Setback Surgery Research Articles

Effect of transcutaneous electrical nerve stimulation on maximum mouth opening after orthognathic surgery: a randomised controlled trial.

The present study aims to determine the effect of transcutaneous electrical nerve stimulation (TENS) on maximum mouth opening (MMO) after orthognathic surgery. This study is a randomised clinical trial. The samples of this study were class III patients who are candidates for Le Fort I osteotomy surgery for maxillary advancement and bilateral sagittal split osteotomy (BSSO) for mandibular setback surgery due to the lack of maxilla growth and mandibular prognathism using the Dalpont method. On the day following surgery, the intervention group received TENS physiotherapy and instructions to take analgesics. In the control group, patients only received analgesics. MMO was measured in both groups using a digital caliper preoperatively, 1 month, and 6 months postoperatively. A total of 82 patients participated in this study, who were divided into two groups of 41, intervention and control. The difference in the mean MMO in different periods after surgery of the intervention group (F=59733.350, P<0.001) and the control group (F=32.480, P<0.001) was significant. The pattern of MMO increase over time was not the same in the two groups. There was a steeper slope in the increase of MMO in the intervention group than in the control group. It can be concluded from the results of this study, that the use of TENS after orthognathic surgery can be effective along with analgesics in reducing pain intensity and, subsequently, recovery in MMO in the short term.

Differential Relapse of Proximal and Distal Segments after Mandibular Setback Surgery

Differential Relapse of Proximal and Distal Segments after Mandibular Setback Surgery

Does mandible ramus height asymmetry affect postoperative skeletal stability in orthognathic surgery patients?

BackgroundRelapses following orthognathic surgery have been reported to exceed 2% to 50%, depending on multiple factors. This study aimed to analyze the stability after orthognathic surgery in patients with mandibular ramus height asymmetry through 3D reconstruction using Cone-beam CT.MethodsThis retrospective cohort study investigated patients who underwent mandibular setback surgery using bilateral sagittal split ramus osteotomy. Three-dimensional CT scans were taken at three different time points. Evaluation of the postoperative stability involved measuring changes in the x, y, and z axes as well as roll and yaw rotations of the mandible at specific landmarks (B point, mental foramen) on 3D CT scans obtained immediately after surgery and 6–12 months postoperatively. They were categorized into four groups based on bilateral mandibular height asymmetry through Asymmetry index (AI). The one-way ANOVA was implemented to compare the intergroup differences and Tukey's post hoc test was employed. Additionally, the Pearson correlation coefficient was also calculated.ResultsA total of 24 patients were included in this study. The corresponding AI, representing the degree of asymmetry in both mandibles, were calculated as Group 1 was 1.25 ± 0.64%, Group 2 was 2.89 ± 0.47%, Group 3 was 5.03 ± 0.51%, and Group 4 was 9.40 ± 1.99%. The x-axis change in Group 4 was significantly larger at 1.71 mm compared to Group 1 at 0.64 mm. The mandibular roll, Group 4 showed a statistically significant increase at 1.33° compared to Group 1 at 0.35°. And there was a significant positive correlation observed between x-axis change and AI (p = 0.019), as well as between mandibular roll and AI (p = 0.025).ConclusionAfter orthognathic surgery, stability was influenced by numerous factors, with the findings of this study suggesting that the degree of ramus height asymmetry in the mandible can be considered one contributing factor.

Three-dimensional changes in the soft tissue chin after mandibular setback surgery in adult Japanese patients with skeletal class III malocclusion

ABSTRACT Purpose The purpose of the present study is to improve the quality of prediction of soft tissue morphology by clarifying the relationship between the amount of three-dimensional (3-D) changes of hard tissue and the morphological differences of the soft tissue chin before and after orthognathic surgery in skeletal class III malocclusion. Materials and methods Preoperative and six-month postoperative CT was used to analyze the changes in 26 adult Japanese skeletal class III patients. The mean age was 25.5 years. Lateral cephalograms were analyzed to evaluate the initial antero-posterior jaw relationship and the changes before and after treatment. Three-D masks and bone structures were reconstructed using 3-D modelling software, and the final chin models were defined for further analysis following voxel-based registration. Correlation and linear regression analyses were performed to clarify the relationship between the movement of the soft tissue chin and the underlying bone. Results The soft tissue chin volume and surface area significantly increased after surgery. The thickness of the chin significantly increased only at pogonion and menton after surgery. Furthermore, a statistically significant correlation between the movement of soft tissue chin and underlying bone was found. Consequently, the regression model predicted the changes in soft tissue chin from the movement of the underlying bone. Conclusion Three-D analysis of the soft tissue chin revealed a significant change in response to surgical orthodontic treatment in skeletal class III adult patients, and soft tissue chin movement could be predicted by using 3-D CT data when planning orthognathic treatment.

“The impact of orthognathic surgery on articulation proficiency and speech intelligibility in skeletal Class III malocclusion: 18 months follow up”

IntroductionOrthognathic surgery results in the positional change of the maxilla and mandible that may affect speech. The present study evaluated the effect of combined maxillary advancement and mandibular setback surgery on articulation proficiency and speech intelligibility in patients with non-syndromic skeletal Class III malocclusion. MethodsIn this prospective study, twenty-five patients with skeletal class III malocclusion and consecutively treated with Lefort-1 maxillary advancement and mandibular setback (BSSO) orthognathic surgery were included in this study. The speech sample was recorded with a digital audio tape recorder one day before surgery and at 3, 6, 9, 12 and 18 months after surgery. Three qualified and experienced speech and language pathologists evaluated articulation errors and intelligibility of speech samples. Repeated One-way analysis of variance was used to compare articulation proficiency and speech intelligibility at different time intervals. ResultsThe substitution, omission, distortion and addition errors showed no significant changes at 3 months and 6 months. The total articulation errors decreased to zero at 9 months and no significant increase was observed till 18 months (P < 0.05). Speech intelligibility showed statistically non-significant improvement at any time interval. Cephalometric skeletal parameters SNA and N ḻ A°. were significantly correlated with addition and total articulation errors at 18 months follow up. ConclusionsThe ortho-surgical treatment improves speech (decreases. articulation errors) in most of the patients usually 6–9 months post-surgery. Speech intelligibility is not affected by bimaxillary orthognathic surgery in skeletal class III patients. The articulation errors were correlated to changes in position of maxilla.

The effect of tongue reduction for preventing adverse effects in patients undergoing class III orthognathic surgery: a three-dimensional comparative analysis.

This study aims to evaluate the potential benefits of combining tongue reduction with mandibular setback surgery in patients undergoing class III orthognathic surgery. Specifically, we investigated whether this combined approach reduced the risk of surgical relapse, condylar resorption, and airway space reduction by mitigating tongue pressure on the mandible. The study retrospectively enrolled patients who had undergone bilateral sagittal split ramus osteotomy (BSSRO) with at least 5 mm of setback and met the criteria of a body mass index > 20 kg/m2 and tongue volume > 100 mm3. The study included 20 patients with 10 in the tongue reduction group (TR, n = 10) and 10 in the BSSRO only group (SO, n = 10). The volumetric changes of the total airway space were significantly different between the TR and SO groups (p = 0.028). However, no significant differences were observed in the condylar resorption and postoperative relapse between the groups (p = 0.927 and 0.913, respectively). The difference between the resorption of the anterior and posterior segments of the condyle was also statistically insignificant (p = 0.826). Postoperative counterclockwise rotation of the proximal segment only demonstrated a significant correlation with postoperative relapse (p = 0.048). The reduction in tongue volume demonstrated a preventive effect on the reduction of the airway space after mandibular setback, although it did not yield statistical significance concerning surgical relapse and condylar volume. The counterclockwise rotation of the proximal segment might be responsible for the forward displacement of the distal segment and postoperative relapse. However, the clinical implications of this finding should be interpreted with caution owing to the limited sample size CLINICAL RELEVANCE: Tongue reduction could potentially serve as a preventive measure in preserving the airway space and might be beneficial in mitigating the risk of obstructive sleep apnea in patients with class III deformity.

Comparison of posttreatment stability after total mandibular arch distalization with mini-implants and mandibular setback surgery.

To compare posttreatment stability in skeletal Class III patients between those treated by total mandibular arch distalization (TMAD) with buccal mini-implants and those by mandibular setback surgery (MSS). The samples included 40 Class III adults, 20 treated by TMAD using buccal interradicular mini-implants and 20 treated with MSS. Lateral cephalograms were taken at pretreatment, posttreatment, and at least 1-year follow-up, and 24 variables were compared using statistical analysis. Mandibular first molars moved distally 1.9 mm with intrusion of 1.1 mm after treatment in the TMAD group. The mandibular incisors moved distally by 2.3 mm. The MSS group exhibited a significant skeletal change of the mandible, whereas the TMAD group did not. During retention, there were no skeletal or dental changes other than 0.6 mm labial movement of the mandibular incisors (P < .05) in the MSS group. There was 1.4° of mesial tipping (P < .01) and 0.4 mm of mesial movement of the mandibular molars and 1.9° of labial tipping (P < .001) and 0.8 mm of mesial movement of the mandibular incisors in the TMAD group. These dental changes were not significantly different between the two groups. The TMAD group showed a slightly decreased overjet with labial tipping of the mandibular incisors and mesial tipping of the first molars during retention. Posttreatment stability of the mandibular dentition was not significantly different between the groups. It can be useful to plan camouflage treatment by TMAD with mini-implants in mild-to-moderate Class III patients.

Cephalometric evaluation of skeletal stability and pharyngeal airway changes after mandibular setback surgery: Bioabsorbable versus titanium plate and screw fixation.

This study compared sequential changes in skeletal stability and the pharyngeal airway following mandibular setback surgery involving fixation with either a titanium or a bioabsorbable plate and screws. Twenty-eight patients with mandibular prognathism undergoing bilateral sagittal split osteotomy by titanium or bioabsorbable fixation were randomly selected in this study. Lateral cephalometric analysis was conducted preoperatively and at 1 week, 3-6 months, and 1 year postoperatively. Mandibular stability was assessed by examining horizontal (BX), vertical (BY), and angular measurements including the sella-nasion to point B angle and the mandibular plane angle (MPA). Pharyngeal airway changes were evaluated by analyzing the nasopharynx, uvula-pharynx, tongue-pharynx, and epiglottis-pharynx (EOP) distances. Mandibular and pharyngeal airway changes were examined sequentially. To evaluate postoperative changes within groups, the Wilcoxon signed-rank test was employed, while the Mann-Whitney U test was used for between-group comparisons. Immediate postoperative changes in the airway were correlated to surgical movements using the Spearman rank test. Significant changes in the MPA were observed in both the titanium and bioabsorbable groups at 3-6 months post-surgery, with significance persisting in the bioabsorbable group at 1 year postoperatively (2.29°±2.28°; P<0.05). The bioabsorbable group also exhibited significant EOP changes (-1.21±1.54 mm; P<0.05) at 3-6 months, which gradually returned to non-significant levels by 1 year postoperatively. Osteofixation using bioabsorbable plates and screws is comparable to that achieved with titanium in long-term skeletal stability and maintaining pharyngeal airway dimensions. However, a tendency for relapse exists, especially regarding the MPA.

Optimizing Orthognathic Surgery: Leveraging the Average Skull as a Dynamic Template for Surgical Simulation and Planning in 30 Patient Cases.

Virtual planning has revolutionized orthognathic surgery (OGS), marking a significant advancement in the field. This study aims to showcase the practical application of our established 3D average skull template as a guiding framework for surgical planning, and to share valuable insights from our clinical experience. We enrolled 30 consecutive Taiwanese patients (18 females and 12 males) who underwent two-jaw orthognathic surgery with surgical simulation, utilizing the average skull template for planning. Results indicate the method's applicability and precision. By adhering to the surgical plan, post-operative outcomes closely aligned with the average skull template, showing negligible deviations of less than 2 mm. Moreover, patients expressed high satisfaction with post-surgery facial changes, with the chin appearance receiving the highest satisfaction scores, while the lowest scores were attributed to nose appearance. Notably, the substantial change in lower jaw position post-mandibular setback surgery contributed to increased satisfaction with the chin position. In conclusion, this study does not seek to replace established surgical planning methods, but underscores that utilizing an average skull as a surgical design template provides a viable, accurate, and efficient option for OGS patients.

Reproducibility of Computerized Cephalometric Analysis Software Compared with Conventional Manual Tracing for Analyzing Skeletal Stability After Orthognathic Surgery.

This study aimed to compare the difference between analyzing skeletal stability after orthognathic surgery by lateral cephalogram measurement created from Dolphin software (version 11.95) compared with the manual technique. Twenty-eight patients who underwent mandibular setback surgery (BSSRO) were randomly selected between 2015 and 2021. Serial lateral cephalograms were analyzed at four different time sets postoperatively, and a total of 112 cephalometric radiographs were obtained. Horizontal measurement (BX), vertical measurement (BY), and 3 angular measurements (SNB, ANB, and Gonial angle) were analyzed by manual tracing and Dolphin software by 2 examiners. The intraclass correlation coefficient determined the intra-rater reliability. Parameter differences between timelines were observed for skeletal stability, and mean values between methods were compared using the Student's t-test. Both examiners were generally consistent in the repeated measurements (ICCs of the manual method ranged from 0.926 to 0.994, and the digital method ranged from 0.719 to 0.956). All variables represented skeletal stability at T0-T1, T0-T2, and T0-T3 showed no statistically significant differences between methods except ANB (T0-T1; p value = 0.009). Computerized cephalometric analysis software is relatively reproducible for assessing skeletal changes after orthognathic surgery and can be used routinely in follow-up.

Does Articular Disc Position Change Following Mandibular Setback Surgery?

BackgroundMaintaining condyle position following bilateral sagittal split ramus osteotomy (BSSO) is crucial to minimizing post-operative relapse. However, the impact of BSSO on the articular disc position remains inconclusive. PurposeThis 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 variablesThe predictor variable was time and articular disc position was assessed at 3 time points, preoperatively (T0), three months post-surgery (T1), and six months post-surgery (T2). Main outcomeThe 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). CovariatesCovariate 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). AnalysesFriedman’s test with 80% power and a significance level of 0.05 was employed. Pairwise comparisons were performed using the Dunn-Bonferroni post hoc test to identify statistically significant differences. ResultsThe study included 16 subjects, six females and ten 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). ConclusionsFollowing 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.

Condylar Changes Following Mandibular Setback Using Manual Guidance

The purpose of this retrospective study was to analyze changes in the position of the condyles following mandibular setback surgery with manual guidance. The study included 28 patients with mandibular prognathism who underwent mandibular setback surgery using manual guidance with a bioabsorbable mesh for mandibular fixation, and changes in the position of the center of the condylar head were compared at three time points: before surgery (T0), within 1 week after surgery (T1), and 6 months after surgery (T2). The results showed significant lateral, anterior, and inferior movements of the condyle at T1 compared to T0, with an average movement of 0.66 ± 0.84 mm along the x-axis, −1.27 ± 0.82 mm along the y-axis, and −0.20 ± 0.69 mm along the z-axis, with a 1.77 ± 0.87 mm linear distance (p &lt; 0.05). At T2, the condylar position had mainly changed inferiorly along the y-axis (−0.17 ± 0.48 mm) (p &lt; 0.05) compared to that at T0. The change in the position along the x-axis (−0.14 ± 0.57 mm), z-axis (−0.05 ± 0.68 mm), and linear distance (0.85 ± 0.57 mm) at T2 was not significantly different from that in the condylar position at T0 (p &gt; 0.05). The study suggests that significant anterior–lateral–inferior condylar movement occurs within 1 week after mandibular setback surgery using manual guidance, but the condyle returns to its original position over time, which is clinically acceptable.

Ultrasonographic evaluation of changes in the thickness, width, elasticity index and echogenic pattern of the masseter muscle after mandibular set-back surgery

IntroductionThe masseter muscle is one of the structures that undergoes significant changes following jaw movements in orthognathic surgery. This study aims to investigate the effects of mandibular setback surgery, performed in patients with skeletal class III deformity, on the thickness, width, elasticity index, and echogenic pattern of the masseter muscle. Material and methodsThis prospective case-control study enrolled patients with class III deformity who underwent mandibular setback surgery, while the control group consisted of class I patients. The predictor variable was the time measured at two different points: preoperative (T1) and postoperative 6 months (T2). The primary outcome variable focused on changes in the internal echogenic pattern of the masseter muscle. Secondary, tertiary, and quaternary outcome variables included changes in the thickness, width, and elasticity index of the masseter muscle, respectively. Gender, age, type of operation, and amount of movement were considered as covariates. Ultrasonography was employed to evaluate the outcome variables. ResultsThe study group comprised 31 patients, including 17 females (mean age 22.24 ± 3.52 years) and 14 males (mean age 23.14 ± 2.65 years). The control group consisted of 16 females (mean age 23.34 ± 1.22 years) and 15 males (mean age 23.12 ± 1.76 years). Masseter muscle thickness increased significantly after mandibular setback surgery (p = 0.015). However, there was no statistically significant difference in masseter muscle width before and after surgery (p = 0.627), nor in the elasticity index (p = 0.588). Furthermore, a statistically significant transformation from Type I to Type II was observed in the internal echogenic pattern of the muscle (p = 0.039). Additionally, there was no statistically significant correlation between the amount of mandibular movement performed and the changes in the masseter muscle. ConclusionsMandibular setback surgery leads to changes in both the physical and structural properties of the masseter muscle.

Upper Airway Changes and OSAS Risk in Patients after Mandibular Setback Surgery to Treat III Class Skeletal Malocclusion.

Mandibular setback surgery (MSS) is one of the treatment options to resolve mandibular prognathism in patients suffering from skeletal class III malocclusion, which cannot be treated with simple orthodontic treatment. The mandibular setback surgical operation can involve changes in the pharyngeal morphology, resulting in a narrowing of the posterior airway space (PAS). This aspect is associated with an increase in airflow resistance, which increases the risk of developing snoring or obstructive sleep apnea syndrome (OSAS). The aim of this study is to evaluate the medium- and long-term effects of mandibular setback surgery on the upper airways and its possible association with OSAS in patients suffering from class III skeletal malocclusion. A total of 12 patients (5 males and 7 females) were enrolled in this study. The statistical tests highlighted a significant change in the PAS and BMI values in relation to T0, before surgery (PAS: 12.7 SD: 1.2; BMI: 21.7 SD: 1.2), and T1, after surgery (PAS: 10.3 SD: 0.6, p < 0.01; BMI: 23.8 SD: 1.2, p < 0.05). Sample size was calculated to detect an effect size of 0.9, with statistical power set at 0.8 and the significance level set at 0.05. No statistically significant correlation was found between the extent of mandibular setback, PAS and BMI change. This study confirms the effects of mandibular setback surgery on the upper airways, reporting a statistically significant PAS reduction in the medium- and long-term follow-up. On the other hand, no direct correlation was identified with OSAS risk, at least for the small mandibular setback (<8 mm), despite the statistically significant increase in BMI.

Evaluation of the effect of bimaxillary, mandibular setback, and advancement surgeries on the pharyngeal airway space and positions of the hyoid bone, soft palate, and tongue

Introduction: This study aims to assess the postoperative changes in the pharyngeal airway space and the positions of the hyoid bone, soft palate, and tongue after mandibular advancement, mandibular setback, and bimaxillary surgeries. It also aims to compare the effects of mandibular setback and bimaxillary surgeries in the treatment of skeletal Class III patients. Materials and method: Lateral cephalograms of the patients were taken preoperatively and in a period of 3 months postoperatively on 21 subjects (3 groups, 7 patients each) who underwent mandibular setback surgery, bimaxillary surgery for Class III correction, and mandibular advancement surgery, respectively. Pre- and postoperative evaluation of skeletal and soft tissue landmarks were conducted to study the dimensions of the pharyngeal airway space and the position of the hyoid bone, soft palate, and tongue. Results: A significant increase in the oropharyngeal airway was observed after mandibular advancement surgeries, with an uprighting of the soft palate and anterior positioning of the tongue. In the mandibular setback group, the nasopharyngeal airway dimension increased significantly, and the hyoid bone was repositioned posteroinferiorly with posterior movement of the tongue. After bimaxillary surgery in Class III subjects, the nasopharyngeal airway space increased significantly associated with postural changes in the soft palate. Conclusion: Mandibular advancement surgeries can provide conditions for increased airway patency. With regard to the PAS, in Class III patients, maxillary advancement should be preferred to mandibular setback. When mandibular setback is indispensable, the association of movements in bimaxillary surgery can neutralize or minimize the effects of the setback.

Proximal segment positioning using pre-bent plates locating surgical guides versus conventional maneuver in mandibular setback surgery. A randomized clinical trial.

Proximal segment positioning using pre-bent plates locating surgical guides versus conventional maneuver in mandibular setback surgery. A randomized clinical trial.

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

The aim of this study was to evaluate the changes in the upper airway following mandibular setback surgery. 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. 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. 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.

Changes of Adenoid and Pharyngeal Airway Space Following Orthognathic Surgery in Class III Patients with Mandibular Prognathism: A Retrospective Analysis

Aim and Background: This retrospective study evaluated the changes in adenoid and pharyngeal airway spaces associated with surgical mandibular setback in skeletal Class III patients. Patients and Methods: Pre- and one- year-post-operative lateral cephalograms of 25 adult patients with mandibular prognathism who had bilateral sagittal split osteotomy (BSSO) were traced. Cephalometric parameters including SNA, SNB, GoGn to SN, y-axis, SPPS, MPS, IPS, PNS-Eb, at-atp, ppw-Ba were calculated, compared, and then data were analyzed using Paired t-test or Sign test. The role of growth pattern and gender factor was analyzed with Fisher exact test. MannWhitney test was utilized to compare between the groups of male/female as well as the groups of vertical/horizontal grower. The results were considered at a maximum level of significance of 5% (P &lt; 0.05). Results: At long-term follow-up, 25 patients (m:8, f:17) with the mean age of 25±4; there was a decrease in MPS value (3.8±6.7) that statistically significant (P=0.001). Although an increase was found in PNS-Eb index (3.1±4.4), the changes were not significant (P=0.03). No significant change was observed in other parameters. Also, growth pattern and gender didn’t affect the mentioned parameters. Conclusion: Mandibular setback surgery causes a long-term effect in some parameters of pharyngeal airway space area. In patients suffering from obstructive sleep apnea or in case of some other risk factors including overweight, short necks, and small pharyngeal airway space, a mandibular setback surgery could possibly predispose to the development of sleep apnea syndrome.

Three-dimensional evaluation of mandibular width after mandibular asymmetric setback surgery using sagittal split ramus osteotomy.

The study aimed to evaluate the changes in mandibular width after sagittal split ramus osteotomy (SSRO) in patients with mandibular asymmetric prognathism using cone-beam computed tomography (CBCT). Seventy patients who underwent SSRO for mandibular setback surgery were included in two groups, symmetric (n = 35) and asymmetric (n = 35), which were divided according to the differences in their right and left setback amounts. The mandibular width was evaluated three-dimensionally using CBCT images taken immediately before surgery (T1), 3 days after surgery (T2), and 6 months after surgery (T3). Repeated measures analysis of variance was applied to verify the differences in mandibular width statistically. Both groups showed a significant increase in the mandibular width at T2, followed by a significant decrease at T3. No significant difference was observed between T1 and T3 in any of the measurements. No significant differences were found between the two groups (p > 0.05). After mandibular asymmetric setback surgery using SSRO, the mandibular width increased immediately but returned to its original width 6 months after surgery.

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

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. 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 10mm under the mandibular foramen level (lower level) parallel to Frankfurt horizontal plane. 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). 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.