Implant–Abutment Interface and Peri-implant Inflammation in One-Piece and Two-Piece Dental Implants: A Narrative Review

Peri-implant diseases are common plaque-related conditions, and implant design may influence peri-implant inflammation. Two-piece systems include an implant–abutment micro-gap, while one-piece implants eliminate this interface. This narrative review aims to integrate microbiological, biomechanical, and clinical evidence to evaluate whether eliminating the implant–abutment micro-gap in one-piece implants is associated with differences in peri-implant inflammation and marginal bone level changes compared with two-piece systems. A focused narrative review was conducted using PubMed/MEDLINE, Scopus, and Web of Science. The search combined keywords related to implant–abutment interface, micro-gap, bacterial leakage, biomechanical behavior, and peri-implant disease. Studies published mainly between 2000 and 2024 were included, together with relevant earlier studies. A series of studies was analyzed across microbiological, biomechanical, and clinical domains. Experimental studies show that micro-gaps in two-piece implants may allow bacterial leakage, especially under loading conditions, potentially contributing to local inflammation. Biomechanical analyses suggest that one-piece implants may distribute occlusal forces more evenly, while some two-piece designs may concentrate stress at the crestal level. Clinical studies generally report similar implant survival and marginal bone levels, with only limited differences in inflammatory parameters. Eliminating the implant–abutment interface may reduce bacterial leakage and micromovement and improve mechanical behavior in certain situations. Current evidence does not demonstrate a clear clinical advantage of one-piece implants, as outcomes are mainly influenced by surgical factors, loading conditions, and long-term maintenance.