HISTOCHEMICAL ANALYSIS OF DENTAL HARD TISSUES FOLLOWING BLEACHING

The effect of commonly used bleaching materials on the dental hard tis sues was tested in extracted human premolars. In each tooth, the apica l two-thirds of the root was removed, and the remaining tooth stump wa s cut longitudinally into two equal segments. The segments were cleane d, dried, and divided into six experimental groups. Each group was tre ated with one of the following bleaching materials: 30% hydrogen perox ide (HP), 10% carbamide peroxide (CP), sodium perborate (SP), Nu-Smile (NS), Opalescence (Op), and DentlBright (DB). Treatment consisted of immersing the specimens in the respective test material followed by in cubation at 37 degrees C for 7 days. The levels of calcium, phosphorus , sulfur, and potassium were measured in the enamel, dentin, and cemen tum. In the enamel, a significant reduction in the calcium/phosphorus (Ca/P) ratio was found following treatment with HP. In the dentin, a s ignificant reduction in Ca/P ratio was found following treatment with HP, CP, DB, and Op. In the cementum, a significant reduction in the Ca /P ratio was found following treatment with HP, CP, NS, and Op. Change s in sulfur and potassium levels also occurred, but were usually not s tatistically significant. Significant reduction in sulfur levels occur red only in the cementum following treatment with CP and SP. Sulfur le vels increased significantly following treatment with NS. Significant reduction in potassium levels occurred only in the dentin following tr eatment with CP. It is concluded that bleaching materials may adversel y affect the dental hard tissues and should be used with caution.