RESUMEN
Statement of Problem: Home bleaching is a common method for whitening the teeth. However, bleaching may lead to a decrease in the hardness of the enamel
Purpose: The purpose of this study was to investigate the effects of two different concentrations of carbomide peroxide [CP] on the hardness of the enamel and also to evaluate the effects of the remineralising agents on the hardness of bleached enamel
Materials and Method: Crowns of 100 intact extracted human anterior teeth were resected from their roots and mounted in acrylic resin in a way that the buccal surface was parallel to the floor [horizontal]. The samples were then divided into 10 groups. The baseline hardness in the middle of the buccal surface was measured through Vickers Micro-hardness test and at a load of 500 gram per second. Then five groups were bleached with 10% carbomide peroxide and other five groups with 22% carbomide peroxide. The bleaching was performed for 21 days and was applied 4 hours each day. The samples were kept in distilled water in the interval time between the applications of bleaching agents. In the next phase the enamel micro-hardness was measured and different demineralising agents were used for each group. The Tooth Mousse [TM] paste; MI paste plus [MI]; and Crest fluoridated toothpaste was applied for 4 hours to the surface of the enamels in three groups. In the forth group, samples were embedded in fresh cow milk for the same period and the fifth group was kept in distilled water as a control group. Then, the final hardness was measured and the collected data were analyzed by t-test, paired sample t-test and One-way ANOVA test
Results: Bleaching with the aforementioned concentration of CP had no effects on enamel microhardness. In the groups with a 10% CP, none of the demineralising agents had any effect on the hardness value. However, the application of milk increased the hardness. In the groups with a 22% CP, TM paste reduced the enamel microhardness value while Crest, increased it. MI paste and milk didn't have any effect on it
Conclusion: The use of TM paste results in lower hardness of the bleached enamel. It seems that the high concentration of fluoride in MI paste may be responsible for increased microhardness of enamel. Milk and fluoridated toothpaste have propensity to increase the enamel hardness
RESUMEN
Statement of Problem: Because dental restorations are time consuming, dental material manufacturers make an attempt to discover new methods for rapidity and increasing the quality of restorations. With this objective in mind, plasma arc curing devices have been manufactured
Purpose: This study was done to compare the effect of plasma arc and halogen light curing on the microleakage of class V resin composite
Methods and Material: In this experimental study, on 80 extracted maxillary central teeth, standard class V cavities were prepared with incisal and gingival margins in the enamel and dentin. After etching and bonding, the teeth were randomly divided into two subgroups of 40 and restored with Amelogen composite. In the first group, halogen light curing for 40 seconds was used and in the second one plasma arc curing was used for four seconds. After thermocycling and sealing, the samples were immersed into the 0.5% fuchsine solution for 24 hours and then washed with water and cut. The microleakage was scored by stereomicroscope with 40X magnification. The data were analyzed using Mann-Whitney and Wilcoxon tests
Results: The mean of incisal wall microleakage in the plasma arc group was 1.42+/-0.98 and in the halogen group it was 0.67+/-0.02. The gingival margin in the plasma are group showed a mean of 1.75+/-1.48 and in the halogen group it was found to be 1.67+/-1.54. There were significant differences in the incisal wall [p =0.0001], but not in the gingival wall [p =0.744]. The average rate of microleakage in the gingival and incisal walls in the plasma arc group was 3.17+/-1.79 and in the halogen group it was 2.76+/-1.92; there were not any significant differences between the groups [p =0.32]
Conclusion: In the restorations with enamel margins halogen light curing and in all composite restorations plasma arc curing are preferred due to the short time of curing
RESUMEN
Statement of Problem: The control of microleakage presents a challenge for posterior composite restorations. The technique for composite placement and treatment technique may cause some modifications in the microleakage. The results of different studies are varied
Purpose: This study aimed to evaluate the marginal microleakage in class II P60 resin composite restorations prepared with two restorative techniques and two polymerization systems
Materials and Method: Standard class II cavity preparations were performed on 56 carries- free extracted molars. Then, the teeth were randomly divided into four groups: 1] Bulk placement and conventional polymerization 2] Incremental placement and conventional polymerization 3] Bulk placement and soft start polymerization 4] Incremental placement and soft start polymerization. All the cavities were restored with single bond and P60 [3M/ESPE] resin composite. After thermo cycling, the specimens were immersed in 2% methylene blue solution for 24 hours and then washed. After sectioning, dye penetration was assessed by light stereomicroscopy at 40x magnification and then evaluated for microleakage by Kruskal-Wallis Test and Mann-Whitney tests
Results: Significant differences were found between the bulk with incremental technique and soft start with conventional polymerization. The highest and lowest rates of microleakage were in bulk conventional and incremental soft start group, respectively. A significant difference was found between groups
Conclusion: The use of incremental placement technique and soft start system results in less microleakage
RESUMEN
Statement of Problem: Bitewing radiography is a suitable clinical technique for the diagnosis of interproximal caries. Many researches performed in this field have shown that direct digital radiography and conventional radiography films in dentistry are similar in detecting inter-proximal caries
Purpose: To compare the effects of image processing mode of colorize on the efficacy of the detection of interproximal carious lesions viewed in direct digital radiography
Methods and Material: A total of 102 proximal surfaces of the extracted human premolar teeth on direct digital images with and without application of pseudocolor filter were evaluated by three observers. The teeth were sectioned and viewed microscopically to determine the gold standard. The kappa value agreement ratio was calculated
Results: Sensitivity and specificity values in normal digital images were found to be 66.7% and 60% and for colorized images 80.5% and 50%, respectively. However, there was no statistically significant difference between the two types of images [p = 0.12]
Conclusion: In this study, application of pseudocolor software failed to result in statistically significant differences between normal and colorized digital images