Reverse Torque Values of Abutment Screws After Dynamic Loading: Effects of Sealant Agents and the Taper of Conical Connections

The purpose of this in vitro study was to evaluate the influence of taper angle in internal conical connections of implant systems and the application of chlorhexidine gel as an antibacterial agent or polyvinyl siloxane sealant on reverse torque values of abutment screws after dynamic loading. Four implant systems having different taper angles (5.4°, 12°, 45°, 60°) were tested in this study. Test specimens were divided into 3 groups: control (neither chlorhexidine gel filled nor silicone sealed), 2% chlorhexidine gel filled, and silicone sealed. The samples were subjected to a dynamic load of 50 N at 1 Hz for 500 000 cycles before reverse torque measurements. The taper angle of conical connections presented a quantitative positive correlation between the degree of the taper angle and the percentage of tightening torque loss. However, it was significant only between 60° angled connection and others except for the sealant applied groups (P = .013 for control groups and P = .007 for chlorhexidine groups). The percentages of decrease in torque values of silicon sealant–applied specimens were significantly higher than both the control and chlorhexidine groups (P values are .001, .002, .001, and .002, respectively, according to increasing taper angles), but the percentage of decrease in torque values due to chlorhexidine application was not statistically significant when compared with control groups. Gel form chlorhexidine application as an antibacterial agent does not significantly affect the implant-abutment connection stability under dynamic loads. Polyvinyl siloxane sealant may cause screw loosening under functional loads.