# Virtual Zirconia Implants Replace Titanium Implants?
## 6 Microbiota and Peri-Implantitis  
Peri-implantitis is an inflammatory process around an osseointegrated implant, including soft tissue inflammation and progressive loss of supporting bone beyond biological bone remodeling [1]. This inflammatory process is the leading cause of loss of implants in the long term. Peri-implantitis results from biofilm dysbiosis deposits surrounding the peri-implants' mucosa, meaning that bacteria deposition is essential to develop the inflammation reaction. In addition, research considering bacterial adhesion on titanium has revealed that the corrosion of titanium increases plaque accumulation. On this matter, zirconia implants have been suggested as a peri-implant mucosa-friendly alternative [90].  
Recent studies show intriguing results promoting the advantage of zirconia implants in this matter regarding biofilm formation and bacterial adhesion in zirconia implants. An in vitro study aimed to compare the biofilm formation in the zirconia or titanium disks using three-species biofilm or human plaque samples in an anaerobic flow chamber mode. The researchers found that zirconia showed a reduction in biofilm thickness and mass compared with titanium, but similar biofilm metabolism was found. These results suggest that zirconia implants can form less plaque, leading to less peri-implant inflammation than titanium implants [20]. Considering the bacterial adhesion in zirconia, the [PERSON] group [22] found that bacterial counts were higher with titanium discs than zirconia, while [PERSON] et al. [23] showed that bacterial adhesion was significantly higher with pure titanium surfaces as compared with zirconium oxide surfaces, as data also supported by [PERSON] and collaborators find [87]. Moreover, these results are supported by an animal model. That is, a study comparing ligature-induced peri-implantitis around zirconia or titanium implants in dogs. They found that the first presented less crestal peri-implant bone loss and no implant failure. In contrast, the second shows one implant loss due to peri-implantitis [21]. Additionally, a recent systematic review with meta-analysis indicated that zirconia accumulated less initial oral biofilm parameters and less roughness in the zirconia surface [91].  
On the other hand, taking into consideration the role of host response in peri-implantitis, a recent study [92] compared the expression of immunohistochemistry markers in the tissues around ceramic and titanium implants. The authors found a similar number of inflammatory cells (T- and B-cells) in mucosa surrounding ceramic implants when compared with titanium ones, concluding that the cellular response to the inflammatory challenge provoked by the biofilm around implants is the same, independent of the material with which the implant is made.  
Besides, the hypothesis has been raised in the literature that not only biofilm is responsible for peri-implantitis in titanium implants, but also foreign body reaction, allergies, cement excess, or even metallosis [93]. Considering all the factors discussed above, it could be assumed that zirconia implants present lower prevalence rates when compared with titanium implants. Nevertheless, according to a systematic review and meta-analysis [94], owing to the heterogeny of assessment and short-term evaluation of the zirconia implants' clinical studies, non-conclusive results are found regarding inflammatory parameters in peri-implant mucosa around zirconia implants. On the other hand, one prospective study that followed up zirconia implants for 7.8 years found no difference between teeth (control group) and implant regarding bleeding index, attachment level, or bacterial colonization. Interestingly, zirconia implants presented less plaque accumulation and recession, but more probing depths when compared with natural dentition [95]. Moreover, another systematic review [96] concluded that zirconia implants had less plaque accumulation and less inflammation around the peri-implant mucosa.