Analysis of stresses in implant-supported rehabilitations using occlusal splints

Abstract

Introduction: The rehabilitation of partially or totally edentulous patients with implant-supported prostheses has been widely used, with high success rates. However, the presence of bruxism has been considered a risk factor for this type of treatment. The use of occlusal splints has been suggested to promote uniform occlusal contacts around the arch in centric occlusion, which may prevent fractures of implant-supported prostheses. Although they are not sufficient to completely reduce the signs of bruxism, occlusal splints are capable of reducing the deviation in mouth opening, although there is still a need for continuous treatment, with fixation of the new position by adhesive restoration methods, prosthetic structures or orthodontic treatment. Objective: To evaluate the distribution of stresses in bone tissue, implant, prosthetic components and zirconia crown in rehabilitations using occlusal splints. Methodology: The research was carried out with in silico testing, through finite element analysis, in order to evaluate the stress distribution in titanium implants with Nickel Chromium (NiCr) abutments and zirconia crowns in order to simulate axial loading and bone tissue in an implant-supported rehabilitation in elements 14 and 16 (first upper right premolar and first upper right molar, respectively) with a pontic in element 15 (second upper right premolar). The three-dimensional models were created to simulate a clinical situation with the absence of elements 14, 15 and 16. These teeth were replaced by titanium implants, external hexagon, 11 x 4 mm, cemented, but the cementation line was disregarded in the FEA, with NiCr abutments and zirconia crowns in order to simulate axial loading. The study factors were the presence or absence of an occlusal splint, and the variables were the maximum principal stress (tensile), minimum principal stress (compression) and von Mises stress in the implant, abutment and bone tissue. The occlusal loads were applied computationally with intensities of 300 N axially along the long axis of the structure. The images of the prosthetic components were obtained through a database. The finite element models were constructed with the aid of finite element software (SolidWorks ANSYS Workbench 14.0; Swanson Analysis Inc) for biomechanical analysis (processing). All these analyses were performed quantitatively and qualitatively. Results: The maximum principal stress in bone in the No Plate (SP) group was higher (29.1 MPa), concentrated in the distopalatal region of the first premolar thread; The minimum principal stress in bone in the Plate group (CP) was higher (10.2 MPa), with greater stress in the distal region of the first premolar thread, and in the distobuccal region in the second molar thread. The von Mises stress in the abutments was higher in the SP group (96.9 MPa), which was concentrated in the upper edge of the two abutments in the premolar region; the highest von Mises stress of the implants was in the SP group (161.18 MPa), which was concentrated in the region of the first thread of both implants in the premolar, molar and in the implants. Conclusion: Occlusal splints reduce the maximum stress produced in implant-supported rehabilitations.