制备高性能氧化锆陶瓷牙科修复体的初步研究

目的 :本文对以氧化钇稳定四方相氧化锆 (Y -TZP)纳米微粉为原料 ,经部分烧结 -牙科计算机辅助设计/计算机辅助制造系统 (CAD/CAM)加工 -完全烧结三步法制备高性能的牙科修复体的工艺路线进行了初步探索。方法 :先经模压成型 ,低温烧结 ,制作了可供CAD/CAM加工的部分烧结Y -TZP陶瓷块 ;然后经牙科CAD/CAM机加工 ,得到初步的牙科修复体 ;最后对此修复体进行完全烧结 ,得到高性能的氧化锆牙科修复体。结果 :部分烧结的陶瓷块的切削性能优良 ,与CAD/CAM预期时间吻合。完全烧结的陶瓷材料机械性能优良 ,弯曲强度达到710MPa,断裂韧性达到 4 .77MPa·m1/ 2 。在完全烧结过程中 ,各个方向收缩均匀一致。得到的牙冠形态逼真 ,无裂纹。结论 :部分烧结 -CAD/CAM加工 -完全烧结三步法制备高性能的牙科修复体的工艺路线为一条切实可行的路线     

渗透陶瓷与松风AL饰面瓷的热匹配性研究

目的 考察氧化铝玻璃渗透陶瓷与松风Vintage AL饰面瓷的热匹配性,以指导临床合理应用.方法 制作氧化铝玻璃渗透陶瓷与松风Vintage AL饰面瓷25mm× 5.0mmx5.0 mm试件,测定550℃至25℃区间的热膨胀曲线及热膨胀系数,评价二者热匹配性.结果 氧化铝玻璃渗透陶瓷,AL牙本质瓷,AL不透明牙本质瓷的热膨胀系数分别为7.6×10-6/℃,6.7x10-6/℃,7.1×10-6/℃,三者之间均能满足热匹配.结论 氧化铝玻璃渗透陶瓷与松风Vintage AL热匹配性良好,完全满足临床需要.     

牙科陶瓷力学性能与可靠性的研究方法

牙科全瓷系统的临床应用日趋普及．但全瓷修复体在口腔环境内行使功能时常出现疲劳失效．导致其使用寿命缩短并限制了其使用范围。因此,全瓷修复体的力学性能及其寿命已引起越来越多的口腔临床工作者及研究者的高度关注。wasserrflann等据循证方法评价了21篇关于全瓷修复体的临床研究．结果显示．对1724个全瓷冠经过1．3～100个月的观察．存留率为86．5％～100％。Burke对48个全瓷冠修复的前牙和前磨牙进行了3-4．5年的前瞻性研究．由瓷层损坏导致的失败率为6％。另有临床研究结果显示．     

牙科陶瓷冠桥修复体材料的发展现状

牙科陶瓷具有良好的化学稳定性和极佳的生物相容性,在口腔修复领域备受青睐.陶瓷材料本身的低抗弯强度和脆性限制了其应用范围.本文阐述了烤瓷熔附金属修复体和瓷全冠修复体各自的特点、增强机制以及发展现状.     

牙科陶瓷表面粗糙度与细菌粘附的实验研究

目的　比较陶瓷抛光和陶瓷上釉后表面粗糙度的差异及变形链球菌在其表面的粘附能力。方法　制作陶瓷样本 30个。A组陶瓷用金刚石抛光膏打磨抛光 ,B组陶瓷上釉 ,C组陶瓷用2 4 0 #Al2 O3 磨头磨平。用轮廓仪测量各组陶瓷样本的表面粗糙度。将各组样本置于变形链球菌悬浮液中 ,37℃培养 1h。图像分析仪计算变形链球菌在各样本表面的粘附面积比。结果　A、B、C组陶瓷的表面粗糙度分别为 (0 1987± 0 0 5 7) μm、(0 1990± 0 0 91) μm及 (0 4 2 6 0± 0 174 ) μm。变形链球菌在A、B、C 3组陶瓷表面的粘附面积比分别为 (15 92± 4 37) %、(16 39± 6 31) %、(41 4 8± 12 1) %。经统计学分析 ,A、B组陶瓷组间表面粗糙度及细菌粘附面积比差异无显著性 (P >0 0 5 ) ,C组陶瓷与其他各组样本表面粗糙度及细菌粘附面积比差异有高度显著性 (P <0 0 1)。结论　陶瓷上釉和抛光表面能达到同样光滑 ,细菌在其表面的粘附量亦基本相同。粗糙陶瓷表面比光滑陶瓷表面更容易粘附口腔细菌     

提高牙科陶瓷强度的研究

陶瓷是制作义齿的重要材料。瓷修复体色泽美观，生物相容性好。但是，瓷性脆，易折裂。本文从表面处理、内部增强和应用高强度底层增强等方面阐述了提高牙科的陶瓷强度的研究进展，旨在为我国牙科了陶瓷的应用研究提供帮助。     

牙科硅藻土基纳米复相陶瓷烧结曲线的研究

目的:探讨牙科硅藻土基纳米复相陶瓷的烧结致密化速率、不同烧结制度对其力学性能及显微结构的影响。方法:采用热膨胀仪检测样品的收缩率曲线及烧结微分曲线,以此为依据,不同温度段采取不同的烧结速率,测不同最高烧结温度下陶瓷烧结体的力学性能,SEM观察断面的显微结构。结果:烧结温度至1100℃时,其弯曲强度、维氏硬度和断裂韧性最佳,显著优于其它温度组(P<0.05),分别达到(207.45±8.00)MPa,(5.77±0.36)GPa,(3.04±0.40)MPa·m1/2。SEM显示陶瓷断面的气孔明显变小,致密度增大。结论:热膨胀曲线可检测陶瓷的烧结致密化过程,进一步实验验证证明1100℃为其最佳烧结温度。     

Plat铸造陶瓷材料的物理性能研究

目的 :初步研究了全瓷修复材料Plat铸造陶瓷材料的物理性能 ,为临床应用提供理论依据。方法 :采用经典的方法对Plat铸造陶瓷的密度 ,热膨胀系数 ,热传导率进行测定。结果 :Plat铸造陶瓷的密度为2.93g/cm3 ,热膨胀系数为9.87×10-6/℃ ,热传导率为0.0035卡/秒.cm.℃。结论 :Plat铸造陶瓷的密度 ,热膨胀系数 ,热传导率均与牙釉质相似 ,是一种有发展前景的口腔修复材料     

提高牙科陶瓷强度的研究

陶瓷是制作义齿的重要材料。瓷修复体色泽美观,生物相容性好。但是,瓷性脆,易折裂。本文从表面处理、内部增强和应用高强度底层增强等方面阐述了提高牙科陶瓷强度的研究进展,旨在为我国牙科陶瓷的应用研究提供帮助。     

牙科陶瓷发展的回顾

对牙科陶瓷在20世纪的发展作了较系统回顾,包括新型牙科陶瓷的组成成分及研究进展。     

表面处理对瓷牙材料机械强度影响的实验研究

目的 比较不同表面处理因素对瓷瓦材料机械强度的影响。方法 制备３００个表面均匀一致的实验标本,对抛光面进行表面处理,处理后的标本用万能实验机进行机械循环,然后用Ｐｉｓｔｏｎ－ｏｎ－ｔｈｒｅｅ ｂａｌｌ方法检查实验标本的挠屈强度。结果 双向卡方检验说明不同表面处理因素及不同循环次数对实验标本挠屈强度的影响都具有显著意义（（Ｐ〈０．０００１）;Ｑ－检验说明自然上釉、酸蚀、喷砂等表面自理和表面抛光相比,     

Residual Thermal Stress Simulation in Three‐Dimensional Molar Crown Systems: A Finite Element Analysis

Purpose: To simulate coefficient of thermal expansion (CTE)‐generated stress fields in monolithic metal and ceramic crowns, and CTE mismatch stresses between metal, alumina, or zirconia cores and veneer layered crowns when cooled from high temperature processing. Materials and Methods: A 3D computer‐aided design model of a mandibular first molar crown was generated. Tooth preparation comprised reduction of proximal walls by 1.5 mm and of occlusal surfaces by 2.0 mm. Crown systems were monolithic (all‐porcelain, alumina, metal, or zirconia) or subdivided into a core (metallic, zirconia, or alumina) and a porcelain veneer layer. The model was thermally loaded from 900°C to 25°C. A finite element mesh of three nodes per edge and a first/last node interval ratio of 1 was used, resulting in approximately 60,000 elements for both solids. Regions and values of maximum principal stress at the core and veneer layers were determined through 3D graphs and software output. Results: The metal‐porcelain and zirconia‐porcelain systems showed compressive fields within the veneer cusp bulk, whereas alumina‐porcelain presented tensile fields. At the core/veneer interface, compressive fields were observed for the metal‐porcelain system, slightly tensile for the zirconia‐porcelain, and higher tensile stress magnitudes for the alumina‐porcelain. Increasingly compressive stresses were observed for the metal, alumina, zirconia, and all‐porcelain monolithic systems. Conclusions: Variations in residual thermal stress levels were observed between bilayered and single‐material systems due to the interaction between crown configuration and material properties.     

4种齿科CAD/CAM陶瓷材料的可加工性能研究

目的：对VITA公司生产的4种不同齿科CAD/CAM陶瓷材料的可加工性能进行比较实验,以明确不同材料可加工性能上的差异。方法：选择临床上常用的4种CDA/CAM可切削陶瓷材料：Mark II、TriLuxe、In-Ce-ram Alumina和In-Ceram Spinell,主要成份分别为：长石质瓷、氧化铝和镁铝尖晶石,采用磨削、钻削和切削3种加工方法,在相同的实验条件下,检测4种陶瓷材料的磨削深度和切削面积,计算4种材料单位时间的去除率;同时在扫描电镜下观察切削面的形貌,并用表面粗糙度仪测试切削面的粗糙度。结果：在3种加工方式中,In-Ce-ram Alumina的加工效率最高,与另外3种材料之间存在统计学差异（P〈0.05）;切削面的表面粗糙度长石质瓷较In-Ceram Alumina和In-Ceram Spinell低;长石质瓷的切削面细致均匀,能清晰地看到切削所留下的规整而细致的划痕;而In-Ceram Alumina和In-Ceram Spinell切削面无明显划痕,呈多孔结构,表面凹凸不平。结论：采用In-Ceram技术的齿科修复陶瓷较长石质瓷具有更好的可加工性能。     

氧化铝-氧化锆纳米复合渗透陶瓷热膨胀特性的研究

目的　本实验旨在研究氧化铝-氧化锆纳米复合渗透陶瓷的热膨胀特性。方法　分别制作氧化铝-氧化锆基体、玻璃体、玻璃渗透复合体试件 ,测定各试件的热膨 胀系数 ,对测定结果及相互关系进行比较。结果　氧化锆含量为 1 0wt%、2 0wt%和 30wt%的复合基体的热膨胀系数分别为 7 6 0 7、7 6 90和 8 1 1 1 μm （m·℃ ） ;AZ8和AZ1 0两种渗透玻 璃的热膨胀系数分别为 6 86 7和 7 333μm （m·℃ ） ;AZ8和AZ1 0玻璃渗透氧化锆含量为1 0wt%～ 30wt%的基体所得渗透复合陶瓷的热膨胀系数为 8 2 0 3～ 8 4 1 3μm （m·℃ ）。 结论 　渗透玻璃的热膨胀系数与复合基体是匹配的 ;氧化铝-氧化锆纳米复合渗透陶瓷的热膨胀系数与几种常用的饰面瓷是匹配的。     

牙科可切削硅藻土全瓷材料的初步研究

目的：制备一种新型的牙科可切削硅藻土陶瓷材料,探讨其结构和性能的关系。方法：选取硅藻土为原料,通过添加纳米增韧剂制备陶瓷材料。采用X射线衍射仪分析陶瓷的晶相成分,扫描电镜观察陶瓷的显微结构,并测量材料的机械性能和切削性能。结果：硅藻土全瓷材料表面光滑,呈现乳白色;电镜下观察材料内部呈现致密多晶结构,晶界清晰,气孔较少;其三点弯曲强度（177.23±7.02）MPa,显微硬度（9.73±0.64）GPa,断裂韧性（3.93±0.58）MPa.m1/2。初烧结的陶瓷材料中烧结温度为700℃的切削性能较好。结论：该材料符合牙科可切削陶瓷材料的基本要求,但强度仍需进一步提高。     

不同环境对玻璃渗透氧化铝陶瓷亚临界裂纹扩展的影响’

、目的：研究口腔临床修复中常用的玻璃渗透氧化铝陶瓷（IA,In-CeramAlumina,IA）在干燥环境和潮湿环境下的亚临界裂纹扩展（SCG）行为的区别。方法：通过三点弯曲强度测量方法测得15个IA样本的强度数据,采用循环疲劳测试法测出干燥环境下15个IA样本以及在潮湿环境下15个IA样本的循环疲劳断裂次数数据;SCG行为通过裂纹扩展速率和应力强度因子（K1）的函数关系来描述。结果：不同环境下IA在循环载荷下发生亚临界裂纹扩展后导致材料断裂,在干燥环境下应力强度因子K1为临界应力因子Knc面的46％时发生裂纹传播;在潮湿环境下应力强度因子K1为临界应力因子Knc的40％时发生裂纹传播。结论：IA在循环载荷下存在SCG行为,当应力强度因子相同时,潮湿环境下样品的裂纹扩展速率较大,说明潮湿环境能加速亚临界裂纹扩展,符合口腔的实际情况。     

The effect of ferrule on the fracture mode of endodontically treated canines restored with fibre posts and metal-ceramic or all-ceramic crowns

Objectives

The aim of this study was to evaluate the fracture mode of endodontically treated canines (ETC) restored with glass-fibre posts (GFP) and either metal-ceramic (MC) or all-ceramic (AC) crowns, in the presence or absence of 2 mm ferrule height.

Methods

Fifty recently extracted human maxillary canines were endodontically treated and randomly divided into 5 groups of 10 specimens each. Four groups (with or without ferrule) were restored with GFP, composite cores and either MC or AC crowns. The fifth group with intact ETC served as control. Teeth were loaded to fracture at a 135° angle to their long axis, at a cross-head speed 0.5 mm/min. The fracture modes were divided through optical microscopy to repairable and irreparable. Statistical analysis was performed by means of the Fisher's Exact test.

Results

All groups presented brittle fracture following bending deformation. Irreparable root fractures were the primary fracture mode independently of ferrule. The percentages (%) of repairable fractures were not statistically significant different amongst the MC and AC restored teeth independently of ferrule. However the 2 mm ferrule was associated to a higher percentage of repairable fractures, especially in teeth restored with AC crowns.

Conclusions

The percentage (%) of repairable fractures was higher in all-ceramic compared to metal-ceramic ETC and in restorations with ferrule, although the differences were not statistically significant.

Clinical significance

This in vitro study supports evidence that neither the type of crown restoration nor the presence of ferrule affects statistically significantly the mode of fracture of ETC restored with GFP.     

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.