To evaluate the influence of veneer pore defects on fracture behavior of bilayered lithium dislicate glass-ceramic (LDG) and zirconia (Y-TZP) molar crowns.

Bilayered lithium dislicate glass-ceramic maxillary first molar crown was fabricated and scanned by micro CT to reconstruct the size and distribution of pore defects in veneering porcelain. After importing the pores in veneer according to the CT data, finite element analysis (FEA) models of bilayered LDG and Y-TZP crowns were constructed for mechanics simulation. For Group A, 200 N of Static loads were applied vertically to the occlusal surfaces of models to simulate the intercusping bite force. For Group B, 200 N loads were applied to functional inclinations at a 45° angle to imitate masticatory force. For Group C, indenter with 1 mm of vertical displacement was imposed on models to simulate the condition of in-vitro test. Maximum principle stress was calculated and analyzed accordingly.

LDG and Y-TZP had similar stress distribution under the same loading protocol. For intercusping bite, stress was concentrated in the contact region and the maximum tensile stress was 51.683 MPa and 50.084 MPa, respectively. While the maximum stress raised to 290.72 MPa and 285.92 MPa when pore defects were existed at cusp contact area. For oblique loading, pore defects were free from stress concentration. Under displacement loading, pores were detrimental to veneer integrity only in regions of tensile stress located at grooves, fissures as well as contact region, the maximum stress was concentrated in pores and raised from 107.3 MPa and 125.41 MPa to 359.93 MPa and 322.39 MPa.

The influence of veneer pore defects was related to loading pattern and the pores located at tensile stress area of veneering porcelain would jeopardize the structure and mechanical integrity of bilayered all-ceramic crowns.