TAKAGI Shinji University of Occupational and Environmental Health, Faculty of Medicine, Resear, 医学部, 助手 (40269072)
OYA Ryoichi University of Occupational and Environmental Health, Faculty of Medicine, Resear, 医学部, 助手 (70194313)
|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1996 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1995 : ¥700,000 (Direct Cost : ¥700,000)
The purpose of our study was to make a masticatory function recovery after segmental mandibulectomy, using dental implants into the bone induced by applying recombinant human bone morphogenetic protein-2 (rhBMP-2) to the bone defect area. To accomplish this purpose, an appropriate carrier for expression of the rhBMP-2 activity should be investigated, and moreover it is desired to develop the plate which sustains the carrier and provides sufficient strength to reconstruct the bone defect until new bone replaces the carrier, and which is then degraded after new bone formation.
1. Osteoinductive activity in rats
(1) The mixture of the rhBMP-2 and its carrier, which was composed of tricalcium phosphate (TCP) and fibrin glue, was implanted subcutaneously and the osteoinductive activity was confirmed. Fibrin glue exhibited many useful benefits as an adhesion agent to other carriers rather than just as a single carrier. The TCP was unsuitable for examining new bone formation by a radiograph, be
cause of radiopacity. The TCP prevents dental implants from planting into the newly induced mandibular bone.
(2) In order to induce the new bone within eleven weeks, more than 50mug/nl of rhBMP-2 seems to be necessary.
2. Development of a bioabsorbable plate for reconstructing a mandible and retaining a carrier using dogs.
The bioabsorbable boly-L-lactide (PLLA) plate, which is amorphous, ca. 26x10^4 in molecular weight and one-millimeter in thickness, was evaluated.
(1) The PLLA and AO plate were used on each side of the mandible, to reconstruct a one-centimeter full thickness defect.Two-point bend testing was performed immediately after mandibular reconstruction. The comparison of both plates revealed that the PLLA plates had a possible adequate fixation force.
(2) Preceding the segmental resection, an impression was taken from the mandibular bone stripped of soft tissue, which was followed by making a plaster model. The PLLA plate was heated between 70-75ﾟC and, then, this plate was pressed to the plaster model. This method allows accurate reproduction of the mandibular bone and a tray-type plate.
(3) PLLA plates were removed three months after mandibular reconstruction. They showed absorption here and there, and three-point bend testing revealed that the mean value of bending strength was 62% in non-used plates.
This PLLA plate fulfillls the requisite for reconstructing a mandible and retaining a carrier, when the new bone can be adequately formed within three months. Less