Effect of firing cycle and etching condition on resin cement tensile bond strength of Li2O-SiO2 system glass ceramics

Abstract

OBJECTIVE: To evaluate if the firing cycles and etching conditions have an effect on the tensile bonding strength (TBS) of IPS e.max-CAD and CeltraDUO. METHODS: Lithium-disilicate (IPS e.max-CAD) ceramic blocks and zirconia reinforced lithium-disilicate (CeltraDUO) were sectioned into rectangular tiles. The tiles were randomly assigned to various treatment groups and heat treated (1, 5, or 9 firing cycles) or (0, 1 or 5 firing cycle) respectively. e.max-CAD and CeltraDUO tiles were etched for different times (20,160, 300 seconds) and (20, 50, 80 seconds) respectively with hydrofluoric-acid gel (9.6% or 5%). Titanium-pins were sand-blasted on the flat end and cemented on the etched tiles using self-adhesive resin cement (TheraCem). A vertical load of 12N was placed for 40 minutes. All the cemented specimens were stored in incubator at 37°C for 48 hours. A tensile test was performed using a mechanical testing machine (Instron-5566A). The load at failure was recorded and the TBS was calculated. The same procedure was followed on another set of 18 e.max-CAD (fired for 5 firing cycles) and 21 CeltraDUO tiles (fired for 1 firing cycle). The same cementation procedure was followed and TBS was calculated. RESULTS: The TBS of both CeltraDUO and e.max-CAD was significantly affected by etching duration and firing cycles (p<0.001), but not significantly affected by etchant concentration (p=0.31). The highest load to failure was observed around 50 and 60 seconds of etching respectively. CONCLUSION: The etching time and firing cycle directly affect the TBS of both materials whereas the etchant concentration does not.