Background & Aim: The purpose of this study was to evaluate the micro-shear bond strength of two kinds of resin-based cements with fluoride release with the usage of five adhesive systems to enamel and dentin. Materials & methods: Bovine flat enamel or dentin surfaces were used in this study. Micro cylinders of resin cement with Xeno Cem Plus (XCP) or Panavia Fluoro Cement (PFC) were bonded to enamel or dentin as followed: XCP or PFC as instructions prior to the usage of their own adhesive systems, Xeno CF II+XCP, SE Bond+PFC, or Clearfil Liner Bond II (CLB) + PFC. After the storage in 37°c water for 24 hrs, micro-shear bond test was applied for all the test groups. The data were statistically analyzed using two-way analysis of variance (ANOVA). After two-way ANOVA, one-way ANOVA and multiple comparisons with Fishers PLSD test were made.Results: Are given as follow (enamel and dentin, mean±SD in MPa); XCP, 13.7±4.0 and 15.5±9.2; PFC, 23.7±10.6 and 15.0±7.3; XCP+XCF II, 35.4±11.5 and 17.1±4.0; PFC+SE, 54.2±9.8 and 41.7±12.0; PFCCLB, 31.39±3.09 and 15.09±4.35. ANOVA (α=0.05) analyze revealed the usage of SE Bond under PFC significantly increased the bond strength to both enamel and dentin. Bonding of Xeno CFII was only improved the bonding to enamel with the application of XCP.Conclusion: Light-cure adhesive systems significantly improve the bonding of current resin cements.

Statement of Problem: In most shear bond strength (SBS) studies, different cross head speeds have been used. The effect of different speeds on the shear bond strength has been studied in very limited researches.Purpose: The aim of this study was to evaluate the influence of changing cross head speed of testing machine on the shear bond strength and failure mode of orthodontic adhesive (Transbond XT) in bracket bonding.Materials and Method: For this experimental study, 175 human premolars with intact enamels were divided into seven equal groups of 25. After surface preparation, brackets were bonded to teeth using transbond XT adhesive. For deboning process various cross head speeds of 0.5, 1, 2.5, 5, 7.5, 10, 25 mm/min were applied. Shear bond strength and Adhesive Remnant Index (ARI) were recorded for different groups. One way ANOVA and Tukey tests were used for bond strength comparison. Data on shear bond strength evaluations and modes of bond failure were analyzed using Kruskal- wallis and spearman tests.Results: The means of shear bond strength for the applied 0.5, 1, 2.5,5, 7.5, 10 and 25 mm/min cross- head speeds were 16.39, 14.37, 13.30, 14.12, 13.32, 16.58, and 13.83 respectively. Shear bond strengths in groups receiving 0.5, 10 mm/min cross head speeds, were significantly greater than other groups. No significant differences were obtained between these two speeds, as well as, between 1, 2.5, 5, 7.5, 25 mm/min speeds, but there were significant differences in the shear bond strengths between the two groups with the cross head speeds of 0.5, 10, and 1, 2.5, 5, 7.5, 25 mm/min. Considering the ARI, no differences were found between the groups. Also, there was no relation between ARI and bond strength in groups with different cross head speeds, except in 5mm/min.Conclusion: Cross head speed of Instron is an effective factor on the SBS of the adhesives, but it does not have significant effect on the failure mode of bonding materials.

In this research the effect of moisture content and cutting speed on the specific cutting energy and shearing stress for four varietiesof almond tree (Mamayy, Rabi, Sefid and Shahrodi12) wood was investigated. Shear properties of almond wood was measured using a universal testing machine (Santam STM20). One side beveled knife with the edge angle of 40 degree was used. Three moisture levels of 18, 25 and 45% (wet basis) wet basis, three cutting speeds 20, 30 and 40 mm/min and three stem diameter of 6, 9 and 12 mm were selected. The results of analysis of variance (ANOVA) showed that the effect specific cutting energy and shearing stress were significant (P<0. 01). The results showed that both specific cutting energy and shearing stress increased at higher moisture content. However, increasing cutting speed from 20 to 40 mm per minute reduced these values. Based on the results of the study, the average specific cutting energy were determined for varieties Mamayy, Rabi, Sefid and Shahrodi12 as 59. 41, 56. 088, 54. 38 and 77. 57 J/ mm2 respectively and shearing stress as 16. 01, 14. 34, 13. 73 and 19. 35 MPa, respectively. Also, according to shear test results, it can be expressed that the moisture content and the variety of almond tree are most effective and the effect cutting speed is relatively low.

Background & Aim: The goal of many researchers conducted nowadays is to achieve adhesive materials that exhibit good bonding capability, simplified application and easy handling. In this regard, self - etching primer systems were introduced to the market. The aim of this study was to evaluate the micro- shear bond strength of two new self - etching materials compared to an already established bonding materials. Methods & Materials: Sections of human third molars (1.5 mm) were used in this study. The tooth surfaces were polished with 600 grit SiC paper nder running water and randomly divided into three groups. In group I Clearfil Protect Bond (Kuraray Japan), in group II, Clearfil SE Bond (Kurary Japan) as control group, and in group ill, Clearfil Tri - S Bond (KUrary Japan) were used due to manufacturer's instruction. Hollow tygon tubes (0.7×0.5mm) were placed on the enamel and dentin surfaces and Clearfil AP-X composite was inserted into the tubes. After 40 seconds light curing, the tygon tubes were removed and samples were stored in distilled water for 24 hours. Micro – shear bond strength was measured (EZ-test, Shimadzu Co., Kyoto, Japan) and the data was statistically analysis by one - way ANOVA and multiple comparison with LSD.Result: Mean bond strength in enamel was 35.76±6.89 mpa in group I; 33.62±5.59 mpa in group II, and 34.65±5.65 mpa in group III. Their difference was not statically significant. Mean bond strength in dentin was 34.47±6.0 mpa in group I, 45.20±10.3 mpa in group II, and 35.99±6.13 mpa in group III. The bond strength in group II was higher than group I and II (P<0.05), and the difference between group I and II was not statistically significant.Conclusion: After 24 hours, the shear bond strength of two new adhesive systems to enamel was similar to SE Bond, however, SE Bond exhibited a higher bond strength to dentine.

Statement of Problem: Evaluation of new adhesives efficacy in bonding orthodontic brackets to enamel has led to different results. The new measuring method, micro-shear bond strength, is preferred as an accurate method due to its ability to reduce confounding factors.Purpose: The purpose of this study was to evaluate and compare the micro-shear bond strength of three different adhesive systems for enamel surface preparation before bracket bonding.Materials and Method: In this experimental study, 90 extracted premolars were randomly divided into three groups of 30. Transbond XT was bonded to enamel after enamel surface preparation with acid etch in the first (control) group, Transbond plus self-etch primer in second group, and Adper prompt L-pop self-etch adhesive in third group. Then each group was randomly divided into two subgroups of 15. Micro-shear bond test was performed after 24 hours (T1) and 3-months (T2). Bond failure mode was also evaluated according to Adhesive Remnant Index (ARI). Two way ANOVA and Tukey tests were used for bond strength evaluation in groups, and mode of bond failure was analyzed with Kruskall Wallis and Mann Whitney tests.Results: The highest bond strength was found in acid etch group (29.17 MPa). Difference of bond strength at two intervals was statistically significant in all groups ( p <0.001). Bond strength difference between T1 and T2 was also significant in three groups ( p <0.001). However changes over time in three groups did not reveal any significant differences ( p = 0.091). Bond failure analysis demonstrated significant differences in ARI between groups.Conclusion: Bond strength of acid etch group was the highest and self etch primer showed higher bond strength than self etch adhesive group. Less adhesive remnant was found in self etch group.

Background: Since three decade ago, the application of the concept of finite element analysis (EEA) have received a keen interest among dental investigators. In practice the FEA provides detailed stress information regarding to a non-homogenious body such as craniofocal skeletal growth, tooth post ceramo-metal crowns and etc. The aim of this study was the determination of the influence of stress distribution at the cement interface of metal ceramic restoration-dentin. Materials and Methods: An idealized metal-ceramic crown model was developed. The model was divided into very small segments. Various loading conditions was applied to the model. A super sap software was used for analyzing the stress distribution. Results & Conclusion: The results of this study suggest that the higher shear stress was developed in the cervical region by two dimensional methods.

Design of new tools for pruning hedges cultivated with a shrub like wild privet can have a great impact on the quality of pruning and their appearance in parks. The movement of wild privet stalk during cutting is considered one of the issues of pruning when using common tools, which usually causes uneven pruning. In order to design a new pruning tool, it is necessary to know the shearing mechanical properties of the stalk, such as shear force, cutting energy and shear strength of the stalk. To determine them, a series of a series of experimental tests were performed. The parameters such as shear force, cutting energy, and shear strength were determined with two quasi-static and impact cutting methods in three cutting positions of the fifth, tenth, and fifteenth internode position. In the quasi-static cutting test, the stem samples were subjected to cutting with four cutting speeds of 5, 10, 15, and 20mm/min, and in the impact cutting test, the samples were subjected to cutting with four speeds of 1, 2, 3, and 4m/s. The average moisture content of the samples at the time of the experiment was measured at 75% on a wet basis. The results of quasi-static stalk cutting showed that cutting speed had a significant effect on the parameters of shear strength (P<0.01), and cutting energy (P<0.05), and the stalk cutting position had a significant effect on shear strength (P<0.05), and cutting energy (P<0.01).

In this research, the phenomenon of stress relaxation in unreinforced and reinforced sandy soil with geotextile layer has been studied using a large-scale direct shear test. To investigate the effect of shear speed and soil density on the amount of resistance loss due to stress relaxation, two shear speeds of 0.5 and 5 mm/min and two relative densities of 35% and 60%, respectively, loose and medium density, have been used. All samples have been tested in direct shear test under vertical stress of 100 kPa. The results show that the amount of resistance loss due to stress relaxation depends on the shear stress level, soil density, presence of a geotextile layer in the soil and shear speed. In such a way that by increasing the level of shear stress and shear speed and by decreasing the density of sand and also with the presence of a geotextile layer in soil, the amount of resistance loss due to stress relaxation increases.

Background: Determination of the correct working length is one of the main factors that lead to success in root canal therapy. This laboratory study aimed to compare the accuracy of conventional (F, E-speed) radiography and Complementary Metal Oxide Semiconductor (CMOS) digital radiography in working length measurement.Materials and Methods: In this laboratory study, access cavities were prepared in 40 extracted maxillary central incisors with straight and single canals. Size 15 K-file was introduced into the each canal until it was appeared through the apical foramen. The file was then removed and measured by a digital caliper with precision of 0.01 mm. Actual working length was considered 1 mm less than the measurement showed by the caliper (Gold standard). At the next stage, each tooth together with its related K-file was positioned in a dried skull and then, periapical conventional and digital radiographies were taken with parallel technique. All the radiographs were measured by two radiologists. Statistical analysis was performed using repeated measures ANOVA and paired t-test.Results: No statistically significant difference was observed between conventional and digital radiographies regarding working length measurement (P>0.05). Conventional and digital radiographies demonstrated significantly higher scores of working length measurement compared to the Gold standard (P<0.001).Conclusion: Although CMOS had no significant superiority over conventional radiography, if both techniques are available, using CMOS is recommended due to significant reduction of radiation dose.