Bone-to-Implant Contact in One-Piece Zirconia and Titanium Implants in Dogs

Objectives: Implants made from zirconia (ZrO₂) seem to have the potential to become an alternative to titanium implants as far as material properties and esthetic appearance are concerned. However, there are very few data with regard to the osseointegration behavior of zirconia in comparison with roughened titanium. Therefore it was the objective of this histometric study in dogs to compare the osseointegration of one-piece implants made from zirconia compared with titanium implants of equal design and surface roughness after 4 months.

Methods: Ten weeks after extraction of lower premolars (P3, P4) and first molars (M1) in 6 mongrel dogs, four one-piece implants of identical geometry were inserted on each side (all of them had a diameter of 3.5 mm and a length of 8 mm): (1) an uncoated zirconia implant (zit-z implant; ziterion GmbH, Uffenheim, Germany), (2) a zirconia implant coated with an osseoconductive titaniumoxide sol-gel layer, (3) an Al₂O₃-blasted titanium implant (control), and (4) an experimental implant made of a synthetic plastic material (implant was not evaluated). All implants had the same surface roughness. After 4 months the animals were sacrificed, and the implants were block-embedded into resin. Thereafter non-decalcified ground sections were made and stained with toluidine blue in order to histologically assess the bone-to-implant contact rates (BIC) in the threaded part of the implants.

Results: Healing was uneventful, and all 48 implants osseointegrated clinically and histologically. Histomorphometrically the BIC was not significantly different between the groups and amounted to 59.1 ± 7.5% for uncoated zirconia, 55.9 ± 13.9% for coated zirconia, and 40.9 ± 10.1% for titanium implants (p>0.05; Friedman test).

Conclusion: Within the limits of this animal study, it is concluded that zirconia implants are capable to establish close contact to living bone tissue as it is known from the osseointegration behavior of roughened titanium implants.