[Comparison of solvent evaporation in the self etch and total etch adhesives in different air draying times]

Different adhesives with different solvents may have different solvent evaporation rates. The purpose of this study was to evaluate the solvent evaporation in the self etch and total etch adhesive in different air drying times. Five adhesives were used in this study: Excite, Prime and Bond NT, UNO, Single Bond, SE Bond Primer. Twelve drops of each adhesive were used for each period of air drying [5, 15, 30 sec]. The percentage of mass loss was measured during each test. Data were analized using two-way ANOVA and Tukey. Acetone base adhesives showed more loss of mass than other adhesives [P<0.01]. P and B NT showed more loss of mass than other adhesives in all air drying times [P<0.01]. Adhesives showed different evaporation rates in different air times [P<0.01]. Adhesives with acetone/ water or alcohol/water solvent shows more stable behavior in comparison with adhesives containing pure aqueous solvents

[Effect of bleaching on the microhardness of tooth-colored restorative materials]

Bleaching agents not only affect the tooth structure, but also may later the properties of restorative materials. The aim of this in vitro study was to evaluate the effect of different bleaching regimens on the microhardness of four tooth-colored restorative materials. Eighty specimens of four restorative materials [Microhybrid resin composite [Z250 [3M, ESPE], nanohybrid composite Z350 [3M, ESPE], packable composite P60 [3M, ESPE], and resin modified glass ionomer Vitremer [3M, ESPE]] were fabricated and were polished after 24 h with Soflex discs [3M,ESPE]. Then the specimens were divided into two groups: In office bleach group, 40 specimens [10 of each restorative material] were bleached with hydrogen peroxide 37.5% for 30 min in two sessions with 7 days interval. In home bleaching group, 40 specimens were bleached with carbamid peroxide 22%, 6 h a day for 14 days. Vickers microhardness test were done before and after bleaching [baseline]. Finally data were evaluated using analysis of Variance. Two bleaching regimens were significantly decreased the microhardness values. In Z250 resin composite, the microhardness values before and after bleaching were 95.30 and 92.67 kg/mm[2], respectively. for office bleaching [P=0.011] and 95.38 and 92.39 kg/mm[2] for home bleaching [P<0.001]. In Z350 resin composite, the microhardness values before and after bleaching were 98.29 and 92.41 kg/mm[2], for office bleaching [P<0.001] and 97.35 and 93.44 kg/mm[2] for home bleaching [P<0.001] respectively. In P60 resin composite, the microhardness values before and after bleaching were 103.10 and 96.16 kg/mm[2], respectively. for office bleaching [P=0.045] and 102.61 and 98.16 kg/mm[2] for home bleaching [P=0.001]. In resin modified glass ionomer [Vitremer], the microhardness values before and after bleaching were 56.79 and 49.41 kg/mm[2], respectively. for office bleaching [P=0.004] and 54.17 and 46.50 kg/mm[2] for home bleaching [P<0.001]. There was no significant difference between two bleaching agents [P=0.365]. Dental bleaching agents decrease the microhardness of tooth-colored restorative materials

[Effect of re-application of microbrush on micro tensile bond strength of an adhesive to dentin]

Re-application of microbrush may affect the micro tensile bond strength of adhesives to dentin. The aim of this study was to evaluate the effect of re-application of microbrushes on the micro tensile bond strength of an adhesive to dentin. Thirty freshly extracted molars teeth were collected and enamel of occlusal surface were removed to expose superficial dentin. Then superficial dentin was etched, washed and partially air dried. According to the times of application of microbrush, teeth were divided into two test groups. In group 1, new microbrushs were used, but in group 2, the ones that were already used for twice were included. Ambar dentin bonding agent [FGM/Brazil] was applied to the etched dentin with microbrushes according to the manufacturer's instructions. Then the crown of teeth was built up with LLiss [FGM/Brazil] composite resin. The teeth were sectioned in buccolingual direction to obtain 1mm slabs. Then 50 hourglass- shape samples were made from 30 teeth [25 Specimens per group]. The microtensile bond strength of the specimens was tested using MTD500 [SD Mechatronik, Germany]. The data were statistically analyzed by T-test. The mean values for the microtensile bond strength were 30.49 +/- 7.18 and 23.61 +/- 9.06 MPa +/- SD for the first and second groups, respectively. There was significant difference between the groups [P=0.005]. Microbrushes should not be used for more than one cavity preparation.

[Effect of two surface sealants on microleakage of class V resin composite restorations]

When composite resin polymerizes, shrinkage stresses tend to produce gaps at the tooth/ restoration interfaces. Surface sealants may reduce or avoid problems related to the marginal interface. The aim of this study was to evaluate the effect of two different surface sealants [Fortify and Optiguard] on the microleakag of class V resin composite restorations. Twenty three sound noncarious molars were collected. Totally, 45 Class V cavities wit the occlusal margins in enamel and cervical margins in cementum were prepared in both buccal and lingua surfaces. The specimens were randomly assigned in three groups [15 cavities in each group] and then restorec with a resin composite. After the finishing and polishing procedures, the restorations in each group were coverec with a specific surface sealant, except for the control samples, which were not sealed. After placing restorations the specimens were thermocycled and then immersed in a 50% silver nitrate solution [tracer agent] for four hours sectioned longitudinally and analyzed for leakage using a stereomicroscope in a blind manner. The margina microleakage was evaluated at the occlusal and cervical interfaces and compared among the three groups using the Kruskall-Wallis and the Mann-Whitney U tests. Microleakage was found in all groups at both occlusal and cervical margins. Significantly greater leakage was observed at the cervical margins compared to the enamel margins of the material groups [P=0.005]. There was no statistically significant difference among the groups at occlusal margins [P=0.66]. In the cervical region, Fortify showed improved results and statistically presented the lowest degree of microleakage [P=0.003]. The used sealant materials presented different rates of effectiveness and Fortify decreased marginal microleakage significantly

Effect of curing direction on microtensile bond strength of fifth and sixth generation dental adhesives

Composite restorative materials and dental adhesives are usually cured with light sources. The light direction may influence the bond strength of dental adhesives. The aim of this study was to evaluate the effect of light direction on the microtensile bond strength of fifth and sixth generation dental adhesives. Prime and Bond NT and Clearfil SE bond were used with different light directions. Sixty human incisor teeth were divided into 4 groups [n=15]. In groups A and C, Clearfil SE bond with light curing direction from buccal was used for bonding a composite resin to dentin. In groups B and D, Prime and Bond NT with light curing direction from composite was used. After thermocycling the specimens were subjected to tensile force until debonding occurred and values for microtensile bond strength were recorded. The data were analyzed using two-way ANOVA and Tukey post hoc test. The findings showed that the bond strength of Clearfil SE bond was significantly higher than that of Prime and Bond NT [P<0.001]. There was no significant difference between light curing directions [P=0.132]. Light curing direction did not have significant effect on the bond strength. Sixth generation adhesives was more successful than fifth generation in terms of bond strength to dentin