Diode laser-activated sodium fluoride and galla chinensis extract as dentin biomodifiers: Effect on microhardness, resin tag length, and shear bond strength of universal adhesive to caries-affected dentin
Abstract
ABSTRACT Objective: To evaluate the effects of dentin biomodifiers sodium fluoride (NaF), blue diode laser (DL) irradiated NaF, Galla chinensis extract (GCE), and bioactive glass nanoparticles (BAGNPs), on the microhardness (MH), shear bond strength (SBS), and resin tag length (RTL) of a self-etch (SE) universal adhesive system bonded to caries-affected dentin (CAD). Methodology: Eighty disinfected permanent molars were included in the study. The present in vitro study was approved by the Ethical Committee of King Khalid University IRB-KKU-COD-ETH-0531. The study duration was four months, from 15th September 2025 to 15th January 2026. CAD was confirmed through visual, tactile, and staining methods. Samples were randomly divided into five groups based on the type of surface modifier(n=16). Group-1: No biomodification, Group-2: NaF, Group-3: Blue DL irradiated NaF, Group-4: BAGNPs, and Group-5: GCE. Surface MH testing was conducted using a Vickers hardness tester (n=4). RTL was identified using a SEM (n=2). The universal adhesive was applied using the SE technique, followed by composite buildup (n=10). SBS testing was performed using a Universal Testing Machine. The fractured specimens were evaluated under a stereomicroscope. ANOVA and Tukey’s post hoc test were used to compare the mean MH, RTL, and bond strength values (p<0.05). Results: Group-3 (DL-irradiated NaF) exhibited the highest MH, whereas the lowest MH was observed in Group-1. Group-5 (GCE) demonstrated the maximum RTL (67.02±3.76μm) and the highest SBS (10.27±0.44 MPa). Conclusion: Galla chinensis extract and diode laser-irradiated sodium fluoride, when used independently, each enhanced the SBS and RTL of the self-etch universal adhesive to caries-affected dentin. Only blue laser-irradiated sodium fluoride was effective in augmenting the MH of caries-affected dentin.