**5. Crestal bone loss around zirconia implants and survival and success rate**

As zirconia implants have been used over relatively few years, a few clinical studies with limited follow-up are available. Furthermore, the results are not easy to compare. It is impor‐ tant to keep this statement in mind analyzing the following studies and the consistent conclusions. The largest prospective clinical study (831 implants in 378 patients) reported a success rate of 95% after 5 years [32]. The success rate of the acid-etched implants was slightly higher than that of coated and noncoated implants. A 1-year follow-up case series analyzed 56 implants (12 in upper jaws and 44 in mandibles) inserted into 28 patients. A survival rate of 98.2% was found, with an average marginal bone loss of almost 2 mm, which appears quite high, lowering the success rate to 60% [33]. A prospective study with a very small number of cases found a success rate of 100%, with a minimal bone loss after 4 years (0.6 mm) [34]. An in vivo study found a greater bone loss around zirconia implants in respect to titanium implants after 12 months of function. However, no difference in the survival rate was recorded [35]. A recent systematic review of 13 studies (maximum follow-up of 4 years) concluded that the survival rate of zirconia implants ranges from 67.6 to 100% [36].

**Figure 3.** The radiographic control of prosthetic crown cemented on a zirconia implant (courtesy of Prof. Andrea Enri‐ co Borgonovo, University of Milan).

In conclusion, from the available data the osseointegration of zirconia implants seems not to be a problem (**Figure 3**) [37]. Nevertheless, survival and success rates of zirconia implants are inferior to those of titanium ones [13]. For this reason, the majority of authors [12] remain cautious and agree that further follow-ups are needed to evaluate the long-term success rates, before a routine use of zirconia implants can be recommend widely.
