Physical And Chemical Properties Of N, O-carboxymethyl Chitosan Complex Tricalcium Phosphate And Mandibular Bone Defects In Experimental Research

Objective: To study the mechanical and chemical characterization of scaffold made of N, O-carboxymethyl chitosan(N, O-CMCS) and tricalcium phosphate(TCP) with various weight ratios.Methods: Three composites of N, O-CMCS/TCP with weight ratios of 2: 1, 1: 1 and 1: 2 were mixed using the same volume of distilled water. The characteristic bands, morphologic structure, compressive strength and Young modulus of the composites were analyzed by infrared spectroscopy(IR), scanning electron microscopy(SEM) and universal testing machine respectively.Results: The shift of IR characteristic bands of -COO and -NH₂ to lower wave number was observed in three composites gradually, which resulted from the complexation of -COO and -NH₂ with calcium ions. The pores of the three- dimensional porous structureand compressive strength of the compositeincreased when there were more N, O-CMCS in the composite. When there were more TCP in the composite, its porosity became less and Young modulus increased, so that the composite demonstrated more rigidity.Conclusions: N, O-CMCS had the capability of complexing with calcium ions. The scaffold made of N, O-CMCS and TCP had the properties of three-dimensional porous structure, flexible remolding and mechanical strength, so it will be a promising bio- material for bone substitute. Objective: A preliminary study was carried out to implant in vivo the novel composites made of soluble N, O-carboxymethyl chitosan (N, O-CMCS) and tricalcium phosphate(TCP) with various weight ratios to repair artificial mandibular defects of rabbits. Following observations and evaluations were undertaken to find out the osteogenetic capability and bioactivity of the composites and to prove the plastic composite a promising bone substitute.Methods: First, 24 adult rabbits were divided into four time groups randomly(6/group), then bilateral mandibles (12sides) of every group animals were divided into 6 subgroups(2sides/group): A: N, O-CMCS group(2×4sides); B: TCP group(2×4 sides); C: N, O-CMCS/TCP (2 : 1 w/w) group(3×4sides); D: N, O-CMCS/TCP(1 : 1 w/w) group(2×4sides); E: N, O-CMCS/TCP (1 : 2 w/w) group (2×4sides); F: blank control group without any material (2×4 sides). The segmental defects of 1.2cm in length and 1.0cm in width were made artificially in the bilateral mandibular bodies of all the rabbits. Then materials of A～F groups were implanted in the prepared defects respectively. Post-operation 4, 8, 12 and 16 weeks, the rabbits of one group were killed randomly according to different operation time and all mandibles were taken off. Then gross observation, X-ray examination, histological analysis, scanning electron microscopy (SEM) and energy disperse analysis were applied to evaluate the osteogenetic capability of the composites.Results: There were few bone formation in group A but plenty of ingrowthed fibrous tissue. The paste of TCP dispersed and migrated gradually after implantion in group B resulted in few bone regeneration. In group C and E especially group D the defect repariations of the mandibles were effective and predominant.Conclusions: The experiment applied N, O-CMCS/TCP composite to remold the mandibular shape demonstrated that the composite had the capability of bone conduction, the proper size of pore to ingrow the osteoblast and vascular endothelial cell(VEC) and the mechanical strength of supporting bone ingrowth and keeping the artificial defect stable. The experiment also showed that the osteogenetic capability of group D was the best among all groups. Meanwhile the preparation and storage of N,O-CMCS/TCP composite were easy and economic, so the biodegrable and plastic composite was a promising bone substitute.