Effect of diode laser and hyaluronic acid on occlusion of dentinal tubules: an in-vitro study on human dentin

Abstract Background Dentin hypersensitivity (DH) is a common clinical condition characterized by short, sharp pain arising from exposed dentinal tubules. Occlusion of dentinal tubules remains a widely accepted approach for managing DH in dental practice. This in vitro study aimed to evaluate and compare the effects of sodium fluoride, hyaluronic acid, diode laser, and their combinations on dentinal tubule occlusion in human dentin. Methods Sixty extracted human impacted third molars were sectioned into dentin discs and randomly allocated into five groups ( n = 12): sodium fluoride varnish (M1), hyaluronic acid (M2), diode laser irradiation (M3), hyaluronic acid + diode laser (M4), and hyaluronic acid + sodium fluoride varnish (M5). All specimens were treated after initial smear layer removal with 17% EDTA. The surface area percentage of open dentinal tubules was evaluated using Environmental Scanning Electron Microscopy (ESEM) and ImageJ software at three time points: baseline (T0), after treatment (T1), and after pH cycling (T2). Data were analyzed using a two-way repeated-measures ANOVA to assess the effects of treatment modality, time, and their interaction, followed by Bonferroni post hoc tests (α = 0.05). Results Repeated-measures ANOVA revealed a statistically significant effect of treatment modality ( p < 0.001), time ( p < 0.001), and a significant treatment × time interaction ( p < 0.001), indicating that changes over time differed among groups. At baseline (T0), no significant differences were observed among groups ( p = 0.190). Following treatment (T1), the lowest mean surface area of open dentinal tubules was recorded in the hyaluronic acid + diode laser group (M4), while the highest was observed in the sodium fluoride group (M1). After pH cycling (T2), all groups showed an increase in tubule openness; however, M4 maintained the lowest values, indicating superior resistance to acidic challenge. Pairwise comparisons demonstrated statistically significant differences among most groups, except between M2 and M5. Conclusions Within the limitations of this in vitro study, all tested modalities were effective in reducing the surface area of open dentinal tubules to varying degrees. The combination of hyaluronic acid and diode laser demonstrated the most pronounced occluding effect, indicating enhanced efficacy compared with the individual treatments. However, given the surface-based and laboratory nature of the assessment, further in vivo studies are required to confirm the clinical relevance and long-term stability of these findings.