The Influence Of Different Retainer Designs On The Stress Distribution Of Two-unit Cantilever Resin-bonded Bridg: A Three-dimensional Finite Element Study

Objectives:To generate the three-dimensional finite element models with three different retainer designs and evaluate in vitro their influence on the strength of two-unit cantilever resin-bonded bridges(CRBB), using three-dimensional finite element analysis.Methods:The maxillary first premolar was scanned using Micro-CT technique. Three models with different retainer designs were constructed on M1 (the groove-shaped group), M2 (the D-shaped group) and M3(the lingual cusp group), using the Mimics10.0,Geomagic Studio 7.0 and ANSYS 10.0 softwares. Vertical and 45 degree oblique loading were applied on the central fossa of the pontic and the stress patterns were analyzed.Results:(1) The three-dimensional finite element models of two-unit cantilever resin-bonded bridge with three different retainer designs were generated,using the maxillary first premolar as the abutment.The mesh number were 553959,468134, 516748, respectively. (2) The maximum principle stress and the von Mises stresses in remaining tooth and prosthesis, respectively, were recorded. Under the vertical and 45 degree oblique loading, the stress concentrations were almost found on the cervix of the abutment and the connector. Under 45 degree oblique loading, the maximum principle stress values were found on the cervix of abutment on M1 (35.732 MPa), while the maximum von Mises stress values were found on the connector of abutment on M2(175.992 MPa). Lower stress distribution values were recorded for M3. The values were 9.291 Mpa and 28.654 Mpa under the vertical loading respectively, while19.077 Mpa and 91.383 Mpa under the 45 degree oblique loading. The maximum principle stress and the von Mises stress values producted in the 45 degree direction were found to be higher than those under the vertical loading.Conclusions:(1) The stress concentration area were found on the connector, so its preparation area should be enlargeded properly. (2) The abutment is better resistant to the vertical loading compared to the 45 degree oblique one. (3) More favorable stress distributions were found on the retainer design of the lingual cusp group.