A Review of Dental Cements

This review provides an in-depth comparison of advantages and disadvantages of different types of dental cements as they are used for cementing base metal alloy crowns in dogs.

Evaluation of effects of porcelain firing on the marginal fit changes of porcelain–fused-to -metal crown fabricated utilizing two different margin designs and two commercially available base metal alloys

Aim: To find the marginal fit of the porcelain fused to metal crowns by two different margin designs (shoulder and chamfer) and two commercially available base metal alloys.Material and Methods: Tooth preparation of first central incisor for porcelain-fused-to-metal crown with shoulder margin and second incisor for porcelain-fused-to-metal crown with chamfer margin was done. Wax pattern of the same was prepared. Impression of both prepared ivorine incisors was made by light body impression material and poured with pattern resin. Both the patterns were invested and casted with cobalt chromium alloy for making master dies. Two wax patterns of unprepared central incisors were fabricated, one with shoulder margin and another with chamfer margin. These patterns were then cut back to the size of the coping. Four rings were invested. In each ring ten patterns, five with shoulder margin and five with deep chamfer margin were sprued together to ensure that each group would pass through the same investing and casting procedure, followed by ceramic firing and measurement.Results: Marginal fit change or marginal discrepancy (before and after firing) between the groups was highly significant.Conclusions: Veneered crowns exhibited highly significant marginal distortion than non- veneered copings after porcelain firing. Shoulder margin is better in minimizing marginal discrepancy compared to deep chamfer margin. Marginal discrepancy is less when cerabond base metal alloy is used with shoulder margin as compared to commend base metal alloy used for shoulder margin.

Evaluation of the Effect of recasting Nickel–chromium Base Metal Alloy on the Metal–ceramic Bond Strength: An in vitro Study

ABSTRACT Aim The aim of this study was to evaluate the effect of recasting base metal alloy on the metal–ceramic bond strength. Materials and methods A total of 60 test samples were prepared from new and recast nickel–chromium alloy and divided into six groups. In group A0, test samples were prepared from 100% new alloy. Groups A1, A2, A3, A4, and A5 were prepared from 50% new alloy and 50% casting remnants (sprue and buttons) of the previous group by weight. All these samples were coated with ceramic (IPS d.SIGN and Ivoclar-Vivadent), and samples were then subjected to three-point bending test to evaluate metal–ceramic bond strength. Results The values were analyzed using one-way analysis of variance and Tukey's post hoc test. The mean bond strength of group A0 was higher than that of groups A1, A2, A3, A4, and A5. Conclusion Metal–ceramic bond strength decreased significantly with multiple recastings. Clinical significance Bond strength between metal and ceramic is a crucial factor for the clinical performance of metal–ceramic restorations. Recasting of alloys may affect the metal oxide layer composition and thickness of metal–ceramic interface, and thereby the metal–ceramic bond. How to cite this article Meenakshi T, Bharathi M, Komala J. Evaluation of the Effect of recasting Nickel–chromium Base Metal Alloy on the Metal–ceramic Bond Strength: An in vitro Study. J Contemp Dent Pract 2017;18(9):837-841.

Evaluation of the Influence of Various Sprue Designs on Surface Porosity and Dimensional Accuracy of Base Metal Alloy Castings - An In Vitro Study

Background and Objectives: Marginal fit of cast restoration is a major factor in long term survival of restoration. The sprue design is one of the variables that affect successful castings. Porosity can occur both on the surface and sub-surface of the casting. Base metal alloys have been used as an alternative to traditional high gold content alloys due to their superior mechanical properties.The purpose of this study was to evaluate and compare the influence of various sprue designs on surface porosity and dimensional accuracy with conventional sprue design on five-unit singlepiece base metal alloy castings. Materials and Method: A metal die that stimulate a five unit Fixed partial denture was fabricated. Three different types of sprue designs was assigned to the pattern and casted. The marginal discrepancy was determined by measuring the space between the margin of the crown and the shoulder finish line of the abutment using Scanning electronic Microscope(100X magnification). Surface porosity was evaluated using stereomicroscope (X10 Magnification). Results: Best marginal fit based on the grand means and standard deviations was in the conventional design group followed by experimental 4mm and 3mmsprue design. Significant differences was present in the 3mm sprue when compared with 4mm sprue(<0.001) as well as the conventional design(<0.001). Interpretation and Conclusion: There was no surface porosity observed under stereomicroscope. When marginal discrepancy was compared with conventional design, 4mm single sprue was more effective than the 3mm single sprue.