Journal of

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Introduction: One of the most important factors affecting the marginal seal of composite restorations is polymerization shrinkage. The aim of this study was to evaluate the micro leakage of two resin composites cured with two light directions. Methods: In this experimental study, forty similar class III preparations were prepared in 40 human anterior teeth. The teeth were randomly divided in two groups according to the resin composite used for filling the cavities (Microfilled composite: Heliomolar or hybrid composite: Spectrum). Etch group was further divided in two subgroups according to the light direction buccal and lingual. All the cavities were filled with the composites and cured for 40 seconds. The teeth were then thermocycled for 500 cycles between 5-55°c and covered with nail polish except for 1mm around cavity margins and immersed in 1% methylene blue for 12 hours. The teeth were sectioned and the dye penetration scores were recorded using stereo microscope. Data was analyzed using non parametric Mann Whitney test. Results: No significant difference was observed between the composite resins (p>0.05) or the light directions used for curing the composite resins (p>0.05). Conclusion: Directions of the light does not have any effect on the micro leakage of hybrid or micro filled composites in class III cavities.

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Introduction: Thermocycling is used in most invitro studies to produce conditions similar to clinical studies, but results about the effect and number of thermocycling cycles have been different in different studies. The purpose of this study was to evaluate the effect of thermocycling on microleakage of self and total etch bondings in class V resin composite restorations. Methods: A total of 80 anterior bovine teeth were collected and class V cavities were prepared with incisal and gingival margins in enamel and dentin. The teeth were randomly divided into two groups. In the first group, prompt L-pop(PLP) and in second group, singlebond(SB) was applied and restored with Z250 resin composite. Each group was divided to four subgroups with zero, 500, 1000, 2500 cycles of thermocycling at 5-55° c. Then the teeth were sealed and immersed in 50% silver nitrate followed by a developer solution for 16 hours. Microleakage rate was evaluated by stereomicroscope with 25x magnification. Data was analyzed by Mann-Whitney and Wilcoxon tests. Results: Both SB and PLP groups showed microleakage. Statistical analysis showed significant difference between enamel and dentin margins of PLP group with 1000 cycles(p=0.02), 2500(p=0.014) and in SB with 2500 cycles P=0.046). Statistical analysis showed significant difference in incisal and cervical margins of SB and PLP groups (p=0.013) (p=0.001). Conclusion: Microleakage was seen in self etch and total etch bondings with minimum 1000 and 2500 cycles.

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Introduction: Fissure sealant is the most effective method to prevent occlusal surface caries of posterior teeth . In recent years, the use of laser for enamel surface pretreatment has been considered as an effective method before applying fissure sealant. Hence, the aim of this study was to investigate the effect of Er:YAG laser conditioning on fissure sealant microleakage. Methods: In this experimental study, total of 60 extracted third molars were randomly assigned into four groups(n=15). The occlusal surfaces were sealed with a sealant (clinpro) after one of the following pretreatments: 1- Phosphoric acid etching + total etch bonding, 2- Laser + self etch bonding, 3- Laser + total etch bonding, 4- Laser + Phosphoric acid etching + total etch bonding. The parameters of used laser was 120 mj energy and pulse duration of 250-500 µs with frequency 4 Hz. After sealing, the teeth were thermocycled at 500 cycles and immersed in methylen blue 1% for 24 hours. The teeth were then sectioned buccolingually and examined for microleakage. Statistical analysis were preformed via applying Kruskal-Wallis and Mann-Whitney. Results: The study results indicated significant differences between 4 groups (p<0.05) except for groups 1 and 4 (p=0.3). Moreover, the highest microleakage was observed in group 3, whereas the lowest was reported in group 4. Conclusion: It seems that conventional acid etching technique is the best and simplest method of Sealant therapy.