Abstract
BACKGROUND: Resolution of peri-implant defects resulting from implant placement in the freshly extracted site demands for a bone graft substitute that stimulates bone regeneration and hence facilitates implant integration. In view of this, the addition of silica to hydroxyapatite (HASi) could enhance the bioactive behavior of ceramic materials and implant surfaces coated with bioactive ceramics might benefit the interaction between bone and implant. PURPOSE: To evaluate the bone response to implants coated with hydroxyapatite-silica (HASi) or hydroxyapatite (HA) and either or not combined with HASi and HA ceramic bone substitute particles, respectively, on bone-to-implant contact (BIC) and bone formation using a rabbit femoral condyle implant model with a gap design. MATERIAL AND METHODS: A total of 32 custom-made, titanium implants (Ti: diameter 5 mm, length 8 mm) with two-sided gaps were fabricated and coated with either HASi or HA using pulsed laser deposition (PLD). The implants were installed bilaterally in the femoral condyles of 16 New Zealand white rabbits. According to a randomization protocol, one gap of HASi-coated and HA-coated implants was filled with HASi particles and HA particles, respectively, and the other gap was left empty. After an implantation period of 8 weeks, the retrieved specimens were analyzed via histology and histomorphometry (i.e., bone to implant contact [BIC] and bone volume [BV]). RESULTS: The BIC and BV around the implants were analysed for HASi- and HA-coated implants with and without the use of HASi and HA bone substitute material. Comparison of HASi- and HA-coated implants showed similar BIC for HASi- (55.7 + 11.0) and HA-coated implants (50.3 + 19.7). When coated implants were combined with bone substitute materials, HASi-coated and particle-filled implants showed higher BIC (64.3 +/- 6.8%) compared with HA-coated and HA-filled implants (54.5 +/- 10.9%). Similarly, the BV within the region of interest showed significantly higher values for the HASi-coated and HASi-filled implants (21.1 +/- 1.7%) compared with HA-coated and HA-filled implants (12.8 +/- 4.9%). CONCLUSIONS AND CLINICAL IMPLICATIONS: Within the limitations of this study, it can be concluded that silicon substitution in HA favors bone regeneration compared with HA, especially when used as bone substitute material. Further studies using different healing periods will elucidate the resorption pattern of HASi granules in comparison with HA.
