Finite element analysis of two-unit cantilever resin-bonded fixed dental prostheses

Materials and Methods: The 3D FEA model consisted of a two-unit cantilever RBFDP replacing a maxillary lateral incisor with a wing-shaped retainer on the central incisor and an adjacent canine. Five different framework materials were compared: direct fibre-reinforced composite (FRC-Z250), laboratory fibre-reinforced composite (FRC-ES), metal (M), glass-ceramic (GC) and zirconia (ZI). A stress of 90 MPa at a 45º angle was applied to the incisal edge of the pontic.

Results: A similar stress pattern, with tensile stresses in the connector area, was observed in RBFDPs for all materials. Maximal principal stress showed a decreasing order: ZI (239.6MPa) > M (197.1MPa) > GC (178.4MPa) > FRC-ES (177.1MPa) > FRC-Z250 (156.9MPa). The maximum displacement of RBFDPs was higher for FRC-Z250 (0.048mm) and FRC-ES (0.035mm) than for M (0.019mm), GC (0.019mm) and ZI (0.017mm). Stress analysis depicted differences in location of the maximum stress at the luting cement interface between materials. For FRC-Z250 and FRC-ES the maximum stress was located in the upper part of the proximal area of the retainer, whereas for M, GC and ZI the maximum stress was located at the cervical outline of the retainer.

Conclusions: Within the limitations of this study, FEA revealed differences in biomechanical behaviour between RBFDPs made of different framework materials. The general observation was that a RBFDP made of FRC provided a more favourable stress distribution than the other materials.