The purpose of this study was to evaluate tooth color and microhardness after 15% carbamide peroxide(CP) bleaching treatments with/without potassium nitrate and fluoride(PF), which were used home bleaching. Thirty tooth specimens were obtained from thirty premolar and were randomly divided into three groups: 1, untreated controls(Distilled water): 2, treatment with 15% CP bleaching agent; 3, treatment with 15% CP bleaching agent (contained 3% potassium nitrate and 0.11% fluoride). All groups were treated 6h per day for 14 days then immersed in distilled water. Changes in enamel color were evaluated on Baseline and Day 14. Microhardness were evaluated on Baseline, Days 7 and 14. All the bleached enamel specimens revealed increased whiteness without control group. Groups 2 and 3 showed significantly decreased enamel microhardness compared to control group. On Day 7, Groups 2-3 showed significantly decreased enamel microhardness compared to control group and respective baseline data. The percentage microhardness loss(PML) look at Day 7 and 14 for Group 1, respectively, there was little difference between 1.7 and 0.8. However, Group 2 was 21.9 and 3.5, Group 3 was 16.7 and 1.4 as a baseline and Day 7 were significantly different (p <0.05). The PML of group 2 was significantly highest than that of group 3 on Day 7. As a result, the data indicate that the addition of PF did not influence the whitening efficacy of the bleaching agent negatively. PF-containing bleaching agent reduce the percentage microhardness loss. PF-containing tooth bleaching your teeth with a whitening effect can be reduced by decreasing the hardness of enamel.■ keyword :|Tooth Bleaching|Carbamide Peroxide|Tooth Color|Microhardness|

The purpose of this study is to investigate correlation between experience of visiting the dentist and oral symptoms with 10,701 high school seniors in the research data of the 8th juvenile online health behavior carried out in 2012. The results of this research showed that the lower academic grades, the more tooth crack they experienced, and the lower economic conditions, the more toothache they tended to experience. The main reasons they visited the dentist were because their teeth ached, tingled or throbbed with pain. Scores of oral symptoms, sex, economic conditions and the number of experience of visiting the dentist were found to have a significant correlation. In order to improve high school students' dental health continually, we need to install the school dental health room and need to systemize continuous dental health care system for high school students, along with development of various school dental health education programs, by vitalizing prevention based school dental health education.

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