Micro-Tensile Bond Strength of a New Bioactive Cement to Lithium Disilicate and Hybrid Ceramics Before and After Thermocycling : In-Vitro Study /

Abstract

The use of dental ceramics has increased enormously due to the rising demands by patients for better appearance, leading to the development of metal-free restorations. Dental ceramics attain high esthetics qualities, color stability and good biocompatibility to the oral tissues. Yet, they are brittle, liable to fracture and they cause wear to the opposing enamel. On the other hand, resin composite restorations are soft, compliant and they do not cause wear to the opposing dentition. However, they are subjected to their own wear and discoloration over time. Researchers and recent advances have led to the discovery of new materials having the advantages of both dental ceramics and resin composites, known as hybrid ceramics, or also known as ceramic-reinforced polymer systems. These hybrid materials are believed to be of higher flexibility and better fracture toughness while retaining less brittleness, rigidity, and hardness than the original materials. Dental ceramics are classified into: Glass-matrix ceramics, Polycrystalline ceramics and resin-based ceramics. Glass ceramics include lithium disilicates (LDC) which are available in the form of ingots (heat pressed), and CAD/CAM blocks. Two main types of the hybrid ceramics are present in the dental market, polymer-infiltrated ceramic network material (PICN) and the resin nanoceramic (RNC) which is based on the nanotechnology. Resin nanoceramics include Cerasmart and Lava Ultimate. Ceramics are known for being brittle; this is why their long-term success depends mainly on adhesive cementation. Resin cements are the most commonly cements used with ceramic materials due to the combination of vitreous and crystalline phases structure of ceramic which allow for etching and provide excellent adhesion. Recently, bioactive cements have been introduced as an innovation in the field of dental cements. Activa BioActive cement is t considered to be an enhancement of the RMGI cement. It is composed of; a bioactive resin matrix, shock absorbing resin component and reactive glass fillers which have physical and chemical properties similar to natural teeth. Durable bonding between ceramic materials and the underlying cement is very important as it improves retention, fracture resistance, marginal adaptation and prevents any leakage or decay. Activa has a different mechanism for bonding than conventional cements. This has to be assessed and investigated by a number of physical and mechanical tests to conclude its properties as there are no enough studies about it. Our goal in this study was to evaluate the micro-tensile bond strength of the newly introduced Activa BioActive cement with LDC e.max and hybrid Cerasmart ceramics in comparison to the conventional resin cements before and after thermocycling.