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This article describes a novel minimally invasive technique for bilateral sagittal split osteotomy (BSSO) that aims to reduce surgical trauma while maintaining bone overlap and rigid internal fixation for proper consolidation of the bone segments. The technique involves a small vestibular mucoperiosteal incision made on the lateral aspect of the mandible between the first and second molars, enabling a standard ramus split, surgical segment movement, and miniplate fixation. A retrospective evaluation of 67 consecutive patients who underwent BSSO using this protocol showed favorable split of the mandible with no unfavorable splits or non-union. Patients were discharged from hospital within an average of 17 h with minimal postoperative complications. This technique provides good surgical visualization with a very small incision and allows standard BSSO surgery without difficulty. [ABSTRACT FROM AUTHOR]

Large degrees of mandibular autorotation during intermediate splint design are prone to transfer error and decrease accuracy. The purpose of this study was to evaluate the amount of mandibular autorotation necessary to design intermediate splints for maxilla- and mandible-first sequences using virtual planning software, to help the clinical decision-making regarding the most adequate sequence for each patient. The influence of specific orthognathic movements (different vertical and sagittal changes at the Le Fort I level, cant correction) and the type of maxillofacial deformity (skeletal Class II, III, anterior open bite) were evaluated to identify those that would require higher levels of autorotation for each sequence. Three-dimensional virtual surgical planning data of 194 patients were reviewed (126 female, 68 male; mean age 26.5 ± 11.0 years; 143 skeletal Class II, 51 skeletal Class III) and subgroup analyses were conducted using the Kruskal–Wallis test and post-hoc pairwise comparisons. As an additional parameter (mandibular autorotation), maxilla-first is indicated for bimaxillary osteotomies with Le Fort I posterior intrusion, anterior open bite, and skeletal Class III, while mandible-first is recommended for Le Fort I global extrusion, especially with maxillary cant correction. [ABSTRACT FROM AUTHOR]

This retrospective study examined long-term (4–5 years) condylar positional and volumetric changes and skeletal stability after bimaxillary orthognathic surgery in skeletal Class III patients. Pre-surgical (T0: 0.9 ± 1.1 months) and post-surgical (T1: 0.6 ± 0.7 months; T2: 12.8 ± 3.1 months; T3: 56.5 ± 6.5 months) cone beam computed tomography (CBCT) images of 22 patients were obtained. CBCT multiplanar reformation (MPR) images were generated, and three-dimensional (3D) condylar models were constructed and superimposed to compare changes in condylar volume from pre- to postoperative. Condylar position in the sagittal and coronal planes altered immediately after surgery; however at long-term follow-up, the condyles had returned to their pre-surgical position. The condyles remained slightly inwardly rotated at short-term (−2.6°, 95% confidence interval −3.5° to −1.7°) and long-term (−1.9°, 95% confidence interval −2.8° to −1.0°) follow-up. Changes in condylar volume were insignificant after surgery. Condylar positional changes had no effect on skeletal stability. However, patients with an increased face height prior to surgery and more retrusive jaw position postoperatively were more prone to condylar resorption. Surgical changes remained stable 4–5 years after surgery. In conclusion, condylar position changed insignificantly following surgical correction in Class III patients provided that the correct surgical technique was employed. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the virtually planned position to the postoperative position of the maxilla, having performed the maxilla-first sequence or mandible-first sequence orthognathic surgery. An audit of 64 patients who underwent bimaxillary surgery between 2017 and 2020 was performed. Thirty patients had maxilla-first surgery and 34 had mandible-first surgery. The planned and post-surgical positions were analyzed using specific skeletal landmarks. Differences were calculated and the two-sample t -test was used to compare the groups. Measured differences between the planned and postoperative results differed significantly between the mandible-first and maxillary-first surgery groups (P < 0.001). The maxillary central incisors were under-advanced in the anterior–posterior direction in both groups. Most data points showed deviation from the surgical plan ≤ 2 mm and ≤ 4°. Secondarily, maxillary under-advancement in the mandible-first cohort was evaluated; these patients were subdivided into rigid and non-rigid fixation groups. The non-rigid fixation group showed less accuracy compared to the rigid fixation group, which was statistically significant (P = 0.014). The findings of this study demonstrate that virtual surgical planning can be less accurate in predicting the maxillary incisor position when performing mandible-first surgery, but this inaccuracy is within the acceptable range and can be mitigated by rigid fixation of the mandible. [ABSTRACT FROM AUTHOR]

Segmental mandibular advancement (SMA) consists of a combination of bilateral sagittal split osteotomy, anterior subapical osteotomy with extraction of the first premolars, and genioplasty, to allow an extended advancement of the mandible for the improvement of tongue base obstruction in moderate-to-severe obstructive sleep apnoea (OSA) and to minimize any unfavourable aesthetic change due to the large jaw advancement. The aim of this pilot study was to evaluate the surgical outcomes and complications following SMA in OSA patients. Twelve patients (nine male, three female) underwent SMA as part or whole of their skeletal advancement procedure for OSA. The apnoea–hypopnoea index (AHI) improved from a mean± standard deviation 42.4 ± 22.0/hour preoperatively to 9.0 ± 17.4/hour at 1 year postoperative. Surgical success (50% reduction in AHI) was achieved in 11 of the 12 patients (91.7%) at 1 year postoperative, while seven patients (58.3%) attained surgical cure (AHI<5/hour). The lowest oxygen saturation (LSAT) increased from a mean 73.3% preoperatively to 78.7% at 1 year postoperative. The airway volume increased from a mean 2.4 ± 1.7 cm3 at baseline to 6.7 ± 3.5 cm3 at 1 year postoperative (P < 0.001). No major complication occurred. This pilot study showed that SMA appears to be safe and effective as part or whole of the skeletal advancement surgery for moderate-to-severe OSA. [ABSTRACT FROM AUTHOR]

The sagittal split ramus osteotomy (SSRO) has been performed mainly on an inpatient basis because of the duration of anaesthesia and the potential risk of postoperative complications, such as bleeding, pain, nausea, and vomiting. However, advances in both surgical and anaesthetic management have enabled the reduction of these risks and shortened the length of hospital stay. Thus, the SSRO may be feasible even in the ambulatory setting in elective cases. The clinical records of all patients who underwent an outpatient SSRO between August 2011 and September 2020 at Lilla Craniofacial Clinic were reviewed retrospectively. Data on age, sex, duration of surgery, operative procedures, intraoperative bleeding, and admission status were investigated. In total, 143 patients underwent a bilateral SSRO. The SSRO was performed as an isolated procedure in 73 patients and concomitantly with other surgical procedures in the remaining 70 patients. Overall, 142 of the 143 patients were discharged on the day of surgery (99.3%); only one (0.7%) required an overnight stay because of a submental haemorrhage after genioplasty. No emergency hospitalizations or readmissions occurred after discharge. Multimodal perioperative management, both surgical and anaesthetic, facilitated enhanced patient recovery after surgery, and SSRO was performed successfully and safely as an ambulatory procedure. [ABSTRACT FROM AUTHOR]

The aim of this systematic review was to investigate whether the presence of third molars (3Ms) during sagittal split osteotomy of the mandible increases the risk of complications. Searches were conducted using MEDLINE via PubMed, LILACS, Cochrane Central, Scopus, DOSS, and SIGLE via OpenGrey up to December 2020. Fifteen articles were included for evaluation and 14 in the meta-analysis, with a total of 3909 patients and 7651 sagittal split osteotomies (670 complications). Inferior alveolar nerve (IAN) exposure in the proximal segment was the most frequent complication (n = 409), followed by bad splits (n = 151). Meta-analysis revealed no significant increase in the incidence of 3M-related IAN exposure (P = 0.45), post-surgical infections (P = 0.15), osteosynthesis material removal (P = 0.37), or bad splits (P = 0.23). The presence of 3Ms was associated with a reduced risk of nerve disorder (P = 0.05) and favoured bad splits in the lingual plate (P = 0.005). The quality of evidence was very low, mainly due to non-randomized study designs, high risk of bias, inconsistency, and imprecision. This systematic review suggests that the removal of 3Ms before sagittal mandibular osteotomy does not reduce the incidence of complications. Thus, we recommend future better-designed studies with rigorous methodologies and adjustments for confounding factors. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate whether differences in the pattern of the lingual plate split in sagittal split ramus osteotomy (SSRO) affect the remodelling of the split site. Sixty-one patients with mandibular prognathism (122 sides) underwent SSRO. Computed tomography (CT) was performed at 1 week and 1 year after SSRO. Bone splits were classified according to the lingual split scale (LSS) and the lateral bone cut end (LBCE) by evaluating CT images at 1 week. The remodelling at the split sites was evaluated by superimposing the CT images obtained at 1 week and 1 year. Regarding the LSS pattern, significant differences were observed in the distance between anteroposterior ramus points (P = 0.033) and the ramus area in the axial image (P = 0.011). The LBCE pattern also showed a significant difference in the distance between anteroposterior ramus points (P = 0.043). In conclusion, the differences in the lingual plate split and ramus cut end of the SSRO influence the postoperative remodelling in the anteroposterior region of the split site. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine whether a relationship exists between the amount of mandibular setback and the amount of airway dimensional changes. Records and cone beam computed tomography (CBCT) of patients who had undergone isolated bilateral sagittal split osteotomy setback between January 1, 2013 and March 16, 2020 at a single institution were reviewed retrospectively. The primary outcome variable was upper airway volume dimension change, and the predictor variable was the magnitude of mandibular setback as measured by six different methods. Thirty-one patients were included in the study, with a mean mandibular setback ranging from 1.41 mm to 6.11 mm. None of the predictor variables showed an association with oropharyngeal (P = 0.54) or hypopharyngeal (P = 0.33) volume. Stepwise regression analysis failed to show any significant relationships. Similarly, there was no statistically significant association between any of the predictor variables and oropharyngeal (P = 0.44) or hypopharyngeal (P = 0.74) minimum axial area. The results showed that no correlation exists between the magnitude of mandibular setback and the amount of static airway dimensional changes; therefore, it may not be possible to predict whether obstructive sleep apnea will develop following mild to moderate mandibular setback based upon CBCT measurements. [ABSTRACT FROM AUTHOR]

Neurosensory disturbance of the inferior alveolar nerve (IAN) is an adverse effect associated with sagittal split osteotomies (SSO). The purpose of this work was to evaluate neurosensory recovery of the IAN when SSOs were performed with piezoelectric (PZ) versus reciprocating (RP) saws. This was a prospective split-mouth study of patients undergoing bilateral SSO using a PZ saw on one side and an RP saw on the other. The primary outcome of interest was neurosensory recovery, as assessed using the functional sensory recovery (FSR) scale defined by the UK Medical Research Council. Descriptive, bivariate, and regression statistics were computed. Twenty patients (40 SSOs) with a mean age of 19.9 ± 3.2 years were included. The mean mandibular movement did not differ significantly (P = 0.50) between the PZ and RP groups. All patients achieved FSR within 1 year of surgery (range 34–249 days). The median time to FSR overall was comparable between the PZ and RP groups (94.5 days and 101.5 days, respectively; P = 0.20). However, at the time FSR was achieved, PZ SSO sites were more likely to have higher neurosensory scores when compared to RP SSO sites (hazard ratio 2.3, 95% confidence interval 1.1–4.9, P = 0.04). [ABSTRACT FROM AUTHOR]

The purpose of this three-dimensional cone beam computed tomography (CBCT) study was to identify the difference between monocortical fixation (MCF) and bicortical fixation (BCF) in mandibular canal penetration after bilateral sagittal split osteotomy (BSSO) to correct mandibular prognathism, where interosseous fixation was done by BCF or MCF. CBCT was performed 1 week postoperatively and Dolphin 3D software was used to assess direct penetration of the mandibular canal by either type of screw. The primary outcome variable was the presence or absence of mandibular canal penetration and was categorized as a binary coded variable. The BCF and MCF groups were compared by χ2 test, and the odds ratio for canal penetration was estimated. Multiple logistic regression was performed to identify factors related to canal penetration. A total of 118 patients were included. The MCF group had only 6% canal penetrations (3/50 patients) and the BCF group had 58.8% canal penetrations (40/68 patients). The regression model showed that BCF was the only factor causing mandibular canal penetration, with an adjusted odds ratio of 52.5. Awareness of the increased risk of canal penetration with BCF and potential nerve injury might influence case selection. [ABSTRACT FROM AUTHOR]

The traditional 'high and short' medial cut of the sagittal ramus osteotomy (Hunsuck modification) is a frequent cause of lingual plate interferences in patients undergoing mandibular yaw or cant corrections. We describe how the modified 'low and short' medial cut of the sagittal ramus osteotomy reduces lingual plate interferences with improved passive alignment of the osteotomy segments. [ABSTRACT FROM AUTHOR]

In the bilateral sagittal split osteotomy, a short lingual cut is made on the medial side of the ramus; however, in some cases, a true fracture occurs on the buccal side of the ramus. The purpose of this study was to evaluate the relationship between the splitting pattern of the mandible and the form of the mandible, the surgical technique used, and the postoperative occurrence of relapse after 'unfavorable' splits. The investigation examined 143 patients in whom a short lingual cut was attempted. The rate of unfavorable split was 14.7% (42/286). A strong correlation was observed between the reach of the lateral bone cut to the inferior border of the mandible and an unfavorable split. According to multivariate regression, the factors leading to an insufficient lateral bone cut were the degree of inward curvature of the ramus (P = 0.001) and the position of the lateral bone cut (P = 0.002). There was no significant difference in relapse between cases of unfavorable and normal splits. An unfavorable split does not affect the prognosis of the occlusion, but it is important to confirm the inward curvature of the ramus and set the position of the lateral bone cut adequately to avoid unfavorable splits. [ABSTRACT FROM AUTHOR]

The sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO) are two common orthognathic procedures for the treatment of mandibular prognathism. This randomized clinical trial compared the surgical morbidities between SSRO and IVRO for patients with mandibular prognathism over the first 2 years postoperative. Ninety-eight patients (40 male, 58 female) with a mean age of 24.4 ± 3.5 years underwent bilateral SSRO (98 sides) or IVRO (98 sides) as part or all of their orthognathic surgery. IVRO presented less short-term and long-term surgical morbidity in general. The SSRO group had a greater incidence of inferior alveolar nerve deficit at all follow-up time points (P < 0.01). There was more TMJ pain at 6 weeks (P = 0.047) and 3 months (P = 0.001) postoperative in the SSRO group. The SSRO group also presented more minor complications, which were related to titanium plate exposure and infection. There were no major complications for either technique in this study. Despite the need for intermaxillary fixation, IVRO appears to be associated with less surgical morbidity than SSRO when performed as a mandibular setback procedure to treat mandibular prognathism. [ABSTRACT FROM AUTHOR]

Skeletal advancement surgery with sagittal split ramus osteotomy (SSRO) or mandibular distraction osteogenesis (MDO) is effective in treating patients with obstructive sleep apnoea (OSA) and may improve their quality of life (QoL). This study aimed to evaluate the longitudinal QoL changes in moderate-to-severe OSA patients after skeletal advancement surgery. Eighteen patients were randomized to receive SSRO (n = 9) or MDO (n = 9) alone or as part of the skeletal advancement surgery. Baseline QoL was compared with that of a control group (n = 36). QoL was compared between the SSRO group and MDO group over a period of 2 years postoperative. The Epworth Sleepiness Scale (ESS), Calgary Sleep Apnea Quality of Life Index (SAQLI), Functional Outcomes of Sleep Questionnaire (FOSQ), and Short Form Health Survey (SF-36) were used as instruments. The OSA group had worse ESS, SF-36, FOSQ, and SAQLI preoperatively than the control group. The MDO and SSRO groups showed significant improvements in ESS at all postoperative time points (P ≤ 0.021). The FOSQ, SAQLI, and SF-36 of both groups at 2 years postoperative were similar to those of the control group. No differences in QoL were found between the SSRO and MDO groups. This study showed QoL was improved in patients with moderate-to-severe OSA after skeletal advancement surgery by SSRO or MDO. [ABSTRACT FROM AUTHOR]

Abstract The aim of this systematic review was to assess the stability of rigid internal fixation (RIF) techniques in sagittal split ramus osteotomy (SSRO) based on in vitro biomechanical assessments, with particular interest in large mandibular advancements. In general, RIF methods can be divided into three groups: bicortical screws, miniplates, and a combination of the two. An electronic search of the PubMed, CINAHL, and Embase databases was performed, and studies published between January 2003 and March 2018 were screened for inclusion. Comparative studies with an in vitro experimental design, using biomechanical assessments to measure the stability of RIF methods in SSRO, were included. Of 104 unique studies identified in the initial search, 24 were included. Twenty-two of these 24 studies analyzed an advancement of the mandible of 7 mm or less. The use of a single four-hole or six-hole miniplate was less stable than the use of bicortical screws, hybrid techniques, double miniplates, or grid plates. Two studies analyzed advancements of 10 mm, for which two miniplates placed in parallel and a grid plate showed most stability. Although there was agreement between studies with regard to results, more biomechanical studies are required to quantify the stability of fixation methods in larger mandibular advancements. [ABSTRACT FROM AUTHOR]

Abstract The sagittal split ramus osteotomy (SSRO) is generally associated with greater postoperative stability than the intraoral vertical ramus osteotomy (IVRO); however, it entails a risk of inferior alveolar nerve damage. In contrast, IVRO has the disadvantages of slow postoperative osseous healing and projection of the antegonial notch, but inferior alveolar nerve damage is believed to be less likely. The purposes of this study were to compare the osseous healing processes associated with SSRO and IVRO and to investigate changes in mandibular width after IVRO in 29 patients undergoing mandibular setback. On computed tomography images, osseous healing was similar in patients undergoing SSRO and IVRO at 1 year after surgery. Projection of the antegonial notch occurred after IVRO, but returned to the preoperative state within 1 year. The results of the study indicate that IVRO is equivalent to SSRO with regard to both bone healing and morphological recovery of the mandible. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the precision of bimaxillary surgery performed to correct vertical maxillary excess, when the procedure is sequenced with mandibular surgery first or maxillary surgery first. Thirty-two patients, divided into two groups, were included in this retrospective study. Group 1 comprised patients who received bimaxillary surgery following the classical sequence with repositioning of the maxilla first. Patients in group 2 received bimaxillary surgery, but the mandible was operated on first. The precision of the maxillomandibular repositioning was determined by comparison of the digital prediction and postoperative tracings superimposed on the cranial base. The data were tabulated and analyzed statistically. In this sample, both surgical sequences provided adequate clinical accuracy. The classical sequence, repositioning the maxilla first, resulted in greater accuracy for A-point and the upper incisor edge vertical position. Repositioning the mandible first allowed greater precision in the vertical position of pogonion. In conclusion, although both surgical sequences may be used, repositioning the mandible first will result in greater imprecision in relation to the predictive tracing than repositioning the maxilla first. The classical sequence resulted in greater accuracy in the vertical position of the maxilla, which is key for aesthetics. [ABSTRACT FROM AUTHOR]

The sagittal split ramus osteotomy and intraoral vertical ramus osteotomy carry the potential risk of postoperative nerve paralysis, bleeding, and fracture and dislocation of the condyle. In 1992, Choung first described the intraoral vertico-sagittal ramus osteotomy for the purpose of avoiding postoperative dislocation of the condyle. However, there is still potential for damaging the inferior alveolar nerve and maxillary artery with this technique. The authors have developed a modified technique to minimize these risks. An evaluation of surgical experience and patient outcomes with the use of this technique is presented herein. One hundred twenty-two sides in 97 Japanese patients diagnosed with a jaw deformity were analyzed. This technique includes a horizontal osteotomy that is performed at a higher position than in the original Choung procedure. Intraoperatively, there was no unexpected bleeding from the operative site. Proximal segment dislocation from the glenoid fossa was observed on one side (0.82%). Non-union of the osteotomy was not observed in any patient. Intraoperative fracture of the coronoid process occurred in 2.46%, but none necessitated treatment of the fracture. Nerve dysfunction was found in 2.46% at the 12-month postoperative follow-up. The modified technique presented herein was developed to reduce postoperative nerve dysfunction and intraoperative hemorrhage. [ABSTRACT FROM AUTHOR]

Intraoperative navigation is a helpful tool in complex anatomical regions or procedures. The mobility of the mandible in relation to the skull base limits the use of navigation tools on the lower jaw if the reference device is installed on the forehead. A new workflow that allows navigation-assisted sagittal split osteotomy in orthognathic surgery using a separate non-invasive mandibular registration technique has been developed. An evaluation of accuracy in different anatomical regions and with different registration techniques was performed on skull models and skulls with movable mandibles. The mean inaccuracy was 1.51 mm, with no significant difference between anatomical sites. Using a splint-based reference device allows the movable mandible to be registered independently from the midface. Registration using metal points in the splint provides higher accuracy than using interdental anatomical landmarks. The workflow could be transferred successfully to patient treatment. Navigation-assisted osteotomy by Obwegeser–Dal Pont technique was performed without any complication in six patients. The mean deviation from the planned osteotomy line was 1.52 mm. The navigated sagittal split ramus osteotomy seems to be a suitable technique to increase patient safety. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of surgical mandibular backward movements on the predictors of a difficult airway. Thirty-seven skeletal class III patients were included in this study. The Mallampati score, body mass index (BMI), maximal inter-incisal distance, and thyromental and sternomental distances of these patients were evaluated preoperatively and at 6 months and 2 years postoperatively. A sagittal split ramus osteotomy (SSRO) without genioplasty was performed in all patients by the same surgical team, and anaesthesia was provided by the same anaesthesiologist using nasotracheal intubation. The paired samples t -test and Wilcoxon signed-rank test were used for statistical comparisons of the data. There were no statistically significant changes in BMI or sternomental and thyromental distances after SSRO. The maximal inter-incisal distance was significantly reduced at 6 months postoperatively ( P < 0.05), but no statistical difference was found between the values obtained preoperatively and at 2 years postoperative. A statistically significant increase in Mallampati score was observed postoperatively ( P < 0.05). Both the patient and practitioner should be aware of the risks associated with an increased postoperative Mallampati score in mandibular setback patients. The amount of mandibular setback in skeletal class III patients with a high preoperative Mallampati score should be limited to prevent potential postoperative airway problems. [ABSTRACT FROM AUTHOR]

The purpose of this retrospective study was to evaluate the changes in computed tomography (CT) values of ramus bone and screws after sagittal split ramus osteotomy (SSRO) setback surgery. The subjects were 64 patients (128 sides) who underwent bilateral SSRO setback surgery. They were divided into six groups according to the fixation plate type used and the use or not of self-setting α-tricalcium phosphate (Biopex): group 1: titanium plate and screws; group 2: titanium plate and screws with Biopex; group 3: poly- l -lactic acid (PLLA) plate and screws; group 4: PLLA plate and screws with Biopex; group 5: uncalcined and unsintered hydroxyapatite particles and poly- l -lactic acid (uHA/PLLA) plate and screws; group 6: PLLA/uHA plate and screws with Biopex. CT values (pixel values) of the lateral cortex, medial cortex, osteotomy site, and screws were measured preoperatively, immediately after surgery, and 1 year postoperatively using horizontal CT images at the mandibular foramen taken parallel to the Frankfort horizontal plane. There were significant differences in the time-course change of pixel values for the lateral cortex ( P < 0.0001) and the osteotomy site ( P < 0.0001) among the six groups. This study suggests that the fixation plate type and use of bone alternative material may affect bone quality during the process of bone healing after SSRO. [ABSTRACT FROM AUTHOR]

The sagittal split ramus osteotomy (SSRO) is a surgical technique used widely to treat many congenital and acquired mandibular discrepancies. Stabilization of the osteotomy site and the potential for skeletal relapse after the procedure are still major problems. The aim of this study was to compare the mechanical stability of six methods of rigid fixation in SSRO using a biomechanical test model. Sixty polyurethane replicas of human hemimandibles were divided into six groups. In group I, the osteotomies were fixed with two four-hole titanium miniplates; in group II, with one four-hole miniplate; in group III, with one four-hole miniplate + a bicortical screw; in group IV, with a grid miniplate; in group V, with a four-hole locking miniplate; and in group VI, with a six-hole miniplate. A linear load in the premolar region was applied to the hemimandibles. The resistance forces (N) needed to displace the distal segment by 1, 3, and 5 mm were recorded and the data transmitted from the load cell to a computer. One-way analysis of variance with Tukey's post hoc test was performed to compare the means between groups. For the three displacement conditions, there was a strong tendency for the 2.0-mm plate + screw and the grid plate to have higher values. [ABSTRACT FROM AUTHOR]

In this study, finite element analysis (FEA) was used to evaluate nine rigid internal fixation techniques for sagittal split ramus osteotomy. To achieve this, a computed tomography (CT) scan of a healthy patient was obtained and used to generate the geometry of a half-mandible. The geometries of bicortical screws, miniplates, and monocortical screws were designed and combined with the mandible in nine models simulating various techniques. Four models used bicortical screws in various arrangements and four used miniplates of various designs. One model represented a hybrid technique. A load of 500 N was applied to the posterior teeth and FEA was applied. The most stable techniques were the hybrid technique and a single straight miniplate, presenting the least displacement among all models. Bicortical screws, while presenting reasonable stability, showed high strain areas near the anterior ramus ridge, superoposterior to the screws, implying a risk of bone fracture in this area. On the other hand, the T-shaped and double Y-shaped miniplates were associated with high von Mises stresses that would impair their rigidity, especially where angles appeared in their designs. We recommend the use of a single straight miniplate because it provides sufficient stable fixation with minimal risks or disadvantages. [ABSTRACT FROM AUTHOR]

We investigated changes in the sensitivity of cutaneous points and the oral mucosa after sagittal split ramus osteotomy (SSRO) and assessed the differences between SSRO and intraoral vertical ramus osteotomy (IVRO). The subjects included in this study were 46 patients with mandibular prognathism who underwent IVRO (88 rami) and 30 patients who underwent SSRO (59 rami). An objective evaluation of the neurosensory status of each patient was completed preoperatively and at 1, 4, 8, 12, and 24 weeks postoperatively. Other variables studied for each patient included sex, age, magnitude of mandibular setback, and amount of blood loss during surgery. We found that a neurosensory recovery occurred earlier in the oral mucosa than at cutaneous points. The number of oral mucosa points showing reduced neurosensory function and neurosensory disturbance after SSRO was significantly higher than after IVRO at 1, 4, and 8 weeks ( P < 0.05). The nerve recovery observed after SSRO was delayed for a longer period than that noted in our previous study of IVRO. In conclusion, we found changes in sensitivity at cutaneous points and the oral mucosa after SSRO and assessed the differences between SSRO and IVRO. [ABSTRACT FROM AUTHOR]

The purpose of this study was to review the current literature for the relationship between the preoperative position of the mandibular canal on three-dimensional (3D) radiographic imaging and postoperative neurosensory disturbance (NSD) following a sagittal split ramus osteotomy (SSRO). A literature search was conducted using PubMed, EMBASE, and the Cochrane Database for articles published from 1 January 2000 through 31 December 2013. Studies that included preoperative 3D imaging and assessment of NSD after surgery were reviewed. Study sample characteristics and results were extracted. Of the 69 articles identified, seven met the inclusion and exclusion criteria. There was no standardization for measuring the canal position or for evaluating NSD. General consensus was that the less space between the mandibular canal and the outer border of the buccal cortex the more frequent the occurrence of NSD. Increased bone density also appeared to contribute to a higher incidence of NSD. Utilization of 3D images to locate and measure the position of the mandibular canal is not standardized. Advances in 3D imaging and evaluation tools allow for new methodologies to be developed. Early attempts are informative, but additional studies are needed to verify the relationship between the location of the nerve and NSD following surgery. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to examine the changes in border movement of the mandible before and after mandibular ramus osteotomy in patients with prognathism. The subjects were 73 patients with mandibular prognathism who underwent sagittal split ramus osteotomy (SSRO) with and without Le Fort I osteotomy. Border movement of the mandible was recorded with a mandibular movement measure system (K7) preoperatively and at 6 months postoperatively. Of the 73 patients, 21 had measurements taken at 1.5 years postoperative. Data were compared between the pre- and postoperative states, and the differences analyzed statistically. There was no significant difference between SSRO alone and SSRO with Le Fort I osteotomy in the time-course change. The values at 6 months postoperative were significantly lower than the preoperative values for maximum vertical opening (P =0.0066), maximum antero-posterior movement from the centric occlusion (P =0.0425), and centric occlusion to maximum opening (P =0.0300). However, there were no significant differences between the preoperative and 1.5 years postoperative measurements. This study suggests that a postoperative temporary reduction in the border movement of the mandible could recover by 1.5 years postoperative, and the additional procedure of a Le Fort I osteotomy does not affect the recovery of mandibular motion after SSRO. [Copyright &y& Elsevier]

Abstract: Prediction of neurosensory deficit in the lower lip and chin after sagittal split ramus osteotomy (SSRO) is challenging. This study aimed to elucidate factors related to the development and improvement of neurosensory disturbance (NSD) after SSRO with respect to surgical procedure and the anatomical and structural characteristics of the craniomaxillofacial skeleton. Subjects comprised 50 patients treated by a single experienced surgeon. Anatomical data and landmarks were obtained by computed tomography (CT) imaging. There was a significant difference between patients with or without NSD for the surgical space on the medial side of mandibular ramus 1 week after SSRO (P =0.006). Less than 15.0mm between the lingula and mandibular notch (relative risk, 6.7; 95% CI, 1.7–33.8) and 195.0mm2 or more space on the medial side of the mandibular ramus (relative risk, 17.2; 95% CI, 3.9–100.4) indicated a significant risk of NSD development at 6 months postoperatively. These results suggested that the development of NSD is related to the surgical space on the medial side of the mandibular ramus and subsequent manipulation of the inferior alveolar nerve (IAN) in that region. Limited periosteal degloving prevents excessive stretching of the IAN during SSRO, thus lowering NSD incidence. [Copyright &y& Elsevier]

Abstract: Recent studies have evaluated many methods of internal fixation for sagittal split ramus osteotomy (SSRO), aiming to increase stability of the bone segments while minimizing condylar displacement. The purpose of this study was to evaluate, through biomechanical testing, the stability of the fixation comparing a specially designed bone plate to other two commonly used methods. Thirty hemimandibles were separated into three equal groups. All specimens received SSRO. In Group I the osteotomies were fixed with three 15mm bicortical positional screws in an inverted-L pattern with an insertion angle of 90°. In Group II, fixation was carried out with a four-hole straight plate and four 6mm monocortical screws. In Group III, fixation was performed with an adjustable sagittal plate and eight 6mm monocortical screws. Hemimandibles were submitted to vertical compressive loads, by a mechanical testing unit. Averages and standard deviations were submitted to analysis of variance using the Tukey test with a 5% level of significance. Bicortical screws presented the greatest values of loading resistance. The adjustable miniplate demonstrated 60% lower resistance compared to bicortical screws. Group II presented on average 40% less resistant to the axial loading. [Copyright &y& Elsevier]

Abstract: The inferior alveolar nerve (IAN) is vulnerable to injury from mandible fractures and surgical procedures so anatomical variations of IAN are important. Postoperative sensory alteration of the lip and chin region is high after mandibular orthognathic surgery. The incidence of IAN paresthesia following sagittal split ramus osteotomy (SSRO) ranges from 54% to 86% at 4–8 days, 41 to 75% at 1 month, 33 to 66% at 3 months, 17 to 58% at 6 months and 15 to 33% at 1 year postoperatively. This study determined the anatomical position of the mandibular canal in relation to cortical bone and molar teeth in Chinese using archived CT records. The mandibular canal was the farthest from the buccal cortex at the second molar region (mean 6.79mm; minimum distance 4.80mm). The anatomical location of the mandibular canal in local Chinese compares with studies on Asian cadavers. The mandible body was thickest in the region of the second molar (11.9mm). The vertical buccal cut for SSRO should be in the region of the mandibular second molar where the bone is thickest and the mandibular canal is furthest from the buccal cortex. The safe depth for the vertical buccal cut is 4.8mm (minimum horizontal distance). [Copyright &y& Elsevier]

Abstract: Bilateral sagittal split ramus osteotomy (BSSO) is widely used to treat mandibular prognathism. Several methods have been described for fixation of the bony segments. This study compared two methods of rigid fixation (bicortical screws and monocortical miniplates) to identify differences in postoperative masticatory function and neurosensory disturbance after 5 years of mandibular set-back correction. 77 women who had undergone BSSO for Class III malocclusion were reviewed, and masticatory functions and neurosensory recovery were examined with the appropriate indicators pre- and postoperatively (at approximately 1 month, and 1, 2, 3, 4, and 5 years). Masticatory function exhibited similar recovery patterns in both groups. Orthognathic surgery improved occlusal force and occlusal contact area, but longer than 4 years after surgery may be required for postoperative occlusal functions in prognathic patients to reach the level of healthy subjects. The groups showed no significant differences in the recovery of parameters of masticatory functions and neurosensory disturbance even 5 years after surgery. In the evaluation of temporomandibular joint function using the Helkimo index, the score was significantly higher for the screw group than for the miniplate group. This suggests that BSSO fixed with miniplates may offer a relatively safe and reliable procedure yielding adequate results and high patient satisfaction. [Copyright &y& Elsevier]

Abstract: This study investigated the specific morphology of the mandibular ramus at the lingual plane in patients with mandibular hyperplasia using spiral computed tomography. The subjects were 25 patients with mandibular hyperplasia undergoing sagittal split ramus osteotomy and there were 20 patients without dentofacial deformities in the control group. The thickness of the mandible, diameter of the inner mandibular canal, width of the buccal bone marrow space, and the width of the buccal cortex and lingual cortex were measured at the lingual plane, which contained the lowest point of the mandibular foramen. The average thickness of the mandible was 8.5mm in prognathic patients and 9.6mm in control patients. The average width of the buccal bone marrow space in mandibular hyperplasia patients was 1.5mm and 2.5mm in control patients. The mandibular ramus in patients with mandibular hyperplasia was thinner and the width of the buccal bone marrow space was smaller than in the control patients. The width of the buccal bone marrow space and the thickness of the mandible were significantly positively correlated. [Copyright &y& Elsevier]

Abstract: A novel modification of a bone repositioning device previously published by the same authors is introduced. A flexible tube to define the intersegmental bony relationship is filled with light-cured resin. It solidifies following exposure to strong visible light for about 1min. This technique can be used for bone positioning after mandibular resection surgery and during positioning of the proximal segment after sagittal split ramus osteotomy. The authors also propose a simple method for determining the contour of the reconstructed mandible to regain the original shape and form. The advantage of this technique is its simplicity and flexibility compared with other methods of bone positioning during mandibular segmental surgery. [Copyright &y& Elsevier]

Abstract: To evaluate the effect of bilateral sagittal split ramus osteotomy setback on the morphology of the pharyngeal airway, especially the structures of the soft palate and pharyngeal airway space (PAS), lateral cephalograms obtained from 49 women before treatment and 1 year after surgery were traced and compared. All patients underwent this osteotomy to correct mandibular hyperplasia. The data were corrected with the use of regression equations for the PAS, taking into account head posture. On average, the SNB angle decreased by 3.9 degrees, resulting in an increase of 4.1 degrees in OPT/NSL (head posture, defined as the craniocervical angulation at the uppermost part of the cervical spine). The morphology of the PAS and soft palate changed significantly (p <0.01). The mean reduction in the PAS was 2.6mm retropalatinally and 4.0mm retrolingually. On average, the soft-palate length increased by 3.2mm and the soft-palate angle increased by 4 degrees. These results show that mandibular setback surgery markedly decreases the PAS and changes the morphology of the soft palate. [Copyright &y& Elsevier]

Abstract: Bilateral sagittal split osteotomy is commonly used to treat mandibular prognathism. Several fixation methods for bony segments have been described. The present study compared masticatory function and neurosensory recovery patterns after mandibular correction between two methods of rigid fixation, bicortical screw (n =38) and monocortical miniplate (n =32). Patients who had undergone bilateral sagittal split osteotomy for Class III malocclusion were reviewed, and masticatory function and neurosensory recovery were studied with the appropriate indicators at 1, 3, 6 and 12 months postoperatively. Minimal differences were seen between groups at 1-year postoperatively, and although patients treated with miniplate fixation tended to recover faster, with regard to masticatory function and neurosensory disturbance, than those treated with screw fixation, no significant differences were identified. As the two methods seem to provide equal comfort and reliability, the choice should be made by the individual surgeon. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to evaluate bite force, occlusal contact area and masticatory efficiency before and after sagittal split ramus osteotomy in 27 patients with mandibular prognathism, in comparison with 27 control subjects with normal occlusion. Bite force and occlusal contact area were simultaneously measured with a computerized occlusal analysis system, the Dental Prescale system. Masticatory efficiency was estimated by a low-adhesive colour-developing chewing-gum system. The data were collected at initial medical consultation, immediately before surgery, and at 6 weeks, 3 months, 6 months, 1 year and more than 2 years after surgery. Both bite force and occlusal contact area of the patients before surgery were significantly less than those of the controls. Although all three parameters had improved after orthognathic surgery, the bite force and occlusal contact area did not reach the values of the controls within 2 years postoperatively; masticatory efficiency at 2 years after surgery drew near to control levels. Bite force correlated with occlusal contact area in the patients postoperatively, whereas masticatory efficiency did not correlate with either of the other two parameters. These results suggest that further adjustment of occlusion and mechanical advantage should be considered before the end of treatment. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to evaluate the mechanical behavior of different fixation methods used in bilateral sagittal split ramus osteotomy (BSSRO). Part 1 comprises of the results of the analysis for mandibular advancement, four different fixation configurations of six hole fragmentation mini plates with monocortical screws and lag screws and posterior loading conditions in the molar and premolar region. The finite element analysis method (FEA) appears suitable for simulating complex mechanical stress situations in the maxillofacial region. The mechanical behavior of selected lag screws with linear or triangular configuration and double parallel or single oblique six hole mini plates with monocortical screws were compared by FEA after 5mm BSSRO advancement procedure. Four separate three-dimensional finite element models of the mandible were created to simulate the BSSRO and corresponding fixation methods. These models consisted of 122,717 elements and 25,048 nodes. The mechanical parameters of the materials studied were adopted from the literature or were based on manufacturer''s information. 500 N posterior occlusal loads were simulated on the distal segments. The commercial finite element solver MSC Marc software was utilized to calculate the stress fields on both the segments and fixative appliances. It was concluded that the use of 2.0mm lag screws placed in a triangular configuration following the BSSRO advancement surgery provides sufficient stability with any rotational movement and less stress fields at the osteotomy site, when compared with the other rigid fixation methods used in the current study. [Copyright &y& Elsevier]