(PO02) Effects of Bleaching on Permeability of Human Teeth with Pre-Existing Cracks

Abstract: Identification of hypersensitivity etiology in caries-free teeth remains a clinical challenge, especially after the bleaching procedure. The present study aimed to investigate the possible effect of cracks and bleaching on the permeability into the pulp. Freshly extracted anterior and premolar teeth, with or without cracks, were selected. The teeth were imaged using Optical Coherence Tomography to detect cracks. The crack percentage was calculated using Amira software. For the evaluation of permeability, the apical half of the root was removed before the root canal was irrigated with 17% EDTA. Two needles connected to two syringes were inserted into the canal and fixed. The specimens were immersed in an Evans blue solution for 4 days. The solution collected from the pulp on day 4 was measured for L*a*b* values with a colorimeter to determine the color difference ΔE. For the bleaching procedures, all specimens were cleaned under copious water before the application of bleaching gel for 20 minutes, twice. There was a significant difference in ΔE between before and after bleaching (p < .001). There was a significant correlation between the ΔE and both the crack propagation area (CPA) and crack length (p < .05), whereas there was no such correlation with crack depth. The incidence of enamel surface cracks on a tooth affected coronal permeability and passive fluid infiltration into the pulp. Surface enamel cracks are more important than crack depth when considering the potential hypersensitivity of a tooth. Bleaching significantly increased the permeability of dentin in vitro.