Effect of Surface Treatments on the Flexural Strength of Heat- Pressed Zirconia Reinforced Lithium Silicate Ceramic and Heat- Pressed Lithium Disilicate Ceramic

Objective: To compare the flexural strength of heat-pressed zirconia-reinforced lithium silicate (Celta Press) with that of heat- pressed lithium disilicate (IPS e.max Press) and to evaluate the effect of surface treatments. Materials and Methods: Sixty-four specimens, with dimensions of 14.5 x 12.5 mm and 1.5 mm thickness, were fabricated using the lost-wax heat press technique and were divided into two groups: Group 1, Celta Press and Group 2, IPS e.max Press. Each group had four subgroups according to the surface treatment protocols: No treatment (A); Polished (B); Glazed (C), and Polished and Glazed (D). The specimens' flexural strength was calculated by a universal testing machine in MPa. Results: IPS e.max Group D, showed the greatest flexural strength (374.22 ± 87.35MPa), while Celtra Press Group C, had the lowest flexural value (164.10 ± 51.97MPa). A two-way ANOVA indicated that IPS e.max exhibited statistically significantly greater flexural strength than Celtra Press. Tukey's HSD test revealed that the polished and glazed group displayed greater flexural strength than the untreated group. Conclusion: IPS e.max Press showed greater flexural strength than Celtra Press among all groups. The combination of a polished and glazed surface produced greater flexural strength than the untreated group. Clinical Significance: With newer dental ceramic materials constantly emerging, there is a need to evaluate their mechanical properties and provide clinical recommendations. The aim of this in vitro study is to compare the flexural strength of two highly esthetic ceramic materials, Celtra Press and IPS e.max Press, and to offer some guidelines regarding their surface treatment protocol.