Purpose: To evaluate the published literature on tooth–tissue supported removable partial dentures (RPDs) and determine the attachment system that provides the best clinical outcome. Materials and Methods: A comprehensive search of studies published up to November 2021 was performed in the PubMed/MEDLINE, Web of Science, and Cochrane Library databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The study protocol was approved and was registered in the International Prospective Register of Systematic Reviews (PROSPERO: CRD42021268449). The PICO question was, “What is the best attachment system used in Kennedy class I and II removable partial dentures?” Results: The search identified 871 articles, of which 21 met the inclusion criteria. The evaluation period in the studies ranged from 3 to 282 months. A total of 1,357 patients were included, of which 526 used prostheses with attachments. The mini SG attachment (extracoronal) was the most commonly used attachment, and the survival rate ranged from 37% to 98.1% in 10 studies, with no significant differences between the systems. Among the 10 studies selected for quantitative analysis, the meta-analysis revealed an overall failure rate of 16.6% (95% CI: 10.4% to 25.4%) and heterogeneity of I² = 65.725 (q value: 26.258, P = .002). Conclusions: Clinical studies comparing different attachment systems for rehabilitation are lacking. Our findings suggest that attachment-retained RPDs have good retention and better esthetics than conventional RPDs, and the extracoronal attachment system is the most viable choice for treatment at the free end.
