| Glass-ceramics are fine-grained polycrystalline materials based on suitable heat treatment and controlled crystallization. After heat treatment, the glass-ceramics can obtain high mechanical strength owing to the crystalline phase; also, due to a certain content of glass phase, the glass-ceramics show high translucent characteristic. Thus, in dental aesthetic restorations, glass-ceramics have the advantages of both glass and ceramic. The aim of the present study was to analyze the possibility of application of experimental glass-ceramic in heat-pressing technique and study the influence of heat-pressing technique on microstructure and properties of experimental glass-ceramic; The shear bond strength between experimental glass-ceramic and veneering ceramics and their susceptibility to thermocycling was investigated. We also analyzed the influence of different surface treatments on the bond strength and fabricated glass-ceramic blocks by appending the pigments with sintering technology.The whole studies were divided into three parts:Partâ… : The possibility of application of experimental glass-ceramics in dental heat-pressing technique1. The feasibility of processing experimental glass-ceramics with current dental heat-pressing equipments was verified and all-ceramic restoratives made with experimental lithium disilicate glass-ceramic showed good performances.2. The effect of heat-pressing technique on the crystalline phases and microstructure of experimental lithium disilicate glass-ceramics was studied. It was showed that dental heat-pressing had no influence on the crystalline composition. Li2Si2O5 represented the main crystalline phase before or after heat-pressing technique. After pressing, crystals aligned along the direction of pressing and glass-ceramics showed higher mechanical strength than these before heat pressing.3. The properties and microstructure of experimental glass-ceramics with different glass powder before and after pressing were compared. Results showed that grain size has a significant effect on the sintering behavior and mechanical properties of the experimental glass-ceramics both before and after heat pressing.Part two: the research on the bonding strength between experimental glass-ceramics and veneering ceramics4. The shear bonding strength between experimental glass-ceramic and veneering ceramics were investigated. No gap was found at the interface between experimental glass-ceramic core and veneering ceramic. And thermocycling had no significant effect on the bonding strength, indicated better long-term durability.5. The effect of different surface treatmentss on the bonding strength was evaluated. It was showed that different surface treatments had a significant effect on bond strength between experimental glass-ceramic and veneering ceramics. Polishing followed with sandblasting could achieve higher bond strength.Part three: the research on the coloration of experimental glass-ceramics 6. Three kinds of pigments with different concentrations were added into base glass powder, then subjected to heat treatment for developing glass- ceramics. Results demonstrated that colored glass-ceramics with good uniformity and color stability were achieved.7. To evaluate the effect of addition of different pigments on the microstructure and properties of experimental glass-ceramics. Results showed that crystalline composition, mechanical properties and microstructure of experimental glass-ceramics were not influenced by adding pigments.8. To investigate the effect of pigments concentration on the color values and to validate if the relationship between pigments concentration and reflective spectrums is suitable for computer color matching. The results indicated that adding three pigments had significant influence on value L, value a and value b, respectively. The relationship between pigments concentrations and chroma value met the principles of color characteristic, which could be regaded as database while establishing computer-color-matching software. |
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