Experimental Study On Dental All-ceramic Restorative Technique Based On 3Y-TZP Framework

For most patients who suffered from tooth or teeth lose, inlay or crown (bridge) should be a good choice to restore dentin integrality and mastication function. At present, Porcelain-fused-to-metal restoration is still the first choice for these patients, unfortunately, the existence of metal brought up some problems, such as non-precious metal 'cervical loop', potential of corrosion, and risk of hazards to patients; even precious metal might cause some patients' hypersensitivity. All-ceramic restorations with outstanding esthetics and excellent biocompatibility can avoid these problems. On the other hand, traditional dental porcelain material is brittle and weak in strength, which is critical to wide-span bridges restorations, especially in the case of a posterior area, because mastication forces is much stronger in the molar region than that of front area. The long-term mechanical behavior is even more critical, since ceramics exhibit a time-dependent strength decrease. This phenomenon is caused by the so-called subcritical crack growth. Microscopic flaws that are statistically distributed in ceramic components can extend as cracks even with a low stress level. The more the microscopic cracks grow,the lower the strength of the ceramic material. So the major direction of research on dental porcelain was to enhance the strength and toughness.However, most of the present all-ceramic materials could not meet both the strength/toughness and aesthetics needs. Multi-lanina structure restorations were widely used to resolve such problems. High strength and toughness ceramics was applied for core structure, but their poor aesthetic propriety decided veneer lamina was need to cover the core structure and simulate the shade and translucency of natural teeth. Various porcelain and glass-ceramics restorations have been used for such aesthetic purpose. Thus there would always be a need for novel dental all-ceramic materials combining both aesthetics and high strength and toughness.Another problem trouble the crown-bridge restorative technique was the loss of patients' healthy tooth, because much healthy tissue was cut and wiped to pioneer enough place for the restorations to have enough strength resist the mastication force. Furthermore, tooth pulp and gingival tissue might also suffer. Inlay has the advantage to avoid such hazards due to less tooth loss during preparation.In former study, 3Y-TZP with high strength and toughness was manufactured. As framework made of 3Y-TZP might be used to support the exterior structure, so suitable superficial material that can be used to restore shape and shade of the retainers or pontics is needed. As zirconia sintered under certain procedure could show color similar to natural dentin, color match is not a problem. The aim of the current study was to choose suitable material which should contain enough glass phase to make it possible or easy to correct the shape of therestorations and get satisfying bonding effect with traditional bonding materials under routine bonding procedure.Three kinds of dental porcelain systems as Vita VMK95 dentin, Vita VMK95 dentin with opaque, Vita In-Ceram Alumina, Vitadur Alpha were sintered on the surface of presintered zirconia ceramic plate under respective procedure. SEM and Energy Distribution Spectrum were applied to evaluate the sintering properties of such interfaces. No satisfying result was obtained in Vita VMK95 opaque, Vita VMK95 dentin with opaque or Vita In-Ceram Alumina sintered on the Zirconia framework material under different sintering temperatures, while Vitadur Alpha and zirconia framework material could acquire good result. Furthermore, chemical combination between two laminae was confirmed by means of Energy Distribution Spectrum. The shear bond strength of 3YTZP-Vitadur Alpha dentin differed under different surface conditioning. The highest shear bond strength appeared in the group conditioned with water sand paper, shear bond strength of the group conditioned with sandblast was better than that of non-condition group, diam...