Effect of a dental unit waterline treatment solution on composite-dentin shear bond strengths

The control of biofilm and effluent contamination of dental unit water lines (DUWL) includes additions of antimicrobial solutions, as well as automatic dosing units. There are, however, varying reports on the effects of such agents on the bond strength of restorative dental materials and, particularly, between these agents and dental hard tissues.

The possible effects of an antimicrobial DUWL treatment solution on the adhesion of composite resin to dentin was evaluated by shear bond strength (SBS) testing. A total of 20 caries-free human molar and premolar teeth were used as the test substrates. The teeth were divided into two sets of 10 teeth which, after appropriate cleaning with water and pumice, were embedded horizontally in dental die stone. The buccal surface of each tooth was ground flat to a 17 microns finish using water-lubricated SiC paper. The teeth were then etched for 15 seconds with 37% H3PO4 and rinsed with either water (control) or a proprietary DUWL treatment (ICX) solution. Thereafter, the teeth were lightly blown dry with clean dry air, and the dentin conditioned with Prime & Bond NT for 20 seconds. The excess solvent was then removed by gentle air drying for 5 seconds, and the conditioner cured with visible light for 10 seconds. A cylinder of composite was placed on the conditioned surface and cured. A second group of 20 caries-free human molar and premolar teeth were used as test substrates to evaluate the effect of the ICX DUWL treatment solution on a different dentin priming system (OptiBond Solo Plus). The teeth in the second group were divided into two sets and after a 15 second etch with 37% H3PO4, were rinsed with water (control) or the proprietary ICX DUWL treatment solution. Thereafter, the teeth were lightly blown dry with clean, dry air and the dentin conditioned with OptiBond Solo for 20 seconds. The excess solvent was then removed by gentle air drying for 5 seconds, and the conditioner cured with visible light for 10 seconds. A cylinder of composite was placed on the conditioned surface and cured. Shear bond strength testing was performed with a universal test machine at the default cross-head speed of 0.1 mm/min. A set of teeth, sectioned, mounted and etched as above but rinsed with a 0.01% mineral oil/water mix prior to conditioning and bonding, was used as the negative control. A separate corrosion testing was performed by immersing brass coupons in water and ICX for 31 days and measuring the weight loss. The brass coupons were bright-dipped, electroless nickel-plated and bright nickel electroplated.

The bonding studies indicated that the DUWL treatment solution applied to a cut and etched dentin surface prior to conditioning and bonding with an adhesive system has no effect (p > 0.05) on bond strength for either group of specimens, compared to water. Negative control specimens were found to have minimal bond strengths. The corrosion study indicated no difference in the behavior of the test specimens in ICX compared to those in water, although differences were noted between the different surface finishes applied to the brass substrate.

The findings of this study demonstrate that exposure of an etched dentin surface to a water-based DUWL treatment mixture has no adverse effects on subsequent adhesion strength. Minimal corrosive attack was noted in the ICX solution and water for brass coupons provided with three different surface finishes.