Dislocation of temporomandibular joint: complication of sagittal split ramus osteotomy

Biomechanical comparison of the effect of bilateral sagittal split ramus osteotomy with or without Le Fort I osteotomy on the temporomandibular joints of the patients with maxillofacial deformities under centric occlusion

Mandibular deformities negatively affect the daily activities of the patients and may cause temporomandibular disorders (TMD). Bilateral sagittal split ramus osteotomy (BSSRO) and Le Fort I osteotomy are effective treatments to correct the mandibular deformities. The aim of this study was to investigate and compare the effects of the BSSRO with or without Le Fort I on the stress distributions of the temporomandibular joints (TMJs) of the patients with mandibular deformities under centric occlusion based on finite element (FE) method. Preoperative and postoperative cone-beam computed tomography (CBCT) images of twenty-four patients diagnosed with mandibular prognathism, including ten patients with BSSRO and another 14 patients with bimaxillary osteotomy (BSSRO with Le Fort I), were used to construct maxillofacial models. Ten asymptomatic individuals were also performed CBCT scanning and defined as the control group. In addition, the muscle forces and boundary conditions corresponding to centric occlusions were applied on each model. For the preoperative groups with both the BSSRO and bimaxillary osteotomies, the average peak contact stresses of the TMJs were both greater than those of the control group. After the surgeries, the contact stresses of the discs and temporal bones of both groups considerably decreased. However, the contact stresses on the condyles slightly increased after BSSRO but decreased after bimaxillary osteotomy. The TMJs of the patients with maxillofacial deformities suffered abnormal tensile and compressive stresses compared with the asymptomatic subjects under centric occlusion. Both of the BSSRO and bimaxillary osteotomy could improve the risk stress distributions of the TMJs.

Correction of Condylar Displacement of the Mandible Using Early Screw Removal following Patient-Customized Orthognathic Surgery

OBJECTIVE

Orthognathic surgery (OGS) is a surgical intervention that corrects dentofacial deformities through the movement of maxillary and mandibular segments to achieve adequate masticatory function, joint health, and facial harmony. However, some patients present with occlusal discrepancies, condylar sag, and/or temporomandibular disorders after OGS. Various methods have been employed to solve these problems after surgery. This study aimed to evaluate the effectiveness of early screw removal in patients with occlusal discrepancies after OGS using three-dimensional cone-beam computed tomography (CBCT).

METHODS

In 44 patients with dentofacial deformities, patient-customized OGSs with customized plates were performed to correct facial deformities using customized guides with computer-aided surgical simulation. Of the 44 patients, eight patients complained of occlusal discrepancies and temporomandibular disorders after OGS. These eight patients underwent screw removal under local anesthesia around four weeks. The temporomandibular joint spaces at three time points (pre-surgical, post-surgical, and after screw removal) in the sagittal and coronal planes were compared using CBCT.

RESULTS

Eight patients showed an increase in joint space on CBCT images immediately after surgery (T1), but after early screw removal (T2), these spaces almost returned to their pre-surgical state, and the temporomandibular joint problem disappeared.

CONCLUSIONS

The removal of screws located in the distal segment under local anesthesia between three and four weeks post-surgically may be a treatment option for patients with post-OGS occlusal discrepancies, condylar sag, and/or temporomandibular disorder.

Effect of sagittal split ramus osteotomy on stress distribution of temporomandibular joints in patients with mandibular prognathism under symmetric occlusions

Sagittal split ramus osteotomy (SSRO) is the representative orthognathic surgery for the patients with mandibular prognathism. It is essential to understand the biomechanical environment of temporomandibular joint (TMJ) to analyse the effects of SSRO. This study aimed to investigate the influence of SSRO on the stress distributions in the TMJs of the patients with mandibular prognathism under symmetric occlusions. Thirteen patients with mandibular prognathism and ten asymptomatic volunteers were recruited. Finite element models of the asymptomatic, preoperative, and postoperative subjects were established, based on the CT of the asymptomatic volunteers and preoperative and postoperative scans of patients with mandibular prognathism. Contact was used to simulate the interactions between discs and articular surfaces, and between the upper and lower dentition. Muscle forces and boundary conditions corresponding to the centric and anterior occlusions were applied on the models. Under both occlusions, the maximum and minimum principal stresses of the articular disc and condyle in the preoperative group were significantly greater than those in the control group. After SSRO, the maximum and minimum principal stresses of the articular disc and condyle of the patients under both occlusions were greatly reduced, but the principal stresses of the articular disc were not significantly higher than those in the control group. Mandibular prognathism led to excessive stress on the TMJ. Severe asymmetric compression between the TMJs on both sides might cause temporomandibular disorder (TMD) symptoms. SSRO could improve the stress distribution of the TMJ and partially relieve the symptoms of TMD.

Usefulness of Early Plate Removal in Patients With Occlusal Discrepancies After Sagittal Split Ramus Osteotomy

The aim of this study was to evaluate the effects of early removal of fixed plates in patients with occlusal discrepancies after sagittal split ramus osteotomy (SSRO) with a focus on the positional relationship of the temporomandibular joint (TMJ). Sagittal split ramus osteotomy with/without Le Fort I osteotomy was performed on 98 patients with mandibular prognathism. Of these 98 patients, 15 with occlusal discrepancies and/or TMJ symptoms underwent early plate removal after SSRO. Finally, 12 consecutive patients were evaluated in this study: 7 underwent bilateral SSRO, 1 underwent unilateral SSRO, and 4 underwent bilateral SSRO with maxillary advancement. The axiolateral TMJ Schuller method was used to evaluate the TMJ position. The authors measured 3 spaces (anterior, superior, and posterior joint spaces) between the condyle and glenoid fossa in the sagittal plane. The anterior and superior joint spaces were significantly larger immediately after the operation than before the operation. After early plate removal, these spaces significantly decreased in size. The posterior joint space increased, but with no significant difference. Three months after SSRO, the size of each of the 3 spaces was closely related to its preoperative size. In conclusion, these results suggest that early removal of fixed plates is 1 treatment option for postoperative occlusal discrepancies after SSRO.

The influence of bilateral sagittal split ramus osteotomy on the stress distributions in the temporomandibular joints of the patients with facial asymmetry under symmetric occlusions

The aim of this study is to compare the differences in the stress distributions in the temporomandibular joints (TMJs) of the patients with facial asymmetry before and after bilateral sagittal split ramus osteotomy (BSSRO) under the symmetric occlusions using the three-dimensional (3D) finite element method.Ten facial asymmetry patients (Preoperative group, age 24.6 ± 4.8 years) and 10 asymptomatic subjects (Control group, age 26.8 ± 4.9 years) were recruited. After the patients underwent BSSRO, they were further assigned as the Postoperative group. 3D geometries of the finite element models of the mandible, disc, maxilla, and teeth were reconstructed according to cone-beam computed tomography (CBCT) image data. Contact elements were used to simulate the interaction of the disc-condyle, disc-temporal bone, and upper-lower dentition. The muscle forces and boundary conditions corresponding to the central and anterior occlusions were applied on the models of the 3 groups. The finite element models were validated with experimental data showing the accuracy of the simulation results.The simulation predicted preoperative significant differences of stresses between non-deviated sides and deviated sides were disappeared after the surgery under the central and anterior occlusions (P < .05). Almost all stresses in the patient models had significantly decreased after BSSRO, leveling it to the stress values of the normal subjects. Moreover, the simulation results coincided with the clinical cases which showed that BSSRO had helped to release or remove the signs and symptoms of temporomandibular disorders (TMD).In conclusion, BSSRO could correct the asymmetric stress distributions of TMJs and decrease the magnitude of the stresses for the patients with facial asymmetry. Those decreases also associated with the recovery of TMD.

Simple Technique for Reducing the Buccal Fat Pad During Mandibular Orthognathic Surgery

Sagittal split ramus osteotomy and intraoral vertical ramus osteotomy are commonly performed for the correction of jaw deformities. However, during mandibular orthognathic surgeries such as sagittal split ramus osteotomy and intraoral vertical ramus osteotomy , the authors sometimes encounter exposure of the buccal fat pad (BFP), which decreases the surgical field. The exposed BFP makes it difficult to perform these operations, may result in unexpected complications, and may increase the operation time. Therefore, the authors herein describe a simple, safe, and convenient technique for reducing the volume of the exposed BFP during mandibular orthognathic surgery using an electric knife in the coagulation mode.

Influence of anatomic position and intraoperative exposure of the inferior alveolar nerve on neurosensory disturbance after sagittal split ramus osteotomy: a three-dimensional computed tomography study

OBJECTIVE

To evaluate the influence of the anatomic position and intraoperative exposure of the inferior alveolar nerve on neurosensory disturbance (NSD) in sagittal split ramus osteotomy.

STUDY DESIGN

The anatomic factors of the nerve were measured on preoperative three-dimensional computed tomography in 98 patients. The intraoperative nerve exposure was assessed. NSD was evaluated for 1 year after surgery. The correlations between NSD and the factors were analyzed.

RESULTS

The NSD decreased as the lateral marrow space from the nerve increased (P < .01). The complete nerve exposure increased NSD by 7.6 times (P = .01). The nerve exposure increased as the buccal plate thickness increased (P = .01) and decreased as the vertical marrow space from the nerve increased (P = .01).

CONCLUSIONS

The nerve exposure and the lateral marrow space from the nerve affected NSD. The buccal plate thickness and the vertical marrow space indirectly affected NSD through nerve exposure.

Professional oral health care reduces the duration of hospital stay in patients undergoing orthognathic surgery

The present study reviewed the records of 58 patients who underwent orthognathic surgery [sagittal split ramus osteotomy (SSRO), Le Fort I osteotomy, genioplasty, anterior maxillary alveolar osteotomy] between 2010 and 2015. To investigate the influence of preoperative oral health care on postoperative inflammation, infection and length of hospital stay in those patients, white blood cell (WBC) count and C-reactive protein (CRP) levels were compared between patients who received and did not receive preoperative oral care. The mean CRP level throughout the postoperative term was lower in the oral care group as compared to the non-oral care group. By contrast, the oral care group had a lower occurrence of postoperative infectious complications (surgical site infection, anastomotic leak) (13.6 vs. 20.8%) and a shorter average length of hospital stay (16.2±3.8 vs. 21.2±7.4 days). These results suggest that preoperative professional oral health care decreases the duration of hospital stay following orthognathic surgery by inhibiting inflammation and infectious complications during the postoperative stage.