Numerical simulation of long span fiber-reinforced provisional fixed partial denture

Objectives: The aim of this study was to investigate the biomechanical interactions between fiber length and thickness of long span fiber-reinforced acrylic resin provisional fixed partial denture (FPD) under different load conditions using finite element (FE) analysis. Methods: Nine three-dimensional FE models of a 4-unit provisional FPD from mandibular first premolar to second molar including three fiber lengths (4mm, 18mm, 30mm) and thicknesses (0.1mm, 0.3mm, 0.5mm) were constructed by reverse engineering and CAD techniques to perform simulations under oblique (45°) and axial (90°) load conditions. The ANOVA test was used to evaluate the relative importance of the investigated factors (load directions, fiber lengths and thicknesses), and main effects for each level of the three investigated factors in terms of the principal stress values. Results: The results indicated that the maximum principal stresses were found at the bottom of mesial connectors and the direction of stress vectors consisted with clinical fracture patterns for all models. Load condition was found as the main factor influencing the stress values among the three investigated factors and oblique load produced high impact to stress values than axial load. The percentage contributions of fiber-reinforcement thickness and length were 57% and 34%, respectively under oblique load. However, the corresponding stress values found did not exhibit obvious differences between fiber thickness and length under axial load. Also, the results addressed that maximum principal stress decreased with thickening the fiber thickness and decreased obviously with fiber length of 18mm and 30mm relative to the 4mm. Conclusion: This study suggested that unfavorable stress caused by oblique load might eliminate through selective occlusal adjustment. More thicken and at least 18 mm length of the reinforced fiber is recommended to design in provisional FPD.