Influence of lingual plate fracture pattern on remodelling site during the healing process of sagittal split ramus osteotomy.

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.

Antibiotic prophylaxis for sagittal split ramus osteotomy using resorbable plate and screw fixation: a randomised trial to compare extended dual-agent and inpatient single-agent regimens.

Resorbable materials are used to fix bony fragments after sagittal split ramus osteotomy (SSRO), but to our knowledge, there is no clear regimen for antibiotic prophylaxis when such materials are used. The purpose of this study therefore was to compare inpatient single-agent and extended dual-agent antibiotic prophylaxis for the prevention of surgical site infections (SSI) in patients after SSRO. This prospective study included 100 patients who underwent SSRO for deformities of the jaw. Cephalometric analysis was performed preoperatively, and at one month and one year postoperatively. Patients were divided into two groups of 50 each. Group A was given cefazolin sodium 1g preoperatively and every eight hours for 48 hours postoperatively. Group B was given cefazolin sodium 1g preoperatively and every eight hours for 48 hours postoperatively, after which they were provided with oral amoxicillin for three days. Both groups were assessed for SSIs for one year postoperatively using the Clavien-Dindo classification. SSIs were documented in seven patients in Group A and six in Group B, with no significant difference between the groups. The two regimens had no significant association with SSI. In conclusion, our results suggest that the inpatient, single-agent, postoperative antibiotic regimen is sufficient to prevent SSI in patients who have SSRO with resorbable plate and screw fixation.

Simplified stress analysis on the temporomandibular joint in Class III patients with and without mandibular asymmetry using a rigid body spring model.

OBJECTIVE: Aim of this study was to investigate the differences in stress on the temporomandibular joint (TMJ) between Class III patients with and without mandibular asymmetry using a rigid body spring model (RBSM). DESIGN: Menton (Me), the centre point of occlusal force on the line that connected the bilateral buccal cusps of the second molars and the most lateral, superior and medial points of the condyle were plotted on frontal cephalograms, and stress on the condyles was calculated with the 2-dimensional RBSM program of fortran. SETTING AND SAMPLE POPULATION: Eighty Japanese patients with diagnosed mandibular prognathism were divided into two groups, a symmetry group and asymmetry group on the basis of the Mx-Md midline position. OUTCOME MEASURE: The degree (force partition) of the resultant force, the direction (angulation) and displacement (X, Y) of each condyle were calculated. The horizontal displacement vector (u), the vertical displacement vector (v) and rotation angle (theta) of the mandibular body at Menton were also calculated. RESULTS: There were significant differences between the deviated and non-deviated sides of both groups regarding resultant force (symmetry group: p = 0.0372, asymmetry group: p = 0.0054), X (symmetry group: p < 0.0001, asymmetry group: p = 0.0001) and Y (symmetry group: p = 0.0354, asymmetry group: p = 0.0043). For angulation, there was a significant difference between the deviated and non-deviated sides in the asymmetry group (p = 0.0095). CONCLUSION: The results of this study suggest that difference in stress angulation on the condyles could be associated with asymmetry in mandibular prognathism.

Use of the Sonopet ultrasonic curettage device in intraoral vertical ramus osteotomy.

This study was designed to evaluate the usefulness of the Sonopet UST-2001 (Miwatec Co., Ltd., Kawasaki, Kanagawa, Japan) ultrasonic curettage device, and to assess the outcome after intraoral vertical ramus osteotomy (IVRO). Thirteen Japanese adults (age range 20-41 years, mean age 29.6 years) presented with jaw deformities diagnosed as mandibular prognathism and asymmetry; they all underwent IVRO of the mandible. This procedure was followed by ultrasonic bone curettage using the Sonopet to make a guiding notch or groove in the lateral cortex of the ramus without damaging the vessels and nerves. After surgery, the osteotomy line was evaluated by three-dimensional computed tomography. In all patients, osteotomy with the Sonopet device was achieved safely, with minimal bleeding and no major complications. The distal segment could be moved into its ideal position and all patients achieved their ideal profiles. Ultrasonic bone curettage is a safe method for making a guiding groove, without damage to surrounding tissue, prior to complete IVRO.

Changes in occlusal force after mandibular ramus osteotomy with and without Le Fort I osteotomy.

The purpose of this study was to evaluate the differences in bite force changes and occlusal contacts after sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO) with and without Le Fort I osteotomy. Sixty female patients with diagnosed mandibular prognathism with or without asymmetry were divided into four groups (SSRO, IVRO, SSRO with Le Fort I osteotomy and IVRO with Le Fort I osteotomy). Bite force and occlusal contacts were measured preoperatively and at 1, 3, 6 and 12 months after surgery with pressure-sensitive sheets. The differences among surgical procedures were examined statistically. Maximum bite force and occlusal contacts returned to preoperative levels after between 3 and 6 months. Regarding time-dependent changes in bite force and occlusal contact area, there were no significant differences among the groups. In conclusion, this study suggests that the combination of IVRO or SSRO and Le Fort I osteotomy does not affect postoperative time-dependent changes.

Condylar and disc positions after intraoral vertical ramus osteotomy with and without a Le Fort I osteotomy.

The purpose of this study was to examine the changes in temporomandibular joint (TMJ) morphology and clinical symptoms after intraoral vertical ramus osteotomy (IVRO) with and without a Le Fort I osteotomy. Of 50 Japanese patients with mandibular prognathism with mandibular and bimaxillary asymmetry, 25 underwent IVRO and 25 underwent IVRO in combination with a Le Fort I osteotomy. The TMJ symptoms and joint morphology, including disc tissue, were assessed preoperatively and postoperatively by magnetic resonance imaging and axial cephalogram. Improvement was seen in just 50% of joints with anterior disc displacement (ADD) that received IVRO and 52% of those that received IVRO with Le Fort I osteotomy. Fewer or no TMJ symptoms were reported postoperatively in 97% of the joints that received IVRO and 90% that received IVRO with Le Fort I osteotomy. Postoperatively, there were significant condylar position changes and horizontal changes in the condylar long axis on both sides in the two groups. There were no significant differences between improved ADD and unimproved ADD in condylar position change and the angle of the condylar long axis, although distinctive postoperative condylar sag was seen. These results suggest that IVRO with or without Le Fort I osteotomy can improve ADD and TMJ symptoms along with condylar position and angle, but it is difficult to predict the amount of improvement in ADD.

A comparison of postoperative hypoesthesia between two types of sagittal split ramus osteotomy and intraoral vertical ramus osteotomy, using the trigeminal somatosensory-evoked potential method.

The purpose of this study was to evaluate hypoesthesia of the lower lip using trigeminal somatosensory-evoked potential following 2 types of sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO). There were 30 patients with mandibular prognathism, with and without asymmetry, who were divided into three groups: the Obwegeser method (Ob) group, the Obwegeser-Dal Pont method (ODP) group and the intraoral vertical ramus osteotomy (IVRO) group. The trigeminal somatosensory-evoked potential was recorded in the region of the lower lip and evaluated preoperatively and postoperatively. The average recovery periods from lower lip hypoesthesia in the IVRO and the Ob group were significantly shorter than in the ODP group (P<0.05). In conclusion, IVRO showed the earliest recovery from hypoesthesia or an absence of hypoesthesia, and lower lip hypoesthesia was less with the Ob method than the ODP method.

Expression of bone morphogenetic protein-2 and proliferating cell nuclear antigen during distraction osteogenesis in the mandible in rabbits.

We examined the expression of bone morphogenetic protein-2 (BMP-2) and proliferating cell nuclear antigen (PCNA) during distraction osteogenesis in the mandible in rabbits. Twenty-four rabbits each had an osteotomy of the left mandibular body, and distraction devices were fixed. The bone was distracted at a rate of 1mm/day for 10 days. Four rabbits were killed at each of 1, 3, 7, 14, and 28 days after completion of distraction, and the mandibles examined radiographically, histologically, and immunohistochemically. Four rabbits that had not been operated on served as controls. Immunohistochemical analysis showed that BMP-2 and PCNA both appeared initially at the edge of the osteogenesis, but tended to disappear after 14 days. After 1, 3, 7, and 14 days after distraction, the ratio of stained cells was significantly higher than in the control group (p<0.05), during the period that active bone formation was shown radiographically and histologically. These results suggest that BMP-2 plays an important part in the induction of bone formation during distraction osteogenesis.

Comparison of the computed tomography values of the bone fragment gap after sagittal split ramus osteotomy in mandibular prognathism with and without asymmetry.

The purpose of this study was to compare computed tomography (CT) Hounsfield unit values of bone fragment gaps after sagittal split ramus osteotomy (SSRO) in patients with and without asymmetry, and to evaluate differences between the deviated and non-deviated sides in asymmetric patients. Thirty-two patients who underwent a bilateral SSRO were included in this retrospective study. Patients were divided into symmetric and asymmetric groups by cephalometric analysis. CT values of the bone fragment gap were measured at 1 week and at 1 year after surgery. There were significant differences between CT values obtained at 1 week and at 1 year after surgery for all measurement points. However, there were no significant differences in CT values between symmetric and asymmetric patients at either 1 week or 1 year after surgery. Among asymmetric patients, there were no significant differences between the deviated and non-deviated sides at 1 week or 1 year after surgery. This study showed ossification of the bone fragments and adaptation to change the mandible form in patients with and without asymmetry following SSRO.

Multidirectional distraction osteogenesis for Crouzon syndrome: technical note.

This report describes multidirectional distraction osteogenesis in a patient with Crouzon syndrome. A RED system and a Hyrax expansion screw were used for lateral expansion of the maxilla. Advancement distraction osteogenesis and a Dyna Form were used for widening distraction osteogenesis of the mandible. The devices were fixed after a quadrangular osteotomy and a bimaxillary midline osteotomy.

Changes in condylar long axis and skeletal stability after bilateral sagittal split ramus osteotomy with poly-L-lactic acid or titanium plate fixation.

This study was designed to assess skeletal stability after bilateral sagittal split ramus osteotomy (BSSO) and fixation with a poly-l-lactic acid (PLLA) plate, as compared to that after BSSO and fixation with a titanium plate, and to analyze the change in the condylar long axis after these procedures. The study group comprised 40 patients who had mandibular prognathism (20, titanium group; 20, PLLA group). The groups were randomized to show similar distributions of preoperative SNB. All patients underwent BSSO setback by the Obwegeser method. Fixation was done with bent titanium plates or bent PLLA plates, applied in a similar manner. Lateral, frontal, and submental-vertical cephalograms were analyzed preoperatively and postoperatively. The maximum mouth opening range and the incidence of temporomandibular disorders were also evaluated. There was no significant difference in the right condylar angle or width between the two groups, but the left condylar angle and width, gonial angle, and ramus inclination differed significantly between them (P<0.05). SNA, SNB, and ANB were similar in both groups. There was no significant difference between the groups in maximum mouth opening range or temporomandibular disorders. We conclude that the change in condylar angle after BSSO and fixation with a titanium plate is greater than that after BSSO and fixation with a PLLA plate, but skeletal stability related to the occlusion is similar for the two procedures.

Changes in the computed tomography (pixel) value of mandibular ramus bone and fixation screws after sagittal split ramus osteotomy.

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.

Changes in occlusal function after orthognathic surgery in mandibular prognathism with and without asymmetry.

This study aimed to evaluate the postoperative changes in masticatory function in patients with jaw deformities with or without asymmetry treated by orthognathic surgery. Thirty female patients who underwent a Le Fort I osteotomy with sagittal split ramus osteotomy (SSRO) were enrolled. The patients were divided into symmetry and asymmetry groups. The bite force, occlusal contact area, and bite force balance were measured before and at 1, 3, and 6 months and 1 year after surgery; these measurements were compared statistically within and between the two groups. In the symmetry group, there was a significant difference in the preoperative bite force and the 1 month postoperative bite force (P=0.0033). In the asymmetry group, the bite force before surgery was significantly different from that at 1 month (P=0.0375) and at 1 year (P=0.0353) after surgery. Significant differences in the bite force were also observed between the following time points: 1 month and 1 year (P=0.0003), 3 months and 1 year (P=0.0034), and 1 month and 6 months (P=0.0486). The occlusal contact area, bite force, and occlusal balance tended to change after Le Fort I osteotomy with SSRO, with a significantly improved bite force in patients with asymmetry before surgery.

Condylar changes after contralateral mandibular osteotomy in the rabbit.

Following orthognathic surgery undesirable changes in the temporomandibular joints (TMJs) are noted sometimes. Altered stress on the condyle and surrounding tissue frequently causes morphological changes in the TMJ. The purpose of the present study was to assess these morphologic changes in a rabbit following mandibular osteotomy and the resulting mandibular body rotation. Adult male Japanese white rabbits (3 kg, 12-16 weeks old) were applied in this study. An experimental mandibular osteotomy was performed on the right side of the body of the mandible. The surgery includes vertical mandibular body osteotomy 5 mm in width after masseter muscle reflection. Then the anterior and posterior osseous segments were fixed with wire at previously made holes. As a result, the condylar medio-lateral width on the contralateral (left) side was significantly larger than that of the ipsilateral side 2 weeks postoperatively (p < 0.05). There were significant differences in the angle between the right and the left condylar heads 4 weeks postoperatively (p < 0.05). The present experimental study demonstrated morphological changes in the contralateral TMJ caused by unilateral mandibular osteotomy. Postoperative morphological changes implied that there is a process of biological adaptation in the rabbit TMJ.

Temporomandibular joint morphology and disc position in skeletal class III patients.

INTRODUCTION: The purpose of this study was to investigate the relationship between temporomandibular joint (TMJ) morphology, including discal tissue and clinical symptoms in class III dentofacial deformity patients. MATERIAL AND METHODS: Forty-four patients were examined with lateral, frontal and axial cephalograms. They were divided into two groups, consisting of a class III symmetry and a class III asymmetry group. By using magnetic resonance imaging the 88 joints could be classified into four types on the basis of disc position and shape: anteriorly displaced disc, anterior type, fully-covered type and posterior type. Furthermore, TMJ morphology was measured tomographically in the sagittal plane. RESULTS: Anteriorly displaced discs in the asymmetry group (56.8%) occurred significantly more frequently than in the symmetry group (18.2%; p <0.05). TMJ symptoms (clicking, crepitus, closed lock, pain) were seen in 17/44 joints (38.6%) of the symmetry and 24/44 joints (54.5%) of the asymmetry group, for a total of 41/88 joints (46.6%). There were no differences in joint space ratio and condyle ratio. However, the fossa ratio on the deviation side was significantly higher than on the nondeviation side in the asymmetry group (p<0.05). CONCLUSION: The incidence of internal derangement in asymmetrical class III patients is higher than in symmetrical mandibular prognathism, and this difference is associated with a difference in TMJ morphology of both sides.

The assessment of trigeminal sensory nerve paraesthesia after bilateral sagittal split osteotomy: modified somatosensory evoked potentials recording method.

Trigeminal neurosensory impairment is frequently observed following orthognathic surgery. The purpose of the present study is to visualize the degree of trigeminal nerve impairment following bilateral sagittal split osteotomy (BSSO). Twenty patients who underwent BSSO were in the present study. To record the modified somatosensory evoked potentials (SEP), two electrostimulation clips were applied. One clip was placed on the mucous surface of the lower lip and the other was placed on the skin surface. Each contact surface contained a separate 2 mm diameter silver anode and cathode attached to a 5 x 15 mm basement plate. The results obtained using this method revealed that complete recovery from neural impairment was observed in 7 cases (36.8%) on the right operative side and 4 (20.0%) on the left side at 6 months postoperatively. A definite delay in latency was observed on the left operative side at all the examination periods. The recovery period evaluated by the SEP method was longer than that of the objective two-point discrimination thresholds. Clinical records obtained showed considerable implications for trigeminal nerve function after BSSO.

Plate fixation after mandibular osteotomy.

Skeletal asymmetry in patients who undergo orthognathic surgery is frequently associated with postoperative temporomandibular joint (TMJ) disorders caused by condylar rotation. This study was designed to elucidate the relation between changes in the condylar long axis and TMJ function after bisagittal split osteotomy (BSSO). A total of 42 patients with mandibular prognathism underwent BSSO. Split osseous fragments were secured by standard titanium plates in 22 patients; bent titanium plates were used to secure fragments in 20 patients. The angle of the bent plates was adjusted to avoid displacement of the condyle after osteotomy, as compared with condylar position on preoperative submental-vertical (S-V) cephalograms. The postoperative position of the condyle was assessed on X-ray film, and changes in TMJ function were evaluated. The condylar long axis differed significantly on X-ray film between patients using a standard titanium plate and those using a bent plate (P<0.05), and no sign of TMJ functional impairment was noted in the bent-plate group. Although the use of bent plates requires further study, maintenance of a suitable position of the condyle relative to the condylar axis is one of the conditions for a successful outcome of BSSO.

Somatosensory-evoked potential to evaluate the trigeminal nerve after sagittal split osteotomy.

OBJECTIVE: The purpose of this study was to assess the onset period of trigeminal nerve hypoesthesia during bilateral sagittal split osteotomy, with the use of the trigeminal somatosensory-evoked potential (TSEP). STUDY DESIGN: Subjects were 10 patients with mandibular prognathism who underwent setback surgery. Intraoperative TSEP was measured 4 times: just before the commencement of the surgery, immediately after the induction of general anesthesia; after the medial periosteal dissection of the alveolar neurovascular bundle; after the sagittal split of bone; and after semirigid fixation with a titanium miniplate with the use of a monocortical screw. Postoperative TSEP was measured after the start of postoperative weeks 2, 4, 12, and 24. Normal records of the TSEP wave comprised peak (13 ms), trough (16 ms), peak (22.7 ms), and trough (36 ms) (N1, P1, N2, P2, respectively). Trigeminal hypoesthesia was assessed by the latency of P1 and N2, because they indicated the most reproducible waveforms. RESULTS: The change in shape of the spectra indicated that prolonged latency was initiated on medial periosteal dissection and was extended further after the sagittal bone split and fixation. However, latency recovery was observed relatively quickly after the start of postoperative weeks 2 and 4. CONCLUSIONS: Trigeminal hypoesthesia appeared to be induced by direct injury to the alveolar nerve during the bone split or by compression injury after fixation. Accordingly, the occurrence of a long-lasting postoperative trigeminal sensory hypoesthesia seemed to depend on nervous involvement of the split surface, the manner of fixation, or the intraoperative care.

New cephalometric images with a workstation. A preliminary report.

OBJECTIVE: This study was designed to test the feasibility of several types of enhancements for cephalometric computed radiographs through use of the Fuji Computed Radiography system (Fuji Photo Film Corp., Tokyo, Japan). STUDY DESIGN: The material consisted of four lateral cephalograms made with the Fuji Computed Radiography system that were enhanced by varying the gradient levels before processing by means of both A-type (straight gradation) curves and workstation-type (peaked) curves. The four workstation-type images were set with optical densities at the peak of the curve at 1.5, 1.7, 1.9, and 2.1. Ten observers evaluated eight anatomic landmarks comparing pairs of workstation-type images. The best workstation-type image was then compared with the A-type image for the same landmarks. RESULTS: For the four workstation-type images the best visualization of the anatomic landmarks was seen with workstation-type image 3, which had a maximum optical density of 1.9. Image 3 was also superior to the results of A-type image processing for most of the landmarks. CONCLUSION: Image enhancement with the application of a computed radiography system is effective for study of lateral cephalograms.

Changes in border movement of the mandible in skeletal Class III before and after orthognathic surgery.

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.