The influence of implant angulation on stress distribution in maxillary central incisor – 3D finite element analysis

Abstract

Background Implant -supported prostheses in the anterior maxilla have been considered a prosthetic and surgical challenge due to the small quantity of bone. Guided bone regeneration technology solves the problem of insufficient bone volume to some extent. Alternatively, the implant may be placed with an angulation, which is simple, cost-effective, less invasive and reduces treatment time. However, implant angulation may increase the likelihood of overloading, leading to implant failure. Aim/Hypothesis The influence of implant angulation on stress distribution is still a matter of debate. The aim of this study was to investigate the stress distribution on the bone around tilted implants in maxillary central incisor by means of finite element analysis. Material and Methods FEA models of a single-unit crown supported by the implant (diameter: 3.5 mm, length: 11.5 mm) and angulated screw channel abutment (NobelProcera ASC) or straight abutment were used. According to the different angulation of the implant placed in bone, solid models were assembled, and divided into 3 groups, totally 9 models. In control group, the implant was placed in an ideal direction, recorded as 0°. In group A(palatal inclination), implants were palatal placed at -10°, -5°. In group B(inclination), the implant was labially placed at 5°, 10°, 15°, 20°, 25°, 20°. Then all the models were meshed in ANSYS 15.0 software. A palatal bite force of 140 N was applied to a point 2 mm below the incisal edge, with an approximately 50° to the long axis of the crown. The von Mises stress distribution in bone around implants were analyzed. Results The general patterns for stress distribution were similar in all models. Stress was mainly concentrated in the crestal bone around the neck of implants, the stress values in cortical bone were higher than that in cancellous bone. With the increase of implant labial inclination, the stress was gradually concentrated in the labial crestal bone. Comparing with the control group, when the implant was labially placed at the angle of 20°, 25°, 30°, the maximum von Mises stress in bone increased significantly. The stress of cortical bone increased by 127.33%, 189.91% and 117.11%, meanwhile increased by 155.26%, 156.76% and 89.19% in cancellous bone. There was no significant correlation between the maximum von Mises stress and the angle of implant tilted. Conclusion and Clinical Implications In the anterior maxilla, the angles ranging from 0 degree to 15 degree are optimal choice for the anterior implants.When the implant tilted labially reached 20 degree, the stress values in bone increased significantly, which may increase the chance of implant failure.