Factors Affect The Strength Of Cerinate Heat-pressed Ceramic And Its Clinical Application

As patients have become more and more demanding regarding the aesthetic as a biocompatible aspects of their dental restorations, a material which the name is heat-pressing system for all-crown dentistry was developed by Wohlwend at the dental institute, Zurich University in the mid-1980s. The heat-pressing system is possible to achieve good marginal adaptation and accurate occlusal restoration relationships with ease, the elimination of opaque alumina or metal substructures aids excellent esthetics and ease to use.The ceramic materials for the heat-pressing system which is a leucite reinforced glass ceramic are suit for inlays, onlays, veneers and crown. But the possible applications for heat-pressing glass ceramic is limited by the limited strength and fracture toughness, the objective of currently study is to increase the flexural strength, reliability and to satisfy the clinical demands. The main purposes of this study were to process the leucite reinforced glass ceramics which use heat-pressing technique with different ceramic surface treatments and to evaluate the effect of the microstructure of the leucite reinforced glass ceramic with different ceramic surface treatments. PartIThe biaxial flexural strength of leucite reinforced glass ceramic which treated with polish treatment, oven-glaze treatment, ion-exchange treatment was tested, and compared the microstructure and compositions explored. The relative hardness and fracture roughness were determined by indentation technique. Part IIThe effect of different thickness and post and core restorations on the fracture resistance of molar crown which made by leucite reinforced glass ceramic firstly,and the fracture resistance of molar crown which made by leucite reinforced glass ceramic treated with ion-exchange treatment in different post and core restorations were tested. The conclusions were as follows:1. The biaxial flexural strength were increased by different ceramic surface treatments, the ion-exchange treatments with KNO3 can significantly increase the short term reliability of leucite reinforced glass ceramic in this test.2. It was found that the ion-exchange treatment in 450癈,llh were adequate increase the strength in this test.3. The relative hardness and fracture roughness were increased by different ceramic surface treatments, storage experiments in artificial saliva up to one month show no significant effect on the ion exchanged surfaces in this test.4.The ion-exchange treatment can increase the fracture resistance of molar crownmade by heat-pressing ceramic systems in this test. 5. It was advised to take the thickness into consideration, the final result ofheat-pressing ceramic systems were not affected when ceramic thickness wasmore than 1.5mm in this test. 6.There was Significant differences in heat-pressing ceramic systems in the meanfracture resistance of the teeth restored compared with metal abutmentsubstrates and resin abutment substrates in this test.7. There were no Significant difference among Cerinate, IPS-Empress and OPC all-ceramic systems in same thickness in this test.8. Crowns constructed in heat-pressing ceramic and place using resinous cement may provide some increase in fracture resistance in this test.