Bioactive glasses in dentin that reduce leakage maintain bond strength

Bonded restorations have one major drawback, leakage.  Previous studies (IADR 2007, CED-IADR 2007) showed that bioactive glasses that form apatite in calcium- and phosphate-containing environments diminished leakage in vitro.  Objective:  Test the hypothesis that powdered bioactive glasses that reduce leakage in resin-bonded dentin have no deleterious effects on bond strength. Methods:  Coronal dentin of human third molars was finished to 320 grit, etched, and rinsed.  Slurries of 10% (w/v) bioactive glass in ethanol, either of Hench's Bioglass^® formula 45S5 or of a novel F- and Mg-containing bioactive glass (“F glass”), of average particle size 1µm, were vacuum-deposited in the etched dentin.  Adhesive (Single Bond, 3M/ESPE) and composite (Z250, 3M/ESPE) were applied and light-cured. Samples (N=6/group) were stored overnight, for 8d, or for 65d in deionized water at 37°C.    Single Plane Lap Shear Bond Strength was determined at a crosshead speed of 5 mm/min.  Results:

	Overnight		8 Days		65 Days
		Mean±SD (MPa)		Mean±SD (MPa)		Mean±SD (MPa)
Negative Control		31.4±11.1		38.6±6.6		29.2±11.7
F Glass		41.9±3.6		36.2±6.0		38.6±6.4
45S5		37.6±7.3		40.8±9.0		31.7±14.2
		p=0.10		p=0.57		p=0.35

Bond strengths were not significantly different at any of the three time points (overnight, p=0.10; 8 days, p=0.57; 65 days, p=0.35, one-way ANOVA).  Bond strengths did not differ significantly over time for each individual treatment (negative controls, p=0.27; F glass-treated samples, p=0.22; 45S5-treated teeth, p=0.35).  Failure tended to be largely cohesive in dentin or composite for glass-treated samples, compared to adhesive failure in the interface for negative controls.  Conclusions: Ground bioactive glass of different formulations that had been previously shown to reduce leakage at bonded interfaces was effectively integrated into the resin bonding process, and allowed the resin to permeate dentin with no decrease in bond strength.  Support: NIH/NIDCR Grant P01DE09859.