Aims: The authors have used an in vitro model to appraise the antimicrobial efficacy of diode lasers with two different power outputs on Streptococcus mutans (SM), Lactobacillus casei (LC), and Actinomyces naeslundii (AN).
Methods and materials: The coronal dentin of thirty human mandibular third molars was prepared with four cylindrical cavities left in contact with SM, LC, and AN for 72 h to facilitate bacterial penetration. Diode laser (810 nm for 30 s in two cycles) with 1.5 W (group I), 1 W (group II), and 2% chlorhexidine gluconate solution for 60 s (group III) was applied on three cavities and the fourth cavity was not subjected to any treatment (control). Similar amounts of dentin debris were collected from the cavity into sterile tubes. The bacterial count was determined by serial dilution and plate count method. Percentage of killing was calculated for comparative analysis.
Results: The percentage of SM killed after exposure was 73.68 ± 23.37, 51.75 ± 25.45, and 26.78 ± 21.8 in three groups, respectively, (P = 0.002; Kruskal-Wallis) with no significant difference between group I and group II (P = 0.089; Mann-Whitney). The percentage of AN killed after exposure was 37.77 ± 49.52, 22 ± 19.48, and 56.86 ± 23.93 in three groups, respectively, (P = 0.013; Kruskal-Wallis) with significant difference between group II and group III (P = 0.002; Mann-Whitney). The percentage of LC killed after exposure was 51.32 ± 39.07, 36.65 ± 38.48, and 75.41 ± 22.6 in three groups, respectively (P = 0.091; Kruskal-Wallis).
Conclusions: Diode lasers exerted antibacterial effect of varying levels against all the three cariogenic bacteria. Although they are recommended as a supplementary antibacterial surface pretreatment technique for efficient removal of cariogenic bacteria, further clinical studies are required to confirm the in vitro findings.
Keywords: Actinomyces; Lactobacillus; Streptococcus mutans; antibacterial effect; bacteria; caries; cavity preparation; diode; disinfection; lasers.