Application of the radiometric method for the evaluation of human dental loss caused by carbamide peroxide bleaching agent

Abstract

During the last years, tooth bleaching has become an important acsthetic and increasingly popular treatment for people that want whiter teeth. Carbamide peroxide is widely used as a vital tooth bleaching agent however its studies on dental loss are very scarce. In this in vitro study, the radiometric method was applied to the evaluation of dental loss caused by 10% carbamide peroxide gel with carbopol when it is applied on the surface layers of enamel and dentin tissues. Also the dental loss caused by the etching with 37% phosphoric acid procedure used in aesthetic restoration was assessed for comparison with those results obtained for beaching treatment. ) Human enamel and dentin samples with same and known surface areas were prepared and they were irradiated with a thermal neutron flux of the IEA-R1 nuclear reactor with a P standard. The irradiated teeth were placed in contact with Opalescence 10% carbamide peroxide or with 37% phosphoric acid solution, both at 37 °C and in a humid environment. The radioactivity of *?P transferred from the radioactive teeth to the bleaching gel or to etching acid was measured using a Geiger Muller detector. The mass of P removed in this treatment was calculated by comparative method of neutron activation analysis. The enamel and dentine losses were calculated after obtaining their P concentrations. Results obtained indicated that enamel and dentin exposed to carbamide peroxide bleaching agent lose phosphorus. The extent of enamel loss was smaller than that obtained for dentin. In the case of acid etching, there was no difference between the results obtained for enamel and dentin loss. Also the dentin loss obtained after a treatment of 30 applications of 10% carbamide peroxide was the same magnitude of that one application of 37% phosphoric acid. The findings indicated that carbamide peroxide used to whiten teeth does not cause damage if it is correctly used. The main advantage of using radiometric method in this study was its high sensitivity that allows to detect small quantity of phosphorus released from the teeth. ( Work supported by CNPq and FAPESP, from Brazil).