Effect of tooth bleaching agents with dicalcium phosphate dihydrate on the tooth whitening and enamel surface properties

Abstract

[한글]

[영문]In recent year, there has been an increasing demand for tooth bleaching in order to improve the esthetic appearance of patients, because it is an easy, effective, and non-destructive treatment to remove these tooth discolorations. Hydrogen peroxide (HP) acts as a strong oxidizing agent through the formation of free radicals, reactive oxygen molecules, and HP anions. Current studies have presented contradictory results concerning the adverse effects of tooth bleaching agent on enamel surfaces. The purpose of this study was to evaluate the tooth whitening and properties of an enamel surface after treatments with tooth bleaching agents that contained dicalcium phosphate dihydrate and HP. DCPD (CaHPO4·2H2O) is known to be a precursor to hydroxyapatite (HA) in the remineralization process. Many studies have shown that supplemental calcium and phosphate in the form of DCPD have an anticaries benefit. In acidic solutions, DCPD was thermodynamically more stable than other calcium phosphates. This study selected 35 % HP and 3.5 % HP, which were used in-office bleaching and home bleaching agent. Sixty enamel specimens were obtained from human premolars and randomly divided into two groups. These groups were then divided into three subgroups (n=10). Tooth bleaching agents were prepared with DCPD (0 g for controls, 0.1 g and 1 g for experimental groups) and HP solution (35 % and 3.5 % HP). In the Group A, DCPD / 35 % HP solutions were applied on sectioned enamel surfaces for 60 min per day for 1 day. In the Group B, DCPD / 3.5 % HP solutions were applied on sectioned enamel surfaces for 8 hours per day for 14 days. pH and mineral composition (ICP-AES) in the tooth bleaching agent were measured. Tooth color, microhardness and surface characterization (SEM and EDX) of enamel surface were measured as well.1. The tooth bleaching agents with DCPD showed a significant increase in pH as compared with the ones without DCPD in the group A (p<0.05). In the group B, however, there was no statistically significant difference (p>0.05). 2. As the concentration of DCPD was increased, the concentration of Ca and P was also increased. The ratio of Ca/P was found to be approximately 1.1 ~ 1.2. 3. In all groups, after the tooth whitening, the tooth color was found to have a value of L* which was significantly increased, while that of a* and b* were significantly decreased as compared with the ones that were seen prior to the tooth whitening (p<0.05). 4. In all groups, the hardness of tooth after bleaching showed a significant decrease in the microhardness as compared with the one prior to tooth bleaching (p<0.05). In both group A and B, however, as DCPD content was increased, the decreasing degree of microhardness was found to be smaller in the experimental group as compared with the control group.5. Following an analysis of the characteristics of enamel surface after bleaching, there were porosity and erosion in the control group. In the groups where the amount of DCPD was the greatest, however, there was no surface change. 6. Following an analysis of the constituents of enamel surface after bleaching, as DCPD content was increased, the amount of Ca and P was significantly increased (p<0.05). Based on the above results, tooth bleaching agents of 35 % and 3.5 % of HP containing DCPD are equally effective to the control group. By raising the pH and thereby effectively reducing the decalcification of tooth surface, a lower degree of the effects are given to the surface characteristics and constituent alterations of enamel. Thus, the commercial availability can be achieved for the constituents of tooth whitening materials.