Diode Laser Irradiation for Cavity Decontamination: A Pilot In Vitro Study on Antimicrobial Efficacy.

Background: This pilot study evaluated the potential of a 980 nm diode laser as a viable option for dental cavity decontamination, comparing its antimicrobial effect with 0.2% chlorhexidine. Material and Methods: Forty-seven extracted human molars with standardized Class I preparations were sterilized, conditioned with sterile stimulated saliva, and inoculated with Streptococcus mutans. The teeth were arbitrarily assigned to three groups: no treatment (n = 7), chlorhexidine 0.2% for 30 seconds (n = 10), and irradiation with a 980 nm diode laser for 30 seconds (n = 30). After incubation in BHI broth for 24 hours at 37°C, bacterial growth was quantified as CFU/mL using non-parametric tests. Results: Both treatments produced a marked reduction in bacterial growth compared with the untreated group (p < 0.001). Chlorhexidine completely suppressed detectable growth, whereas the laser showed residual contamination in a few samples, though always at much lower levels than the control. The difference between chlorhexidine and laser was not statistically significant (p = 0.253). Conclusions: Despite its small scale, this pilot study indicates that 980 nm diode irradiation can substantially lower S. mutans levels in contaminated cavities. While not conceived as a substitute for chemical disinfectants, the laser presents characteristics that merit attention: no chemical residues, no contribution to bacterial resistance, and potential implications for future adhesive-interface investigations. These aspects may justify further investigation into its use as an adjunctive step within restorative procedures, particularly in protocols aiming to limit chemical agents or to enhance substrate conditioning.