Mao Miyazaki

Skeletal stability after mandibular setback surgery: comparisons among unsintered hydroxyapatite/poly-L-lactic acid plate, poly-L-lactic acid plate, and titanium plate.

PURPOSE The purpose of this study is to compare the time-course changes in condylar long-axis and skeletal stability after sagittal split ramus osteotomy (SSRO) with an unsintered hydroxyapatite (u-HA)/poly-L-lactic acid (PLLA) plate, PLLA plate, or titanium plate. PATIENTS AND METHODS Of 60 Japanese patients diagnosed with mandibular prognathism, 20 underwent SSRO with a u-HA/PLLA plate system, 20 underwent SSRO with a PLLA plate system, and 20 underwent SSRO with a conventional titanium plate system. The time-course changes in condylar long-axis and skeletal stability were assessed by use of axial, frontal, and lateral cephalograms. RESULTS Compared with the u-HA/PLLA group, the titanium group showed a significantly greater change in the right condyle angle between initially and 1 month (P = .0105) and intercondylar axes angle between 1 and 3 months (P = .0013). The PLLA group showed a significantly greater change than the titanium group (P = .0043) and u-HA/PLLA group (P = .0002) in terms of ramus inclination between 1 and 3 months; however, there were no significant differences among the 3 groups in the other measurements for each time interval. CONCLUSION This study suggests that there are no significant differences in postoperative time-course changes among a u-HA/PLLA plate system, PLLA plate system, and conventional titanium plate system.

Assessment of bone healing after Le Fort I osteotomy with 3-dimensional computed tomography

PURPOSE The purpose of this study was to examine bone healing after Le Fort I osteotomy in Class III patients. PATIENTS AND METHODS The study group consisted of 18 Japanese patients with mandibular prognathism with and without asymmetry, maxillary retrognathism or open bite. A total of 36 sides were examined. Le Fort I osteotomy was performed without a pterygoid osteotome, with an ultrasonic curette used to remove interference at the pterygomaxillary region. Titanium plates (Universal Mid-face fixation module, Stryker, Freiburg, German) were used for four patients, absorbable plates (poly-L-lactic acid (PLLA): NEOFIX(®), Gunze, kyoto, Japan) were used for four patients and other absorbable plates (uncalcined and unsintered hydroxyapatite and poly-L-lactic acid (uHA/PLLA): super FIXSORB(®)MX, Takiron Co. Ltd, Osaka, Japan) were used for 10 patients, in the same manner. Postoperative computed tomography (CT) was analyzed for all patients pre-operatively and 1 year postoperative. The anterior and lateral areas between the maxillary segments were measured with 3-dimensional (3D) CT. Bone healing at the pterygomaxillary region was also assessed. RESULTS There were no significant differences in the area of bone defect healing among the plate types. The areas of bone defect after 1 year were significantly smaller than that immediately after surgery on the right side (p=0.0145) and left side (p=0.0010) in the frontal view and right side in the lateral view (p=0.0118). Bone healing at the pterygomaxillary junction was found in all cases without artificial pterygoid plate fracture. Fourteen of 22 sides with artificial pterygoid plate fracture by an ultrasonic curette showed bone continuity between the pterygoid plate and posterior part of maxilla. CONCLUSION This study suggested that bony healing could occur in spaces between the segments of maxilla and pterygomaxillary regions as well as the region of the anterior and lateral walls in the maxilla, but it is not always complete within 1 year after Le Fort I osteotomy.

Effect of self-setting α-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy

AIMS The aim of this study was to evaluate hypoaesthesia of the lower lip and bone formation using self-setting α-tricalcium phosphate (Biopex(®)) between the proximal and distal segments following sagittal split ramus osteotomy (SSRO) with bent absorbable plate fixation. SUBJECTS AND METHODS The subjects were 40 patients (80 sides) who underwent bilateral SSRO setback surgery. They were divided into a Biopex(®) group (40 sides) and a control group (40 sides). The Biopex(®) was inserted into the anterior part of the gap between the segments in the Biopex(®) group. Trigeminal nerve hypoaesthesia in the region of the lower lip was assessed bilaterally using the trigeminal somatosensory-evoked potential (TSEP) method. Ramus square, ramus length, and ramus width, the square of the Biopex(®) at the horizontal plane under the mandibular foramen were assessed preoperatively, immediately after surgery, and 1year postoperatively by computed tomography (CT). RESULTS The mean measurable period and standard deviation were 9.3±15.7weeks in the control group, 5.3±8.3weeks in the Biopex(®) group, and there was no significant difference. Ramus square after 1year was significantly larger than that prior to surgery and new bone formation was found between the segments in both groups (P<0.05). In the Biopex(®) group, the square of the Biopex(®) after 1year was significantly smaller than that immediately after surgery (P<0.05). CONCLUSION This study suggested that inserting Biopex(®) in the gap between the proximal and distal segments was useful for new bone formation and it did not prevent the recovery of lower lip hypoaesthesia after SSRO with bent absorbable plate fixation.

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.

Changes in the lip closing force of patients with Class III malocclusion before and after orthognathic surgery

The purpose of this study was to examine the changes in lip pressure before and after orthognathic surgery for skeletal class III patients. The subject groups were 32 female and 31 male patients diagnosed with mandibular prognathism and/or maxillary retrognathism who underwent orthognathic surgery. Control groups consisted of 20 women and 20 men with normal occlusion without dento-alveolar deformity. Maximum and minimum lip closing force was measured with Lip De Cum® for the control groups and subject groups preoperatively and 6 months postoperatively. The difference between the pre- and postoperative values of the groups was examined statistically. The maximum lip closing force in men was significantly larger than that in women in both the preoperative class III group (p=0.0330) and the control group (p=0.0097). The preoperative class III group was significantly smaller than the control group in maximum lip closing force in both men (p<0.0001) and women (p<0.0001). The postoperative maximum lip closing force was significantly larger than the preoperative value in both men (p=0.0037) and women (p=0.0273) in the Class III group. This study suggested that the maximum lip closing force increases after orthognathic surgery in Class III patients.

Assessment of ramus, condyle, masseter muscle, and occlusal force before and after sagittal split ramus osteotomy in patients with mandibular prognathism.

PURPOSE The purpose of this study was to examine the relationship between the morphologies of the masseter muscle and the ramus and occlusal force before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. PATIENTS AND METHODS The study group consisted of 26 patients with mandibular prognathism. All patients underwent bilateral SSRO as well as 3-dimensional computed tomography on which the masseter muscle, ramus, and condyle were measured preoperatively and at 1 year postoperation. Occlusal force and contact area were also recorded with pressure-sensitive sheets. RESULTS In the cross-sectional area of the masseter muscle, there were no significant differences between the pre- and postoperative status. However, postoperative ramus width and area were significantly larger than preoperative values (P < .0001). Postoperative right condylar area was significantly larger than the preoperative value (P = .0120). Occlusal force and contact area 1 year after surgery were significantly larger than the preoperative values (P = .0016, P = .0190). CONCLUSION This study suggested that the masseter muscle area did not significantly differ from preoperative status 1 year after SSRO, although occlusal force, contact area, and ramus area and width increased significantly 1 year after SSRO.

An experimental study of use of absorbable plate in combination with self-setting α-tricalcium phosphate for orthognathic surgery

OBJECTIVE The purpose of this study was to histologically and immunohistochemically evaluate bone formation using both self-setting α-tricalcium phosphate (α-TCP; Biopex) and absorbable plate (Super Fixsorb-MX) in rabbit cranium bone. STUDY DESIGN Twelve adult male Japanese white rabbits (12-16 wk, 2.5-3.0 kg) were used. The surgical defects were made in the nasal bone of a rabbit, and Biopex was implanted in the left side and no material in the right side. Two-hole absorbable plate and 2 screws (Super Fixsorb-MX) were fixed across the defect in each side. The rabbits were killed at 1, 4, 12, and 24 weeks after surgery, and formalin-fixed specimens were embedded in acrylic resin. The specimens were stained with hematoxylin and eosin. For immunohistochemical analysis, the specimens were treated with bone morphogenetic protein 2 (BMP-2) antibodies. Finally, these were evaluated microscopically. RESULTS New bone formation was observed in the region of absorbable plate and nasal membrane after >4 weeks. The area of new bone with Biopex was significantly larger than that of the control side after 1, 4, and 12 weeks (P < .05). The number of BMP-2-stained cells in the experimental side was significantly larger than in the control side after 4 and 12 weeks (P < .05). CONCLUSION This study suggests that the use of absorbable plate (Super Fixsorb-MX) in combination with Biopex could be useful and that both of Super Fixsorb-MX and Biopex could provide adequate bone regeneration.

Position of Mandibular Canal and Ramus Morphology Before and After Sagittal Split Ramus Osteotomy

PURPOSE The purpose of this study was to evaluate changes in the mandibular canal and ramus morphology before and after a sagittal split ramus osteotomy. PATIENTS AND METHODS The subjects were 30 patients (60 sides) with mandibular prognathism who had undergone bilateral sagittal split ramus osteotomy setback surgery. The mandibular canal position and ramus morphology were measured at the 3 horizontal planes under the mandibular foramen level (level A), 1 cm lower than level A (level B), and 2 cm lower than level A (level C) preoperatively and 1 year postoperatively by computed tomography. RESULTS Postoperative ramus width, lateral distance, lateral marrow distance, and canal length were significantly larger than the preoperative values at the foramen, 1 cm lower, and 2 cm lower. The mandibular canal completely contacted the lateral cortex without lateral bone marrow in 6 sides (10%) in levels A and B and 4 sides (6.7%) in level C preoperatively and 6 sides (10%) in level C postoperatively. CONCLUSION This study suggested that postoperative mandibular canal position was located more posteriorly and the postoperative lateral bone marrow became thicker compared with the preoperative state.

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(®).