The effect of surface finish on the flexural strength of all ceramic crown materials

Statement of Problem: Despite the esthetic advantage of finishing and polishing, there remains concern that these procedures might reduce the strength of a finished ceramic restoration. Purpose: The aim of this study was to evaluate the effect of surface finishing procedures on the flexural strength of four dental ceramic materials. Material and Methods: The materials used were feldspathic porcelain (Vitadur N), Dicor, IPS Empress glass ceramic, and In-Ceram aluminous core porcelain. Abiaxial flexure test was conducted on a total of 10 specimens each in 9 groups. These groups were as-fired, polished and glazed Vitadur N discs; as-cast and polished Dicor discs; as-cast and polished IPS Empress discs; and as-fired and polished In-Ceram core porcelain discs. The flexural strength was evaluated using biaxial Piston on three ball test. Results: The mean biaxial flexural strength values were 63±4 MPa for as fired feldspathic porcelain specimens, 100±9 MPa for polished feldspathic porcelain, and 66±7 MPa for glazed porcelain, 106±13 MPa for as cast Dicor specimens and 229±13 MPa for their polished counterparts. 109±9 MPa for IPS Empress specimens and 218±13 MPa for their polished counterparts 343±34 MPa for nonpolished IN-Ceram core porcelained discs and 536±37 MPa for their polished counterparts. The In-Ceram core materials resulted in the highest mean flexural strength values regardless of the surface finish. Though polished In-Ceram core specimens were 56% stronger than their as fired counterpart. The strength of glass ceramic specimens (Dicor and IPS Empress specimens) was double that of their unpolished counterparts indicating a higher sensitivity to surface finish. Conclusion: In general, within the limitation of this experiment, the results suggests that strength of a ceramic restoration may be increased by finishing and polishing. Nevertheless, clinical trials are necessary to confirm these findings. Clinical Implications: The results of this in vitro experiment suggest that surface finishing may have an effect on the strength of the ceramic specimens tested.King Saud Universit