Biofilms occurring in dental unit water system have long been reported as sources for potential infections. The manufacturer recommends briefly flushing the tubing with disinfecting solution as an alternative to autoclaving. Objectives: This study investigated the effect of prolonged immersion in disinfectants on the tensile strength of polyurethane dental syringe tubing. Methods: Forty specimens of A-dec tubing (7 in. long, 1/8 in diameter) were placed in each of 4 separate glass tubes (10 specimens each) filled with either Bio2000® or VacusolUltra® solutions. Each tube was closed and allowed to sit for periods of either 2 weeks or 6 weeks. The tensile strength of the soaked and original tubing (as control, n=10) at ambient temperature was then measured using an Instron 4411 testing machine at crosshead speed of 50 mm/min. One-way ANOVA and Tukey's HSD mean separation procedure were performed at the 5% significance level to compare mean tensile strength and modulus values across the three treatments (Bio2000, VacusolUltra, Control). Results: The mean values (standard deviation) of the maximum tensile strength (MPa) were: control 35.07 (4.70); at 2-weeks: Bio2000 26.53 (4.34), VacusolUltra 32.48 (5.35); at 6-weeks: Bio2000 26.04 (4.82), VacusolUltra 33.85 (5.13). The Young's modulus (Std. Dev.) were: control 17.00 (5.49); at 2-weeks: Bio2000 14.70 (3.27), VacusolUltra 16.57 (3.34); at 6-weeks: Bio2000 18.94 (2.96), VacusolUltra 16.21 (5.07). Conclusion: Specimens treated with Bio2000 had significantly lower tensile strength than untreated control specimens while VacusolUltra-treated specimens had statistically the same tensile strength as control at 2-weeks (p=0.0016) and at 6-weeks (p=0.0005). Treatments did not significantly change the Young's modulus at either the 2-weeks-2 or 6-weeks (p=0.4333 and p=0.4115, respectively).

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