An Experimental Study Of Recombinant Human Bone Morphogenetic Protein-2 Membrane And PDLLA-nano/HA Plates And Screws Treating Mandibular Fractures Of Rabbit

Objectives To investigate the role of rhBMP-2 in the healing of mandibular fractures of rabbits. To evaluate the advantage of using PDLLA-nano/HA plates and rhBMP-2 in the treatment of mandibular fractures of rabbits. To elucidate the temporal and spatial expression pattern of Alkaline phosphatase and PCNA in the healing of mandibular fractures of rabbits with and without rhBMP-2.Methods 36 healthy adult New Zealand rabbits were divided randomly into 4 time intervals(2;4;8;12 weeks after operation) and 9 rabbits in each time interval were classified into 3 groups. Every rabbit was operated on to create a fracture by means of osteotomy in the body of mandible. Then the 3 rabbits in the first group were fixed with PDLLA-nano/HA plates only. The second group was fixed with PDLLA-nano/HA plates and the sites of osteotomy were coated with collagen sponge without rhBMP-2. The third group was fixed with PDLLA-nano/HA plates and the sites of osteotomy were coated with collagen sponge with rhBMP-2. The rabbits were sacrificed respectively 2; 4; 8;12 weeks after operation. Then the mandibles were picked up and taken X ray radiographs. Consequently, specimens were processed in the routine method to produce paraffin sections. Then some sections were dyed with HE method to appraise the outcome of healing.Some sections were processed to display the expression and change of Alkaline phosphatenase. Some sections were processed with immunohistochemistry method to analyse the expression of PCNA.Results :General observation showed all incisions healed normally. The occlusions of rabbits were normal. There were no plates deviating from original sites. X ray showed fractureshealed faster in rhBMP-2 group than the other two groups at 2; 4; 8 weeks after operation. HEsections showed the hone formation was most remarkable in rhBMP-2 groups in all time intervals.In rhBMP-2 group, the expression of Alkaline phosphatenase increased at 2 weeks after the operation and peaked at 4 weeks.Then the expression of Alkaline phosphatenase decreased a little at 8 weeks.At 12 weeks,the expression of Alkaline phosphatenase became normal.In the other two groups,the expression of Alkaline phosphatenase peaked at 8 weeks,and at 2,4 and 8 weeks, the expression of Alkaline phosphatenase was not so strong as that of rhBMP-2 group.The expression of PCNA in all groups increased at 2 and 4 weeks then decreased at 8 weeks .At 12 weeks,the expression of PCNA was normal. The expression of PCNA in rhBMP-2 group was stronger at 2 and 4 weeks than the other two contrast groups.Conclusion: PDLLA-nano/HA plate and rhBMP-2 together showed remarkable effect in accelerating the healing of mandibular fractures of rabbits.