Statement of Problem: Nowadays economical issues on high gold alloys have changed the practice of metal-ceramic restorations toward base-metal alloys. Minalux is one of the base-metal alloys produced in Iran. MARGINAL fitness is of high importance to be evaluated in dental alloys.Purpose: The aim of the present study was to compare the MARGINAL adaptation of two base-metal alloys, Minalux (Mavadkaran Co. Iran) and VeraBond2 (Albadent Co. USA ) during firing cycles of porcelain.Materials and Methods: In an experimental study 24 standard brass dies, with 135 chamfer finishing line were fabricated by Computer Numeric Controlled (CNC) milling machine. The samples were randomly divided in two groups, A and B, 12 in each. Following wax-up, the samples were equally cast with two mentioned alloys. In each group, there were 4 controlled samples, which proceeded to firing cycle without veneering porcelain. Scanning electron microscope (SEM) measurements of MARGINAL GAP from buccal and lingual aspects were performed after 4 stages of casting, degassing, porcelain application and glazing. The data were analyzed using Four-way ANOVA and multiple comparative tests based on Tukey criteria.Results: The findings of this study revealed that there was no significant difference in the MARGINAL GAP of Minalux (31.10±7.8 m) and VeraBond2 (30.27±6.96 m) with confidence level at 0.95 (P=0.43). For both alloys the greatest GAP was observed after degassing stage (P<0.05). Porcelain and porcelain veneering proximity caused significant changes in the MARGINAL GAP of Minalux castings (P<0.05), however, such changes did not occur in VeraBond2 (P<0.05).Conclusion: Based on the findings of this study, the MARGINAL GAPs of two base metal alloys, Minalux and VeraBond2, were proved to be identical and that of the Minalux alloy existed in the range of acceptable clinical application. It was also concluded that Minalux dental alloys could provide proper MARGINAL adaptation.

MARGINAL fit of restorations is important for longevity and periodontal health maintenance. The purpose of this study was to compare the MARGINAL fit adaptation of metal ceramic crowns in three different finish lines, fabricated with base metal alloys. 33 metallic dies were prepared in three groups of finish line: Shoulder 1350, Shoulder and Chisel. Dies were lubricated and wax patterns formed with use of a wax bath. Wax specimens were invested and cast with base metal alloy. After placement of porcelain on surface of castings, all crowns were luted with cement under a constant load. All specimens were then embedded in acrylic resin block and sectioned. The MARGINAL fit of the crowns were evaluated by measuring film thickness of cement in the margins. The differences between groups were evaluated with ANOVA and LSD test. Statistical difference between Shoulder and the other groups was significant (P<0.001). By considering discussed advantages of 1350 Shoulder finish line for metal-ceramic restorations, this finish line is recommended for metal ceramic restorations made from base metal alloys.

Background and Aim: An important criterion for success assessment of implant-supported prostheses is MARGINAL fit. Vertical and horizontal discrepancy can result in loosening of the prosthetic screw, crestal bone resorption, peri-implantitis and loss of osseointegration. Despite careful attention to waxing, investing, and casting, MARGINAL discrepancies are inevitable. The aim of this study was to evaluate the MARGINAL GAP and overhang in three casting methods with two different alloys in ITI implants.Materials and Methods: In this experimental in vitro study 48 analog abutments were randomly divided into six groups as follows: 1) burn out cap + BegoStar, 2) impression cap + BegoStar, 3) conventional wax up + BegoStar, 4) burn out cap + Verabond2, 5) impression cap + Verabond2, 6) conventional wax up + Verabond2. Waxing was done in 0.7 mm thickness verified by a digital gauge and a putty index was made for all groups. Reamer was used for correction of the finish line after casting in all groups. Castings were seated on analog abutments and embedded in acrylic resin. Specimens were sectioned by isomet instrument and polished and cleaned by ultrasonic cleaner for 10 min. The MARGINAL GAP and overextended margins of castings were examined under a Scanning Electron Microscope (SEM) (X200). The mean GAP and margin overextension were calculated for each group. Data were analyzed by multivariate analysis and Bonferroni post-hoc test with p<0.05 as the level of significance.Results: No significant difference in GAP size was observed among the three casting methods with two alloys (P=0.056). The MARGINAL GAP was not different in the studied casting methods (P=0.092). Gold alloy crowns showed lower MARGINAL GAPs compared to base metal alloy crowns (P<0.001). No significant difference in overhang size was observed among casting methods with two alloys (P=0.093). Base metal alloy crowns showed less overhang compared to gold alloy crowns (P<0.001). There was a significant correlation between overhang and use of impression cap in base metal alloys (P<0.001).Conclusion: Based on the results of this study, vertical discrepancy of frameworks made with gold alloy were less than those made with base metal alloy. Base metal alloy demonstrated fewer overhangs. Conventional wax up or using burn out caps produced less horizontal discrepancy.

Background and Aim: Metal ceramic restorations are widely used in crowns. The MARGINAL fitness of these artificial crowns is prone to alteration during the firing cycle of porcelain. Gold electroformed metal-ceramic restorations have been introduced as alternatives to conventional metal-ceramic restorations. However little is known about the relationship between procelain firing procedures and MARGINAL adaptation of this type of crown. The aim of the present study was to evaluate the influence of firing procedures on the MARGINAL adaptation of electroformed metal-ceramic crown restoration.Materials & Methods: One steel die was prepared for maxillary molar crowns with deep chamfer finishing line design. Ten standardized gold electroformed copings were fabricated. MARGINAL discrepancy was measured at four sites along the circumferential margin of each coping (Midbuccal - Midpalatal - Midmesial - Middistal) using SEM (Mag: X400) prior to and after porcelain firing procedure. Data among the 2 different groups (before porcelain firing) were statistically analyzed using the paired t-test (a=0.05) analysis.Results: The MARGINAL discrepancy of the postfiring procedures (21.45±2.27 mm) were significantly greater than those of the prefiring procedures (18.23±1.96 mm) (p<0.002).Conclusion: The porcelain-firing procedures influenced the MARGINAL distortion of electroformed metal-ceramic crown restorations, but the MARGINAL discrepancies for all copings and examined design are clinically acceptable (less than 100 mm).

Introduction: Dental porcelains have an important role in fabrication of the most beautiful restorations. Biocompatibility and translucency in ceramics make them one of the most agreeable restorative materials. Introduction of inceram system has been considered as a great change in the field of restoration. Inceram is made by two ways including Sprint technique and Conventional Method. The purpose of this study was comparing internal MARGINAL GAP in Sprint and conventional Alumina methods for making Inceram copings.Materials & Methods: In this in vitro study, 60-die resin-base with 6-millimeter length and 5-millimeter diameter in the cervical area were fabricated. They were prepared with a 10-degree, convergence angle and 1-millimeter shoulder width with 90-degree shoulder angle. The specimens were then divided into two groups. Next, in one 30-item group, the cores were prepared via Sprint method and in the other group, via conventional method (Alumina). After the cores were set, they were cemented by Panavia and for measuring the rate of internal GAP, the specimens were examined via optical microscope Olympus BH60 with 1-micron precision. The data were compared statistically by students t-tests (a=0.05). Results: Examining the mean internal GAP between two groups, it was revealed that the mean internal GAP in the Sprint group (181.6 microns) was greater than Alumina group (114.2 microns) and the difference was significant (P=0.015). Conclusion: Considering the limitations of this study, MARGINAL adaptation in Sprint method was less than conventional method of core fabricating (Alumina).

Background and Aims: One of the most important challenges for dentists is providing a crown with appropriate MARGINAL fit and GAP. The 135-degree tooth preparation found to have some advantages such as technical ease and appropriate finish line record. Despite the advantages of 135-degree tooth preparation, scant research has been done in this area. Therefore, the aim of this study was to compare 135-degree and deep chamfer tooth preparation on the MARGINAL fit and MARGINAL GAP of posterior metal-ceramic crowns. Materials and Methods: Deep chamfer and 135-degree tooth preparation were performed on the two first mandibular molars with healthy coronal tissue and similar size. Impression was taken from each tooth and 30 crowns were made on each die. The sample plastered with fit checkers were pressed under the force of 40 N for 3 min in a universal testing machine. They were measured and recorded under a loop with 40x power in three points on each aspect. Data were analyzed by Wilcoxon and Kolmogorov-Smirnov tests using SPSS version 24. Results: The mean MARGINAL fit values in deep chamfer and 135-degree were 48. 5417μ m and 55. 3333 μ m, respectively with no statistically significant difference (P>0. 05). While the mean MARGINAL GAP in deep chamfer (2. 4833 μ m) was significantly higher (P<0. 05) than 135-degree (1. 0083). Conclusion: It can be concluded that the MARGINAL GAP by 135-degree’ s tooth preparation was lower than that of deep chamfer in metal-ceramic crowns. However, no significant difference in the MARGINAL fit between the deep chamfer and 135-degree tooth preparation was found.

Background and purpose: One of the major challenges for dentists is providing the patients with a crown of appropriate MARGINAL fit and MARGINAL GAP. Preparation of a 135° finish line has some advantages such as technical ease and appropriate finish line record. Nevertheless, few studies investigated this type of finish line. The current study aimed at comparing MARGINAL fit and MARGINAL GAP in 135° finish line and shoulder bevel finish line. Materials and methods: In this quasi-experiment study, 135° finish line and shoulder bevel finish line were performed in two first mandibular molars with healthy coronal tissue and similar size. Impression was taken from each tooth and 31 crowns were made on each die. Samples plastered with fit checker were pressed under 40 N for three minutes in universal testing machine. They were measured and recorded under a loop with 40x power at three points on each side. To analyze the data, Wilcoxon and Kolmogorov-Smirnov tests were applied in SPSS V24. Results: Mean values for the MARGINAL fit in shoulder bevel and 135° finish line were 55. 0907 µ and 55. 2587 µ , respectively. The mean values for MARGINAL GAP were 19. 7245 µ and 0. 9745, respectively (P=0. 000). Conclusion: According to current study, a 135° finish line may have better clinical efficacy than a shoulder bevel.