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Introduction: Metals are widely used in direct and indirect restorative materials, both in prosthetics and orthodontics. The biocompatibility of these metals depends on their chemical nature, the number of ions released, and the period of contact of these metals. This study aims to compare two different electropolish temperatures on the release of cobalt ion from chromium-cobalt alloy. Materials & Methods: In this experimental study, 24 wax patterns were cut in the form of a circle with a diameter of 15 mm and a thickness of 1 mm. Then, the samples were sprued and invested. Burn out and casting were used to cast the alloy. The samples were sandblasted and polished with aluminum oxide. They were randomly divided into two 12-number groups and electropolished at 45° and 55° C. Samples were placed in artificial saliva and sent to atomic absorption spectrophotometer for 15 and 30 days to read the cobalt. Data were then analyzed by Independent t-test and Paired t-test (p value = 0.05). Results: The average release of cobalt from chromium cobalt alloy on the 30th day was higher than the 15th day at both 45°C and 55°C. This difference was significant at 45°C (p value = 0.036) while not significant at 55°C (p value = 0.0754). Regarding the comparison of the ion release at 45° and 55°C, the difference was not significant on the 15th day (p value = 0.067) and 30th day (p value = 0.0754). Conclusion: The amount of cobalt ions released from the cobalt-chromium alloy at 45°C is fewer than at 55°C over time. [ABSTRACT FROM AUTHOR]

Background and Aims: All metal components of orthodontic appliances are somewhat corroded in the oral environment due to some changes in chemical, mechanical, thermal, microbiological and enzymatic factors which facilitates ion release. Ionic release can result in a discoloration of the surrounding soft tissue or allergic reactions in sensitive patients or even local pain in the area. In general, ions can cause toxic and biological side effects if their values reach the threshold, so the release of ions from the metal components of orthodontic appliances is important to us. The aim of this review article to determine the rate of orthodontic appliances ion release in different solutions. Materials and Methods: A review of the literature was carried out in Pubmed, Google Scholare and Web of science database using selected key words (Saliva/ Titanium/Normal Saline/ Ion release Orthodontic appliance/ Mouth wash/ Nickel/ Chromium). These searches were limited to the articles published from 2005 to 2018. According to the inclusion and exclusion criteria, 25 articles were obtained. Results: Because of conflicts in the reported results, it was necessary to synchronize the measurement methods and also to use artificial saliva medium with normal pH as a control to achieve better systematic comparison. Conclusions: There was significant differences in the ion release between mouthwashes. In all studies, the effect of pH and acidity has been shown to increase the release of these ions. In addition, stainless steel (SS) instruments had the least biocompatibility among all types of alloys evaluated. [ABSTRACT FROM AUTHOR]

Background and Aims: The aim of this study was to evaluate the effects of two fluoride containing mouth rinses on the color stability of two different resin composites. Materials and Methods: 27 specimens (2×4×5 mm) were prepared from each of the following materials: a micro filled composite (Gradia, GC) and nanohybrid (Grandio). The specimens were polished by Soflex fine and superfine disks and then incubated in artificial saliva at 37°C for 24 h. The baseline color values (L, a, b) of each specimen were measured using an Easyshade spectrophotometer according to the CIELab color scale. The specimens were immersed in 20 mL of each mouth rinse and stored in an incubator at 37°C for 12 h. After incubation, the color values of all specimens were measured again, and the color change value (ΔE) was calculated. Data were analyzed by a 2-way analysis of variance at a significance level of 0.05. Results: None of the mouth rinses created clinical significant color changes in the samples. There was no statistically significant difference among color susceptibility between resin composites (P=0.330). The interaction between the effect of mouth rinses and type of restorative materials was not statistically significant (P>0.05). Conclusion: Accordance to the results of this study, the fluoride containing mouth rinses does not create color change in resin composites. [ABSTRACT FROM AUTHOR]

Background and Aims: The aim of this study was to evaluate the effects of two fluoride containing mouth rinses on the color stability of two different resin composites. Materials and Methods: 27 specimens (2×4×5 mm) were prepared from each of the following materials: a micro filled composite (Gradia, GC) and nanohybrid (Grandio). The specimens were polished by Soflex fine and superfine disks and then incubated in artificial saliva at 37°C for 24 h. The baseline color values (L, a, b) of each specimen were measured using an Easyshade spectrophotometer according to the CIELab color scale. The specimens were immersed in 20 mL of each mouth rinse and stored in an incubator at 37°C for 12 h. After incubation, the color values of all specimens were measured again, and the color change value (ΔE) was calculated. Data were analyzed by a 2-way analysis of variance at a significance level of 0.05. Results: None of the mouth rinses created clinical significant color changes in the samples. There was no statistically significant difference among color susceptibility between resin composites (P=0.330). The interaction between the effect of mouth rinses and type of restorative materials was not statistically significant (P>0.05). Conclusion: Accordance to the results of this study, the fluoride containing mouth rinses does not create color change in resin composites. [ABSTRACT FROM AUTHOR]

AbstractIntroduction: Toxicity of dental alloys depends on their composition and element release, which may, in turn, be affected by re-casting of the alloy. The aim of this study was to evaluate the effect of re-casting on the release of elements from Verabond base metal alloy.Materials and Methods: In this laboratory study Verabond base metal alloy was evaluated. At first cubic wax patterns measuring 11×13×1.4 mm were prepared. Then alloy disks were cast as follows: 100% new alloy; 50% new with 50% re-cast alloy; and 100% re-cast alloy. Each alloy specimen was finished and polished under simulated clinical conditions and sterilized in an autoclave. Each specimen was conditioned in artificial saliva at 37°C for 72 hours. The specimens were retrieved from artificial saliva and release of elements from the alloys was investigated by Atomic Absorption Spectrophotometry. Data was analyzed by one-way ANOVA and a post hoc Tukey test (α = 0.05).Results: ANOVA revealed significant differences between the cast and re-cast Verabond groups; release of titanium, nickel, aluminum and chloride were respectively higher in recast alloys compared to cast alloys (p value < 0.05). The amounts of Be, Mo, Co were not quantified by spectrophotometry due to their low concentrations.Conclusion: Based on the results of the present study, re-casting of alloys significantly increases the release of elements. Therefore, re-casting of alloys should be avoided. Key words: Artificial saliva, Atomic Emission spectrophotometry, Dental casting alloy.

Introduction: Bonding orthodontic attachments to large amalgam restorations of posterior teeth is a challenge. The aim of this study was to evaluate and compare the shear bond strength (SBS) of orthodontic attachments bonded to amalgam with different chemical surface preparations.Materials and methods: In this in vitro study 105 convex amalgam surface samples were subjected to aluminium oxide sandblasting. The amalgam sampless were randomly divided into three equal groups. In each group buccal tubes were bonded with Transbond Plus using Reliance Metal Primer (RMP), All Bond II (AB2), and Alloy Primer (AP). Thirty-five human teeth served as the controls to test buccal tube bonding to acid-etched enamel with Transbond Plus and Transbond XT. All the samples were stored in artificial saliva; after thermocycling for 1000 times, all the sampels were tested for SBS. Data were analysed with Kruskal-Wallis and Mann-Whitney tests.Results: There were statistically significant differences in SBS values between all the groups (p value < 0.001). AB2 created the strongest bond to amalgam (6.75 MPa). However, there were no significant differences between SBS values achieved with AB2 and those in the control group (p value = 0.455). No Significant differences were observed between AP and RMP (p value = 0.051) but both had significant differences with the control group (p value < 0.001).Conclusion: The results of the present study revealed that AB2 intermediate resin is useful for strong bonding of metal orthodontic attachments to dental amalgam.Key words: Acrylic resin, Artificial saliva, Dental amalgam, Shear bond strength.

Wear characteristics of dental amalgams were investigated by in vivo and in vitro tests. Wear"nof dental amalgam was studied and evaluated using a three - body abrasion test and Pin-On-Disk"nmethod. Porcelain was used for preparing disk and materials such as toothpaste, artificial saliva and"nnaturally saliva were used as the third material that was contributed in tribologic system"nThe results showed that effects of various toothpastes on the wear of dental amalgam are considerably"ndifferent and size, shape and chemical composition of amalgam are important too.