Bone tissue response to implant surfaces functionalized with phosphate-containing polymers.

OBJECTIVES: Inorganic polyphosphates are said to stimulate the activity of osteoblast-like cells in vitro. The purpose of this study was to evaluate in vivo bone regeneration around implants treated with polyphosphoric acid (PPA) and phosphorylated pullulan (PPL). MATERIAL AND METHODS: Two types of implants with different surface roughness (R1: Sa approximately 0.23 mum; R2: Sa approximately 1.35 mum) were treated with three solutions (distilled water, 10%wt PPA, or 10%wt PPL) prior to implantation in both tibia of twelve female white rabbits. Each animal received six implants randomly positioned according to their surface roughness and treatment: R1 + water; R1 + PPA; R1 + PPL; R2 + water; R2 + PPA; R2 + PPL. Animals were sacrificed after 1 or 4 weeks, and samples were prepared for histological and histomorphometrical analysis. Bone regeneration areas were evaluated for bone-to-implant contact (BIC) and bone fraction (BF) in areas 100 and 500 mum remote from the implant surface. Data were statistically analyzed by means of Friedman and Wilcoxon matched-pair tests (P < 0.05). RESULTS: After 1 week, bone tissue was rarely formed in the regeneration areas. After 4 weeks, implants treated with PPA presented higher ratios of BIC (R1 = 52.3 +/- 13.1; R2 = 54.6 +/- 11.0) than the ones treated with water (R1 = 24.1 +/- 15.1; R2 = 32.4 +/- 13.0). On the other hand, around the implant surface (100 mum), PPL-treated implants induced higher BF (R1 = 78.3 +/- 34.1; R2 = 71.2 +/- 21.8) as compared with the water-treated ones (R1 = 46.1 +/- 22.0; R2 = 49.6 +/- 21.0). At 500 mum, however, no statistically significant differences in BF were found among the groups evaluated (P > 0.05). Surface roughness influenced neither BIC nor BF. CONCLUSIONS: Implant surface treatment with phosphate-containing polymers may positively influence osseointegration.