism.

Does Clockwise Rotation of Maxillomandibular Complex Using Surgery-First Approach to Correct Mandibular Prognathism Improve Facial Appearance?

BACKGROUND: Facial aesthetics may be optimized based on a deeper understanding of soft tissue changes after orthognathic surgery. PURPOSE: The purpose of the study was to delineate facial soft tissue changes after clockwise rotation (CWR) of the maxillomandibular complex (MMC) to correct mandibular prognathism using the surgery-first approach. STUDY DESIGN, SETTING, SAMPLE: This prospective cohort study enrolled patients over 18 years of age with skeletal Class III malocclusion in the craniofacial center. The patients were excluded with previous history of craniofacial syndrome, orthognathic surgery trauma, infection at surgical sites, chin deviation (menton deviation ≥4 mm), 2 or more missing data points after surgery, or without informed consent. This study compared significant facial changes before (T0) and after orthodontic debonding (T1) in the CWR and control groups. PREDICTOR VARIABLE: The patients were divided in accordance with maxillary occlusal plane change (OPC) after surgery into CWR (OPC >4°) and control (OPC ≤4°) groups. MAIN OUTCOME VARIABLE: The primary outcome variable was frontal lip curvature (FLC: Right Cheilion-Stomion-Left Cheilion, degree) with or without upper lip curving upward at T1, where upper lip curving upward was considered more favorable. COVARIATES: The covariates included age, sex, and various cephalometric measurements. ANALYSES: The Mann-Whitney U test, paired, and independent t-test were implemented to compare the intragroup and intergroup differences. Statistical significance was indicated by P value <.05. RESULTS: The study comprised 34 patients (21 women) in the control group and 37 (29 women) in the CWR group; their mean ages were 23.64 ± 4.38 and 24.21 ± 3.84 years, respectively (P value = .562). At T1, the CWR group had significant increased FLC (P value = .001), alar width (P value = .034), and lower vermilion height (P value = .018), and decreased lower lip length (P value = .004). The high FLC group had significant decreased upper lip projection (P value = .002) and increased nasolabial angle (P value = .013). The significant relationship between CWR and high FLC was supported by the χ2 test (P value = .018) and multiple logistic regression (P value = .017). CONCLUSION: Greater CWR of the MMC increased FLC and lower vermilion height and reduced lower lip length. High FLC resulting from the CWR of the MMC improved facial appearance by moving the upper lip curve upward.

Application of Surgery-First Approach in Treating Skeletal Dentofacial Asymmetry with Orthognathic Surgery.

BACKGROUND: Skeletal dentofacial asymmetry decreases patient's attractiveness by deteriorating symmetry of facial appearance which is of great significance to individuals. Surgery-first orthognathic approach manifests its advantages of shortening treatment time and improving patient's quality of life. However, current literature on surgery-first approach mainly focuses on treating prognathism, overlooking its efficacy in improving facial symmetry of skeletal dentofacial asymmetry patients. This study aimed to assess SFA's efficacy in improving facial appearance by analyzing morphological features of asymmetric bone and facial soft tissue in a three-dimensional manner. METHODS: Thirty-four patients who received orthognathic surgery in a surgery-first fashion were included. Based on three-dimensional CT reconstruction, bilateral preoperative morphological features and postoperative symmetry of hard tissue were compared respectively. Efficacy of facial soft tissue symmetry restoration was evaluated using root mean square deviation (RMSD). RESULTS: Asymmetric features mainly located in menton, mandibular body length, angulation between ramus and midsagittal plane (MSP), distance between gonion and MSP and so on, which were significantly restored after the whole treatment. RMSD of facial soft tissue surface were significantly declined after the treatment and prognathism was corrected simultaneously if existed. CONCLUSIONS: Surgery-first orthognathic approach is proved to be capable of treating skeletal dentofacial asymmetry effectively and efficiently.

Long-term evaluation of the upper airway following mandibular setback surgery in the patients with mandibular prognathism.

OBJECTIVE: The aim of this study was to evaluate the changes in the upper airway following mandibular setback surgery. METHODS: The patients underwent mandibular setback surgery and cone-beam computed tomography scan data obtained at four time points: before surgery, immediately after surgery, short- and long-term follow-up. Upper airway geometries were segmented and extracted at each time point. Time-averaged airflow through the upper airway was evaluated at each time point. The measurements of airway volume and minimum cross-sectional areas were obtained at four time points. RESULTS: The airway volume and cross-sectional areas of airway significantly decreased immediately after surgery (p = 0.013 for airway volume and 0.016 for cross-sectional area). At short-term follow-up, the decreased airway volume and cross-sectional areas still showed statistically significant difference to original dimension (p = 0.017 for airway volume and 0.006 for cross-sectional area). At long-term follow-up, although there were no statistical significances (p = 0.859 for airway volume and 0.721 for cross-sectional area), the airway volume and cross-sectional areas had increased slightly compared to those at short-term follow-up. CONCLUSIONS: Although the airflow and dimensional parameters of the upper airway worsened following mandibular setback surgery, there was a tendency to gradually recover during long-term follow-up.

Change in CT Value at Mandibular Ramus After Mandibular Setback and Advancement Surgery With Bicortical Absorbable Plate Fixation.

PURPOSE: This study aimed to evaluate changes in computed tomography (CT) value of ramus bone after sagittal split ramus osteotomy (SSRO) in class II and class III patients using absorbable plates and screws. PATIENTS AND METHODS: In the retrospective study, the participants were female patients with jaw deformities who underwent bilateral SSRO with Le Fort I osteotomy. Maximum CT values (pixel values) of lateral and medial cortexes at anterior and posterior sites of the ramus were measured preoperatively and 1 year postoperatively by using horizontal planes at the mandibular foramen level (upper level) and 10 mm under the mandibular foramen level (lower level) parallel to Frankfurt horizontal plane. RESULTS: Fifty-seven patients and 114 sides (28 class II: 56 sides and 29 class III: 58 sides) were evaluated. Although CT values decreased at most sites of the ramus cortical bone after 1 year of surgery, they increased at the posterior-medial site at the upper level in class II ( P =0.0012) and the lower level in class III ( P =0.0346). CONCLUSION: This study suggested that bone quality at the mandibular ramus could change after 1 year of surgery, and there could be differences between mandibular advancement and setback surgery.

Comparative study of stability between two different fixation systems after orthognathic surgery in mandibular prognathism skeleton.

OBJECTIVE: This study is intended to compare the skeleton stability of bioabsorbable and titanium systems after orthognathic surgery in mandibular prognathism patients. STUDY DESIGN: A Retrospective study of 28 mandibular prognathism patients who underwent BSSRO setback surgery at Chulalongkorn University. Both titanium and the bioabsorbable group would take lateral cephalometrics immediately postoperative in 1-week(T0), 3(T1), 6(T2), and 12(T3) months. These radiographs were analyzed with Dolphin imaging programTM. The vertical, horizontal, and angular indices were measured. To compare immediately postoperative and follow-up periods within the group, the Friedman difference was used, and the Man-Whitney U test was used between the two groups. RESULT: The measurements within the group presented no statistically significant differences. But this study showed that at T0-T1, there was a statistically significant difference between the two groups in the mean of Me in horizontal linear measurement. T0-T2 found differences between Me in both horizontal and vertical linear measurements, and the difference between ANB. The differences between B-point, Pog, and Me in vertical linear measurements at T0-T3 were also reported. CONCLUSION: The significant difference values were within the normal range which indicated that using the bioabsorbable system could be well maintained as well as the titanium system. STATEMENT OF CLINICAL RELEVANCE: The second operation for removing titanium plate and screw after conventional orthognathic surgery may leads patient discomforts. While a resorbable system might be the role change if the stability is place on the same level.

What are the Effects of Internal Fixation on Trigeminal Neurosensory Function and the Temporomandibular Joints Following Intraoral Vertical Ramus Osteotomy?

PURPOSE: Intraoral vertical ramus osteotomy (IVRO) has, traditionally, been accomplished without internal fixation, necessitating a period of maxillomandibular fixation (MMF). With advances in instrumentation, internal fixation of IVRO is feasible, obviating the need for MMF. The purpose is to investigate the effects of transoral internal fixation on the prevalence of third division trigeminal nerve (CNV3) injury, temporomandibular joint (TMJ) arthralgia, and surgical site bleeding following IVRO. MATERIALS AND METHODS: A retrospective study was conducted on patients who underwent IVRO at Vanderbilt University Medical Center between January 2017 and December 2020. The primary predictor variable was fixation status-internal fixation versus MMF. The primary outcome variable was postoperative CNV3 neurosensory disturbance. The secondary outcome variables were TMJ arthralgia and surgical site bleeding. Statistical analysis included Fisher's exact test and McNemar's Chi-squared test. RESULTS: Seventy two subjects (59 IVROs without internal fixation and 65 IVROs with internal fixation) were studied. The frequency of CNV3 neurosensory deficit was 0% in the IVRO without internal fixation group and 3.1% in the IVRO with internal fixation group (P = .49). Within group analysis showed a decreased frequency of postoperative TMJ arthralgia compared to preoperative records in both groups (IVRO without internal fixation group, P = .04 and IVRO with internal fixation group, P = .004). The frequency of active surgical site bleeding controlled with local measures was 1.7% in the IVRO without internal fixation group and 3.1% in the IVRO with internal fixation group (P = 1). CONCLUSION: Internal fixation of IVRO is associated with low incidence of neurosensory deficit, TMJ arthralgia, and active surgical site bleeding.

Comparison of the quality of life changes of patients receiving sagittal split ramus osteotomy or intraoral vertical subsigmoid osteotomy for mandibular prognathism.

OBJECTIVE: To investigate and compare the effect of two orthognathic procedures for mandibular setback, namely, sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO), on oral health, mental- and physical health-related quality of life across time. MATERIALS AND METHODS: Patients with mandibular prognathism and planned for orthognathic surgery were recruited in this study. Patients were randomized into two groups (IVRO and SSRO groups). Quality of life (QoL) was assessed with the 14-item Short-Form Oral Health Impact Profile (OHIP-14) and the 36-item Short-Form Health Survey (SF-36) preoperatively (T0), postoperative 2 weeks (T1), 6 weeks (T2), 3 months (T3), 6 months (T4), 12 months (T5), and 24 months (T6). A comparison of OHIP-14 and SF-36 scores between two groups was conducted. RESULTS: Ninety-eight patients (49 SSRO group, 49 IVRO group) participated in this study. There was no significant difference in OHIP-14 scores between SSRO and IVRO throughout the treatment process. SSRO group had significant reduction of OHIP-14 score (i.e., improving oral health-related QoL) since postoperative 2 weeks, whereas IVRO group had significant reduction since postoperative 6 weeks. Starting from postoperative 3 months, the oral health-related QoL of both groups was already significantly better than the baseline level and continued to steadily improve afterwards. For SF-36, both groups had increased physical health summary score starting from postoperative 2 weeks, indicating an early and gradual recovery of physical health-related QoL. The mental health summary score of the SSRO group began to increase from postoperative 2 weeks, but that of the IVRO group only began to increase from postoperative 6 weeks. Patient age at the time of surgery was positively correlated with OHIP scores in the postoperative period. CONCLUSIONS: The study concludes that both SSRO and IVRO contributed to the improvement of QoL in the long term, but oral health- and mental health-related QoL of SSRO groups showed earlier improvement. CLINICAL RELEVANCE: Undergoing orthognathic surgery at early ages is advised, as older age of patients appeared to have worse QoL. TRIAL REGISTRATION: Clinical trial registration number: HKUCTR-1985. Date of Registration: 14 Apr 2015.

Swallowing Functions after Sagittal Split Ramus Osteotomy with Loose Fixation for Mandibular Prognathism: A Retrospective Case Series Research.

Sagittal split ramus osteotomy (SSRO) is a standard surgical technique for patients with mandibular prognathism. However, the appropriate position of the proximal fragment is not strictly defined, and rigid fixation can induce early postoperative skeletal relapse and temporomandibular (TMJ) disorders. Loose fixation can be expected to seat the proximal bone fragments in a physiologically appropriate position, thereby reducing adverse events. Although long-term skeletal stability has been achieved using SSRO without fixation, the evaluation of preoperative and postoperative eating and swallowing functions remains unclear, and this study aimed to clarify this point. We evaluated mastication time, oral transfer time, and pharyngeal transfer time using videofluorography (VF) preoperatively, two months postoperatively, and six months postoperatively, and along with the position of anatomical landmarks using cephalometric radiographs, modified water swallowing test (MWST), food test (FT), and repetitive saliva swallowing test (RSST) were used to evaluate postoperative swallowing function. Four patients (one male, three females; mean (range) age 26.5 (18-51) years) were included, with a mean setback of 9.5 mm and 6.5 mm on the right and left sides, respectively. Postoperative eating and swallowing functions were good in VF, cephalometric analysis, MWST, FT, and RSST. In the present study, good results for postoperative eating and swallowing functions were obtained in SSRO with loose fixation of the proximal and distal bone segments.

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.

Bite force changes after surgical correction of mandibular prognathism in subjects with increased vertical dimension : A prospective clinical trial.

PURPOSE: Occlusal bite force (OBF) is the most important parameter in assessing biting efficiency. The aim of this study was to record OBF changes after surgical correction of high angle maxillary/mandibular (Max/Mand) class III patients and to compare these with that recorded in class III patients with average Max/Mand angle. MATERIALS AND METHODS: Initially included were 42 patients with severe class III skeletal malocclusion who were scheduled for orthodontic surgery: group 1-22 patients with increased vertical relationship scheduled for bimaxillary surgery; group 2-20 patients with average vertical relationship scheduled for mandibular setback only. OBF measurements before surgery (T0), at debonding (T1) and at least 3 months after debonding (T2) were recorded using a portable occlusal force gauge. The following were also measured: maximum OBF (MOBF) achieved by the subject on each side, averaged OBF on each side (AOBF) and maximum OBF at the incisal region (MIOBF). At T2, only 33 patients (group 1: 17 and group 2: 16) were included in the analysis due to loss to follow-up. RESULTS: MOBF increased significantly in group 1, while no significant changes were detected in group 2. MIOBF increased after surgical correction in both groups. Significant increase in MIOBF was observed at T1 (P < 0.001) followed by an insignificant decrease during the observation period (3-6 months after treatment; P > 0.05). The two groups differed significantly in MOBF at T1 and T2, while no statistically significant differences were detected between the groups for MIOBF changes at the various time intervals (P > 0.05). The number of posterior teeth with occlusal contacts increased in both groups. Relapse was detected in group 1 where the number of posterior teeth in contact decreased during the observation period (T1-T2). CONCLUSION: OBF greatly improved after surgical correction of the vertical morphology. Correction of high angle mandibular prognathism improves oral function in addition to esthetics.

Evaluation of alveolar bone changes around mandibular incisors during surgical orthodontic treatment of patients with mandibular prognathism: Surgery-first approach vs conventional orthognathic surgery.

INTRODUCTION: This retrospective study aimed to investigate the alveolar bone changes around mandibular incisors in patients with skeletal Class III malocclusion treated with surgery-first orthognathic approach (SFA) and conventional orthognathic surgery (COS) using cone-beam computed tomography scans. METHODS: Sixty-four patients were divided into 2 groups according to the inclusion of presurgical orthodontic treatment; the SFA group included 32 patients treated without presurgical orthodontic treatment, and the COS group included 32 patients treated with presurgical orthodontic treatment. Cone-beam computed tomography scans were obtained before treatment, after presurgical orthodontic treatment, and after treatment for the COS group and were obtained before and after treatment for the SFA group. The measurements of vertical alveolar bone height and horizontal bone thickness at 4 levels and the alveolar bone area surrounding the mandibular incisors were compared according to the treatment progress and groups. RESULTS: The vertical bone levels and horizontal bone thickness of the labial and lingual sides and the area of the alveolar bone around the mandibular incisors were reduced after treatment in both SFA and COS groups. Vertical bone loss was more prominent than horizontal bone loss after treatment in both groups, and alveolar bone loss was greater on the lingual side than on the labial side. There were no significant differences in alveolar bone changes around the mandibular incisor between the SFA and COS groups. However, the alveolar bone was reduced more in the COS group than in the SFA group. CONCLUSIONS: The results indicate that SFA and COS may trigger degeneration of the alveolar bone around the mandibular incisors after treatment in patients with mandibular prognathism. Careful consideration is needed to avoid iatrogenic degeneration of the periodontal support around the incisors, particularly during presurgical orthodontic treatment.

Evaluation of bony changes observed in mandibular osteotomy lines and mandibular condyles following bilateral sagittal ramus osteotomy by fractal analysis.

OBJECTIVES: This study aimed to evaluate the surgically impacted trabecular changes in mandibular osteotomy lines and mandibular condyles after bilateral sagittal split ramus osteotomy using the fractal analysis method. MATERIALS AND METHOD: The study population consisted of 30 patients (9 male, 21 female) diagnosed with mandibular prognathism and operated with bilateral sagittal split ramus osteotomy under general anesthesia. Fractal analyses observed the alterations on the trabecular structure of osteotomy lines, and mandibular condyles on panoramic radiographs obtained preoperatively, postoperatively, 1st week, 6th month, and 12th month. The box-counting method was used to evaluate the changes in trabecular structure by fractal analysis. P-values of less than 0.05 were considered significant. RESULTS: The fractal dimension values in both osteotomy lines and mandibular condyles were significantly decreased on postoperative 1st week regarding preoperative values. However, fractal dimension values commenced increasing in the following postoperative period. The fractal dimension values of the horizontal and vertical osteotomy lines reached their preoperative values on postoperative 6th and 12th month, respectively. The decreased fractal dimension values observed in the early postoperative period in the right and left condyles reached their preoperative values at the 6th postoperative month. CONCLUSION: Fractal analyses performed postoperatively can provide information about trabecular changes and bone healing of structures such as osteotomy lines directly affected by bilateral sagittal split ramus osteotomy and indirectly affected mandibular condyles. The results support that fractal analysis can be used together with clinical data in the evaluation of bone healing process.

A detailed radiomorphometric analysis of the mandibular foramen, lingula and anti-lingula with a special emphasis on mandibular prognathism.

INTRODUCTION: The aim of this study was to evaluate radiomorphometric differences of mandibular foramen (MF), lingula (Li), and anti-lingula (AL) between prognathic and non-prognathic patients, using cone-beam computed tomography (CBCT). METHODS: A total of 228 3D CBCT images of 57 prognathic and 57 non-prognathic patients were retrospectively evaluated. The distances between MF or Li to occlusal plane (OP), anterior border of ramus (AR), posterior border of ramus (PR), sigmoid notch (SN), gonion (Go) and distances Li to MF were measured. The presence of AL, and the distances to Li were also assessed in both groups. RESULTS: In prognathic patients the mean distances of MF-AR and Li-PR were lesser, and Li-OP was greater (p < 0.05). However, distances from MF or Li to the other ramal landmarks were similar in both groups (p > 0.05). Presence of AL was found at 53 sides in prognathic and 20 sides in non-prognathic groups (p < 0.05). The horizontal distance of Li-MF was greater in prognathic patients (p < 0.05). On the other hand, there was no difference between groups regarding the horizontal distance of Li-Al, and the vertical distances of Li-MF and Li-AL (p > 0.05). CONCLUSION: The present study provided valuable data regarding morphological differences of MF-AR, Li-MF and Li-OP, which should be considered in the preoperative assessment of patients with mandibular prognathism. Presence of AL was more common in prognathic patients and mainly located above Li. 3D CBCT applications facilitated assessment of AL and its relationship with Li.

Does Clockwise Rotation of Maxillomandibular Complex Using Surgery-First Approach to Correct Mandibular Prognathism Affect Surgical Movement and Stability?

PURPOSE: Orthognathic surgery (OGS) using the surgery-first approach (SFA) can decrease treatment time and increase patient satisfaction. Clockwise rotation (CWR) of the maxillomandibular complex to correct mandibular prognathism leads to optimized functional, aesthetic, and stable outcomes. This study examined the combined effect of SFA and CWR of the maxillomandibular complex to correct mandibular prognathism by comparing the surgical movement before (T0) and immediately after OGS (T1) and the stability between T1 and 12 months after OGS (T2). METHODS: This prospective cohort study enrolled patients with skeletal Class III malocclusion who underwent SFA involving Le Fort I osteotomy and bilateral sagittal split osteotomy, with or without genioplasty. Based on the occlusal plane (OP) change at T0-T1, the patients were divided into CWR (OP > 4°) and control (C) groups (OP ≤ 4°). The predictor variable was OP change at T0-T1. The primary outcome variable was the stability of pogonion (Pog) at T1-T2. The covariates included demographic factors, cephalometric measurements (anterior facial height, posterior facial height, OP, mandibular plane angle, incisor mandibular plane angle, overjet, and overbite), and 3-dimensional landmark displacement (anterior nasal spine, A-point, upper central incisor, upper first molar, lower central incisor, lower first molar, Pog, gonion, and condylion). An independent t-test was used to compare between these 2 groups when appropriate. The level of significance was set at P < .05. RESULTS: The sample included 28 patients (17 females) in the C group and 36 (24 females) in the CWR group; the mean ages were 23.89 ± 3.35 and 24.08 ± 4.02 years, respectively. For the surgical movement at T0-T1, the CWR group showed an association with vertical movement of the maxilla at posterior nasal spine (P = .005), anterior nasal spine (P < .001), and A-point (P < .001) and horizontal backward movement of the mandible at B-point (P < .001), Pog (P < .001), and gonion (P = .042). At T1-T2, all landmarks remained stable without clinically significant difference between the 2 groups. CONCLUSION: Surgical movement in the CWR group could vertically displace the maxilla and setback mandible more than that in the C group. Postoperative skeletal stability remained the same between the 2 groups at 1 year after OGS.

Surgical cutting guide and single plate fixation for intraoral vertical ramus osteotomy.

With the advancement of digital technology over the last few decades, the use of virtual surgical planning and fabrication of surgical guides have tremendously improved the outcomes of various maxillofacial surgical procedures. The intraoral vertical ramus osteotomy (IVRO) is an orthognathic surgical procedure largely employed for mandibular setback in correcting dentofacial deformities. This study describes the design and application of a surgical cutting guide for IVRO. The guide can also be used to facilitate the placement of miniplate fixation. The initial experience at the authors' centre suggests that the guide has allowed the osteotomy to be performed with increased precision and confidence. Furthermore, the use of miniplate fixation decreased the period of maxillomandibular fixation. However, a larger series is required to evaluate the utility of this system more thoroughly.