Griggs Jason A, Kishen Anil, Le Kim Nga
Department of Biomaterials Science, Baylor College of Dentistry, TAMUS HSC, 3302 Gaston Avenue, Dallas, TX 75246, USA.
Dent Mater. 2003 Nov;19(7):625-31. doi: 10.1016/s0109-5641(03)00005-8.
The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC, to determine the effects of such a layer on mechanical material properties, and to identify a specific mechanism responsible for any strength increase observed.
Specimens were fabricated from dentin porcelain by a vibration blotting technique and were prepared to have either blunt or sharp surface flaws. Half of the specimens underwent accelerated aging. Specimens were fractured in three-point flexure to measure their strength, and fractographic analysis was used to determine fracture toughness and residual surface stress. Surface hardness and elastic modulus were measured using a microindentation method. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to determine the composition of the surface layer.
The aging treatment modified the porcelain surface topography but did not create a layer with increased hydroxyl ion content. Porcelain strength increased upon aging, and the increase was proportional to initial flaw severity. The apparent fracture toughness of sharp flaw specimens increased to match that for specimens containing blunt flaws upon aging. Surface hardness and elastic modulus decreased upon aging.
Previous studies on the strength increase of hydrothermal porcelain were contradictory because a variety of specimen preparation procedures were used. This study resolves the apparent contradiction by determining the effect of specimen preparation on material strength.
本研究的目的是验证在Duceram LFC上是否形成水解表面层，确定该层对材料机械性能的影响，并确定导致观察到的强度增加的具体机制。
通过振动印迹技术用牙本质瓷制作标本，并制备成具有钝表面缺陷或尖锐表面缺陷的标本。一半标本进行加速老化。标本在三点弯曲试验中断裂以测量其强度，并用断口分析确定断裂韧性和残余表面应力。使用微压痕法测量表面硬度和弹性模量。使用原子力显微镜检查瓷表面形貌，并用傅里叶变换红外光谱法确定表面层的成分。
老化处理改变了瓷表面形貌，但未形成羟基离子含量增加的层。老化后瓷强度增加，且增加量与初始缺陷严重程度成正比。老化后尖锐缺陷标本的表观断裂韧性增加到与含钝缺陷标本的断裂韧性相匹配。老化后表面硬度和弹性模量降低。
先前关于热液瓷强度增加的研究相互矛盾，因为使用了各种标本制备程序。本研究通过确定标本制备对材料强度的影响解决了明显的矛盾。
