THE MICRO-TENSILE BOND STRENGTH BETWEEN PRECRYSTALLIZED LITHIUM DISILICATE CERAMICS AND RESIN CEMENT

Abstract

Objective: To compare the micro-tensile bond strength (µTBS) of different precrystallized lithium disilicate ceramics bonded with resin cement before and after thermocycling. Methods: Two lithium disilicate blocks (size 16×14×4 mm³) were prepared for each of three CAD/CAM lithium disilicates: IPS e.max CAD, Amber Mill, and CEREC Tessera. The designated bonding surfaces were polished with abrasive paper. The blocks were then crystallized according to the manufacturers' instructions and ultrasonically cleaned with distilled water. The bonding surfaces were etched with 5% hydrofluoric acid and applied with primer (G-Multi PRIMER). Pairs of identical blocks were bonded using resin cement (G-Cem ONE). Each bonded block was sectioned into sticks with a cross-sectional area of 1.0 mm² (n = 20 per group) and stored in distilled water for 24 h. The specimens were then divided into two conditions: non-aged and aged (10,000 thermocycles). The µTBS was measured, and the failure mode, and contact angle were evaluated. Results: The type of lithium disilicate material and thermocycling significantly affected the µTBS. Thermocycling significantly decreased bond strength across all materials tested. IPS e.max CAD exhibited the highest µTBS values under both aging conditions. Hydrofluoric acid treatment significantly improved surface wettability across all groups. Adhesive failure was the most frequently observed failure mode. Conclusion: The bond strength between lithium disilicate ceramics and resin cement was significantly affected by the ceramic material and aging conditions. IPS e.max CAD exhibited the highest bond strength. Thermocycling significantly decreased bond strength across all groups.

Keywords: Micro-Tensile Bond Strength, Precrystallized Lithium Disilicate, Thermocycling, Wettability, Failure Mode