Effect of Contaminants on Reverse Torque Values of Implant Abutment Screws: A Systematic Review and Partial Meta-Analysis of In Vitro Studies

Abstract

Introduction: Screw loosening is a common complication in implant systems, often influenced by contamination during abutment placement. Reverse torque values (RTVs) are used to assess implant-abutment joint integrity.

Objectives To evaluate the effect of various contaminants on RTVs of implant abutment screws using data from in vitro studies.

Methods This systematic review and meta-analysis was registered in PROSPERO (CRD420251064053) and conducted according to PRISMA guidelines. Literature searches of PubMed, Scopus, and Cochrane (2000–2024) identified studies assessing saliva, blood, chlorhexidine, fluoride, tetracycline, and artificial saliva. Risk of bias was assessed using ROB 2. Statistical analyses included two-way ANOVA and Tukey’s HSD.

Results: Twelve studies were included. Saliva consistently produced the highest RTVs, while blood showed the lowest. ANOVA revealed significant differences between groups (F(2,93) = 292.64, p < 0.00001). Tukey’s test confirmed significant pairwise differences: Contaminant vs. Torque (Q = 32.01, p < 0.00001), Contaminant vs. Reverse Torque (Q = 26.46, p < 0.00001), and Torque vs. Reverse Torque (Q = 5.56, p = 0.00048). Saliva provided the most favorable torque retention, followed by chlorhexidine and fluoride.

Conclusions: Contaminants significantly affect implant-abutment stability. Saliva may improve torque retention, whereas blood is most detrimental. Standardized protocols and in vivo validation are needed.