In vitro integrity of implant external hexagon after application of surgical placement torque simulating implant locking

Abstract

The aim of this study was to evaluate the integrity of the external hexagon of an implant system with internal and external hexagons but with prosthetic connection through the external hexagon (Internal Torque, IT) in comparison with that of an implant system with external hexagon with mount (External Hexagon, EH). A device was made to measure the rotational freedom angles between implant and abutment hexagons in 10 implants from each group after the application of surgical placement torques of 45, 60 and 80 Ncm simulating implant locking. The distances between the vertices of the external hexagon were also obtained. Rotational freedom data were subjected to ANOVA and Tukey's test (P < .05) showing no significant difference between the angles of the intact implants (EH -3.31 ± 0.41° and IT -3.30 ± 0.17°) and after application of a 45 Ncm torque (EH -3.27 ± 0.38° and IT -3.31 ± 0.22°). However, after application of a 60 Ncm torque there were significant differences (IT -3.40 ± 0.20° and EH -4.03 ± 0.54°). After application of a 80 Ncm torque, the IT implant presented values of 3.39 ± 0.21° whereas the EH did not support the torque, suffering deformation of its external hexagon. Within the limits of this study, it can be concluded that the IT implant system may be preferable in clinical situations where implant placement within a certain bone density could generate torques higher than 60 Ncm.

Evaluaton of hexagon deformation of dental implant regarding to the insertion force

“…In this study, the implants were inserted in self-curing acrylic resin rigid plates in pattern way using liners. It enables a specimen evaluation with appropriately fixed on the acrylic in order to decease external variables that could interfere on the results, as bone type and quality, implant thread macro and micro geometry and eve implant surface treatment [25][26][27][28][29][30] . .…”

External Hexagon Deformation in Implants Subjected to Internal Torque

“…Deformations in the geometry of EH caused by external torque (16) have led to the use of internal torque, since the internal area of the implant exhibits greater resistance as compared to the external area. Therefore, in order to identify possible changes in the internal area of the implant and to exclude interfering variables, the static positioning of the implants into the acrylic model was chosen for the application of torque in this study.…”

“…However, the level of changes observed in the EA of both N80 and S40, 0.59% (0.038 mm 2 ) and 0.49% (0.032 mm 2 ) respectively, may affect the correct fit of the prosthesis to the implant. Studies indicate a direct correlation between implant-abutment rotational misfit and screw loosening (10,(16)(17)(18)(19).…”

An Overview Regarding Contemporary Biomechanical Aspects on Immediate Loading Dental Implants

“…Afterwards, the external hexagon was also shown to work as an antirotational mechanism and to orient the abutment in single tooth prostheses (Davi et al, 2008). The biomechanical complications reported are loosening or fracturing of the abutment and prostheses screws (Merz et al, 2000).…”

“…However, the weak-link to the fixture of the external hexagon configuration, is often referred as a fail-self mechanism for over-loading situations (Maeda et al, 2006). Davi et al (2008) evaluated the integrity of the external hexagon of an implant system with internal and external hexagons but with prosthetic connection through the external hexagon (internal torque) in comparison with that of an implant system with external hexagon with mount (external hexagon). They concluded that the internal torque implant system may be preferable in clinical situations where implant placement within a certain bone density could generate torques higher than 60 N.cm.…”