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