Relevance of the finite element method to optimize fixed partial denture design. Part I. Influence of the size of the connector on the magnitude of strain.

Four three-dimensional numerical models of a fixed partial denture were constructed, analyzed, and compared by means of the finite element method. Each model consisted of three elements destined to compensate the loss of a first molar. The second proemolar and the second molar were used as abutments. The connector surface was varied and then tested. A unidirectional axial force was applied to the center of the occlusal surface of the pontic. For each model, we measured the strain undergone by the connectors that link the pontic to each abutment. Results show that the strain measured in the mesio-distal direction was much more significant than in any other direction. Strain originated on either side of the loading point, centrally located on the cervical side of the pontic. The 0.15% strain threshold, beyond which rupture is possible, was only reached in one model (connector surface = 3.3 mm2). Increasing both the height and the width of the connectors by 1 mm resulted in extending the surface by 3.3 to 7.95 mm2. Although the surface increased by 141%, the strain threshold was not reached. This first result indicates that extending the surface of the connectors, which is less consistent with periodontal clinical requirements, is not necessary to ensure resistance to rupture.