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A comparison on the flexural strength of a new dental porcelain (D.} Dentin) with Vita company Dentin porcelain (VMK 68N)
A. Ghahramanloo , A. Yossefl ,
Volume 17, Issue 1 (4-2004)
Abstract

Statement of Problem: Dental porcelain is one of the best materials ever used in dentistry. Excellent tissue compatibility, esthetics, very low solubility in oral fluids, high compressive strength, and the lowest bacterial plaque accumulation on the glazed porcelain are some of its advantages. Porcelain brittleness due to its low tensile strength, impact strength and the occlusal attrition of opposing teeth enamel are some of its disadvantages. The most important mechanical properties of dental porcelains are their flexural strength that is the ability of a porcelain to resist fracture when loaded from above. Different ways have been proposed to eliminate porcelain brittleness and develop its flexural strength, among which baking porcelain on a metal framework is more commonly used.
Purpose: Considering that restoration and replacement of teeth by porcelain fused to metal restorations is still the most commonly used technique, the aim of the present study was to measure the flexural strength of a porcelain bonded to metal powder, D4 Dentin, and to compare it with Vita Dentin powder.
Materials and Methods: In this experimental study, a stainless steel box, 25x5x2mm was made according to ISO 6872: 1995 (E) Standard and filled with D4 Dentin powder and Vita Dentin (VMK 68N) and baked in Vita furnace. Then 10 blocks of D^ Dentin and 10 of Vita Dentin were made. Samples were placed on the three point bending test machine and force was applied the middle of each block. To analyze the data, t- student test and co-variance analysis were used.
Results: Mean flexural strength of D4 Dentin was 53.40±1.35 MPa and that of Vita Dentin was 53.86+7.38 MPa. The difference was not statistically significant.

Conclusion: According to ISO 6872: 1995 (E) standard, the flexural strength of all D4 Dentin samples were greater than 50 Mpa.


Comparison of the marginal fit of different types of dental ceramic systems (In-vitro)
Gholamreza Esfahanizadeh, Mahmood Aghel, Saeed Mohammadi Asl, Elnaz Bayat,
Volume 30, Issue 4 (1-2018)
Abstract
Background and Aims: Marginal gap measurement in all ceramic restorations they are of fundamental important for the successful used. As some studies led to contradiction results, yhe aim of this study is to compare marginal gap restorations between 4 kinds of ceramic restorations Inceram, IPS-e.max Press, Zirconia (CAD/CAM) and PFM.
Materials and Methods: In this In-vitro experimental research, one stainless steel die with deep chamfer finish line design (1 mm depth) was prepared on a maxillary premolar. 40 epoxy resin dies were made, dies were divided in to 4 groups (n=10), Zirconia, IPS e.max press, Inceram, Mental Ceramic systems (MC). Then, the prepared crowns were put on the stainless steel die and observed their marginal mismatch under sterio microscope before cementation. Data were analyzed by One- way ANOVA, and one sample kolmogorosmirnov tests.
Resultes: There was significant difference in the marginal gaps between (MC) (102.92±28.7), Inceram (98.41±24.91), IPS e.max press (128.22±25.48), and Zirconia (69.5±10.9) (P=0.0001).
Conclusion: The comparison of marginal gap for the four groups was significant test. Therefore, it can be concluded that marginal gap, the probability of leakage and recurrence of caries in Zirconia systems is the least and in the IPS e.max press systems is the most.

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