Histological analysis of loaded zirconia and titanium dental implants: an experimental study in the dog mandible

Objective To assess whether or not peri‐implant soft tissue dimensions and hard tissue integration of loaded zirconia implants are similar to those of a titanium implant. Materials and methods In six dogs, two one‐piece zirconia implants (VC, ZD), a two‐piece zirconia implant (BPI) and a control one‐piece titanium implant (STM) were randomly placed. CAD/CAM crowns were cemented at 6 months. Six months later, animals were killed and histomorphometric analyses were performed, including: the level of the mucosal margin, the extent of the peri‐implant mucosa, the marginal bone loss and the bone‐to‐implant contact (BIC). Means of outcomes variables were calculated together with their corresponding 95% confidence intervals. Results In general, the mucosal margin was located coronally to the implant shoulder. The buccal peri‐implant mucosa ranged between 2.64 ± 0.70 mm (VC) and 3.03 ± 1.71 mm (ZD) (for all median comparisons p > 0.05). The relative marginal bone loss ranged between 0.65 ± 0.61 mm (BPI) and 1.73 ± 1.68 mm (ZD) (buccal side), and between 0.55 ± 0.37 mm (VC) and 1.69 ± 1.56 mm (ZD) (lingual side) (p > 0.05). The mean BIC ranged between 78.6% ± 17.3% (ZD) and 87.9% ± 13.6% (STM) without statistically significant differences between the groups (p > 0.05). Conclusions One‐ and two‐piece zirconia rendered similar peri‐implant soft tissue dimensions and osseointegration compared to titanium implants that were placed at 6 months of loading. Zirconia implants, however, exhibited a relatively high fracture rate.