Parameters that affect in vitro bonding of glass-ionomer liners to dentin

The purpose of this study was to evaluate the effects of two concentrations of poly (acrylic acid) (10 and 25%), three treatments (untreated, passive conditioning, and active conditioning), and two storage conditions (24 hours in 37 degrees C water and thermal cycling) on the in vitro tensile bond strength of three commercial glass-ionomer liners to human dentin. Bond strengths to untreated dentin after storage for 24 hours ranged from 19.0 to 21.7 kg/cm2 for Glasionomer Base Cement, Cement/Liner, and Ketac-Bond, but dropped to a range of 4.9 to 9.7 kg/cm2 after thermal cycling. Active conditioning with 10% acid resulted in bond strengths after 24-hour storage that ranged from 23.5 to 44.0 kg/cm2, compared with values from 21.7 to 38.0 kg/cm2 with active conditioning using 25% acid. Active conditioning with 10% acid resulted in bond strengths after thermal cycling that were in the range of 15.8 to 27.4 kg/cm2 and were 80 to 320 percent higher than values resulting from passive conditioning under these conditions. Active conditioning with 10% acid for 30 seconds produced a bond strength for Glasionomer Base Cement of 44.0 kg/cm2, compared with a bond strength of 28.7 kg/cm2 for a 10-second active conditioning. Qualitative analysis of scanning electron photomicrographs showed that dentin tubules were opened to a greater extent by active conditioning with 25% acid than by passive conditioning with 10% acid.