Evaluation of shear bond strength and translucency of zirconia-reinforced lithium silicate and lithium disilicate: An in vitro study

Aim: To analyze the effect of various surface treatment protocols on shear bond strength between the ceramic and resin cement (RC) and influence of zirconia on the translucency of LD as compared to zirconia-reinforced lithium silicate (ZLS). Setting and Design: In-Vitro Study. Materials and Methods: Specimens (14 mm x 12 mm x 2 mm) (n = 135) and (14 mm x 12 mm x 1 mm) (n = 45) of ZLS computer-aided design/computer-aided manufacturing glass ceramic block and LD were fabricated, respectively. All the ZLS specimens were crystallized and were tested for the translucency parameter and ceramic-resin shear bond strength. Two different types of surface treatment were used on the ZLS and LD samples. The specimens were treated using the hydrofluoric acid (HF) etching or air abrasion with diamond particles (DPs). The specimens were then bonded using self-adhesive RC to a composite disc of 10 mm and thermocycling was performed. A universal testing machine was used to evaluate ceramic-resin shear bond strength after 24 h. The translucency of the specimens was evaluated using the spectrophotometer by calculating the difference in color between the readings over a black background and a white background. Statistical Analysis Used: Data were statistically analyzed using the independent sample t-test and analysis of variance with Bonferroni's correction and comparison was made between the specimens. Results: Independent sample t-test demonstrated statistically significantly higher translucency for group ZLS (61.44 +/- 22) as compared to group LD (20.16 +/- 8.39) (P < 0.001). Group ZLS showed statistically significant higher shear bond strength when surface treatment using HF or air abrasion with synthetic DPs was performed as compared to untreated group (3.58 +/- 0.45) (P < 0.001). Moreover, air abrasion group (16.79 +/- 2.11 megapascal [MPa]) demonstrated statistically significant higher shear bond strength as compared to HF etched group (8.25 +/- 0.30 MPa) (P < 0.001). Furthermore, statistically significant higher shear bond strength was noted when air abrasion was done for group ZLS (16.79 +/- 2.11 MPa) as compared to group LD (10.82 +/- 1.92 MPa) (P < 0.001). However, on surface treatment with HF, a statistically significantly lower shear bond strength was noted for group ZLS (8.25 +/- 0.30 MPa) as compared to group LD (11.29 +/- 0.58 MPa) (P = 0.001). Conclusion: ZLS demonstrated higher translucency compared to LD restorations. DP abrasion of ZLS is recommended to achieve higher shear bond strength between the ceramic and RC.