Comparative evaluation of chlorhexidine, er, cr: ysgg laser, and iron oxide nanoparticles as dentin disinfectants: effects on streptococcus mutans inhibition and glass ionomer bond strength in primary molars

Abstract

Objective: To find out the influence of different dentin disinfectants—chlorhexidine (CHX), Er, Cr: YSGG laser (ECYL), and iron oxide nanoparticles (Fe₃O₄NPs)—on inhibition of Streptococcus mutans and shear bond strength (SBS) of glass ionomer cement (GIC) in primary molars.

Methodology: This in vitro study was conducted at King Khalid University, approved under IRB# KKU 2025-2026-161. The study duration was three months, 15th September, 2025 - 20th December, 2025. Forty extracted primary second molars with ICDAS scores of five were selected. CAD was identified through visual inspection, surface hardness assessment, and dye staining. Teeth were randomly divided into four groups (n=10): Group-I (no disinfection), Group-II (2% CHX), Group-III (ECYL at 2.5W, 20Hz), and Group-IV (Fe₃O₄NPs). Antibacterial efficacy against S. mutans was assessed using the agar diffusion test. GIC restorations were placed and subjected to thermocycling. SBS testing was performed using a universal testing machine, and failure modes were analyzed under stereomicroscopy. Data were analyzed using one-way ANOVA and Tukey’s post hoc test (α=0.05).

Results: CHX (Group-II) demonstrated the largest zone of inhibition (15.95±1.54 mm). The control group showed the smallest inhibition zone (6.24±1.13 mm). ECYL (Group-III) exhibited the highest SBS (7.33±0.34 MPa), statistically superior to all groups (p<0.05). Fe₃O₄NPs (Group-IV) displayed the lowest bond strength (4.02±0.25 MPa). Mixed failure patterns predominated across all groups.

Conclusion: Er, Cr: YSGG laser demonstrated optimal performance as a cavity disinfectant, combining effective antimicrobial activity with superior bond strength preservation in primary molars.