ABSTRACT
Endodontic therapy is considered as one of the most stressful dental treatments. This study was designed with the aim of comparing stress levels during different stages of endodontic treatment among endodontic professionals under- and post-graduate students. In this ex-post facto investigation, three groups including professional endodontists [n=36], undergraduate [n=41] and postgraduate dental students [n=47] were involved by convenience sampling. A questionnaire including 48 items, with five-point scales [very few to very much], was prepared for this study based on interview. The questionnaire was filled out by participants in a self report method. Data were analyzed by multivariate analysis of variance and Scheffe's post - hoc tests. The stress among undergraduate dental students in all fields were more than those of professionals and postgraduate dental students, except for the stress of local anesthetic injection with lidocaine. Stress levels of all three groups were significantly different in inferior alveolar block injections with lidocaine, with professionals having more stress than under- and post- graduate dental students. The most stressful aspect of endodontic treatment, among the three groups was canal obturation, followed by obturation of the molar canals, preparing molar access cavities in special conditions and taking the final radiographs. The suggested methods offered for occupational stress reduction, was experience and knowledge, adequate knowledge, concentration and self confidence, and trust to God, respectively. The stress among under graduate dental students in all fields was more than professionals and post graduate dental students, except for the stress of local anesthetic injections with lidocaine
ABSTRACT
Along with improvements in aesthetics and longevity of restorations, finishing and polishing, can produce potentially injurious temperature rise within the pulp chamber. The purpose of the current study was to find whether different polishing methods and thickness of composites have any effect on temperature rise of composite restorative materials. Sixty composite resin specimens 9 mm in diameter were prepared and assigned to three experimental groups with three sample thicknesses [2, 3 and 4mm]. Each group was divided into four subgroups randomly. Polishing in subgroups 1 and 2 [continuous and intermittent dry polishing] and subgroups 3 and 4 [continuous and intermittent wet polishing] was carried out with a slow speed contra-angle hand piece at a medium speed for 120 seconds in a roll on motion. Immediately after polishing, temperature was measured on the top and bottom surface of each sample using a laser thermometer. One and two way ANOVA, Duncan, and paired T-test was used to analyze the data. The mean temperature rise after polishing in different methods was significant; continuous dry polishing produced the maximum temperature rise. In addition, increasing the thickness of composite resin up to 4mm did not significantly affect thermal transfer from the top surface to the base during polishing. Copious use of water coolant during finishing and polishing procedures is considered a simple and effective method for pulpal protection. Increasing the thickness of composite resin does not have a significant role in compensating the heat generated during polishing procedure
ABSTRACT
Composite resins require time to complete their polymerization. This process usually reaches its maximum rate after 24 hours. On the other hand, immediately after restoration, water sorption results in hygroscopic expansion of composite resins and the mentioned two factors usually reachequilibrium after a week. Considering the effect of mentioned processes on the microleakage of composite restorations, the purpose of the present study was to evaluate the effect of finishing and polishing time on the mean microleakage of composite restorations. In this in-vitro experimental study, 60 sound human premolar teeth were selected. A standard Class V cavity was prepared measuring 1.5 mm in depth, 3 mm in width and 2 mm in length on the buccal surface of each tooth and incrementally restored with composite resin. Next, the teeth were randomly divided into 4 groups. The teeth in groups 1, 2, 3 and 4 were finished and polished immediately, 15 min, 24 h and one week after storage in distilled water at 37°C, respectively. Specimens in each group were subjected to 500 thermal cycles. The teeth were then coated with adhesive wax and nail varnish and immersed in 2% fuchsin solution for 24h. The specimens were washed and each sample was longitudinally sectioned in half by a diamond saw. Both halves were evaluated in terms of dye penetration under a stereomicroscope at 28X magnification. For each sample, the section with greater degree of microleakage was selected. Kruskal Wallis test and Mann Whitney U test were used for data analysis with a 99.1% confidence interval. The lowest mean microleakage was observed in the occlusal margin of group 3 teeth; while the highest mean microleakage belonged to the occlusal and gingival margins of teeth in group 2. A significant difference was noted between the 4 groups in occlusal margin microleakage [P<0.009]. However, no such difference was found in gingival margin. This study showed that the finishing and polishing timewas effective on the mean microleakage in the enamel margin of composite restorations. The best time of finishing and polishing was 24h after the restoration. Time of finishing and polishing had no effect on microleakage in dentin margins of restorations. Key words: Composite resins, polishing, microleakage
ABSTRACT
Bleaching may cause decrease in Calcium, Phosphate and Fluoride content of enamel. However, the topical use of fluoride can help reabsorb those minerals. The aim of this study was to determine the effect of fluoride therapy before and after bleaching on enamel dye penetration. Sixty extracted carries-free human premolars were selected. All teeth surfaces were covered by nail varnish, except a square about 6 mm[2] on the buccal surfaces for exposure to fluoride and bleaching agent. The teeth were randomly divided into 5 groups [n=12] and then stored in artificial saliva at 37°C for 7 days. Each group was processed as below: Group 1: Specimens with no treatment were immersed in 50% silver nitrate solution. Group2: Specimens were bleached by 45% carbamide peroxide for 30 minutes twice a day for 5 days. Group3: the sodium fluoride varnish was used on specimens for 5 minutes. Group4: After bleaching like group2, specimens were stored in artificial saliva. Fluoride therapy was performed next like group3. Group5: All processes were conducted like group4 after fluoride therapy. All specimens were cut bucco-lingually along the longitudinal axis and stored in developer solution for 6 hours. Stereotactic microscope images were captured by digital camera for dye penetration assessment. Data was analyzed using SPSS [11.5] software and ANOVA and Kruskal Wallis tests. Data showed that bleaching can significantly [P=0.001] increase dye penetration. However, fluoride treatment can significantly decrease dye penetration [P=0.001]. Fluoride therapy is highly recommended after bleaching process
Subject(s)
Humans , Fluorides , Tooth Bleaching , Esthetics, DentalABSTRACT
Bleaching teeth can lead to decreased calcium, phosphate and fluoride content of enamel which may cause decreased enamel micro-hardness. Reportedly, the topical use of fluoride can help regaining those minerals. The aim of this study was to evaluate the effect of fluoride therapy on enamel micro-hardness when used before or after bleaching. Total of 60 premolar teeth were divided into 5 groups. The occlusal surface in all teeth were flattened and covered with nail varnish. Initially, all specimens were inserted in artificial saliva for 7 days. Group 1 used as negative control. Samples in group 2 were bleached 2 times with 30 minutes interval for 5 days, using 45% carbamid peroxide. Group 3 samples were exposed to fluoride varnish for 5 minutes. Group 4 exposed to fluoride varnish for 5 minutes, bleached 2 times for 30 minutes in 5 day intervals. Group 5 samples were treated same as group 4, however, followed by fluoride varnish for 5 minutes. Micro hardness for each group measured in 3 points after cleaning the occlusal section. The LSD and ANOVA tests were used for data analysis. This study showed, reduction in enamel surface hardness can be compensated by fluoride application. Group 2 [bleached only] showed the minimum micro hardness [294.38], and group 3 [exposed to fluoride only] showed the maximum micro hardness [455.36]. Fluoride therapy can affect enamel micro-hardness before and after bleaching. The application of fluoride varnish is recommended after exposing teeth to bleaching agents