Effect of Epigallocatechin Gallate on shear bond strength of composite resin to bleached enamel: an in vitro study

OBJECTIVES: The aim of this study was to determine the effect of epigallocatechin gallate (EGCG) on the shear bond strength of composite resin to bleached enamel. MATERIALS AND METHODS: Ninety enamel surfaces of maxillary incisors were randomly divided into 9 groups as follows: G1: control (no bleaching); G2: bleaching; G3: bleaching and storage for seven days; G4 - 6: bleaching and application of 600, 800 and 1,000 micromol of EGCG-containing solution for 10 minutes, respectively; G7 - 9: bleaching and application of 600, 800 and 1,000 micromol of EGCG-containing solution for 20 minutes, respectively. The specimens were bleached with 30% hydrogen peroxide gel and a composite resin cylinder was bonded on each specimen using a bonding agent. Shear bond strength of the samples were measured in MPa. Data was analyzed using the two-way ANOVA and Tukey HSD tests (alpha = 0.05). RESULTS: The maximum and minimum mean shear bond strength values were observed in G1 and G2, respectively. Time and concentration of EGCG showed no significant effects on bond strength of the groups (p > 0.05). Multiple comparison of groups did not reveal any significant differences between the groups except for G2 and all the other groups (p < 0.05). CONCLUSIONS: There is a significant decrease in bond strength of composite resin to enamel immediately after bleaching. A delay of one week before bonding and the use of EGCG increased bond strength of composite resin to bleached enamel.

[Studying the effective factors of attracting and maintaining volunteers, youth and relief groups in Red Crescent society of Bushehr province]

Red Crescent and Red Cross national societies have duty to offer humanitarian services and support the needy people around the world. Red Crescent society helps the needy by organizing and utilizing the power of people who are willing to participate in the humanitarian purposes. This research studies the effective factors that attract and maintain volunteers, youth and relief groups in Red Crescent society of Bushehr province. In this descriptive study, all volunteers, young and relief groups in Red Crescent society of Bushehr [7217] were studied. About 391 ones were selected in three groups of volunteers [104], youth [134], and relief [154] by using Korejci and Morgan's formula. By using one-stage cluster sampling, some townships of Bushehr province were selected such as Bushehr, Dashtestan, Dashti, Genaveh, Kangan, and Tangestan. Face validity of the questionnaire was examined by experts. Alpha Cronbach's was r=0/86 and r=0/83 in the first and second questionnaires respectively. The results indicated a high level of internal consistency among the questions. According to the results, the most important factors on attracting people were such as advertising factors of influential people, street advertising, organizational support, social motivation, communication, media, intrinsic motivation and material encouragement. Also, the important factors in continuous cooperation were such as health and safety, human relations, organizational culture, material and immaterial encouragement and education. Several factors are involved in attracting and keeping volunteers, youth and relief groups in Red Crescent society. Given the age average in the country and the risk of natural and unnatural disasters, authorities is recommended to pay attention to the research findings in order to adopt appropriate polices to attract and maintain all groups in Red Crescent society