[Experimental comparison of hygroscopic expansion in three different composite resins]

These days dental composites are very popular because they look good and are similar to human teeth regarding color. Hygroscopic expansion is one of the physical properties of dental composites. A dental composite may lose its efficiency as a restoration material because of water absorption. The objective of this study was to compare the hygroscopic expansion of three dental composites. In this experimental study, to assess the effective factors of hygroscopic expansion, we used three different dental composites [Kalore, P90 and Z250]. The length of these composites in water and saliva were measured eighteen times in a three-month period. We used the marginal modeling technique, in which the correlation between response data can be included for analysis. The results of marginal modeling showed that the type of composite is significantly related to hygroscopic expansion [P<0.05]; demonstrating the highest hygroscopic expansion for P90 and the lowest for Z250. In addition, time as an independent variable had a statistically significant effect on hygroscopic expansion [P<0.05]. However, we found no significant difference between the hygroscopic expansion of saliva and water [P>0.05]. Overall, our findings showed that hygroscopic expansion is significantly related to the type of composite and time. Therefore, we should utilize the composites with lower hygroscopic expansion [such as Z250] for filling the patients' teeth

Evaluation of solid waste management in the chemistry laboratories of Tehran Universities

Particular importance of hazardous wastes is due to having characteristics such as toxicity, flammability, corrosively and reactivity. Some of the chemical wastes due to having hazardous materials must be collected and managed in a proper manner, since they are potentially harmful to the environment. Owing to the fact that educational centers have important roles in developing countries, so the main objective of the present study was to investigate, hazardous waste management in chemistry laboratories of Ministry of Science universities, in Tehran, Iran. Study area of this research includes all chemistry laboratories in Tehran universities which were covered by Ministry of Science. To obtain the number of samples, based on Scientific Principles and identification formula, 64 samples were calculated. In addition, sampling was done by Stratified sampling. Validated checklists were used for data gathering. Data analysis were done by Descriptive statistics [mean, frequency and etc.] and inferential statistics [kruskal-wallis test]. results obtained in this study indicate that Sharif University by obtaining the mean score of 60.5 and Tehran University by obtaining the mean score of 4.5-6 are placed in best and worst rank, respectively. Beheshty, Alzahra and Tarbiat Moallem univesities by acquiring the mean score of 20-28.5 have a same position in ranking table. Results show that most of the studied laboratories do not have any collection program and only 26.5 percent of them have acceptable programs.The separation and storing program observed in about 12.5 percent. Hazardous wastes* management in chemistry laboratory of Tehran Universities was not in good status. And from the standpoint of management, only 12.5 percent of studied cases are in good status, while 75 percent was in undesirable status

[Oral health related quality of life among Iranian children: Part I - Validity, reliability, prevalence and seventy assessment of daily impact factors]

Given the current need for studies evaluating oral health related quality of life among the Iranian children, this study was designed to test the validity and reliability of a Persian version of Child-OIDP index and also evaluate the prevalence and impact of oral disorders on the quality of life of 11-14-year-old Iranian children. In this cross-sectional study, after translation of Child-OIDP instrument into Persian language, the psychometric properties of this index were evaluated in terms of face, content and construct validity. In addition, the internal and test-retest reliability were evaluated. A sample of 384 Iranian children aged 11-14-years old completed the instrument via a face-to-face interview. Each interview was followed by a clinical examination as well as completion of a self-administered questionnaire providing the information on demographic and oral health behaviors. The Persian version of Child-OIDP demonstrated excellent validity and reliability. The index showed significant associations between perceived oral treatment needs and perceived satisfaction regarding their oral cavity [P<0.001]. ICC was 0.784, and Cronbacrf s alpha was 0.59. About 54% of children reported dental disorders over the past 3 months that impacted on daily performances, according to Child-OIDP index. The most prevalent affected activities were eating and oral hygiene performance. The most prevalent oral disorder leading to impact were sensitivity tooth and gingival bleeding. Based on the results of this study, it can be concluded that the Persian version of Child-OIDP index is a valid and reliable instrument for evaluation of oral health-related quality of life as applied to Iranian children. The prevalence of oral impacts was moderate. The pattern of impacts differed according to the type of self-perceived oral problem

[Fatigue resistance and failure mode of endodontically restored premolars with indirect composite resin restoration-in vitro]

The present study aimed at determination of the fatigue resistance and failure mode of cusp-replacing onlays in endodontically treated premolars using indirect composite resin restorations. In this experimental study, 84 human premolars were randomly divided into 7 groups of 12. These groups were prepared as follows: Intact teeth used in group1 as control, the second group covers the endodontically treated teeth, restored with indirect onlays using Z-250 composite resin, the next two groups [i.e. 3, 4] were similar to the second group, but subjected to 1 and 2 million fatigue load cycles, respectively. Groups 5, 6, 7 were similar to groups 2, 3, 4, respectively, however, in these groups Tetric Ceram used as the restorative material. All specimens were loaded using a Universal Testing Machine until fracture occurred and the mode of failure observed with naked eye. Kruskal-Wallis and Chi-Square tests were used to analyze the data [alpha=.05]. All specimens withstood the masticating simulation. The mean fracture strength for groups 1 to 7 were: 1276.92, 1269.05, 1217.80, 1188.13, 1228.97, 1127.86, 1105.58, respectively. No statistically significant differences were found between the groups in fracture strength and failure mode. There was no statistically significant difference between two types of resin composite [P=0.203] and load cycles [P=0.298] after zero, 4 and 8 years aging. Within the limitation of this study, restored premolars with indirect composite onlays show fatigue resistance equal to natural tooth up to 8 years after restoration. Furthermore, no statistically significant differences were found between 4 and 8 years of load cycles. Tetric Ceram Z-250 restoration agent showed no effect on the tooth fracture resistance with the most observed fractures to be occur under CEJ with no capability to be restored