The Effect of Anaerobic Sealants on Prosthetic Screw Removal Torque

Failure of dental implant screwed joints is a common treatment complication, which usually results from screw loosening. This can have many causes and results in loss of pretension in the joint, much of which occurs shortly after tightening. Industrially, wide use is made of anaerobic sealants to reduce this problem; however these have received little attention in implant dentistry. Objectives: This study tested the hypothesis that there was no difference in the removal torque of prosthetic screws with and without the use of anaerobic sealants. Methods: A pilot study identified the preferred surface preparation techniques, activator, and sealant types and volume. Thirty-six new titanium prosthetic screws (Southern Implants) were allocated to six groups: one control and five different sealants. All screws were treated with acetone, and then a proprietary cleaner and primer (Loctite^TM types 6039 and 7649 respectively). 2µl of the selected sealer (Loctite^TM 290 and 932, and Impact Adhesive Co Screwlock 101, Nutlock 103 and Penetrating 107) was applied to the screw. This was then inserted through a gold cylinder into a standard abutment (Southern Implants) and tightened to 10Ncm using a bench-top custom-built screwdriver rig rotating at 0.896 rpm with a downward load of 3.5N. The drive was disengaged electromechanically at a preset tightening torque of 10Ncm. After leaving the joint for three hours the screw was removed by running the driver in reverse whilst recording the removal torque electronically. Results: An ANOVA and Bonferroni post hoc tests showed there was a significant difference (p<0.001) in the removal torque between groups, being significantly higher for the sealants Loctite^TM 290 (8.82 ± 0.91N) and Impact Adhesives Penetrating 107 (9.46 ± 1.87N) than the control (7.42 ± 0.73N)). Conclusions: It is concluded that some types of anaerobic sealant can significantly increase the removal torque of titanium prosthetic screws.