Background: Dentin hypersensitivity, often occurring after dental treatments or from erosive lesions, is a prevalent patient complaint. This study introduces a paste combining 8% L-arginine, calcium carbonate, and potassium nitrate to evaluate its impact on dentinal tubules occlusion, dentin permeability, and tooth sensitivity. Methods: Dentin surfaces from 24 third molars (thickness: 2 mm) were divided into two groups of 12. One received the experimental paste, while the other received a placebo without desensitizer. Permeability and sealing ability were assessed through scanning electron microscopy (SEM) and dentin permeability measurement. The pastes’ effects on hypersensitivity were then examined in a triple-blind, randomized parallel-armed clinical trial with 16 eligible patients. Sensitivity to cold, touch, and spontaneous stimuli was recorded using the VAS scale at various intervals post-treatment. Statistical analysis was conducted using Shapiro-Wilk, Mann-Whitney U, Friedman, and Wilcoxon tests (α = 0.05). Results: The permeability test demonstrated a significant reduction in dentin permeability in the experimental group (P = 0.002) compared to the control (P = 0.178). SEM images revealed most dentinal tubules in the intervention samples to be occluded. Clinically, both groups showed a significant decrease in the three types of evaluated sensitivity throughout the study. However, no significant difference in sensitivities between the two groups was observed, with the exception of cold sensitivity at three months post-treatment (P = 0.054). Conclusion: The innovative desensitizing paste featuring 8% L-arginine, calcium carbonate, and potassium nitrate effectively occluded dentinal tubules and reduced dentin permeability. It mitigated immediate and prolonged dentin hypersensitivity to various stimuli, supporting its potential role in managing dentin hypersensitivity. Trial registration: http://irct.ir: IRCT20220829055822N1, September 9th, 2022.

Nudge theory proposes using subtle interventions to encourage individuals to make better decisions. The aim of this study was to evaluate the effectiveness of the Nudge theory in plaque control and assess caries experience among third-grade primary schoolchildren with refugee and immigrant backgrounds in Mashhad, Iran. Moreover, Afghan and Iranian schoolchildren were compared to assess differences in oral health outcomes. A quasi-experimental field trial was conducted in three public primary schools, comprising 309 participants approximately 9 years old. Interventions were randomly assigned to three schools: School I Messages based on Social Norms (MSN), School II Messages based on Fear of Negative Outcome (MFNO), and School III control group (C). MSN and MFNO received customized motivational video clips at baseline, while C only received Oral hygiene instruction (OHI). All participants received OHI, a brush, and toothpaste. Baseline plaque index (PI) and caries experience in primary and permanent dentition (dmft/DMFT) were recorded. PI was reassessed at two weeks, two months, and six months post-intervention. All data were subjected to statistical analysis. The mean PI decreased significantly in all three groups at the two-week follow-up (p < 0.01). The PI improvements declined over a six-month follow-up period in all groups, and the mean PI difference after six months compared to the pre-intervention was significant only in MSN and MFNO (p < 0.01), while C reverted almost to the pre-study level. Schoolchildren with at least one filled tooth or Iranian nationality showed a greater PI reduction (p < 0.01, p = 0.05). The overall mean ± SD dmft and DMFT were 4.24 ± 2.11 and 1.70 ± 1.24, respectively. Among all the examined participants, 32 (10.40%) individuals were caries-free. The mean dmft was statistically significantly higher in Afghan children than in Iranians (p = 0.01). MSN was more effective on PI reduction in the short term, while MFNO was more long-lasting. Using the Nudge theory via visual aids was more effective in motivating children to perform better oral self-care than solely traditional OHI.

Tooth bleaching, a routine esthetic dental procedure, can compromise bond strength to enamel and dentin, especially if composite restorations are bonded immediately post-bleaching due to residual peroxide and free radicals. To address this, various treatments, including antioxidants like sodium ascorbate (SA), have been used, though SA may increase bacterial accumulation. Rosmarinic acid (RA), an alternative antioxidant, offers additional antibacterial and adhesive benefits. This study evaluates the effect of RA application time on shear bond strength (SBS) in bleached enamel, comparing its efficacy with SA under varying treatment durations. Three null hypotheses regarding RA’s impact on SBS are tested. The labial surfaces of 60 freshly extracted bovine incisors were randomly assigned into 6 groups and subjected to a specific surface treatment as follows: no bleaching procedure (NBL), bleaching with 38% hydrogen peroxide (BL), BL+ 10% sodium ascorbate for 10 min (SA), BL+ RA for 10 seconds (RA1), 60 seconds (RA2) and 10 min (RA3). The resin composite was bonded to enamels s immediately after these treatments. After storage in water for 24 hours, the bonded samples were mounted on a universal testing machine and loaded to the fracture point. Data analysis was performed using Kolmogorov-Smirnov, Lilliefors, One-way analysis of variance and Games-Howell tests. The NBL group had the highest SBS, comparable only to SA (P= 0.908). SA outperformed all RA groups (P< 0.001). RA3 showed the lowest SBS, significantly lower than RA1 (P= 0.011). The main fracture mode in all research groups was adhesive failure. Rosmarinic acid was not able to reverse the bond strength to enamel immediately after the bleaching process, regardless of the duration of application. Key words:Antioxidant agents, Dental bleaching, Enamel, Rosmarinic acid, Shear bond strength.