Surface Degradation of Titanium and Zirconia Dental Implants in the Oral Environment: A Scoping Review of Mechanisms and Clinical Implications

Titanium dental implants are widely regarded as the gold standard for the rehabilitation of missing teeth due to their high survival rates and favorable mechanical properties. However, in the oral environment, implant materials are continuously exposed to complex chemical, mechanical, and biological factors that may lead to surface degradation, including corrosion, tribocorrosion, and mechanical wear. These processes can alter implant surface characteristics and influence biological responses in peri-implant tissues. Zirconia implants have been introduced as alternative material due to their favorable aesthetics and biocompatibility. Nevertheless, zirconia ceramics are also susceptible to degradation phenomena, including hydrothermal aging, phase transformation, and surface wear under specific conditions, although their clinical relevance remains unclear. In addition, emerging hybrid titanium–zirconia implant systems introduce new considerations regarding surface stability. This scoping review, conducted in accordance with PRISMA-ScR guidelines, summarizes the current evidence on degradation mechanisms affecting titanium, zirconia, and hybrid dental implants, with particular focus on processes occurring in the oral environment and their biological and clinical implications. The available evidence differs substantially between the two materials. While titanium degradation is well documented and supported by both experimental and clinical studies, the evidence for a hybrid implant remains limited and is largely based on in vitro and mechanistic data.