Expression of bone morphogenetic protein 2 and fibroblast growth factor 2 during bone regeneration using different implant materials as an onlay bone graft in rabbit mandibles.

OBJECTIVES: The purpose of this study was to histologically and immunohistochemically evaluate bone regeneration using 3 different implant materials in rabbit mandibles and to compare the bone regenerative capability of these materials in an animal model. STUDY DESIGN: Adult male Japanese white rabbits (n = 48; 12-16 wks old; 2.5-3.0 kg) were divided into 4 groups, consisting of 12 animals each. The implant materials were beta-tricalcium phosphate (beta-TCP), autologous bone derived from the radius, and recombinant human bone morphogenetic protein 2 (rhBMP-2) with polylactic acid/polyglycolic acid copolymer and gelatin sponge (PGS) complex. After incising along the inferior border of the mandible, the materials were implanted as only grafts and covered by titanium mesh with screws. No material was implanted into the control group. The rabbits were killed at 2, 4, 8, 12, and 24 wks postoperatively, and formalin-fixed specimens containing titanium mesh were embedded in acrylic resin. The specimens were stained with hematoxylin and eosin. For immunohistochemical analysis, the specimens were treated with BMP-2 and fibroblast growth factor 2 (FGF-2) antibodies. Finally, they were examined microscopically. RESULTS: The autologous bone induced substantially more new bone formation compared with beta-TCP at 4 wks postoperatively. However, rhBMP-2/PGS induced new bone formation at 8 wks postoperatively. No growth of bony tissue was observed in the control group at any period. In the autologous bone and rhBMP-2/PGS groups, both BMP-2 and FGF-2 were observed later in the beta-TCP group than in other groups. CONCLUSION: This study suggests that autologous bone as well as rhBMP-2/PGS implants induce expression of both BMP-2 and FGF-2 specifically at the operated sites, even at early stages.

Relationship between the morphologies of the masseter muscle and the ramus and occlusal force 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 in patients with mandibular prognathism. PATIENTS AND METHODS: The study group consisted of 71 patients with mandibular prognathism. They were divided into 2 groups, consisting of prognathism with or without symmetry, determined by frontal cephalogram analysis. All patients underwent 3-dimensional (3D) computed tomography (CT) and occlusal force was recorded with pressure-sensitive sheets. RESULTS: In the cross-sectional area of masseter muscle, there were no significant differences between the right and left sides in the symmetry and asymmetry groups. In occlusal force, there was no significant difference between the symmetry and asymmetry groups. Occlusal force was not significantly correlated to the cross-sectional area of the ramus, but it was significantly positively correlated to the cross-sectional area of the masseter muscle (P < .05). CONCLUSION: Occlusal force was associated with the ipsilateral cross-sectional area of masseter muscle in patients with prognathism; however, it was not associated significantly with the degree of mandibular deviation.

The use of polylactic acid/polyglycolic acid copolymer and gelatin sponge complex containing human recombinant bone morphogenetic protein-2 following condylectomy in rabbits.

PURPOSE: To examine the results of a polylactic acid/polyglycolic acid copolymer and gelatin sponge complex (PGS) with or without recombinant human bone morphogenetic protein-2 (rhBMP-2) used to treat condylar defects in rabbits. MATERIAL AND METHODS: Adult male Japanese white rabbits (n=60; 3kg; 12-16 weeks old) were divided into three groups of 20 each. All rabbits underwent condylectomy. In the two implanted groups, PGS with or without 5 microg of rhBMP-2 was implanted to the condylar defect without fixation. No material was implanted into the control group. Animals were sacrificed at 2, 4, 8, 12 and 24 weeks postoperatively, and the temporomandibular joints (TMJs) were examined histologically. RESULTS: Four weeks after implantation, growth of bone and cartilage-like tissue was observed in all rabbits that received PGS implants (with and without rhBMP-2). A cartilage-like layer was derived from the bone marrow at the operated surface. There was no growth of bone tissue in the control rabbits, but they also had a cartilage-like layer directly derived from the operated surface. CONCLUSION: This study demonstrated that PGS with or without rhBMP-2 could induce regeneration of new bone and cartilage-like tissue in the TMJ.