# Antimicrobial and Morphological Effect of Er,Cr:YSGG Laser Irradiation on Primary Dentine Infected by Microorganisms Associated With Early Childhood Caries

## TL;DR

This study shows that Er,Cr:YSGG laser irradiation can kill bacteria in primary dentine and change its surface structure.

## Contribution

The novel contribution is demonstrating the antimicrobial efficacy and morphological impact of Er,Cr:YSGG laser on dentine infected with Lactobacillus spp. and Candida albicans.

## Key findings

- Er,Cr:YSGG laser reduced Lactobacillus spp. and Candida albicans by 99% and 98%, respectively.
- Laser-treated dentine showed irregular surfaces with micro-erosion and microcavities.

## Abstract

Laser technology enables a less stressful lesion removal with antimicrobial effects, this study was addressed to evaluate the antimicrobial and morphological effect of Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) laser on infected primary dentine with Lactobacillus spp. and Candida albicans.

In-vitro experimental study, where 35 samples of primary dentine were randomly distributed into 5 groups (n = 7): 3 controls (non-irradiated G1_C, G2_LB and G3_CA) and 2 experimental (G4_LB+Er,Cr:YSGG and G5_CA+Er,Cr:YSGG). The samples were placed in culture media pre-inoculated with Lactobacillus spp. and C. albicans, according to the experimental group, and maintained under optimal temperature and sterility conditions; then groups G4_LB+Er,Cr:YSGG and G5_CA+Er,Cr:YSGG were irradiated with Er,Cr:YSGG laser at 4.5 w, 15 Hz, 1 s/mm2 (H mode) and 53.6 J/cm2. Subsequently, they were transferred to sterile culture media, and microbial colony-forming units (CFUs) were performed in triplicate after 24 h using serial dilutions. The adherent bacteria and morphology of primary dentine were observed with scanning electron microscopy (SEM).

There were significant differences among control groups (G2_LB and G3_CA) and experimental (G4_LB+Er,Cr:YSGG and G5_CA+Er,Cr:YSGG) groups (P < 0.001); additionally, the percentage reduction after laser treatment was 99% for group G4_LB+Er,Cr:YSGG and 98% for G5_CA+Er,Cr:YSGG, indicating a significant reduction. On the other hand, samples irradiated with laser Er,Cr:YSGG [G4_LB + Er,Cr:YSGG], [G5_CA + ErCr:YSGG] showed an irregular surface with areas exhibiting micro-erosion and microcavities.

Er,Cr:YSGG laser irradiation presented an antimicrobial effect against Lactobacillus spp. and C. albicans. Moreover, this procedure can alter the dentinal surface structure.