Osseointegration of zirconia and titanium dental implants: a histological and histomorphometrical study in the maxilla of pigs

Objectives: The purpose of the present study was to histologically compare the bone tissue responses to surface‐modified zirconia and titanium implants. Methods: Threaded zirconia implants were produced using a new low‐pressure injection moulding technique and thereafter surface treated by acid etching. Titanium implants with the exact shape and surface treated by sandblasting and acid etching (SLA) served as controls. Fifteen adult pigs received both implant types in the maxilla 6 months after extraction of the second and third incisors. The animals were sacrificed after 4, 8 and 12 weeks and 30 implants with surrounding bone were retrieved. Results: Histological evaluation showed osseous integration for both materials. Zirconia implants revealed mean peri‐implant bone density values of 42.3% (SD ± 14.5) at 4 weeks, 52.6% (SD ± 5.7) at 8 weeks and 54.6% (SD ± 11.5) at 12 weeks after implantation, whereas Ti‐SLA implants demonstrated mean values of 29% (SD ± 10), 44.1% (SD ± 18) and 51.6% (SD ± 8.6) at corresponding time intervals. With respect to the bone–implant contact ratio, the mean values for zirconia ranged between 27.1% (SD ± 3.5) and 51.1% (SD ± 12.4) and for Ti‐SLA, it ranged between 23.5% (SD ± 7.5) and 58.5% (SD ± 11.4). For the parameters investigated, no statistically significant differences between both types of implants could be detected at any time point. Conclusions: No statistical difference between implants could be demonstrated with any of the methods used. The limited number of animals per group, however, does not allow to conclude that there is no difference in osseointegration between the two types of implants, although the data tend to suggest such a trend.