The Clinical Impact of Dental Implant Placement in Close Proximity to Natural Teeth: A Systematic Review and Meta-Analysis

The spatial relationship between dental implants and adjacent natural teeth is critical for maintaining peri-implant health and avoiding iatrogenic complications. This systematic review and meta-analysis evaluated the biological and structural effects of implant placement within 1.5 mm of natural tooth roots or in direct contact with them. Electronic searches were performed in PubMed/MEDLINE, Cochrane Library, Scopus, Web of Science, ScienceDirect, Google Scholar, and Semantic Scholar databases from inception to January 2025, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines (PROSPERO ID CRD42024499790). Eleven studies met the inclusion criteria, comprising eight observational studies and three case series, representing 1,727 participants and over 2,000 implants. Pulpal and periapical pathology were the most frequently reported adverse outcomes, with 20%-25% of affected teeth requiring root canal therapy in proximity-contact cases. Marginal bone resorption and peri-implantitis were observed in up to 4% of implants placed less than 1 mm from adjacent roots. Secondary caries and cervical structural defects were reported less consistently but were more prevalent in posterior regions. Meta-analysis using a random-effects model yielded a pooled effect size of 0.11 (95% confidence interval: 0.03-0.22), indicating a low yet clinically relevant risk of proximity-related complications, with an overall implant survival exceeding 95%. The certainty of evidence was moderate for pulpal and bone outcomes and low for caries or structural changes. Within the limitations of the available data, implants placed closer than 1.5 mm to natural teeth may cause localized biological damage without significantly compromising implant longevity. Meticulous presurgical planning and guided placement are essential to prevent avoidable injury.