The effect of different etching times of acidulated phosphate fluoride gel on the shear bond strength of high-leucite ceramics bonded to composite resin

Abstract

A 10-minute treatment with acidulated phosphate fluoride (APF) gel has been used as an alternative in ceramic surface etching before repairing with composite resin. However, the optimal etching time for APF gel is still unknown. The purpose of this study was to determine the in vitro shear bond strengths of composite resin on high-leucite ceramics after APF gel treatment over different time periods. One hundred and twenty high-leucite ceramic (Empress 1) specimens (12 mm in diameter and 1.5 mm thick) were prepared and divided into 12 groups (n=10). Ten experimental groups were surface treated with 1.23% APF gel, each group receiving 1 to 10 minutes of etching time in 1 minute increments. One group was treated with 9.6% hydrofluoric acid for 4 minutes and the final group received no treatment and served as a control. The surface condition of the treated specimens was analyzed under a scanning electron microscope (SEM). All specimens received a silane application and were bonded to a composite resin Filtek (Z250) cylinder with an adhesive system (Scotchbond Multi-Purpose Plus adhesive) and then stored in 100% humidity at 37 degrees C for 24 hours before shear bond strength testing in a universal testing machine. Mean bond strengths (MPa) were analyzed with 1-way ANOVA and the Tukey HSD test (alpha=.05). Hydrofluoric acid etching produced the highest mean shear bond strength (SD) between composite resin and the ceramic (17.64 (1.48) MPa). Overall, APF gel etching produced lower bond strengths. No significant difference in mean bond strength (SD) was observed between etching with hydrofluoric acid and etching with APF gel for 7 to 10 minutes (15.21 (1.93) to 17.33 (1.43)). The lowest mean shear bond strengths (SD) were recorded in the untreated group (7.61 (1.03) MPa) (P<.05). Within the limitations of this study, shear bond strength values between composite resin and high-leucite ceramics after etching with 1.23% APF gel for 7 to 10 minutes were not significantly different than that after etching with 9.6% hydrofluoric acid for 4 minutes.