Incorporation of calcium hydroxide to experimental self-etch adhesives for improved long-term dentin bonding

Abstract

This study investigated the degree of conversion (DC), calcium release (CaR), and long-term dentin bond stability (DBS) of experimental self-etch adhesive systems containing calcium hydroxide. Four adhesive systems were formulated including UDMA, HEMA, GDMA-P monomers, TPO and diphenyl iodonium as photoinitiator system, and ethanol/water as solvent with different mass fractions of calcium hydroxide: 0% (control), 1%, 2% and 4%. The DC was evaluated through Fourier Transform Infrared spectroscopy coupled to an attenuated total reflectance device. The CaR was evaluated through a spectrophotometer after 3 h up to 168 h. The DBS was measured through the microtensile bond strength method through a microtensile testing machine after 24 h and 12 months of water storage. The data were statistically evaluated using one- and two-way ANOVA and Tukey's post-test (p < 0.05). The DC of all adhesive systems was statistically similar (p > 0.05). No material released calcium up to 168 h after photoactivation. For DBS, adhesive systems containing 0%, 1% and 4% calcium hydroxide showed statistically similar means between immediate (24 h) and 12-month time-points. The adhesive system containing 2% calcium hydroxide showed statistically higher bond strength at 12-month time-point (p = 0.001). The inclusion of calcium hydroxide to experimental adhesive systems tested did not affect the DC and calcium release. However, the inclusion of 2% calcium hydroxide was able to improve long-term dentin bond strength.