Hertzian Load-bearing capacity of hybrid and nano-hybrid resin composites stored dry and wet

Statement of Problem: Hertzian indentation test has been proven to be an efficient and reliable alternative upon Vickers hardness test. This method has been used to test dental ceramics, amalgams, glass ionomers and luting cements.There is limited published information about the load-bearing capacity of resin composites using Hertizian indentation test

Objectives: To investigate the load-bearing capacity of hybrid and nano-hybrid resin composites stored dry or wet up to 30 days, using Hertzian indentation test

Materials and Methods: Three resin composites were used: two nano-hybrids [Filtek Supreme, and Luna] and one hybrid, [Rok]. A total of 108 disc-shaped specimens [1mm thick x 10 mm diameter] were prepared using polyethylene mould. The specimens of each material were randomly divided into 6 groups of 6 [n=6] and stored at 37[degree]C either in distilled water or dry for 1, 7 and 30 days. The specimens were tested using Hertzian jig aligned in the universal testing machine. The specimen was placed on the top of a disc-shaped substrate. The load was applied at the center of each specimen and the load at the first crack was recorded. Data were analyzed by ANOVA, Tukey' sand student's t-test using SPSS version 18.0

Results: Three-way ANOVA showed a significant interaction between all the factors [p = .0001]. The load bearing capacity of almost all materials reduced significantly in the wet condition in comparison with the dry condition [p = .0001]. After seven days of immersion in distilled water, Filtek Supreme had significantly lower values than those of Rok and Luna, there was no significant differences between materials in the dry condition

Conclusions: In contrast to dry condition, the load-bearing capacity of specimens stored in distilled water decreased significantly over the 30 days of immersion. The load bearing capacity of nano-hybrid composites tested in this study was shown to be comparable with that of the hybrid composite

[ knowledge and practice of dentists about medical emergency in private dental offices]

In order to get ready for medical emergencies, sufficient scientific knowledge, suitable facilities and emergency drugs are necessary. This study aimed to investigate the emergency facilities, drugs and the knowledge of dentists about emergency cases in dental offices of Kerman in 1386. This is cross-sectional and descriptive study using questioners. Some active dental offices were selected and the questioners were given to them. The completed forms were gathered. The data were extracted and analyzed by t-test, fisher, chi[2], using SPSS 13.5 statistical program. In the present study, 101 dentist were enrolled. 25 dentists, [24.7%] had emergency cases in their office, and the most prevalent case was vasodepressor syncope. The mean knowledge of the dentist was 5.89 +/- 1.39. 76.2% of the dentists expressed that they ask the patients about their medical emergency history. This study shows that the knowledge and information of dentists enhance with an increase in working hours, and decrease with an increase usage and wok experience. Also, it is found that the most prevalent drugs used in dental office as emergency drugs were oxygen and nitroglycerine tablets. This study indicates that some emergency events take place in dental offices in Kerman as in many other countries but, unfortunately, there is not sufficient equipment and facilities to deal with these emergency cases. The present condition can be improved with teaching in universities, holding some educational workshops and preparation of pamphlets