Abstract: PURPOSE: To observe the effect of subcutaneous ectopic osteogenesis using different proportional mixtures of hydroxyapatite (HAP) and human mandible in nude mice. METHODS: After obtaining external oblique ridge of mandible, autologous bone was mixed with HAP according to certain proportion. The mixtures were divided into 5 groups (group A: autologous bone/HAP=2/1; Group B: autologous bone/HAP=1/1; Group C: autologous bone/HAP=1/2; Group D: autologous bone/HAP=a quarter; Group E: HAP). The 5 groups of mixtures were respectively implanted into nude mice subcutaneously. After 8 weeks, the specimens were obtained and hard tissue sections were completed. The new bone formation was measured after trinitrophenol staining. The data was analyzed with SPSS 13.0 software package. RESULTS: The hard tissue section showed that new ectopic bone formation area was 9.1% (Group A), 16.1% (Group B), 6.1% (Group C), 3.8% (Group D), and 1.3% (Group E), respectively. New bone formation was the most in group B, while it was the least in group E. Significant differences were found between group B and other groups(P<0.05). However, there was no significant difference between group E and group C or D (P>0.05). The retention rate of HAP was the most in group E (30.3%) and the least (16.3%) in group A. CONCLUSIONS: During 8 weeks, human autologous bone mixed with HAP helps new bone formation in nude mice. The best ratio autologous bone and HAP was 1:1. This study provides certain reference basis for dentist to make lifting surgery outside the maxillary sinus using artificial bone graft.

Key words: HAP, Autogenous bone, Ectopic bone formation, Nude mouse