Mandibular Setback Research Articles

Differential Relapse of Proximal and Distal Segments after Mandibular Setback Surgery

Differential Relapse of Proximal and Distal Segments after Mandibular Setback Surgery

The Stress Effects of Mandibular Movements on the Temporomandibular Joint With Sagittal Split Ramus Osteotomy.

The aim of this study was to evaluate the stress changes in the temporomandibular joint (TMJ) after sagittal split ramus osteotomy (SSRO) with finite element analysis (FEA). 5 and 10mm mandibular setback and advancement were applied to models by using SSRO and a control model without osteotomy evaluated. The articular disc was modeled as superelastic, and the stresses on the articular fossa, disc, and condyle were evaluated. The stresses on the cartilage were 1.150 MPa on the 5mm advancement model and 1.506 MPa on the 10mm advancement model. The stresses on the disc were 11.56 MPa on the 5mm advancement model, 7.94 MPa on the 10mm advancement model and the amount were significantly higher than other models. The stress, especially in the cartilage, increased with the amount of advancement. In the setback models, the stresses on the condylar cartilage and the disc were higher than in the control model, and the stress in the condylar cartilage increased with the amount of setback. SSRO increases the stresses in the TMJ components and stresses increase depending on the amount of advancement and setback and may cause the development of joint problems.

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

Background: The present study aims to determine the effect of transcutaneous electrical nerve stimulation (TENS) on maximum mouth opening (MMO) after orthognathic surgery. Materials and Methods: 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, one month, and six months postoperatively. Results: 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 2 groups. There was a steeper slope in the increase of MMO in the intervention group than in the control group. Conclusion: 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.

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.

Evaluation of Minimum Axial Airway Area and Airway Volume in Orthognathic Surgery Patients.

The aim of this study was to compare preoperative and postoperative linear, planar, and volumetric measurements in the pharyngeal airway in orthognathic surgery patients. Preoperative and postoperative cone beam computed tomography (CBCT) images of 60 patients, who underwent maxillary advancement with mandibular setback (Group I, n=25) and bimaxillary advancement (Group II, n=35), were compared. The airway was divided into 3 regions as nasopharynx, oropharynx, and hypopharynx. Linear and planar measurements were made on the reference sections of each region. The minimum axial airway area, the volume of 3 regions, and total airway volume were also measured. Regarding the linear, planar, and volumetric measurements, while there was a statistically significant increase in the measurements for all three regions in Group II, in Group I only the measurements in the nasopharyngeal region demonstrated a statistically significant increase postoperatively ( P <0.05). There was an increase in minimum axial airway areas in both groups; however, it was only statistically significant in Group II ( P <0.05). There was a statistically significant increase in total airway volumes in both groups ( P <0.05). A positive and good correlation was found between the percent increase in the minimum axial area and the percent increase in the total volume ( P <0.05). While bimaxillary advancement surgery results in a significant increase in the pharyngeal airway, mandibular setback with maxillary advancement caused an increase in the total airway. Changes that may occur in the airway should be considered while planning orthognathic surgery.

Augmentation genioplasty using discarded bone fragments following proximal segment osteotomy of the ramus in intraoral vertical ramus osteotomy (IVRO)

BackgroundBased on a three-dimensional (3D) orthognathic simulation, this technical report introduces a method for augmentation genioplasty using a proximal bone fragment of the mandible, which is typically discarded in intraoral vertical ramus osteotomy (IVRO).ResultsA 43-year-old female patient diagnosed with Class III malocclusion, presenting with a protruding mandible and long facial height, underwent surgical treatment. The surgical plan involved mandibular setback position using IVRO and augmentation genioplasty. The 3D orthognathic surgery including augmentation genioplasty simulation was performed. An excessively elongated proximal segment was sectioned following IVRO. The inferior part of the sectioned proximal bone fragment of the mandible was positioned to align with the requirements of advancement genioplasty. After ensuring that the placement of the fragment matched that of the simulated surgery, each bone fragment was fixed. At 1.5 years post-surgery, the grafted bone on the augmentation genioplasty was well maintained, with slight bone resorption.ConclusionsAugmentation genioplasty using the proximal bone fragment of the mandible, which is typically discarded in IVRO, reduces the surgical complications associated with chin osteotomy. When a secondary genioplasty is required, genioplasty with osteotomy, movement of the cut bone fragments, partial bone-shaving osteotomy, and additional bone grafting are viable options.

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.

Hard to Soft Tissue Profile Changes in Skeletal Class III Dentofacial Deformities After Maxillary Advancement and Mandibular Setback Orthognathic Surgery

Objective To correlate the sagittal hard tissue movement and soft tissue changes among patients with skeletal class III malocclusion following bimaxillary orthognathic surgery. Material and Methods Fifty-nine subjects with skeletal class III malocclusion treated consecutively with maxillary advancement and mandibular setback were assessed for skeletal and soft tissue linear changes using presurgical (T1) and post-treatment (T2) lateral cephalograms. Pearson’s correlation coefficient test was used to correlate hard and soft tissue parameters. Results The sagittal hard tissue movement and soft tissue changes for all the parameters assessed in maxilla and mandible showed statistically significant correlations. The ratios of changes for the maxillary protrusion [N-A (HP)] to horizontal subnasale (Sn), superior labial sulcus (Sls), and labrale superioris (Ls) were 0.574:1, 0.703:1, and 0.721:1 respectively. The ratio of horizontal labrale inferioris (Li), mentolabial fold (Mlf), and soft tissue (Pg′) to mandibular protrusion [N-B (HP)] were 0.992:1, 0.970:1, and 0.590:1 respectively and to chin protrusion [N-Pg (HP)] were 1.293:1, 1.252:1, and 1.001:1, respectively. The ratios were different for males and females in maxilla and mandible. Conclusion Sagittal hard tissue movement and soft tissue changes are significantly correlated. The soft tissue movement in the mandible were more proportionate compared to the maxilla. The sagittal hard tissue to soft tissues movement ratios were greater in maxilla and lesser at pogonion and mentolabial sulcus in females compared to males. The ratios obtained can be used for predicting postsurgical soft tissue changes.

Three-Dimensional Changes of Condylar Position After Bimaxillary Surgery to Correct Skeletal III Malocclusion: Cone Beam Computed Tomography Voxel-Based Superimposition Analysis

BackgroundThe stability of the condylar position within the first three months after orthognathic surgery in patients with skeletal Class III malocclusion is crucial for subsequent orthodontic treatment. PurposeThe purpose was to compare condylar positional changes three months after bimaxillary surgery to correct skeletal Class III deformities, utilizing the conventional two-dimensional (2D) combined with the cone beam computed tomography (CBCT) voxel-based superimposition analysis. Study design, setting, sampleThis retrospective cohort study included skeletal Class III patients undergoing bimaxillary orthognathic surgery at Khon Kaen University, Thailand in 2020. Exclusion criteria were patients with temporomandibular disorder (TMD) symptoms, facial asymmetry prior to the surgery, or surgical complications. Exposure variableThe exposure variable was the timing, both preoperatively and 3 months postoperatively. This 3-month postoperative time point was chosen because complete healing of the bimaxillary surgery is expected by then, without any potential influence of condylar changes resulting from subsequent orthodontic treatment. Main outcome variablesThe outcome variable is condylar position measurement, joint space (mm) and axial condylar angle (degrees). CovariatesDemographics (age, sex), and surgical details (direction and amount of movement) were collected as covariates. AnalysesStatistical analysis of condylar positional changes and correlations was performed using paired t-test and linear correlation (P-value < 0.05), respectively. ResultsThe sample included 11 subjects (22 condyles), with a mean age of 24±5.24 years. Both 2D measurements and voxel-based 3D superimposition showed significant changes in condylar position three months after bimaxillary surgery: inferior (0.45±0.26 mm, P < 0.001), posterior (0.46±0.39 mm, P = 0.003), lateral (0.38±0.42 mm, P = 0.01) displacement, and inward rotation (5.21±2.54°, P < 0.001). No significant correlation was found between jaw movement distance and condylar changes. Conclusions and relevanceTo our knowledge, this is the first study to report measures of condylar changes at 3 months, when complete healing of the osteotomies would be expected, using Le Fort I osteotomy for maxillary advancement combined with bilateral sagittal split ramus osteotomy (BSSRO) for mandibular setback. These changes are small in magnitude and may be of little relevance to patient care.

“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.

Assessment of Masseter Volume and Postoperative Stability After Orthognathic Surgery in Patients With Skeletal Class III Malocclusion With Facial Asymmetry.

This study aimed to evaluate the effect of orthognathic surgery on masseter volume in patients with skeletal Class III malocclusion with facial asymmetry and the effect of masseter volume on stability in orthognathic surgery. This research studied 16 patients with Class III malocclusion with facial asymmetry who received combined orthodontic-orthognathic treatment and underwent craniofacial computed tomography (CT) before (T0), 2 weeks after (T1), and 6 months after (T2) surgery. Three-dimensional (3D) CT images were retrospectively analyzed, using 3D volume reconstruction to obtain the masseter volume and examine the impact of the masseter volume on stability in orthognathic surgery. A statistically significant difference ( P < 0.05) in the volume of the masseter was found up to 6 months after orthognathic surgery compared with the preoperative period, and the reduction in the masticatory muscle volume on the lengthened side is greater than on the shortened side ( P < 0.05). The volume of both masseters differed according to facial asymmetry, and the difference was significantly reduced after orthognathic surgery ( P < 0.05). During the period time (T1-T2), cephalometric maxillary marker points were not significantly different ( P > 0.05), and mandibular marker points were significantly anteriorly shifted ( P < 0.05). There was an association between the masseter volume and anterior shift of point B (R > 0.5, P < 0.05), the upward and anterior shifts of the gonion point differed between the lengthened and shortened sides ( P < 0.05). The size of the masseter becomes smaller 6 months after orthognathic surgery, and orthognathic surgery improves both bone and soft tissue symmetry. A larger sagittal relapse of mandibular setback occurred in patients with greater masseter volume. Considering these alterations may be helpful in planning orthognathic surgery.

Impacts of mandibular setback with or without maxillary advancement for class III skeletal correction on sleep-related respiratory parameters: A systematic review and meta-analysis.

A systematic review and meta-analysis was conducted to evaluate the impacts of mandibular setback with or without maxillary advancement for class III skeletal correction on respiratory parameters measured by polysomnography (PSG) and to compare these respiratory parameters between these procedures for class III skeletal correction. Six electronic databases were searched up to June 2023. Studies comparing PSG parameters before and after orthognathic surgery for skeletal class III patients were selected for further analysis. The outcomes of interest were apnoea-hypopnea index (AHI), respiratory disturbance index (RDI), the lowest oxygen saturation (lowest SpO2), the average oxygen saturation (mean SpO2), and the 3% oxygen desaturation index (3% ODI). Data extraction, methodological quality assessment, risk of bias assessment, meta-analysis, and subgroup analysis were performed. Sixteen studies with a total of 476 patients who underwent orthognathic surgery for class III skeletal correction were included for meta-analysis. The risk of bias level was moderate for most studies. All PSG parameters before and after orthognathic surgery were not significantly different. The different surgical procedures also did not significantly affect post-operative PSG parameters. 5.8% of patients developed post-operative obstructive sleep apnoea (OSA). Most of them underwent a large distance of mandibular setback. There is a moderate level of evidence that mandibular setback with or without maxillary advancement for class III skeletal correction does not pre-dispose young and healthy patients to obstructive sleep apnoea when evaluated in the short term after surgery. However, post-operatively developed OSA was found in several isolated cases that underwent a large amount of mandibular setback with or without maxillary advancement.

Surgical Management of Laterognathia with Bilateral Sagittal Split Osteotomy: A Serial Case Report

Introduction: Laterognathia is characterized by the mandibular deviation to one of the sides affected which often caused by unilateral overgrowth of the mandible and age-related adaptive remodeling changes in the temporomandibular joint (TMJ) that affected masticatory function and aesthetics. The aim of this serial case report is to discuss the surgical management for laterognathia with bilateral sagittal split osteotomy (BSSO) on a clinical case of asymmetrical dentofacial deformity due to an excessive mandibular unilateral laterognathia. Case Report: This case report contains two cases of mandibular laterognathia. Both of our patients underwent a corrective procedure with bilateral sagittal split ramus osteotomy (BSSO) that performed mandibular setback and rotation. Post-operative follow-up showed the patient was in good condition and no complications were noted. Conclusion: The mandibular setback and rotation procedure can be performed with a bilateral sagittal split ramus osteotomy (BSSO). Significant improvement of laterognathia in occlusion, masticatory function, and facial appearance was achieved by surgical management with BSSO procedure. Keywords: laterognathia, bilateral sagittal split osteotomy, mandibular setback.

Mandibular Body Osteotomy Combined with Sagittal Split Ramus Osteotomy for the Treatment of Severe Skeletal Class Ⅲ Malocclusion with Ankylosed Teeth.

This study presents a combination of 2 different surgery procedures performed on the mandible as part of the treatment aiming to improve the facial profile and occlusal function of patients with severe skeletal class Ⅲ malocclusion and bilateral edentulous gaps. The teeth next to the edentulous gaps were found to be ankylosed. Mandibular setback by bilateral sagittal split ramus osteotomies and mandibular body osteotomies, combined with Le Fort Ⅰ level maxillary advancement were performed, since the chief complaint of the patient was a concave profile. As a result, the skeletal class Ⅲ malocclusion had been corrected, a satisfying facial profile had been achieved, and no apparent adverse effect was found. Thus, it has been proved that the combination of sagittal split ramus osteotomy and mandibular body osteotomy is available for correcting skeletal class Ⅲ malocclusion.

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.

Assessment of Patient Satisfaction and Functional Outcomes in Orthognathic Surgery.

Orthognathic surgery is a surgical procedure performed to correct severe jaw misalignments that can affect a patient's facial aesthetics and functional occlusion. While the primary goal of orthognathic surgery is to improve functional outcomes and facial appearance, it is essential to assess patient satisfaction as a crucial aspect of overall treatment success. Patient selection: We conducted a prospective study involving 50 patients who underwent orthognathic surgery. All patients had a confirmed diagnosis of severe jaw misalignment, as determined by clinical and radiographic assessments. The surgical procedures performed included maxillary advancement, mandibular setback, or a combination of both, depending on the patient's specific diagnosis. Preoperative orthodontic treatment was provided to align the teeth and prepare the patient for surgery. Patients were evaluated preoperatively and at postoperative intervals of 3 months, 6 months, and 1 year. Patient satisfaction scores and functional outcomes were as follows: aesthetics of facial profile (1-year post-op): mean score = 4.6, chewing function (1-year post-op): mean score = 4.4, speech function (1-year post-op): mean score = 4.3, and overall satisfaction with surgical outcome (1-year post-op): mean score = 4.5. Objective assessments revealed a significant improvement in occlusion and facial aesthetics. The mean reduction in overjet was 4.8 mm, and the mean reduction in overbite was 3.2 mm. Additionally, the mean postoperative ANB angle improved by 3.7°, indicating a better facial balance. Orthognathic surgery in our cohort of 50 patients resulted in high levels of patient satisfaction with both functional outcomes and facial aesthetics. Objective measurements also indicated significant improvements in occlusion and facial balance.

Comparison between one-jaw and two-jaw designs in virtual surgery planning for patients with class III malocclusion

Orthognathic surgery is highly effective for treating maxillomandibular discrepancies in patients with class III malocclusion. However, whether one- or two-jaw surgery should be selected remains controversial. Our study aimed to evaluate quantitative differences between one-jaw and two-jaw surgical designs.In total, 100 consecutive patients with skeletal class III malocclusion who underwent orthognathic surgery with preoperative three-dimensional simulation between August 2016 and November 2021 were recruited. Based on the same final occlusal setup, a two-jaw surgery design and two types of one-jaw design were created. In total, 400 image sets, including preoperative images and three types of surgical simulation, were measured and compared.The one-jaw mandibular setback design led to improvement in most cephalometric measurements and facial symmetry. Although the one-jaw maxillary advancement design improved the ANB angle and facial convexity, it induced maxillary protrusion and reduced facial symmetry. Compared with the other designs, the two-jaw design provided significantly closer cephalometric measurements to the normative values, better symmetry, and less occlusal cant.Overall, the two-jaw design provided a quantitatively better facial appearance in terms of symmetry, proportion, and profile. Although an optimal surgical design necessitates thorough preoperative evaluation and a shared decision-making process, two-jaw surgery can be considered for improving overall facial esthetics and harmony.

Orthognathic surgery in a patient with von Willebrand disease

Aim: This study aims to report the perioperative management of a patient with von Willebrand disease (vWd) who underwent orthognathic surgery. The report follows the guidelines of the Case Report Guidelines (CARE) and focuses on the steps taken to prevent bleeding during the surgical procedure. Methods: A 39-year-old female patient with skeletal Class III was treated with maxillary advancement and mandibular setback. Despite normal test results for ristocetin cofactor activity, measures were taken to prevent bleeding, including atraumatic surgical techniques, use of antifibrinolytic medication, induced hypotension during anesthesia, and preparation of blood products for transfusion during trans and postoperative periods if needed. In the end, these measures were not required. Results: The patient did not experience any bleeding during the surgical procedure or postoperative period, demonstrating the effectiveness of the measures taken to manage their blood dyscrasia. Two years after the surgery, the patient had satisfactory aesthetic and functional results and no evidence of relapse. Conclusion: Thus, this case report demonstrates that vWd does not prevent largescale oral and maxillofacial surgeries such as orthognathic surgery as long as proper precautions are taken pre-, intraand postoperatively.

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.