Numerical investigation of macro- and micro-mechanics of a ceramic veneer bonded with various cement thicknesses using the typical and submodeling finite element approaches.

OBJECTIVES

This study investigates the influence of cement thickness on the macro- and micro-mechanical responses in a ceramic veneer adjacent to an incisal overlapped incisor.

METHODS

Seven finite element (FE) ceramic veneer macro-models with different cement thicknesses (10-180mum) were generated. A 10N load was applied with an angulation of 60 degrees to the longitudinal tooth axis. Seven FE micro-models corresponding to the macro-models were constructed at an enamel-adhesive interface where the stress concentration was found. Based on an interfacial scanning electron microscope (SEM) micrograph, morphology of resin tags in the micro-models was generated. The micro-model boundary conditions were determined from the macro-model results. The principal stress on each node in the macro- and micro-models was calculated to investigate interfacial mechanics. A tensile test was performed to obtain an ultimate cement tensile strength to determine the material failure parameters.

RESULTS

The highest stress concentration within the cement was found at the resin tag base of the enamel-adhesive interface in lingual side. Maximum stress values from 10.6 to 14.7MPa for the micro-models were higher (44-48%) than that from 7.2 to 10.0MPa for the macro-models when the cement layers increased. Based on the ultimate tensile strength (11.8MPa), bonding failure could found when the micro-models with the cement layers presented more than about 50mum. This seems to correspond with data from previous studies.

CONCLUSIONS

Higher stresses develop in the adhesive as the cement thickness increases. Cement thicknesses less than 50mum might reduce the adhesive bonding failure.