Impact of the digestive enzyme pepsin on enamel erosion and the protective efficacy of surface pre-reacted glass-ionomer particle gel.

OBJECTIVES: To evaluate in vitro the impact of pepsin on enamel erosion in the presence of an acquired pellicle and assess the protective efficacy of a bioactive gel containing surface pre-reacted glass-ionomer (S-PRG) particles by measuring surface hardness loss. METHODS: Bovine enamel blocks were prepared, standardized, and randomly assigned to two groups (n = 24/group): HCl-only erosive model and HCl+Pep - an erosive model with pepsin. Each group was further divided into two pre-treatment conditions (n = 12/group): SPRG (exposure to S-PRG bioactive gel) and DW (immersion in deionized water, control). Baseline enamel superficial microhardness was measured. Acquired pellicle was formed using human saliva and the samples were subjected to an erosive challenge for 9 days. Surface hardness loss (%SHL), morphological and mineral composition changes (scanning electron microscopy [SEM]/energy-dispersive X-ray spectroscopy), and crystal characteristics (X-ray diffraction [XRD]) were analyzed. Statistical analysis was performed using one-way analysis of variance (p < 0.05). RESULTS: The HCl+Pep group exhibited significantly higher %SHL than the HCl-only group (p < 0.001). Pre-treatment with S-PRG gel did not significantly reduce %SHL (p > 0.05). SEM images revealed severe mineral loss in the interprismatic regions of the HCl+Pep/DW group, whereas the HCl/SPRG group exhibited less degradation. XRD analysis indicated modifications in hydroxyapatite (HAp) microstructure, with the formation of octacalcium phosphate, in the HCl/SPRG. CONCLUSIONS: Pepsin exacerbates enamel erosion by increasing %SHL and altering the morphology and structural pattern of HAp crystals. Although S-PRG gel pre-treatment did not prevent %SHL, it facilitated the formation of a new crystalline phase and reduced enamel degradation. CLINICAL SIGNIFICANCE: Pepsin exacerbates enamel erosion by intensifying mineral loss despite the acquired pellicle. Although it does not prevent hardness loss, bioactive materials are emerging as a promising supportive strategy - minimizing surface degradation through possible crystal structure modification, particularly in gastroesophageal reflux-related erosion conditions.