Influence of different agents on the preload force of implant abutment screws

Screw loosening is a common problem in implant dentistry; however, information is sparse on the influence of different fluids on the screw threads.

The purpose of this in vitro study was to investigate the influence of 4 different fluids and agents (saliva, blood, chlorhexidine [CHX] gel, and special sealing silicone) on the preload force of abutment screws.

The test specimens (N=50) consisted of a thread sleeve resembling the implant, an abutment analog, and an abutment screw. The tightening of the screw with a torque wrench was performed in 5 steps (15 Ncm, 20 Ncm, 25 Ncm, 30 Ncm, and 35 Ncm). Each agent was applied in the lumen of the thread sleeve of 10 specimens. Ten dry thread sleeves served as the control. Comparisons between 2 independent groups were performed with the t test or Wilcoxon-Mann-Whitney test, as appropriate. The Bonferroni correction was used for multiple comparisons (α=.05).

Preload forces increased linearly with the applied tightening torque for dry implant lumina, as well as for saliva, blood, silicone, and CHX gel in the implant lumina or thread sleeves. In general, none of the tested agents resulted in significantly higher preload forces compared with the dry control.

The agents investigated did not have any lubricant action on implant abutment screws.