Background and Aims: Using the conservative adhesive resin restoration (CAR) in uncooperative children lead to numerous problems because of being time consuming. The purpose of this study was to compare the microleakage of conservative adhesive resin restoration under separate curing and co-curing.Materials and Methods: In this experimental study, 120 intact premolar teeth were collected and 120 vertical grooves were prepared on them. Then the teeth were divided into four groups: group 1, separated curing of bonding agent, flowable composite and sealant; group 2, co-curing of all materials for 60 seconds; group 3, co-curing of all materials for 40 seconds and group 4, co-curing of all materials for 20 seconds. Then the specimens were thermocycled and immersed in basic fuchsin solution. The teeth were sectioned horizontally and dye penetration was evaluated with stereomicroscope. Dates were analyzed using one-way ANOVA and Scheffe test.Results: Mean value of dye penetration in groups 1, 2, 3, and 4 was 1.53±0.6, 2.06±0.6, 2.5±0.7 and 3.53±0.6, respectively. There was a statistically significant difference between group 1 and the other groups (P=0.0001).Conclusion: Considering the problems caused by microleakage in conservative resin adhesive restorations, cocuring method should not be used. In the case of using co-curing method, 60 second curing time is suggested for sufficient polymerization.

Objectives: The aim of this study was to compare polymerization depth of two bulk-fill and one conventional composite cured for different times.Methods: This in vitro experimental study was conducted on 54 composite samples (2×4×10mm) fabricated of Tetric N-Ceram bulk-fill, x-tra fil bulk-fill, and Grandio conventional composite cured for 20, 30, and 40 seconds. The microhardness of samples was measured at 0.1, 2, 2.5, 3, 3.5, 4, and 4.5mm depths using a Vickers hardness tester. The results were analyzed using ANOVA, t-test, and Tukey’s test.Results: The x-tra fil, Tetric N-Ceram and Grandio had maximum microhardness at 0.1mm depth after curing for 40 seconds. The microhardness decreased as the depth of composite increased. Microhardness of x-tra fil was higher than that of Tetric N Ceram. By increasing the curing time, the microhardness value of x-tra fil significantly increased up to 2mm depth. In Tetric N-Ceram, by increasing the curing time from 20 to 30 seconds microhardness increased significantly (P<0.05) by up to 3.5mm depth. By increase from 20 to 30 seconds, no significant change occurred in microhardness of Grandio samples at 0.1 and 2mm depths, but further increase from 30 to 40 seconds significantly increased the microhardness at all depths (P<0.05).Conclusion: The maximum microhardness was obtained for x-tra fil at 0.1mm depth following 40 seconds of curing. Microhardness in deep areas (>2mm depth) depends on the type of composite, curing time and depth. Overall, 20 seconds of curing for x-tra fil and 30 seconds for Tetric N-Ceram seem appropriate.

Background: Despite improvements in the optical properties of composite resins, their color stability is still a matter of discussion. This study sought to assess the effect of light intensity and curing time by a light-emitting diode (LED) light-curing unit on color stability of a methacrylate-based composite resin. Methods: In this in vitro study, 60 discs (8 × 2 mm) were fabricated of A2 shade of Z250 composite. Specimens were polished and divided into 4 groups (n = 15) for curing for 20 or 40 seconds with a light intensity of 600 or 1200 mW/cm2. After immersion in distilled water at 37° C for 24 hours, colorimetry was performed using a spectroradiometer. The specimens were then immersed in tea solution for 7 days (3 times a day, each time for one hour) and were subjected to colorimetry again. Color change (Δ E) was calculated and analyzed using two-way ANOVA. Results: Significant color change was noted following an increase in curing time (P < 0. 05). No improvement in color stability was noted after increasing the light intensity (P > 0. 05). The interaction effect of light intensity and curing time on color change was significant (P < 0. 05). Conclusions: Curing time is an important factor affecting the color stability of composite resin polymerized with LED light curing unit. On the other hand, increasing the light intensity over the standard threshold showed no significant effect.

Objectives: The aim of this in-vitro study was to assess the thermal effect of light emitting diode (LED) light curing unit on the enamel etching time.Materials and Methods: Three treatment groups with 15 enamel specimens each were used in this study: G1: Fifteen seconds of etching, G2: Five seconds of etching, G3: Five seconds of etching plus LED light irradiation (simultaneously). The micro shear bond strength (mSBS) of composite resin to enamel was measured.Results: The mean mSBS values ± standard deviation were 51.28±2.35, 40.47±2.75 and 50.00±2.59 MPa in groups 1, 2 and 3, respectively. There was a significant difference between groups 1 and 2 (P=0.013) and between groups 2 and 3 (P=0.032) in this respect, while there was no difference between groups 1 and 3 (P=0.932).Conclusion: Simultaneous application of phosphoric acid gel over enamel surface and light irradiation using a LED light curing unit decreased enamel etching time to five seconds without compromising the mSBS.

Background and Objective: The colored compomers are a group of restorative materials that are introduced for filling of primary dentition since 2002. These materials have been used in pediatric dentistry because of their attractive colors and their simple handling properties. But their characteristics have not been evaluated and compared completely. Since a change in the color of these materials can change its physical characteristics, the aim of this study was evaluation of colored compomer micro-hardness in 20, 40 and 60 second time curing.Materials and Methods: In this in vitro study, 180 composite discs were prepared. Then, each color (blue, green, lemon, golden, silver and pink) was packed into the discs, and was cured for 20, 40 and 60 s. Specimens were stored for 10 days in an incubator with distilled water at 37oC and away from direct light. Then, surface micro-hardness measurements were carried out using a Vickers micro-hardness tester in three different points on the top and bottom surface of each sample.Results: Silver color had maximum micro-hardness value (44.19), and blue color had minimum micro-hardness value (39.52). Green, golden, pink and lemon had average micro-hardness values (42). Statistical analysis shows that compomer color and side of specimen had significant influence on compomer micro-hardness. However, no significant influence in various time of curing on compomer micro-hardness was found out. A comparison between colors showed that blue color had minimum micro-hardness and silver color had maximum micro-hardness (p<0.05).Conclusion: Based on the results of this study, the color of compomer influences micro-hardness. Due to maximum micro-hardness of two colors, i.e. silver and lemon, these are recommended for restoration of primary dentition.

Introduction: The use of earthen materials is common in hot and dry areas around the world, due to a cheap, abundant and easy access to materials. Today, the use of earthen materials is common in urban and rural areas in developing countries. In Iran earthen materials have partly shaped our architectural culture and identity. Kahgel is one of the oldest traditional plastering and mortars in Iran, which has been used to insulate the roof and facades of buildings from moisture and rainfall. Although the importance of processing and curing mortars and plasters is well known among architecture and building professionals and builders, no research has been conducted on the effect of processing time upon the physical quality and mechanical properties of traditional mortars, especially Kahgel. The main purpose of this study is to evaluate the importance and duration of curing process on the physical and mechanical properties of Kahgel using experimental methods. Material and methods: As the first step, soil samples were taken from different areas of Isfahan and then these samples were examined using different experimental methods. Then the most appropriate soil sample in terms of physical and mechanical properties was selected. Several samples of Kahgel mortars were produced using the selected soil sample and different percentages of straw fibers. For these kahgel samples the compressive strength, tensile strength, linear shrinkage and cracking were measured to determine the most appropriate combination of selected soil mixed with straw fibers. In the second phase of the study, the type of soil and straw percentage were not changed, while the processing time was considered as an independent variable. The new Kahgel samples were prepared by a variety of processing time and then their compressive strength and tensile strength were measured to examine the effect of the curing time on the mechanical properties of Kahgel. Results: The results indicate that the compressive strength dropped with increasing straw fiber content and increased with increasing soil content. The results of all the tests indicate that tensile strength of Kahgel increased with increasing straw fiber content up to 6 %, but the higher straw contents decreased tensile strength. The linear shrinkage of samples decreased with increasing straw fiber content. The results showed that the curing time of Kahgel affects its mechanical properties, especially compressive strength and tensile strength. Therefore, the mechanical properties of Kahgel can be improved by increasing the duration of curing time.

Background. This study aimed to measure the shear bond strength and compressive strength of orthodontic adhesives at different curing times and intensities. Methods. Ninety extracted human premolars were used. Orthodontic brackets were bonded on the buccal surface of the teeth with orthodontic adhesive light-cured using VRN-VAFU LED curing light at different curing times (1, 3 and 5 seconds) and intensities (1000, 1600 and 2300 mW/cm2). A universal testing machine was used to measure the shear bond strength. The ratio of the adhesive remnant and compressive strength of the orthodontic adhesive, at each curing time at the different intensities, were also evaluated. The results were statistically analyzed using one-way analysis of variance followed by Tukey’, s test. Results. The lowest bond strength values (6. 4, 9. 9 and 12. 6 MPa) were recorded with 1000 mW/ cm2 intensity (at all curing times) in comparison with the other intensities (P < 0. 05). Increasing the curing time significantly increased the bond strength of the orthodontic brackets (P < 0. 05), except when the curing time was increased from 3 sec to 5 sec at 1600 mW/cm2 intensity. The highest compressive strength values (130. 3, 147. 1 and 174 MPa) were recorded at 2300 mW/ cm2 intensity (at all curing times) compared to the other intensities (P < 0. 05). The highest values of the ratio of the adhesive remnants were recorded at 1000 mW/cm2 intensity (at all curing times) compared to the other intensities (P < 0. 05). Conclusion. Although, increasing the curing time and\or the curing intensity has a positive effect on the bond strength and compressive strength of the orthodontic adhesive, it might be possible to suggest reducing the curing time of orthodontic adhesive to 1 sec at curing intensity of 2300 mW/cm2.

Building the buildings and other engineering structures on weak or soft soil is very risky because such soil is prone to different settlements due to its low shear resistance and high compreessibility. Improving some soil properties such as bearing capacity and shear resistance characteristics can be done by one of the methods of improvement, which is stabilization. In this article, the effect of cement on soil properties in the southeast region of Semnan was investigated. The main objective of this research is to investigate the effect of cement on the compressive strength of sandy clay with silty soil. The tests used in this research included compaction and unconfined compressive strength. Laboratory samples were prepared by static compaction method. The samples were made in 95% of the maximum dry unit mass in order to achieve the best density and with different percentages of cement (2, 4, 6, 8, 10). With increasing the cement from 2% to 8%, the unconfined compressive strength of the cement soil increases and adding more cement causes the unconfined compressive strength to decrease. With increasing the amount of cement from 2% to 8%, the elasticity coefficient increased with a low slope, but with the increase of cement up to 10%, the trend of changes was strongly increasing. Adding cement increases the maximum dry unit weight. By adding cement to the soil, its resistance increases; This increase in strength is a function of the percentage of cement used and the curing time. The results obtained from the soil elasticity coefficient indicate an increase in the brittleness of the soil mixed with cement, which increases with the increase in the percentage of cement used or the curing time. Adding cement changes the fracture of the samples from soft to brittle.