USAF Dental Evaluation & Consultation Service Effect of Handpiece Lubricant on Bond Strengths

Residual lubricants retained in the handpiece may be displaced onto the tooth surface. A few studies have examined the effect of contamination from handpiece lubrication oils on enamel and dentin bond strengths, but the results have been equivocal. 1,2 The purpose of this study was to evaluate the effect of dental-handpiece lubricant on dentinal shear bond strength. A lubrication-free handpiece (Star 430 SWL, DentalEZ Group, Lancaster, PA) and a handpiece requiring lubrication (W&H 98L, W&H DentalWerk, Burmoos, Austria) were used. The W&H handpiece was manually lubricated with the manufacturers aerosol cleaner/lubricant as recommended. Automatic lubrication of the W&H handpiece was accomplished using the Assistina Plus 301 Cleaning and Lubricating Unit (W&H DentalWerk). Extracted human molars were ground to expose a flat dentin surface. Six different handpiece combinations were used. A control consisted of no exposure of the dentin to handpiece lubricant. The lubrication-free handpiece without lubrication was used for the second combination. The third and fourth combination consisted of the handpiece that required lubrication to receive lubrication either manually or automatically prior to autoclaving. The fifth and sixth combination was similar to the third and fourth combination, except lubrication was also completed after autoclaving. The dentin was exposed for 30 seconds to water spray from the handpieces. Three different adhesives were used per handpiece combination for a total of 18 groups (six handpiece combinations x 3 adhesives) with ten specimens per group (n = 10). A button of composite resin (Z100, 3M ESPE, St. Paul, MN) was bonded to the dentin surface with either a two-step, total etch (Single Bond, 3M ESPE), two-step, self-etch (Clearfil SE, Kuraray, New York, NY), or a one-step, self-etch (One-Up Bond F, J Morita, Irvine, CA) adhesive. The specimens were thermocycled and tested to failure in shear at seven days. Mean bond strength data were analyzed using Dunnetts multiple-comparison test (a = 0.05) and debonded surfaces were examined to determine failure mode. There were no significant differences in bond strengths between the control and the handpiece combinations within each adhesive type. The authors concluded that neither handpiece lubrication nor maintenance method produced significant differences in dentinal shear bond strengths.