Background: White spot formation is one of the common side effects in orthodontic treatments and multiple enamel conditioning might happen even during on session of fixed orthodontic treatments. The aim of the present study was to evaluate the impact of multiple enamel conditioning with different methods on enamel Micro‑, hardness (MH). Materials and Methods: In this In vitro experimental study, the buccal surfaces of 105 extracted premolars were evaluated in seven groups: One control and six experimental groups. The enamel conditioning was performed in three ways: Etching with phosphoric acid 37%, etching with phosphoric acid 37% followed by primer application and conditioning with self‑, etch primer. The conditioning process in each way was also performed twice consecutively. The specimens were submitted in pH cycling model with demineralization and re‑, mineralization solutions for 14 days. Afterward Vickers MH test was applied with 0. 981N force on the teeth for 10 s indentation time. Data were analyzed using One‑, Way ANOVA and Tukey HSD (honestly significant difference) test for multiple comparisons. A value of P < 0. 05 was considered statistically significant. Results: MH analysis showed statistically significant differences between the control group and the other conditioned groups (P < 0. 05). The groups conditioned with acid‑, etch and primer, particularly twice, showed the lowest amount of MH in comparison to other groups. Self‑, etch primer had the least effect on MH of the enamel. Single time etching without using primer, made no considerable difference when compared to multiple etching. Conclusion: Etching process and covering the enamel with primer decrease enamel MH. Using self‑, etch primer is a more conservative method of enamel conditioning.

Statement of the Problem: Although sumac extract (SE) is reported as a collagen cross linker, the available data regarding its effect on the dentine Micro-hardness is quite sparse. Purpose: Therefore, the aim of this study includes evaluating the effect of different concen-trations of SE on dentine Micro-hardness comparing to grape seed extract (GSE). Materials and Method: In this experimental study, the GSE was purchased from available market and convert to 5% solution. Meanwhile the 5, 10, and 20% of SE solutions were prepared experimentally. The base line Micro-hardness of 60 samples (30 premolars divided to buccal and lingual segments) was recorded triplicate for each specimen and they were randomly divided into 5 groups (four abovementioned experimental solutions and de-ionized water as negative control). For 35 consecutive days, each sample was twice pH cycled and treated by solutions. Ultimately, the final Micro-hardness was recorded triplicate again for each sample and the numerical data was compared with each other using one-way ANOVA and Tukey HSD Post Hoc tests (α, =0. 05). Results: The mean, SD values of Micro-hardness for the groups was recorded as 54. 45,13. 4, 65. 65, 18. 5, 39. 57, 2. 26, 41. 13, 1. 66 and 43. 79, 4. 96 at base line and 10. 4, 0. 99, 11. 85,0. 75, 10. 16, 1. 84, 8. 48, 1. 16 and 6. 31, 1. 01 at final stage for control, GSE 5%, SE 5%, SE 10% and SE 20% respectively. There was no significant difference among the mi-cro-hardness of the groups before treatment (p= 0. 369). However, after experimental treat-ment, there was significant difference between the groups (p= 0. 024) while in pairwise comparison just two groups (GSE 5% and SE 20%) had significant difference with each other (p= 0. 017). Conclusion: The efficacy of SE was reversely related to its concentration. Moreover, nei-ther GSE nor SE had significant effect on dentine Micro-hardness after 35 day pH cycling.

Current experimental investigation deals with the effects of asymmetrical rolling parameters on the inhomogeneity, Microstructure, mechanical, and geometrical properties of rolled brass wire. Toward this end, a roll machine with three different roll radii ratios was set up. The asymmetrical conditions are arranged using three different sets of rolls with different diameters that result into different reductions. Investigating the effects of the inhomogeneous structure of unrolled brass wire on the output radius, total width, and width of the rolled part (in the z direction) are the aim of this study. Furthermore, the influences of three unlike roll radius ratios on the grain size, inhomogeneity and mechanical properties of the rolled brass wire are considered. In addition, the Micro-Vickers measurements on the rolled brass wire are performed. It is shown that the regions near to faster roll with greater strain quantities have higher values of hardness compared to the other areas.

Background: This study investigated the effect of exposure of enamel surfaces to dried fruit suspension including dates, raisins, and dried apricot on their Microhardness changes. Methods: In this in vitro study, fifty enamel sections of bovine incisor teeth were mounted inside the acrylic resin so that the enamel surface would not be exposed to the acrylic. After surface polishing, the initial Micro-hardness was measured by a Vickers hardness-testing machine. The samples were randomly placed into five different solutions including apricot, raisin and date suspension, citric acid (positive control) or sorbitol (negative control), 5 times a day, each time for 5 minutes, and then in artificial saliva for 60 minutes. This process was repeated for 20 days. Eventually, the final Micro-hardness of the samples was measured. Micro-hardness changes between groups were compared through ANOVA and TUKEY test using SPSS 23 software with a significance level of P<0. 05. Results: After exposure, the Micro-hardness of the teeth was significantly reduced in all three suspensions prepared from dried fruit (P<0. 05). Apricot and date had the highest and lowest effects on reducing the Micro-hardness of teeth, respectively. Sorbitol solution did not have a significant effect on changing the Micro-hardness of teeth (P=0. 13). Conclusion: The suspension of studied fruits (apricot, raisin, date) causes a significant reduction in Micro-hardness of the dental enamel surface, indicating the negative effect of frequent consumption of dried fruits over long periods of time on dental health.