3d finite element analysis of stresses in a mandibular removable partial denture with attachments

Introduction: Removable partial dentures are moving during use in directions and with magnitudes depending on the Kennedy class of the edentulous situation and on the size, direction and point of application of masticatory forces transmitted to the denture. These movements can harm the soft and hard tissues and also the denture, especially in free-end saddle situations. The aim of this study is to examine the distribution of stresses on a mandibular removable partial denture with attachments under occlusal forces, using finite element method analysis. Material and method: a class I Kennedy mandibular removable partial denture with extracoronary attachments was put in a CT scan and the images were used to achieve a 3-dimensional model in Autodesk Inventor software. First, the 3D model of half of the denture was developed and then the whole denture using the "mirror" technique was obtained. On this model, forces both in the long axis of the teeth and in bucco-lingual direction were applied. All materials were assumed to be homogeneous, isotropic and having linear elasticity. Results and discussion: masticatory forces create displacements, tensions and specific deformation in the denture's structure. The study demonstrates the effect of sagittal tipping of the free-end saddle dentures under the occlusal load, compared to the ideal situation in which the dentures wouldn't suffer any displacement. The saddle deformation is higher in the extreme distal area where there is only acrylate compared to the mesial area where the saddle is metalo-acrylic. The greatest deformation has been reported on the matrix of attachment. Conclusions: Through a proper design, the removable partial denture with attachments is able of dealing with almost all displacements trends. Keywords: removable partial dentures, 3D modeling, FEM analysis, stresses