Er: YAG laser and superparamagnetic iron oxide nanoparticle-modified adhesive: A comparative study on antimicrobial efficacy and bond strength in caries-affected dentin.

OBJECTIVE

Evaluating the efficacy of various cavity sterilants (CHX and Er: YAG) laser on the Streptococcus mutans (S. mutans) inhibition zone, resin tag length (RTL) and shear bond strength (SBS) of 5th generation adhesive integrated with superparamagnetic iron oxide nanoparticles (SPIONs) bonded to cariously affected dentin (CAD).

METHODOLOGY: The present in vitro study was conducted for four months, from 1st July 2025 to 30th October 2025. Forty-eight mandibular molars with ICDAS scores of 5 were included. CAD was retained and teeth were divided into four groups based on disinfection and adhesive type. Group-1A: CHX + Unmodified adhesive (UA), Group-1B: CHX+ SPIONs modified adhesive, Group-2A: Er: YAG laser+UA and Group-2B:Er: YAG laser+SPIONs modified adhesive. S mutans inhibition zone was identified using the agar diffusion test. RTL was assessed via SEM. SBS and failure patterns were analyzed using a Universal testing machine and a stereomicroscope, respectively. Data were analyzed via one-way ANOVA with post-hoc Tukey (p ≤ 0.05).

RESULTS

CHX and Er: YAG laser-treated S. mutans exhibited comparable inhibition zone thicknesses. Group-2B (Er: YAG laser + SPION-modified adhesive) showed the longest resin tags (20.55 ± 0.23 μm) and the highest SBS (8.23 ± 0.56 MPa). In contrast, Group-1A (CHX + unmodified adhesive) demonstrated the shortest resin tags (8.44 ± 0.52 μm) and the lowest bond strength (4.23 ± 0.43 MPa).

CONCLUSION

Er: YAG laser appears to be an effective method for disinfecting CAD. Moreover, adhesives containing superparamagnetic iron oxide nanoparticles demonstrated superior performance, enhancing both RTL and SBS.