Some properties of dental ceramics

The rather exacting aesthetic requirements of dental restorations has largely dictated the composition of dental ceramic materials. The so-called dental porcelains have evolved from the traditional whiteware formula of feldspar, clay and quartz. One of the first variables which might be considered is that of chemical composition. It is, however, generally accepted that for ceramic materials small variations in composition are not critical. Since the early work of Watts in 1918, little interest has been expressed in the chemical composition of dental porcelain. The composition of traditional dental porcelains has evolved over a period of many years by practical trial and error, as discussed by Jones (1971). The development of dental porcelains advanced to the point where any major improvements in physical properties could only be achieved by major changes in composition and technique as advocated by McLean & Hughes (1965). The resulting alumina/glass composites which have been developed use a technique which involves the build up of an inner core which contains a high proportion of crystalline alumina (45–50 %) embedded in a glass matrix surrounded by a transparent outer veneer. This work compares the effect of such inter-related variables as composition, inclusion of filler, viscosity, texture, hardness, and strength of the fired product.     

Effect of hydrothermal aging on the optical properties of precolored dental monolithic zirconia ceramics

Statement of problem

The long-term color stability of precolored monolithic zirconia has not been thoroughly investigated.

The strength of dental ceramics

Considerable changes have taken place in the range of ceramic materials available for dental use. Although the appearance of dental porcelain is good and biocompatibility excellent, its mechanical properties are somewhat limited. As a consequence, a number of distinct developments have taken place primarily to achieve greater strength; other goals having been to improve accuracy and simplification of production procedure. Progress has been made, but at the present time newer ceramics must still be regarded as complementary to established porcelains.     

Zirconia toughened mica glass ceramics for dental restorations: Wear,thermal, optical and cytocompatibility properties

BackgroundIn an effort to design novel zirconia reinforced mica glass ceramics for dental restorations, clinically relevant properties such as wear, coefficient of thermal expansion, optical transmittance, and cytocompatibility with human gingival fibroblast cell lines were investigated in the present study.Materials & MethodsMicrostructure analysis of two body wear of heat treated mica glass ceramic ceramics (47.2 SiO₂–16.7 Al₂O₃–9.5 K₂O–14.5 MgO–8.5 B₂O₃–6.3 F wt.%) reinforced with 20 wt.% YSZ, were evaluated against a steatite antagonist in a chewing simulator following Willytec Munich method. In addition, Coefficient of thermal expansion (CTE), total transmittance, scattering coefficient and cytocompatibility on human gingival fibroblast cell lines were performed and compared to the commercially available dental ceramic systems.ResultsThe experimental mica glass ceramic demonstrate micro-ploughing, pull out and debris formation along the cutting surface, indicating abrasive wear mechanism. Thermal expansion of mica glass ceramic composite was recorded as 5 × 10⁻⁶/°C, which is lower than the thermal expansion of commercially available core and veneering ceramics. Further, significant differences of transmittance and scattering coefficient of mica glass ceramics with 20 wt.% YSZ with commercial dental ceramics was found and extensive fibroblast cell spreading with filopodial extension, cell-to-cell bridges and proliferation with human gingival fibroblast cell lines.ConclusionWith acceptable cytocompatibility with human gingival fibroblast cells and better wear properties with respect to commercial IPS emax Press, the mica glass ceramic composites (47.2 SiO₂–16.7Al₂O₃–9.5 K₂O–14.5 MgO–8.5 B₂O₃–6.3 F wt.%) with 20 wt.% YSZ have the potential for dental restorative applications as machinable veneering ceramics.     

The importance of dental implants

Implant dentistry has evolved into the mainstream of restorative practices all over the world. Maintenance of bone after tooth loss to improve or maintain facial esthetics and improved retention, function, and performance of removable restorations are only some of the advantages for the edentulous patient. No longer are implants considered only when traditional restorations cannot be fabricated. Evidence-based reports indicate implant restorations last longer than those on teeth and the abutment teeth are at less risk of loss or complication.     

微观结构和组成对牙科全瓷材料光学性能的影响

全瓷修复体因具有良好的美观效果,在临床中得以广泛应用.全瓷材料的光学性能是影响修复体再现天然牙色泽和半透明性的主要因素之一,材料的微观结构和组成决定了其光学性能.本文就牙科全瓷材料光学性能的特点和重要性,微观结构和组成对全瓷材料半透明性的影响以及着色剂元素的原子结构和组成对牙科全瓷材料颜色的影响作一综述.     

牙科着色氧化钇稳定四方多晶氧化锆陶瓷的制备及颜色性能

目的添加不同着色剂组合配制着色的牙科氧化钇稳定四方多晶氧化锆（3Y-TZP）陶瓷,并测定其颜色性能。方法将TZ-3Y-S粉体与一定组分的着色剂球磨混合后,在200 MPa压力下等静压成型,在1 500 ℃烧结2 h,烧制5种具有一定颜色的氧化锆材料,每个颜色组分别制备10 mm×10 mm×0.5 mm和10 mm×10 mm×1 mm着色氧化锆陶瓷片,在黑色背景下用柯尼卡美能达CM-2600d分光光度计进行颜色测定,并与VITA In-Ceram YZ染色液比色板颜色作比较。结果通过对粉体进行着色,配制出具有一定颜色的本体着色氧化锆陶瓷材料,颜色明度逐级降低,饱和度逐渐增大,2种厚度3Y-TZP陶瓷的颜色片色差较小,颜色空间范围是L*：67.76～77.78;a*：-2.19～3.80;b*：12.13～25.01。与VITA In-Ceram YZ染色液比色板相比,颜色空间近似,但明度的最低值仍较高。结论着色氧化锆陶瓷材料适宜用于临床上与饰面瓷颜色匹配,有必要再进一步研究低明度的着色氧化锆色片。