Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins has an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful results. In this study the shear bond strength (SBS) between targis (a ceromer) and two ALLOYS (noble and BASE metal) was studied and the effect of thermocycling on the bond investigated. Materials and Methods: In this experimental study, ALLOYS samples were prepared according to the manufacturer. After sandblasting of bonding surfaces with 50µ AI2o3 Targis was bonded to the alloy using Targis I link. All of the samples were placed in 37°C water for a period of 24 hours. Then half of the samples were subjected to 1000 cycles of thermocycling at temperatures of 5°C and 55°C. Planear shear test was used to test the bond strength in the Instron machine with the speed rate of 0.5mm/min. Data were analyzed by SPSS software. Two-way analysis of variance was used to compare the bond strength among the groups. T test was used to compare the ALLOYS. The influence of thermocycling and alloy type on bond strength was studied using Mann Whitney test. P<0.05 was considered as the limit of significance.Result: The studied ALLOYS did not differ significantly, when the samples were not thermocycled (P=0.136) but after thermocycling a significant difference was observed in SBS of resin to different ALLOYS (P=000.1). Thermal stress and alloy type had significant interaction, with regard to shear bond strength (P=0.003). There was a significant difference in SBS before and after thermocycling in noble ALLOYS (P=0.009), but this was not true in BASE metals (P=0.29). Maximum SBS (19.09 Mpa) belonged to Degubond 4, before thermocycling. Minimum SBS (8.21 Mpa) was seen in Degubond 4 after thermocycling. Conclusion: The effect of thermocycling in reducing bond strength of resin to metal depends on the type of alloy. The noble metal studied is significantly affected by thermal tensions.

Statement of Problem: One of the greatest problems in metal –ceramic restorations is debonding of porcelain from dental ALLOYS. Production of dental ALLOYS by Iranian companies necessitates the evaluation of physical and handling properties of these products. Purpose: In this study the bond strength between porcelain and two types of BASE metal ALLOYS, Supercast (with beryllium) and Minalux (without beryllium) was investigated. Materials and Methods: In this experimental study 10 cylindric bars from each BASE metal alloy were prepared. The bars were degassed and porcelain was applied around them in a disc form (8 mm diameter and 2 mm thickness). The bond strength of porcelain to metal bars was tested with the shear strength test by Instron. Data were analyzed with student t-test and P<0.05 was considered as the limit of significance. Results: The mean failure load was 71.58±6.4 KgF for Supercast and 67.34±5.48 for Minalux alloy. The bond strength of Supercast and Minalux were 55.85±4.99 MPa and 52.54±4.27 MPa respectively. The difference was statistically significant (P<0.001). Conclusions: This study showed that nickel-chromium-beryllium alloy (Supercast) produced significantly better ceramometal bonding than nickel chromium alloy without beryllium (Minalux).

Introduction: Color matching, visual combination and accurate shade selection with natural teeth are important issues in restorative dentistry. In ceramometal restorations, the type of substructure alloy affects the final color of bonded porcelain. Minalux alloy, is the most commonly used Iranian product which is a BASE metal alloy (Ni-Cr). The aim of this study is to compare the effect of three BASE metal ALLOYS (Wirron 99, Bellabond and Minalux) on their masking of porcelain color and to assess various color dimentions between them. Material & Methods: In this in vitro study, ten disks, approximately 0.3 mm thick and 1 cm diameter, were prepared from each alloy. Then a 1 mm thickness layer of vita VMK68 porcelain shade A2 was baked onto them, following the manufacture's instruction. Ten samples with 5 mm thickness were prepared from the same porcelain and designated the "control group". All samples, with similartining and in similar conditions of environmental light were assessed by a computer colorimetry instrument; and color values such as l*, a* and b* under CLE-LAB system were measured. The data were analyzed by one-way-Anova and Tukey tests. Results: Three ALLOYS in this study as compared with the control group, had significant effect on the three variables l*, a* and b* (respectively P=0.004, P=0.037, P<0.001). In these ALLOYS, Wirron 99 and Bellabond, had significant difference on the two variables l* (P-value=0.025) and a* (P-value=0.037); but Minalux alloy did not have any significant difference with other groups. The comparison between the average of ΔE quantities ALLOYS, indicated that the difference of Vita porcelain shade A2 baked on Wirron 99 and Bellabond was significant.Conclusion: The effect of Iranian minalux alloy on color's parts and it's related ΔE quantity, is in a similar range of two foreign alloy products Wirron 99 and Bellabond.

Statement of the Problem: The success of metal-ceramic restorations depends on the bond strength between porcelain and alloy. These restorations can be fabricated through different casting and computer-aided design/computer-aided manufacturing (CAD/CAM) techniques. Purpose: This study aimed to compare the bond strength of porcelain to milled sintered (Sintron) and casting (Co-Cr and Ni-Cr) BASE metal ALLOYS. Materials and Method: In this in vitro experimental study, 63 rectangular bars (25×3×0. 5 mm) were fabricated of three BASE metal ALLOYS: casting Ni-Cr, casting Co-Cr, and milled sintered Co-Cr alloy. Feldspathic porcelain (3×8 mm) was applied at the center of each bar with 1. 5 mm thickness. The specimens were thermally aged. Bond strength was evaluated through three-point flexural test. Failure mode was evaluated by optical and electron micro-scope. Data were analyzed with one-way ANOVA and Tukey's post hoc test (α =0. 05). Results: The mean flexural bond strength of porcelain to milled sintered Co-Cr alloy (24. 58± 5. 16 MPa) was significantly higher than that of casting Ni-Cr (21. 13± 6. 34 MPa) (p= 0. 03) and casting Co-Cr (20. 98± 4. 84 MPa) ALLOYS (p= 0. 04). However, the two casting ALLOYS were not significantly different in this regard (p= 0. 93). The failure mode in all specimens was of cohesive type. Conclusion: Bond strength of CAD/CAM milled sintered Co-Cr alloy was better than that of the conventional casting ALLOYS and could serve as a suitable alternative to those ALLOYS.

Both ZIRCONIUM-BASEd ALLOYS and 321 stainless steel are widely used as engineering ALLOYS due to their good mechanical properties. Conventional fusion welding techniques for Zr ALLOYS and stainless steel are not feasible due to the formation of brittle intermetallic compounds such as (Zr3Fe, ZrFe2 and Zr2Fe) and corrosion cracking. Brazing is one of the most widely used techniques for joining dissimilar ALLOYS.Using titanium BASE filler metal decreases the diffusion and the formation of brittle intermetallic compounds. In this study, wetting experiments were done at 820, 850, 865oC and 3, 5, 7 and 10 min. Also, joining of these two ALLOYS was carried out at 850 and 865oC for 10 and 15 minutes. Optical microscope, scanning electron microscope (SEM), XRD, shear test and micro-hardness test were used for metallurgical and mechanical investigations. The results show that 20oC/min heating and cooling rates at 850oC and 10 min brazing condition lead to a proper joint without any brittle intermetallic compounds.

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.

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. The aim of this study was to compare the effect of repeated porcelain firing on the bond strength of two BASE metal ALLOYS (Minalux and Verabond II). Sixteen metal plates (20 5 0.5) from each alloy were cast and prepared according to the manufacturers instruction. Porcelain with uniform thickness (1mm) was applied on the middle one third of metal plates. After this stage, each alloy group divided to three subgroups. Group I was fired for the second time to form the final glaze, group II and III were fired two and four more times respectively. Specimens were subjected to 3-point flexural test in a digital tritest machine. Results showed no significant differences between bond strength of two ALLOYS. Also results showed repeated firing had no significant effect on bond strength. Due to these findings, this study support similarity of two ALLOYS (Minalux and Verabond II) in their bond strength with porcelain.