Yuri Ishihara

Changes in temporomandibular joint and ramus after sagittal split ramus osteotomy in mandibular prognathism patients with and without asymmetry

The purpose of this study was to examine the changes in the temporomandibular joint (TMJ) and ramus after sagittal split ramus osteotomy (SSRO) with and without Le Fort I osteotomy. The subjects consisted of 87 Japanese patients diagnosed with mandibular prognathism with and without asymmetry. They were divided into 2 groups (42 symmetric patients and 45 asymmetric patients). The TMJ disc tissue was assessed by magnetic resonance imaging (MRI) and the TMJ space, condylar and ramus angle were assessed by computed tomography (CT) preoperatively and postoperatively. Medial joint space on the deviation side in the asymmetry group was significantly larger than that in the symmetry group (P = 0.0043), and coronal ramus angle on the non-deviation side in the asymmetry group was significantly larger than that in the symmetry group preoperatively (P = 0.0240). The horizontal condylar angle on the deviation side in the asymmetry group was significantly larger than that in the symmetry group (P = 0.0302), posterior joint space on the non-deviation side in the symmetry group was significantly larger than that in the asymmetry group postoperatively (P = 0.00391). The postoperative anterior joint space was significantly larger than the preoperative value on both sides in both groups (the deviation side in the symmetry group: P = 0.0016, the non-deviation side in the symmetry group: P < 0.0001, the deviation side in the asymmetry group: P = 0.0040, the non-deviation side in the asymmetry group: P = 0.0024). The preoperative disc position could was not changed in either group. These results suggest that significant expansion of anterior joint space could occur on the deviation side and non-deviation side in the asymmetry group as well as on both sides in the symmetry group, although disc position did not change in either group.

A hypothesis on the desired postoperative position of the condyle in orthognathic surgery: a review.

It is very important to clarify the relationship between a dentofacial structure and a temporomandibular joint (TMJ) structure in orthognathic surgery. Recently, it was reported that the skeletal and occlusal patterns were associated with the TMJ morphology, including the disk position. In orthognathic surgery, some surgeons state that alterations in the condylar position from surgery can lead to malocclusion associated with the risk of early relapse, and also favor the development of temporomandibular disorders. For these reasons, several positioning devices have been proposed and applied, but now there is no scientific evidence to support the use of condylar positioning devices. There are some reasons why scientific evidence cannot be obtained; however, it also includes the question of whether the preoperative position of the condyle is the desired postoperative position. The purpose of this study was to verify the desired condylar position in orthognathic surgery, based on literature on the postoperative condylar position in orthognathic surgery. From the studies reviewed, it was suggested that the preoperative position of the condyle was not the desired postoperative position in orthognathic surgery.

Assessment of bone healing and hypoesthesia in the upper lip after Le Fort I osteotomy with self-setting α-tricalcium phosphate and absorbable plates

PURPOSE The purpose of this study was to evaluate hypoesthesia of the upper lip and bone formation using self-setting α-tricalcium phosphate (Biopex(®)) between the segments following Le Fort I osteotomy with bent absorbable plate fixation. SUBJECTS AND METHODS The subjects were 47 patients (94 sides) who underwent Le Fort I osteotomy with and without mandibular osteotomy. They were divided into a Biopex(®) group (48 sides) and a control group (46 sides). The Biopex(®) was inserted into the anterior part of the gap between the segments in the Biopex(®) group. Trigeminal nerve hypoesthesia at the region of the upper lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method. The area of the Biopex(®) at the anterior part in the maxilla was assessed immediately after surgery and 1 year postoperatively by computed tomography (CT). RESULTS The mean measurable period and standard deviation were 13.2 ± 18.5 weeks in the control group, 14.5 ± 17.9 weeks in the Biopex(®) group, and there was no significant difference in TSEP. The area of the Biopex(®) after 1 year was significantly smaller than that immediately after surgery (right side: P = 0.0024, left side: P = 0.0001) and bone defects between the segments could not be found in the Biopex(®) group. In the control group, although the areas of bone defect after 1 year were significantly smaller than that immediately after surgery on the right side (P = 0.0133) and left side (P = 0.0469) in the frontal view, complete healing of the bone defects could be seen in 12 of 46 sides after 1 year. CONCLUSION This study suggested that inserting Biopex(®) in the gap between the maxillary segments was useful for new bone formation and it did not prevent the recovery of upper lip hypoesthesia after Le Fort I osteotomy with absorbable plate fixation.

Bone regeneration by statin and low-intensity pulsed ultrasound (LIPUS) in rabbit nasal bone.

OBJECTIVES To compare bone regeneration between local implantation of statin and low-intensity pulsed ultrasound (LIPUS), and the combination of statin with LIPUS in rabbit nasal bone using histological and immunohistochemical methods. STUDY DESIGN Thirty-two adult male Japanese white rabbits (age: 12-16 weeks, weight: 2.5-3.0 kg) were used in this study. Two bone circular defects (5 mm in diameter) per rabbit were created in the nasal bone while preserving the nasal membrane. The two defects in each rabbit were filled with 2.5 mg/ml simvastatin in 0.2 ml water with an atelocollagen sponge (ACS) and ACS alone respectively. Sixteen rabbits (32 sides) received the LIPUS application; the remaining 16 rabbits (32 sides) did not. Therefore, the subjects composed of 4 groups, namely, (1) LIPUS + ACS + simvastatin (the LAS group), (2) LIPUS + ACS (the LA group), (3) ACS + simvastatin (the AS group) and (4) ACS alone (the A group). Four animals were killed in each period, at 1, 2, 4 and 8 weeks postoperative. The parts that had been operated on were removed and prepared for histological assessment. The expression of BMP-2 and the bone area ratio were evaluated using histological and immunohistochemical methods. RESULTS Bone square in the LAS group was significantly larger than that in the AS group after 1 (P < 0.0001) and 2 week (P = 0.0113). The bone square in the LA group was significantly larger than that in the A group after 1 (P < 0.0001) and 2 weeks (P = 0.0090). However, there was no significant difference between the LAS and LA groups. In the number of cells that stained positive for BMP-2, the LAS group was significantly larger than that in the AS group after 1 (P < 0.0001) and 2 weeks (P = 0.0113). CONCLUSION This study suggests that bone regeneration can be promoted by LIPUS alone and statin alone, respectively. However the combination use of LIPUS with statin does not differ from LIPUS alone or statin alone.

Maxillary stability after Le Fort I osteotomy using three different plate systems.

The purpose of this study was to compare postoperative changes in maxillary stability after Le Fort I osteotomy in three groups: with an unsintered hydroxyapatite (u-HA)/poly-L-lactic acid (PLLA) plate; a PLLA plate; and a titanium plate. Subjects comprised 60 Japanese patients diagnosed with mandibular prognathism. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy. All patients were randomized in groups of 20 to a u-HA/PLLA group, a PLLA plate group and a titanium plate group. Changes in postoperative time intervals between the plate groups were compared using lateral and posteroanterior cephalography. The uHA/PLLA group had significantly larger values than the PLLA group regarding change of mx1-S perpendicular to SN between 3 and 12 months (T3) (P=0.0269). The uHA/PLLA group had a significantly larger value than the PLLA group regarding change of S-A perpendicular to SN between baseline and 1 month (T1) (P=0.0257). There was no significant difference in the other measurements. This study suggests that maxillary stability with satisfactory results could be obtained in the u-HA/PLLA, PLLA plate and titanium plate groups, although there was a slight difference between the u-HA/PLLA and PLLA plate systems in Le Fort I osteotomy.

Evaluation of factors affecting recovery period in lower lip hypoesthesia after sagittal split ramus osteotomy in mandibular prognathism patients

PURPOSE The purpose of this study was to evaluate the factors affecting the recovery period of lower lip hypoesthesia after sagittal split ramus osteotomy (SSRO) in mandibular prognathism patients using multivariate analysis, retrospectively. SUBJECTS AND METHODS The subjects were 222 patients (444 sides) who underwent bilateral SSRO setback surgery with and without Le Fort I osteotomy. Trigeminal nerve hypoesthesia at the region of the lower lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method pre- and post-operatively. Recovery period was determined as the time when TSEP was first measurable post-operatively. Age, sex, presence or absence of third molars, setback amount and osteotomy type and fixation method were selected as covariates in the multivariate analysis. The factor affecting the recovery period in lower lip hypoesthesia was examined with Coxs proportional hazard regression. RESULTS Sex and osteotomy fixation method affected the recovery period in lower lip hypoesthesia significantly (P = 0.0132 and P = 0.0394). However, the other factors did not affect the recovery period. CONCLUSION This study suggested that sex and osteotomy type and fixation method may affect the recovery period in lower lip hypoesthesia after SSRO setback surgery.

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.

Bone regeneration by periosteal elevation using conventional orthodontic wire and uHA/PLLA mesh

This study evaluated bone regeneration by periosteal elevation using conventional orthodontic wire and an unsintered hydroxyapatite (u-HA)/poly-L-lactic acid (PLLA) mesh in rabbit frontal bone. Thirty two rabbits (12-16 weeks: 2.5-3.0 kg) were used in this study. In the experimental group, 1 week after the mesh was inserted under the periosteal membrane, it was elevated by traction using the mesh connected with wire and two anchor screws. In the control group, the mesh was kept inserted under the periosteal membrane. Four animals were killed in each period in both groups, at 2, 3, 5 and 9 weeks postoperatively. Operated parts in the frontal bone were removed and prepared for radiological and histological assessment. The distance between the mesh and pristine bone (elevation length), the bone area and the expression of BMP-2 were evaluated. The value in the experimental group was significantly higher when compared to the control group (length P < 0.0001, bone area P < 0.0010, BMP-2 P = 0.0015). The BMP-2 labelling index after 3 weeks tended to be the largest in both groups. This study suggests that bone regeneration can be induced by periosteal elevation using a conventional orthodontic wire and an uHA/PLLA mesh.

Evaluation of recovery in lip closing pressure and occlusal force and contact area after orthognathic surgery

PURPOSE The purpose of this study was to evaluate the relationship between lip closing force, occlusal contact area and occlusal force after orthognathic surgery in skeletal Class III patients. SUBJECTS AND METHODS The subjects consisted of 54 patients (28 female and 26 male) diagnosed with mandibular prognathism who underwent sagittal split ramus osteotomy with and without Le Fort I osteotomy. Maximum and minimum lip closing forces, occlusal contact area and occlusal force were measured pre-operatively, 6 months and 1 year post-operative. RESULTS Maximum and minimum lip closing forces, occlusal contact area and occlusal force increased with time after surgery, however a significant increase was not found in the occlusal contact area in women. In increased ratio (6 months/pre-operative and 1 year/pre-operative), the maximum lip closing force was significantly correlated with the occlusal contact area (P < 0.0001). CONCLUSIONS This study suggested that orthognathic surgery could improve the occlusal force, contact area and lip closing force, and an increase ratio in maximum lip closing force was associated with an increased ratio in occlusal contact area.

Maxillary stability after Le Fort I osteotomy with self-setting α-tricalcium phosphate and an absorbable plate

The purpose of this study was to compare retrospectively postoperative differences in maxillary stability after Le Fort I osteotomy and fixation with an unsintered hydroxyapatite (u-HA)/poly-l-lactic acid (PLLA) plate with or without self-setting α-tricalcium phosphate (Biopex(®)) as interpositional material. Subjects comprised 45 patients diagnosed with mandibular prognathism with maxillary retrognathism and mandibular prognathism with bimaxillary asymmetry. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy with fixation by uHA/PLLA plates. Patients were divided into 4 groups consisting of 9 maxillary impaction cases with Biopex(®) (group 1) to fill the gap between the bone segments, 14 maxillary advancement cases with Biopex(®) (group 2), 8 maxillary impaction cases without Biopex(®) (group 3) and 14 maxillary advancement cases without Biopex(®) (group 4). Changes in cepahalometric parameters at time intervals (1, 3 and 12 months) between the groups were compared. Results showed that stability did not depend on the use or otherwise of Biopex(®).