The bleaching effect of office bleaching agents containing S-PRG filler evaluated by pH value and electron spin resonance

Objectives: Surface reaction-type pre-reacted glass-ionomer (S-PRG) filler releases six types of ions with a neutralizing ability. This study evaluated the effect of S-PRG filler incorporation in an H₂O₂-based bleaching material on the bleaching efficacy, pH, and reaction state. Materials and methods: The experimental bleaching material was formulated by the addition of 5% or 10% S-PRG fillers to the powder part. The stained bovine teeth were treated with the prepared bleaching paste. Commission internationale de l’éclairage (CIE) L*a*b* color space values were recorded before and after bleaching, and the color difference (ΔE) and whiteness index (WI _D) were calculated. Moreover, the used bleaching formulations were assessed for their pH values and reaction state by evaluating the oxidation state of manganese (Mn⁺²) using electron spin resonance (ESR). Results: The results of ΔE and WI _D showed that the addition of S-PRG filler increased the bleaching effect, but there was no significant difference between the groups with 5% and 10% S-PRG filler. A significant increase in pH in S-PRG filler groups (5% pH 6.7, 10% pH 6.8) was found compared to the 0% group (pH 4.8). ESR measurements showed that the signal emitted from Mn⁺² decreased over time. The S-PRG filler groups showed a significantly higher reduction in Mn⁺² compared to the 0% group, with no significant difference between the 5% and 10% S-PRG groups. Conclusions: S-PRG filler addition resulted in improved bleaching efficacy, higher reaction rate, and pH values that are close to neutral. Clinical relevance: S-PRG filler addition may be effective on the bleaching outcome of H₂O₂-based materials.