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.