Periimplant Soft Tissue Barrier at Experimental One‐Piece Mini‐implants with Different Surface Topography in Humans: A Light‐Microscopic Overview and Histometric Analysis

ABSTRACT Background: Following connection to the oral cavity, osseointegrated dental implants and surrounding tissues are exposed to microbiologic and biomechanical challenges. The establishment of a firm functional periimplant soft tissue barrier (PSTB) is considered to be important to protect the implant's interface from invasion of bacteria. The current knowledge on the histologic architecture of the PSTB is mainly based on animal experiments. Purpose: The aim of this study was to histologically characterize the PSTB formed in humans around experimental one‐piece mini‐implants with different surface topography. Materials and Methods: Five patients received a total of 12 experimental titanium, one‐piece mini‐implants with an oxidized ( n = 4), an acid‐etched ( n = 4), or a machined ( n = 4) surface distal to therapeutic implants. Following transmucosal healing of 8 weeks and at abutment connection of the regular implants, the mini‐implants were harvested with a layer of surrounding hard and soft tissue. The specimens were fixed and processed for histologic sectioning according to standard procedures. The most central bucco‐oral section cut in the long axis was used for morphologic analyses of the PSTB. The vertical soft tissue morphology was quantified using histometric measurements. Results: The overall height of the soft tissue, that is, the biologic width, was around 4 to 4.5 mm and consisted of an epithelial and a supracrestal connective tissue barrier. The junctional epithelium established the attachment to the implant surface, whereas the collagen fibers and fibroblasts of the connective tissue seal were oriented parallel to the implant. The epithelial attachment was shorter at the oxidized and acid‐etched surfaces compared with the machined surfaces. Accordingly, the oxidized and acid‐etched mini‐implants exhibited a longer zone of connective tissue seal. Conclusion: The periimplant soft tissue formed at the experimental one‐piece mini‐implants in humans was of a character similar to that described in animal studies. The oxidized and acid‐etched implants revealed less epithelial downgrowth and longer connective tissue seal than machined implants.