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Background: The object of this study was to investigate the dimension change after bone of the outer mandibular table had been grafted to different facial recipient sites., Methods: Six cases of hemifacial skeleton dysplasia had accepted therapeutics of onlay bone grafting at both mandibular angle and infraorbital regions of the affected side. Grafted bones had been harvested from the outer mandibular table of the uninjured side. For each patient, computed tomography scans were taken of immediate postoperative and 6 months postoperative results. By a technique based on 3-dimensional spiral computed tomography separated reconstruction and registration, grafted bones both at mandibular angle and infraorbital regions were independent. Volume of the grafted bone was measured, and 3-dimensional analysis was done., Results: At 6 months after the operation, the volume of the bone that had been grafted to the infraorbital region had a reduction rate of 11.2% ± 2.3%, and for the bone that had been grafted to the mandibular angle region, the volumetric reduction rate was 20.8% ± 7.2%. The difference of grafted bone resorption rate between the 2 recipient areas has statistical significance (<0.05). Three-dimensional analysis of grafted bones shows that the resorption took place mainly at the length-breadth direction and decreased thickness was less. Of the bone that had been grafted to the mandibular angle area, resorption mainly occurred at the inferior and posterior border of mandible., Conclusions: As an autogenous bone graft resource for reparation and reconstruction of maxillofacial bone deformity, the outer mandibular table has a different rate of resorption after it had been onlay grafted to various maxillofacial recipient sites, and the difference of the local mechanical environment maybe an influencing factor. Quantization of bone resorption rate could better guide the clinical use of outer mandibular table as an onlay bone graft resource.

Objective: To illustrate the morphological changes of mandible after angle-splitting ostectomy., Methods: From January 2006 to April 2008, 10 cases had undergone mandibular angle-splitting ostectomy to reduce the width of the lower face. For each patient, CT datum of mandible at three stages (preoperative, immediate postoperative, 6 months postoperative) were collected. By the application software of reverse engineering (Surfacer V9) and true-up and dissection techniques based on three-dimensional spiral computed tomography (3D-CT), operative efficacy and bone regeneration at the operation area of angle-splitting ostectomy were evaluated 6 months postoperative., Results: 1) Concavity could be seen at the angle-splitting ostectomy area 6 months postoperative, especially at the mandibular external oblique line region. Average cup depth was (3.64 +/- 1.67) mm by contrasted to preoperative. Diminution of bone volume was 55% +/- 9% for the local operative area 6 months postoperative. 2) Bone regeneration could be seen at the area that mandibular outer cortex had been removed. Compared with immediate postoperative, ratio of neoformative bone was 84.6% +/- 7.3% 6 months postoperative. The main region of bone regeneration was mandibular angle., Conclusion: Mandibular angle-splitting ostectomy is an effective technique for reducing the width of the lower face. Masseter muscular movement should be restricted postoperative to prevent hyperostosis at the angle area.

Objective: To illustrate the volume changes of mandibular outer cortex after been grafted to different recipient sites of facies cranii., Methods: Six cases underwent onlay bone graft to the angle and body part of mandible and malar surface simultaneously by using mandibular outer cortex. Three dimensional computed tomography (3D-CT) datum of immediate postoperative and 6 months postoperative of each case were collected systematically. By true-up and dissection techniques based on 3D-CT, volume changes of bone graft at different recipient sites were observed and analyzed 6 months postoperative., Results: 6 months after onlay bone grafted, bone resorption occurred. To different recipient sites, bone resorption rate was unequal. At the mandible area, bone resorption rate was 20.8% +/- 7.2%, the main site of resorption was at the lower and posterior border of mandible. At the anterior part of maxilla, bone resorption rate was 11.2% +/- 2.3%. Statistics showed significant difference of resorption rate between the two sites (P<0.05)., Conclusion: Bone resorption of mandibular outer cortex after onlay graft treatment is variant according to different craniofacial recipient sites. The difference of mechanical environment at variant recipient sites is considered to be an influencing factor. Quantization of bone resorption rate can guide a better clinical use.

Objective: To investigate the change of morphology, biomechanics and histology after osteotomy of mandibular outer cortex., Methods: The mandibular outer cortex that involves angle and part of body was removed at one side in 8 minitype pigs aged 8-12 months. 2 pigs were selected randomly for histologic examination 12 weeks after operation. The other 6 animals were killed 24 weeks after operation. The thickness of new-formed mandibular outer cortex was measured and compared with that of operated side. Biomechanical test was performed in bilateral angles. Histological observation was made in the operated side., Results: The thickness of outer cortex was (2.1 +/- 0.3) mm and (2.5 +/- 0.4) mm in the operated side and opposite side, respectively, showing a significant difference between them (P < 0.01). The maximum load was (401.76 +/- 204.91) N and (585.42 +/- 413.07) N in the operated side and opposite side, respectively (P > 0.05). The Rigidity was (2172.19 +/- 1174.73) N/mm and (2363.90 +/- 1547.48) N/mm (P > 0.05). There was no statistical difference in biomechanics between the two sides. The histologic study showed histologically complete regeneration of outer cortex 24 weeks after mandibular outer cortex osteotomy., Conclusions: After resection of mandibular outer cortex, the histologic restoration is complete, but the new-formed outer cortex is thinner with local depression. Bone tubercle can be seen at the angle after bone regeneration. There is no obvious change in biomechanics after outer cortex osteotomy.

Background: The purpose of this study was to illustrate the morphologic changes of the mandible after outer cortex osteotomy., Methods: Ten patients had undergone mandibular outer cortex osteotomy. By using the true-up and dissection techniques based on three-dimensional spiral computed tomography, variables of effect and bone regeneration were evaluated 6 months postoperatively., Results: Concavity could be seen in the area from which the mandibular outer cortex had been removed 6 months postoperatively, especially at the external oblique line region. The average cup depth was 3.64 +/- 1.67 mm postoperatively. Diminution of bone volume was 1.7 +/- 0.5 percent for the entire mandible and 55 +/- 9 percent for the local area 6 months postoperatively. Bone regeneration could be seen in the area from which the mandibular outer cortex had been removed. Compared with immediately postoperatively, the ratio of neoformative bone was 84.6 +/- 7.3 percent 6 months postoperatively. The main region of bone regeneration was the mandibular angle., Conclusions: Mandibular outer cortex osteotomy is an effective technique for reducing the width of the lower face. Masseter muscular movement should be restricted postoperatively to prevent hyperostosis at the angle area.

Objective: To investigate the value of application of mandibular outer cortex as bone graft by comparing its bone absorption with cranial outer cortex., Methods: 8 minitype grown-up pigs at the age of 8 - 12 months underwent surgery of taking out the same size (2.5 cm x 1.0 cm) of outer cortex from mandible and craninium. The volume of the outer cortex was measured by volume-displacement method. Then the outer cortex of mandible and cranium were onlay grafted to the each side of the pig snout, respectively. 12 weeks later, 2 pigs were randomly selected for histological examination. The other 6 pigs were killed 24 weeks after surgery for measurement of the bone graft volume and histologic examination., Results: The bone graft absorption rate was (41 +/- 5)% for mandibular outer cortex and (46 +/- 12)% for cranial outer cortex, showing no significant difference between them (P = 0.51). The histologic examination results also had no marked difference in the bony healing and reforming between the two graft., Conclusions: Mandibular outer cortex is a good donor site for onlay bone graft in craniofacial region.

Objective: To investigate the local changes of biomechanics after osteotomy of mandibular outer cortex in body and angle areas., Methods: Six minitype pigs at the age of 8 to 12 months were selected. The mandibular outer cortex that involves angle and part of body was removed in one side. The animals were killed 24 weeks after operation. Bone strut was taken from mandibular angle region bilaterally and sent for biomechanical test, Results: There was no biomechanical difference between the two angle areas of experimental and normal sides 24 weeks after mandibular outer cortex osteotomy (maximum load P > 0.05, rigidity P > 0.05)., Conclusions: Mandibular outer cortex osteotomy had no influence on local biomechanics.