Failure of prosthetic screws on 971 implants

Abstract

Aim: To evaluate the presence of failures in prosthetic screws and whether these failures are related to the type of prosthesis, abutment angulation and presence or not of intermediate. Methods:Two-hundred and sixty-seven patients were evaluated at the Federal University of Santa Catarina, totaling 971 external hexagonal implants in place for at least one year. A Tobit regression model for censored variables was used and the explanatory variables were subjected to percentage analysis. Results: The results demonstrated a relationship between the failure in prosthetic screws and the investigated factors with a significance of F=0.003 and p<0.05. The percentage analysis showed that the prosthetic screw failed in 8.82% of 238 unitary prostheses and 10.1% of 773 multiple prostheses. Among 912 abutments, 9.43% failed and in the 59 angled abutments, failures appeared in 15.25%. A total of 200 prostheses were placed over the implant platform and 13% failed. A total of 771 prostheses were made over abutment and 8.95% of these screws failed. Conclusions: Through multiple linear regression it could be concluded that the type of prosthesis showed no significant influence on the prosthetic screw failure, but other variables were related to this mechanical failure. There was a significant relationship among the variables, demonstrating the need for greater attention in choosing the type of prosthesis, the abutment angulation and whether the prosthesis will be placed directly on the implant platform or on the abutment.

Effect of different angulations and collar lengths of conical hybrid implant abutment on screw loosening after dynamic cyclic loading

“…These results are in agreement with previous studies which stated that the difference in abutment screw RTV after load showed better results when less angulation abutment was used and studies have failed to show any contraindication to their use [4, 19, 29]. Ha et al [30], in an evaluation of the influence of abutment angulation on screw loosening of implants in the anterior maxilla, found that the angled abutments showed higher RTV ( P < .05) than the straight and gold premachined UCLA-type abutments and the difference between them was not significant.…”

“…This supports the concept of eliminating unnecessary occlusal and off-axial forces on implant-supported restorations [4]. With clinical loading of implants restored using angled abutments, lateral occlusal forces may increase creating torsional force which increases screw loosening [12, 29]. Any direction of load that is not in the long axis of the implant will magnify the crestal stresses to the implant–bone interface and to the abutment screws in the restoration [8].…”

“…This micromotion may explain the screw failure. However, no screw failure occurred in a study with 2261 angled abutment evaluated for 96 months [29, 32].…”

Implant-Supported Restoration with Straight and Angled Hybrid Abutments: Digital Image Correlation and 3D-Finite Element Analysis

“…32 The higher amount of stress due to the off-axis load on the inclined implant suggests a higher chance for prosthetic complications such as screw loosening. [42][43][44] Screw loosening can be explained by the present results which showed that the stress peak was located at the screw threads.…”