Oral implants enlarge the treatment options to replace missing teeth and have been proven to be successful as shown in systematic reviews with long‐term follow‐up. Although survival rates appear convincing, peri‐implantitis around dental implants is a challenge in daily practice, with a prevalence around 20%. The prevalence rate of peri‐implantitis is highly variable and seems to be affected by clinical case definition and local factors such as implant characteristics. Peri‐implantitis is defined by the Consensus Conference of the American Academy of Periodontology and the European Federation of Periodontology as a “plaque‐associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri‐implant mucosa and subsequent progressive loss of supporting bone”. However, current articles with varying evidence consider additional trigger mechanisms for peri‐implant bone loss, such as prosthetic, surgical, and biomechanical factors. For the identification of possible etiologic factors of a disease it is necessary to study the immunohistological composition as known from studies regarding aseptic loosening of orthopedic implants. The cellular composition of peri‐implantitis around titanium implants is characterized by the existence of neutrophils, macrophages, and/or T‐ and B‐cells. The infiltrated connective tissue (ICT) in peri‐implantitis is more than twice as large as the ICT of periodontitis and presents a significantly higher number of CD68 and myeloperoxidase‐positive cells. Further, current histological studies showed a distinct macrophage M1 polarization compared with periodontitis.

Even though titanium and its alloys are the most commonly used materials for oral implants and its components, ceramic oral implants are increasingly being placed. Three zirconia‐containing ceramic systems are established in implant dentistry: yttrium‐stabilized tetragonal zirconia polycrystals (Y‐TZP), alumina‐toughened zirconia (ATZ) and zirconia‐toughened alumina (ZTA). Currently, there are mainly one‐piece implants on the dental market, however more and more two‐piece ceramic implants are available. To produce a roughened zirconia surface, sintering particles onto the implant surface, nanotechnology, laser technology, sandblasting, or sandblasting and acid etching with a mixture of hydrofluoric and sulfuric acid have been used leading to different manufacturer dependent microtopographys. Y‐TZP has been described to exhibit various benefits including excellent biocompatibility. Since zirconia implant surfaces show a difference in biofilm formation in comparison with titanium implant surfaces, the peri‐implant immunological cellular response might be different between titanium und zirconia implants. Peri‐implantitis also occurs around ceramic implants but due to missing data the prevalence is unknown. To date, there is no histological analysis of the tissues around ceramic implants with signs of peri‐implantitis. Although there might be some similarities between the clinical appearance of peri‐implantitis around titanium and ceramic implants, a congruence between these conditions hasn't been shown on a histological level to date.

The aim of this pilot study was the histologic classification of the inflamed peri‐implant soft tissue around ceramic implants in comparison with titanium implants.