Finite element analysis on dental implant–supported prostheses without passive fit

Abstract

Purpose: The purpose of this study is to use finite element analysis to investigate the effect of misfit prostheses, cantilever prostheses, and various occlusal forces on the stress distribution in the prostheses, implant components, and surrounding bone.Materials and Methods: Two 3-dimensional finite element models were constructed: (1) a 2-implant-supported, 2-unit fixed partial denture and (2) a 2-implant-supported, 2-unit fixed partial denture with a distal cantilever. Variations of the standard finite element models were made by placing a 111-m gap between the gold cylinder on either the mesial or distal implant. The effects of load of 100 N were tested on all models. Subsequently, loads of 50 N, 200 N, and 300 N were evaluated on the cantilever model.Results: When the gap was positioned near to the applied force, the stress in both models increased significantly in the implant components and surrounding bone. The stress increase in each component ranged from 8% to 64% in the non-cantilever models and 43% to 85% in the cantilever models. The greatest stress was found in the distal gold screw. The effect of the gap was clearly shown by the pattern of stress distribution in both models. Additionally, the presence of a cantilever and excessive occlusal force amplified the effect of prosthesis misfit.Conclusions: Prosthesis misfit influenced the pattern and magnitude of stress distribution in the prosthesis, implant components, and surrounding bone, and the presence of the cantilever or greater occlusal force amplified the effect of misfit.

Stress distribution in fixed-partial prosthesis and peri-implant bone tissue with different framework materials and vertical misfit levels: a three-dimensional finite element analysis

“…The retention screw of the molar presented high stress values, which were observed in the long axis and probably caused by tensile forces. A considerable increase in stress was observed in the framework, porcelain veneer, and retention screw proportional to the increase in misfit, which is in agreement with previous studies (8,11,18,21). It has been suggested that these structures are more sensitive to a lack of passive fit and are directly responsible for clinical failures such as loosening or fracture of the abutment or prosthetic screw and fracture of the framework or veneers (18) due to asymmetric contact among the various components of the system (28).…”

“…The changes in vertical misfit showed a considerable influence on the stress values in peri-implant bone tissue; this fact was also observed in other FEA reports (8,17). Previous studies performed in primates (9) and rabbits (10,30,31) evaluated the consequences of different levels of vertical misfit on the peri-implant bone tissue.…”

“…Some studies associate these complications with the misfit of the prosthesis (6,7). However, the exact relationship between prosthesis misfit and implant complications is still poorly understood (8).…”

“…Stresses are also created when ill-fitting prostheses are installed (15,16), and the values of these generated stresses vary with the stiffness of the framework material (13). Previous finite element analyses (FEA) were used to evaluate the influence of the increase in vertical misfit in implant-supported fixed prostheses (8,17) and overdenture-retaining bars supported by two implants (11,18). However, controversial results were observed as the misfit amplification caused a considerable increase in stresses in peri-implant bone tissue in implant-supported fixed prostheses and did not influence the stress values in peri-implant bone in overdenture retaining systems.…”

Análise comparativa do grau de rotação de parafusos para sistema UCLA em estruturas fundidas em monobloco, soldadas com solda TIG e solda convencional

“…A revisão da literatura mostra que grande parte dessas complicações estão relacionados aos parafusos protéticos, responsáveis pela fixação entre a prótese aos implantes (McGLUMPHY;MENDEL;HOLLOWAY, 1998;HOLLWEG, 2000;DUYCK et al, 2001;KUNAVISARUT et al, 2002).…”