The study evaluated the in vitro effects of 30% carbamide peroxide on human enamel by microhardness tests.
Materials and method. 20 enamel slices were obtained from recently extracted premolars. To determine the microhardness index, the dental crowns were sectioned longitudinally into two mesial and distal halves. Sections were embedded in a self-polymerising epoxy resin, leaving open the enamel surface subjected to analysis. Enamel samples were randomly divided into two equal groups (n = 10), as follows: control group 1 – sections without whitening procedures, experimental group 2 – sections bleached with 30% carbamide peroxide for 15 min per day, along 14 days. After removing the bleaching gel, the specimens were stored in 250 ml artificial saliva at 37C, an operation repeated twice a day. Enamel microhardness evaluation was performed using Vicker’s microhardness test, applied in the beginning and end of treatment.
Results. In the control group (1), the registered enamel hardness values ranged between 312 and 328 Mpa, with a mean value of 320.20 (p = 0.3>0.05); in the experimental group (2), the enamel hardness values ranged between 254 and 301 Mpa, with a mean value of 278.40 (p = 0.09>0.05). Intergroup comparison of microhardness values showed a statistically significant difference (p = 0.001 < 0.05). Conclusions. The results obtained demonstrated a significant decrease of enamel microhardness, induced by the action of the carbamide peroxide whitening product tested in the study.