Experimental evaluation in rabbits of the effects of thread concavities in bone formation with different titanium implant surfaces.

BACKGROUND: Differences in implant microtexture are important in conditioning the bone response around dental implants. PURPOSE: The aim of the present study was an evaluation of the bone response in machined (M), blasted with apatitic calcium phosphate (tricalcium phosphate/hydrossyapatite [HA] blend) particles (resorbable blast texturing [RBT]), and coated with HA implants. METHODS: A total of 48 (16 M, 16 RBT, and 16 HA) threaded screw-shaped implants were inserted into the tibia of 12 rabbits. The specimens were retrieved after 1, 2, 4, and 8 weeks and processed for histology. RESULTS: All experimental groups showed an increase of the bone-implant contact percentages through the study period. Higher and highly statistically significant differences were found in the percentages of bone observed in the concavities rather than in the convexities of the implants retrieved after 1, 2, and 4 weeks, while no significant differences were found after 8 weeks. In the different time periods, higher percentages of bone-implant contact were found in the RBT and HA-coated implants both in the concavities and in the convexities, but these differences were not statistically significant. CONCLUSIONS: The newly formed bone present in the concavity of the threads was not influenced by the implant surface in the first healing period, while after 4 to 8 weeks, the percentage of bone observed in the concavities and convexities was similar. Additional histological studies are necessary to further evaluate the critical role of the concave geometry in bone differentiation and formation around dental implants.