Shear stresses in the adhesive layer under porcelain veneers. A finite element method study

A finite element study was made investigating the shear stresses in the composite cement layer and the enamel bond under loaded porcelain veneers. The maximum shear stresses were calculated under various conditions concerning loading angle, laminating extension, and cervical design. The result of the study was that maximum shear stresses did not exceed the stress level for debonding, but that great differences in maximum shear stress appeared with varying loss of bond and different loading angle. The fully laminated facing showed stress levels in the composite cement only 1/5 of those in the facing with a lack of adhesion in the periphery, and 1/15 in the enamel bond. The maximum stresses increased about 4 times when the load angle was 30 degrees as compared with 0 degrees, and increased about 1.5 times from 30 degrees to 60 degrees. The importance of getting a full lamination of the veneer and avoiding unfavorable loading conditions is emphasized in this study.