Optimal acidulated phosphate fluoride gel etching time for surface treatment of feldspathic porcelain: on shear bond strength to resin composite

OBJECTIVES This in vitro study evaluated the shear bond strength (SBS) of resin composite to feldspathic porcelain after acidulated phosphate fluoride (APF) gel treatment over different periods of time. METHODS One hundred and fifty-six feldspathic specimens were divided into 12 groups. Group C received no treatment (control group). Groups APF1 through APF10, ten experimental groups, were treated with 1.23% APF gel. Each group obtained 1 to 10 minutes of etching time in 1 minute increments, respectively. Group HF2 was treated with 9.6% hydrofluoric acid (HF) for 2 minutes. All specimens were then bonded to a resin composite cylinder using Adper Scotchbond Multi-purpose (3M ESPE) after silane (Monobond-S, Ivoclar Vivadent AG) application. Specimens were stored at 37ºC for 24 hours before the SBS was performed and were recorded in MPa at fracture. Data were analyzed using one-way ANOVA and Tukey's test (α=.05). RESULTS HF etching yielded the highest SBS (18.0 ± 1.5 MPa), which was not significantly different from APF gel etching for 6 to 10 minutes (16.0 ± 2.1 to 17.2 ± 1.6 MPa) (P>.05). CONCLUSIONS APF gel etching for 6 minutes might be used as an alternative etchant to HF acid for bonding resin composite to silanized feldspathic porcelain.