Biological response to titanium implants coated with nanocrystals calcium phosphate or type 1 collagen in a dog model

Objective The current study aimed to evaluate the osteogenic potential of electrosprayed organic and non-organic surface coatings in a gap-implant model over 4 and 12weeks of implantation into the dog mandible. Material and methods Sixteen Beagle dogs received experimental titanium implants in the mandible 3months after removal of left premolars (P2, P3 and P4). Three types of implants were installed in each animal: non-coated implant, nano-CaP coated implant and implant with type 1 collagen coating. Both micro-CT and histomorphometry were used to evaluate peri-implant bone response after implantation periods of 4 and 12weeks. The bone area percentage was assessed histomorphometrically in three different zones (inner: 0300m; middle: 300600m; and outer: 6001000m) around the implant surface. Bone-bridging of the gap was also calculated for each sample. Results Four weeks after implantation, nano-CaP and collagen-coated implants showed significantly higher bone volume (BV) in the inner zone compared with non-coated implants (P<0.05 and P<0.01). After 12weeks, histomorphometric analysis showed comparable amounts of BV between all experimental groups. Also, no significant difference was found in the BV, as measured using micro-CT, between the implant groups. Absolute bone ingrowth measurements were highest for collagen-coated implants, but these differences were not significant. Conclusion The obtained data failed to provide a consistent favourable effect on bone formation of the collagen coating over 3months of implantation. It is concluded that the source of the collagen as well as the limited osseous environment overshadowed a possible effect of the applied implant surface modifications. Similarly, the tested nano-apatite surface coating did not improve peri-implant bone ingrowth into a gap-implant model.