تصفح هذه الورقة الالكترونية بتقنية Media To Flash Paper
The influence of water storage and soldering on types of failure (adhesive and cohesive) in porcelain fused to metal samples.(An invitro study)Ahmed G mehdi
ABSTRACT:Background:Failure of bonding between porcelain and metal is not uncommon problem in porcelain fused to metal restorations, since the bonding process between metal and porcelain is complex, critical and need great attention to all details mentioned in the literatures according to authors.Materials and Methods:Forty cylindrical metal (Ni-Cr alloy) specimens were prepared; 8 mm in diameter and 3 mm in height. 20 of these specimens were made in such a way so that it has perforation in the center of 1mm in diameter; the later group is then soldered. All the samples were oxidized, and then sandblasted with aluminum oxide. The ceramic material (vita VMK 95) was applied, the final thickness of ceramic was about 1.5 mm, and then the samples was finished and glazed. 10 of the soldered and 10 of non soldered samples were stored in distilled water for one week, and then shear test was applied for all samples. After the testing, all samples were inspected visually and microscopically to detect the nature of failure.Results and Conclusion:The result revealed that the non soldered groups have higher percentage of cohesive failure than soldered groups which has higher percentage of adhesive failure, and there is no influence of the water storage on the nature of failure. Key words: Soldering, Porcelain fused to metal, shear bond test, cohesive and adhesive failure. INTRODUCTION:Adhesion or bonding is the process of forming an adhesive joint. The initial substrate is called the adherend, whereas the material producing the interface is generally called the adhesive. If two substrates are being joined, the adhesive produces two interfaces as part of the adhesive joint. In dentistry, most adhesive joints involve two interfaces (1). Ceramic-metal restorations consist of a cast metallic framework (or core) on which at least two layers of ceramic are baked. The first layer applied is the opaque layer, consisting of ceramic, rich in opacifying oxides; its role is to mask the darkness of the oxidized metal framework to achieve adequate esthetics. As the first layer, it also provides ceramic-metal bond. (2) The formation of a strong bond between the opaque porcelain layer and the cast alloy is essential for the longevity of the metal-ceramic restoration. The tensile strength of the metal-ceramic bond should exceed 28
- وصف الــ Tags لهذا الموضوع
- ceramic failure, adhesive failure, cohesive failure
|