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

Abstract

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 5^th generation adhesive integrated with superparamagnetic iron oxide nanoparticles (SPIONs) bonded to cariously affected dentin (CAD).

Methodology: The present in vitro study was approved by the ethical committee of King Saud University, CDRC# FC-289-25 and followed CRIS guidelines. The duration of the study was four months, from 1^st July 2025 to 30^th 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.