Effect of Salivary Flow on Bleached Enamel Roughness and Mineral Content: anIn SituandIn VitroStudy

Abstract

SUMMARYThis study aimed to evaluate the effect of human saliva in vitro and salivary flow in situ on the roughness and mineral content of bleached enamel. Dental specimens were divided into five groups (n=15): not bleached (NB); bleached (35% hydrogen peroxide) and exposed to distilled water (DW); human saliva in vitro (IV); normal salivary flow in situ (NSF); and low salivary flow (LSF) in situ. Enamel roughness (Ra, Rz) and calcium/phosphorus contents were evaluated with laser profilometry and energy-dispersive spectroscopy, respectively, at baseline (T1), after bleaching (T2), and after seven days (T3). Salivary pH and buffer capacity were evaluated with colorimetric strips and salivary calcium and phosphorus with absorbance spectrophotometry. Data were analyzed with non-parametric tests and linear regression (α=0.05). After contact with saliva, Ra and Rz of LSF=DW>IV=NSF=NB was found. For DW and LSF, the roughness of T1<T2=T3 was found. For IV, T1<T3<T2; for NSF, T1=T3<T2. Enamel calcium/phosphorus content did not change with bleaching or with saliva contact (p≥0.05). Buffer capacity and calcium concentration did not differ between LSF and NSF. Phosphorus was higher, and pH was lower in LSF. Ra and Rz were, respectively, 0.14 and 1.95 lower with NSF than LSF. The conclusions were that NSF in situ and human saliva in vitro recovered original enamel roughness. The experimental conditions did not affect enamel mineral content. Recovery of bleached enamel roughness was higher in NSF when compared to LSF, regardless of salivary pH, calcium and phosphorus concentrations, and buffer capacity.