Effect of type I collagen, osteoblast and PTH mixture on bone formation of the bony defects around implant in minipigs. Mesenchymal stem cells derived from adult bone marrow are multipotent cells capable of differentiating along several lineage pathways. Cell-driven approaches, especially the biophysical stimulation of the host cell population surrounded by the bone defect, are common treatment methods in maxillofacial surgery. Others, such as autogenous cell implantation, have now gained acceptance for clinical trials. All of the cell-driven repair strategies are under intensive investigation in an effort to provide surgeons with a limitless supply of tissue for bone repair and reconstruction in future procedures. An overview of the basic biological aspects as well as the inherent constraints of different cell-based approaches are given in this paper. The aim of this study was to evaluate the bone formation effects of mesenchymal stem cells & PTH as a cytokine in bone defects around implants in Minipig models. Ten minipigs were divided into 4 groups. We made 4 wall-defects(10 mm in diameter, 8 mm in height) on the lower jaw, and the following materials were applied: fibrin glue as control and type I collagen, type I collagen + osteoblast, and type I collagen + osteoblast + PTH as experimental groups. Each defects were implanted with 3 mm wide and 8 mm long implants in center. Experimental minipigs were sacrificed at 1, 2, 4, 8 and 12 weeks after operation. We evaluated the defects clinically, histologically and histomorphologically(bone implant contact). The results were as follows; (1) Osteogenesis in Type I collagen mixed with osteoblast and osteoblast with PTH groups was more active than control group. (2) Most experimental groups, especially the PTH group, at 4 weeks to 8 weeks, showed larger amount of bone implant contact increase than control group.