Abstract
Purpose To examine the effects of fluid contamination on the reverse torque value (RTV) of abutment screws. 484 titanium fixtures were mounted into the stainless-steel holders. Methods 11 groups (44 specimens in each group) of implants were mounted in acrylic resin. Ten groups of fixture screw holes were contaminated with chlorhexidine, saliva, blood, fluoride, or combination groups, and one group served as a control without contamination. To simulate the oral environment, samples were subjected to thermal cycling and cyclic loading. Results The RTV means were less than the initial torque in both control and contamination groups. The maximum RTV mean was observed in the fluoride group (26.00 ± 1.02 Ncm). In other groups, this rate for control, blood, saliva, and chlorhexidine groups were 18.00 ± 1.78 Ncm, 22.12 ± 1.56 Ncm, 21.56 ± 1.43 Ncm, and 21.89 ± 1.02 Ncm, respectively. In combination groups, the maximum RTV mean was observed in the saliva+CHX group (23.89 ± 1.92 Ncm). In other combination groups, this rate for the blood+CHX, blood+saliva, saliva+fluoride, fluoride+CHX, and fluoride+blood groups were 22.56 ± 1.73 Ncm, 22.00 ± 1.54 Ncm, 20.11 ± 1.58 Ncm, 23.51 ± 1.19 Ncm, 21.02 ± 1.38 Ncm, and 20.11 ± 1.58 Ncm, respectively. The RTV was statistically significant (p < 0.05) for the contamination groups (except saliva) and combination groups compared to the control group. There is no statistically significant difference (p > 0.05) between the reverse torque value mean of the blood and saliva groups and between that of the fluoride and chlorhexidine groups. Conclusion Implant-abutment specimens are suggested to be placed in a saliva environment and should be subjected to cyclic loading.
Highlights
Studies indicate a remarkable improvement in the life quality of patients who have received dental implants [1]
The results indicated that reverse torque value (RTV) values were less than initial torque (30 Ncm) in both of the control and contamination groups
The contamination groups’ RTV means were more than the control group, and this difference was statistically significant for the blood (p = 0:04), chlorhexidine (p = 0:03), and fluoride groups (p = 0:01)
Summary
Studies indicate a remarkable improvement in the life quality of patients who have received dental implants [1]. Advances in implant materials and manufacturing processes cannot reduce the mechanical complications to zero [2]. These mechanical complications can influence dental implant success and include opposing prosthesis fracture, material and component fracture, and screw loosening [3]. When a screw is tightened by the application of torque (a force applied to a tooth to produce or maintain a crown), it elongates and creates tension [8]. This tension is called preloading, a direct determinant of clamping force [9]. Several factors may affect preload, including screw design and materials, applied torque magnitude [10, 11], torque delivery system [12], and environmental factors affecting the interactions such as presence and type of fluid contaminations and lubrication [13]
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