Influence of proximal contact on stress distribution in FPD models

Objectives: Investigate the influence of proximal contact on the stress distribution in three-unit metal-ceramic and all-ceramic fixed partial dentures (FPD) models and anatomical structures by means of static loading in mathematical two-dimensional models using the finite element method (FEM). Methods: A sagittal image of a mandible was used to preprocess vectored images in MSC / PATRAN simulating a load of 100N divided among 17 points on the occlusal areas of a three-unit FPD, extending from the mandibular second premolar to the second molar. The creation of a proximal contact between the first premolar and the FPD was considered. In the pre-processing stage 5883 nodes were created with 11369 triangular elements. Four two-dimensional finite element models were created with the same boundary conditions: Models A (metal-ceramic) and B (all-ceramic) with proximal contact on the first premolar, and models C (metal-ceramic) and D (all-ceramic) without proximal contact. Results: In the two models without proximal contacts (C and D), the stress results (6.25 MPa) in the lower-middle portion of the mesial connector were around 50% lower than those found in the same region of models with proximal contacts. Increased stresses in the apical portion of the post, dentin and periodontal ligament showed the largest displacement of FPDs with the lack of proximal contact on the first premolar. Conclusion: The establishment of proximal contacts in mathematical models is a fundamental condition for true and reliable results, and the all-ceramic system presented a satisfactory mechanical behavior when compared with the metal-ceramic system.