Evaluating microbial load on dental curing lights and the impact of protective barriers on resin composites

The contamination of dental curing light tips was evaluated before and after treatment and after their use and disinfection. The influence of a plastic protective barrier over the flexural strength and the modulus of elasticity of resin composites were also analyzed. Microbiological sampling was conducted at initial contamination (T0), in Log 10 CFU/4 mL; after dental treatment (T1); and after disinfection with 70% ethanol (v/v) (T2). The results were analyzed by descriptive statistics and analysis of variance. The flexural strength and the modulus of elasticity analyses were performed using bar-shaped test specimens of three commercial resin composites with and without barriers, and the tests were subjected to a statistical normality test. Turbidity was observed in the media in 60.7% of the tubes at T0, 100.0% at T1, and 57.1% at T2. The microbial contamination was similar at T0 and T2, but a significant increase was observed at T1. The recovered microbial load differed significantly between T1 and T2 (p < 0.05). The results of the flexural strength and modulus of elasticity analyses showed no significant differences with or without a barrier for any of the different colors of resin, polymerization time, or the three resins. Under the present experimental conditions, 70% ethanol significantly reduced the levels of microbial contamination, but it did not guarantee the inactivation of all microbial cells. The use of plastic protective barriers did not alter the flexural strength or the modulus of elasticity of any of the tested resin composites, indicating that they are a safe and viable measure to prevent cross-contamination when using a dental curing light.