Objectives: The purpose of the study is to investigate the need for the preparation of old age of dental hygienists and happy life. Methods: This study is a descriptive study. A self-reported questionnaire in Likert 5 scale was completed by the dental hygienists in Korea through online report or written report from December, 2012 to June, 2013. Except incomplete answers, 200 data were analyzed. The questionnaire consisted of 10 questions of preparation for old age and awareness for old ages, 9 questions of physical preparation, and 9 questions of emotional preparation. Cronbach's alpha of old age preparation and awareness of old age was 0.634 in the study. Cronbach's alpha was 0.709 and 0.757 in physical preparation and emotional preparation, respectively. The final analyses of 200 copies were conducted using SPSS 11.5 software for Windows(SPSS Inc., Chicago, lllinois, USA). Results: Awareness toward preparation for old age of dental hygienists was 3.72 points, physical preparation was 2.94 points, and emotional preparation was 2.91 points. Awareness toward preparation for old age of dental hygienists showed the relationship between birth date, marital status, education level, and subjective health condition. Physical preparation was closely related to birth date, marital status, education level, and the workplace. Emotional preparation was closely related to birth date, marital status, education level, and the workplace. Conclusions: This study suggested that preparation for old age of dental hygienists was very important and the preparation must be connected with the social welfare policy.

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Objectives : The purpose of this study was to investigate of the color change, tooth surface and intra-pulpal temperature of tooth bleaching by light activation Methods : Forty-eight extracted bovine teeth were immersed into a tea solution for 24 hours.The specimens were randomly divided into four groups(n=15):(G1) 15% HP + without light activation, (G2) 15% HP + light activation, (G3) 25% HP + without light activation, (G4) 25% HP + light activation. All specimens were bleached for 15 minutes three times. The spectrophotometer (CM-2600d, Konica Minolta, Osaka, Japan) was used including before bleaching, immediately after bleaching, 1 week, 1 and 3 months after the end of bleaching. The temperature rise were measured in the pulpal chamber and tooth surface with a digital thermocouple thermometer(Termopar Digital Multimeter, Tektronix DMM916, USA). Between the tested time points, the specimens were stored in distilled water. The data were analyzed by ANOVA, t-test and Tukey's post hoc test set at 0.05.