Microhardness of enamel with pellicle and bioactive mint against erosion

Objectives: To evaluate the effect of experimental mint formulation (EBMF) with/without salivary pellicle on enamel erosion on the relative surface microhardness (rSMH%).

Methods: Polished enamel specimens (n=100) from extracted human molars were assigned to ten groups (n=10) based on solution [natural saliva (S) or deionized water (DW)] and timing of EBMF containing green tea extract (500mg/ml DW) application (3 timings) totalling six experimental groups. Two positive controls (Citric Acid (CA) or S+CA) and two negative controls (S or DW alone) were also included. Timing 1, EBMF was applied for 2 minutes, followed by 2 hours in S or DW for pellicle formation, then an erosion cycle [10-minute acid exposure (0.3% CA, pH 3.2) and a 2-minute rinse]. Timing 2, specimens were immersed in S or DW for 2 hours, treated with EBMF for 2 minutes, then the same erosion cycle. Timing 3, specimens were immersed in S or DW for 2 hours, same erosion cycle, then treated with EBMF for 2 minutes, and rinsed. Each timing protocol was repeated three times. Vickers microhardness measured (rSMH%). Kruskal Wallis and post-hoc Bonferroni tests compared groups.

Results: The CA group showed significantly lower rSMH% [70.7 (9.8)] compared to the DW [93.1 (8.6)] and S [99.8 (3.6), p < .05] groups. Application of EBMF, either before or after 2 hours of DW immersion prior to erosion, resulted in significantly higher rSMH% [88.3 (7.4) and 87.9 (9.0), p < .05 respectively] compared to CA. SP formation alone did not significantly increase rSMH% relative to CA. However, when SP was formed prior to the erosion cycle and EBMF was applied afterward, a notable increase in rSMH% was observed [82.7 (8.5), p < .05].

Conclusions: EBMF plays a significant role in enamel remineralisation, particularly when used after the formation of salivary pellicle on enamel to provide better acid protection to the enamel surface.