Effect of fluid contamination on the reverse torque values of abutment screws at implant-abutment connections

Statement of problem Screw loosening is still among the most important complications of dental implants. Identifying effective factors in screw loosening plays an important role in preventing this problem. Purpose The purpose of this in vitro study was to assess the effect of fluid contamination on the reverse torque values (RTVs) of abutment screws at implant-abutment connections. Material and methods Five groups (9 specimens in each group) of implants were mounted in acrylic resin. Four groups of fixture screw holes were contaminated with chlorhexidine (CG), saliva (SG), blood (BG), or fluoride (FG), and a fifth group served as a control with no contamination (NC). Abutment screws were tightened by using a digital torque meter. The RTVs were recorded after thermocycling. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference test (α=.05). Results RTVs were lower in SG (13.65 ±0.91 Ncm) than NC (16.55 ±1.82 Ncm), while the values were significantly higher in CG (19.74 ±1.79 Ncm) than NC. No statistically significant difference was reported in BG (16.30 ±1.66 Ncm) and FG (15.92 ±1.82 Ncm) compared with the control group. Conclusions RTVs were significantly reduced by saliva contamination in comparison with those of other groups. The highest RTVs were detected in CG.