Background and Aim: There are several factors which play an important role in the retention of resin bonded retainers (RBRs) such as prothesis design, type of alloy and thickness of retainers. The purpose of this study was to compare the retention of wings made up of Vera bond, super cast and Ticonium alloys.Materials and Methods: In this experimental study, the samples consisted of fifteen RBR made on 15 metal central incisors and canines (mounted with a distance equal to a lateral incisor tooth) on an acrylic block. The samples were divided into three groups of five with retainers with thicknesses of 0.2mm consisting of three different alloys; namely, Vera bond, super cast and Ticonium. They were cemented with resin cement panavia F. Samples were then placed in instron machine for determining the force needed to separate the retainers. Data were analyzed by one way ANOVA test.Results: Vera bond wings had a tensile bond strength of 35.2440 Kgf; whereas supercast and Ticonium had a tensile bond strength of 24.8520 Kgf and 21.0860 Kgf, respectively.Conclusion: Results showed that the mean retention of RBRs with wings made up of Vera bond alloy was significantly higher than that of super cast and Ticonium. In addition, the difference between the mean retention of wings made up of super cast and Ticonium was not statistically different.

The purpose of this study was to investigate the effect of heat treatment including solution treatment and aging on the microstructure of cast nickel-based IN100 super alloy including size, volume fraction and morphology of primary g' and different kinds of carbides. For this purpose, different solution heat treatment cycles and a constant aging cycle were implemented on cast ingot samples and the microstructure of the samples were analyzed by scanning electron microscopy and optical microscopy. It was found that, the alloy in the full + partial + aging treated condition had the optimal combination of g′ morphology, volume fraction and size. In this condition, the alloy possesses a cubic primary g′ with 45% volume fraction which is a significant increase as compared to other cycles. Discrete M23C6 carbides were formed at the grain boundaries and the morphology of the cubic MC carbide was changed to the spherical shape.

Introduction: Regarding the use of nickel-chromium (Ni-Cr) alloy in porcelain-fused to metal-restorations and the need for high temperature for porcelain firing, there are probable alterations in the microstructure of the alloy, the corrosion resistance, and the rate of ion release. The aim of the present study was to evaluate the effect of multiple firings on the corrosion resistance and surface characteristics of two Ni-Cr alloys. Materials and Methods: In total, 24 discs were made from each Ni-Cr alloys without beryllium (Dam cast) and with beryllium (super cast). They were then assigned into four subgroups based on the number of firings: (1) without firing, (2) four times firing, (3) four times firing and a correctional firing, and (4) four times firing and two correctional firings. The corrosion resistance was evaluated using an electrochemical potentiostat device. The ions release was measured after immersing samples in Fusayama artificial saliva (pH of 5, at 37 ◦ c) for 30 days by ICP-AES technique. The surface of the alloys was evaluated with a metallurgical light microscope and scanning electron microscope. Data were analyzed in SPSS software. P-value less than 0. 05 was considered statistically significant. Results: According to the results, the impedance of both alloys decreased significantly with increasing the frequency of firings. A significant decrease was observed in the impedance and corrosion resistance of super cast alloy using correctional firings (the third and fourth firings), compared to Porcelain firing samples. However, no significant decrease was observed in Dam cast. In addition, the number of released ions was significantly increased with an increase in the number of firings in both alloys. Nevertheless, there was no difference between the alloys regarding the released ions. The concentration of released ions was higher in super cast alloy, compared to that in DAM cast. Increased levels of corrosion were observed on the surface of super cast alloys using a microscopic evaluation. Conclusion: Multiple firings had lower effects on the corrosion resistance of Dam cast alloy without beryllium, compared to super cast alloy with beryllium.

Introduction: Researches about conventional soldering of base metal alloys have shown that they are unpredictable and too technique sensitive. The objective of this study was the introduction of cast to technique (casting for second time) and comparison of its flexural strength with conventional soldering.Materials & Methods: In this experimental in vitro study, 30 cylindrical metal patterns with 60mm length and 3mm diameter from base metal alloy "super cast" were prepared. Each was divided into two identical 30mm components by Cr-Co disc and subgrouped into two equal groups (N=30). In the first group, samples were placed on a plaster index with an interplaster distance of 0.3mm. Then this distance was filled with duralay acryl, and soldering process was accomplished on these 15 samples. In the second group, after creating an appropriate undercut at the end of each sample, specimens were attached with Duralay, a 10 gauge sprue with 12mm length was attached in the center of all samples and again the samples were burnout and cast with super cast alloy again. 3 point flexure test with zwick instron testing machine was accomplished and data were analyzed with F & T tests.Results: The flexure strength comparison of conventional soldering and cast to technique showed that there was no statistical difference between them. According to coefficient of variation, dispersive investigation of flexure strength for both groups was accomplished and showed that in soldering group, it was 1.5 times greater than cast to group.Conclusion: This study showed that flexural strength of cast to technique was comparable with conventional soldering. However, the results of cast to technique were more predictable than those of conventional soldering.

Introduction: The formation of oxides on the surface of the metal is proven to contribute to the formation of strong bonding. However, the base metal alloys are expected to exhibit more oxidation than high gold alloys, increase in oxide layer thickness due to repeated firing in them can reduce the bond strength. Objective: The aim of this study was to compare the effect of porcelain firing on the bond strength of two base metal allays (Iranian super cast and original super cast) The cast of original alloy is more expensive that Iranian one and there was no Comparison between the bond strength of these two alloys.Material & Methods: A sample from both alloys with dimensions of 24´6´0.5 was obtained and applied on the middle one third of metal plates and there tested in a instrun 1195 machine and data were analyzed with student t test (P≤0.05)Result : The mean of bond strength Iranian super cast was 13 N and original was 13.13 N. That results showed no significant differences between bonds and (P=0.651) both alloys passed the ISO 9693 exam.

Background: Different soldering techniques have a variety of applications in dentistry. One of the most important uses of soldering is to join multiple-unit fixed partial dentures together. In this Study, two base metal alloys (supercast and Minalux) were soldered and their tensile, compressive and flexural strengths were measured and compared to each other. Materials and methods: In this in-vitro study, an aluminum pattern was made by a milling machine according to ASTM (American Society for Testing Material). Eighteen acrylic resin Patterns were duplicated by flasking using putty indices according to the original aluminum pattern. Acrylic resin patterns were divided into two groups of nine and each group was cast with two different alloys named supercast and Minalux. All eighteen metal rods were separated by 0. 008-inch disc and soldered with Vera-solder by means of gas-oxygen torch. Three patterns of each alloy were selected for each of the compression, tensile and flexural tests. Tensile strength was measured by Instron a universal machine and flexural and compression strengths were measured by Dartec machine. Statistical analysis was done by Mann-Whitney test. Results: The mean tensile, flexural and compressive strengths for supercast alloy was 347. 6, 44. 01 and 1014. 8MPa respectively and the mean for tensile, flexural and compressive strengths for Minalux alloy was 350. 03, 51. 70 and 938. 17 MPa respectively. Statistical analysis showed no significant differences between the two alloys in all the three mentioned tests. (p>0. 05) Conclusion: Tensile, flexural and compressive strengths of the two soldered alloys, Minalux and supercast, showed no significant differences. Minalux is an alloy manufactured in Iran with the advantage of not including Beryllium, a cariogenic element, as one of the ingredients of the alloy; therefore, it is suggested that Minalux be used instead of supercast in soldering procedures in fixed prosthodontics.

In May 2005 on some branches of Pinus eldarica collected in Tehran showed to be infested with Buprestid larvae. The infested branches put in rearing boxes for emergence of adult beetles. The adults emerged on early July proved to be chrysobothris solieri. It is the first record of this species from Iran. Among chrysobothris larvae are observed speciemens parasitized with two following parasitic wasps that identified by J. Macek from Prague museum of Hungary. 1- Liotryphon sp. (Hym.: Ichneumonidae)2- Hockeria sp. (Hym.: Chalcididae)

Statement of Problem: Ceramics and resins belong to the earliest tooth restorative materials. Nowadays new generations of these materials have provided a revolution in cosmetic dentistry. Ceramic Optimized polymer (Ceromer) is a newly made product that the bond between this material and base metal alloys, which are used widely today, is paid too much attention.Purpose: The aim of this study was to evaluate the bond strength of targis (Ceromer) to three types of base metal alloys through three different surface treatment methods.Materials and Methods: In this experimental study, ninety plates of Rexillium III, Silver cast and super cast alloys (30 5 0.4) were prepared and surface treated through three different methods (air oxidation, vaccum oxidation and sandblast). All samples were then veneered with 1.mm thickness of Targis. After thermocycling, three-point bending test was performed by universal testing machine (Instron) to evaluate the amount of forces at crack or fracture times in Targis. The type of failure (cohesive or adhesive) was also evaluated microscopically. Statistical analyses were made using 2-factor ANOVA and Duncan tests.Results: The type of surface treatment method caused a statistically significant difference in force rate required for crack and fracture in Targis. Sandblasting was found as the best method. The type of alloys, in all three methods, had a significant effect just on crack creation attributing the largest amount of force to Rexillium III. Adhesive type of failure occurred mostly in super-cast alloys through air-oxidation method, and cohesive type was more among silver cast alloys and sandblast method.Conclusion: According to the results of this study, bond strength between Ceromer materials and base metal alloys is significantly great and Rexillium III alloy associated with sandblast technique the best combination.

Background and Aim: In order to improve the retention and stability of the mandibular removable prosthesis with distal extension, it is usually required to make a secondary impression (the altered cast impression). This study was designed to clinically evaluate the conventional method of altered cast technique with modified altered cast technique. Materials and Methods: This prospective experimental study was conducted with 15 patients. They were treated with two methods of conventional and modified altered cast techniques. Following an oral examination, a questionnaire was used to collect clinical information on the occurrence of ulceration on the ridge, denture border areas, buccal shelf and retromolar pad areas, as well as the sufficiency of denture base extension. Patients were followed up 24 hours and one week after using the partial dentures. In conventional altered cast impression technique, it is required to dissect the casts and form the impression boxing in order to make sure that the master cast is properly registering the distal extension ridge anatomical features. Separation of the edentulous portion from the master cast is eliminated in the modified altered cast impression technique. This makes it more efficient, convenient for patient and less time consuming procedure. The X2 and fisher’s exact tests were used to detect significant levels. Results: The percent of ulceration on the ridge, denture border areas, and buccal shelf as well as the retromolar pad areas were lower in modified altered cast impression technique compared with the conventional altered cast impression method. The percentage of the denture base extension in the modified altered cast impression technique was better than the conventional altered cast impression method. The extension of denture base in distolingual areas of modified altered cast impression technique was the same as the conventional altered cast technique. The difference between the two procedures was not statistically significant. Conclusion: The modified alerted cast technique can result in saving time, increasing the patient’s satisfaction and comfort, which makes it the recommendable procedure for making removable partial dentures with distal extensions.