[Effect of two mouth-rinses on the surface hardness of two types of direct and indirect composites]

Mouth-rinses may soften composite restorations even when the composite is light cured or heat treated. The use of certain mouth-rinses may have less adverse effect on composite restorations. The aim of this study was to evaluate the effect of alcoholic and non alcoholic mouth washes on the surface hardness of two types of direct [Z100] and indirect [Gradia] composites. Sixty disc shape samples of Gradia [n=30] and Z100 [n=30] composite were prepared and cured for 40 seconds by halogen light cure unit. Gradia composite specimens were post cured with labolight machine for 5 minutes and then were stored in distilled water for one week at 37c°. The samples were exposed to 3 different solutions of alcoholic, non-alcoholic mouth-rinses, and water for 24 hours at room tempreture. Surface hardness [VHN] was measured and data were analyzed by using One-way ANOVA and Scheffe tests [alpha <0.05]. Statistical analysis revealed that, indirect composites which were kept in alcoholic, and non alcoholic solution showed less hardness than control group [water] [p0.0001]. Direct composite specimens which were kept in alcoholic mouthwash had less hardness than control group [p0.003]. Surface hardness of indirect composite specimens kept in alcoholic and nonalcoholic mouth-rinses was significantly higher than direct composites in these solutions [p0.002 and p=0.008, respectively]. Alcoholic and non alcoholic mouth-rinses caused reduction of surface hardness of direct and indirect composites and it seems that the effect of mouth-rinse on surface hardness of these composites is material dependent. Indirect composite showed to be harder than direct composite in all solutions

[Effect of fiber orientation and position on fracture resistance and failure mode of cuspal coverage composite restorations]

Position and orientation of fiber may lead to increase load bearing capacity and prevent undesirable fractures in cuspal coverage composite restorations. The aim was to evaluate the effect of fiber position and orientation on fracture resistance and failure mode of composite cusp capping restorations. In this experimental study, MOD cavities with 2.5mm cuspal reduction were prepared in 50 human maxillary premolars. The teeth were divided into five groups [n=10] and all teeth were restored with packable composite resin [P60]. In the first group no fibers were applied. In the second group one strip of fiber was inserted into resin composite in buccal to palatal direction. In the third group two strips of fiber were inserted in buccal to palatal and mesial to distal direction by crossing in central part of cavity. In the forth group, one strip was directed from mesiobuccal to distopalatal and the other from distobuccal to mesiopalatal line angle. In the fifth group, two strips of fiber were inserted in buccal to palatal direction with 1.5 mm distance. The teeth were stored in water for 7 days in room temperature and then thermocycled 500 times between 6 +/- 2 and 60 +/- 2 centigrade degrees. The specimens were subjected to compressive loading perpendicular to the occlusal surface. The necessary fracture loads were recorded in [KN] and the results were statistically analyzed by Mann-Whitney and ANOVA tests. Mode of fracture was analyzed by using Fisher test. Statistical analysis showed a significant increase of fracture load from control to the other four groups [p<0.05]. There were statistically significant differences between second and third groups [p=0.034] as well as second and fifth groups [p=0.041]. No significant differences were found between other pairs of groups. Also significant differences were observed in failure mode between composite restorations with and without fiber, except for second group [p<0.005]. Fiber reinforced composites improve fracture resistance and failure mode of restorations with cusp capping. With increase use of fiber strips in special directions, fracture resistance will be rised

[Comparison of the effects of three postcuring techniques with microwave, labolite and oven on surface hardness of two different direct composites]

Postcuring techniques improve mechanical properties of indirect composites significantly. Eventhought this technique has been suggested for direct composites, but its effect for direct composites is still questionable. This study was undertaken to evaluate the effect of various postcuring techniques on surface hardness of two different types of composites. Eighty circular specimens of Nulite F [40 specimens] and Gradia [40 specimens] composites were made and light cured. Ten of each type was kept as control group and 10 of each type was postcured with oven for 5 minutes at 120 degree C. The other ten ones was postcured with microwave for 5 minutes and the last 10 ones were postcured with labolite for 5 minutes. The specimens were polished and were kept in 37 degree C water for one week. Then surface hardness testing was performed and data were analyzed using one-way ANOVA and Kruskal wallis tests. The results revealed that the surface hardness [VHN] of Nulite F composite in control group was greater than Gradia composite in control group [p<0.05]. All postcuring techniques increased the VHN of all groups significantly. The effects of postcuring on increasing surface hardness of Nulite F were more significant in all techniques, especially by the usage of labolite set in Nulite F composite in comparison with Gradia composite. There was no statistically significant difference between surface hardness of microwave and oven groups in Nulite F composite. No statistically significant difference was noticed between surface hardness of microwave and labolite groups in Gradia composite. The effect of postcuring with oven on surface hardness of Gradia composite was statistically significant compared to the two other techniques. By evaluation of various samples in this study it was concluded that all postcuring techniques [labolite, microwave and oven] increased the surface hardness [VHN] of both direct composites [Gradia and Neulife F] significantly

Comparison of the effect of deconex [solarsept], micro 10 and cidex in disinfecting dental instruments

Infection control is the main step of prevention in dentistry. Effects of disinfectant solution must be evaluated in this process. The aim of this study was to evaluate the disinfecting effect of Deconex [solarsept], Cidex, and Micro 10 on high and low speed handpiece surfaces after cavity preparation. In this experimental study, 105 specimens were obtained from surfaces of high and low speed handpieces after cavity preparation by sterile swab and were divided into 7 groups. Each group contained fifteen specimens which were carried to thioglycolate media. Samples were incubated and remained for 48 hours at 37°C. Microorganisms were cultured in different media, and the rate of microbial growth were calculated. Following the various stages of investigation, it was found that all specimens from the surfaces of high and low speed handpieces, after cavity preparation, were infected, but no microbial growth and colony formation were detected after disinfecting the surfaces by disinfectants solutions used in the study. By evaluation of various sampling stages and microbial cultures in this study, it was concluded that the three disinfectants were able to destroy specific kinds of microorganisms after cavity preparation procedures, if they were provided and used by manufacturer instructions in order to decrease infection transmission