單晶形陶瓷矯正托架之斷裂分析

Fracture Analysis of single-crystal Ceramic Brackets

郭香君(Hsiang-Chun Kuo) ； 蘇明仁(Ming-Zen Su) ； 張心涪(Frank Hsin-Fu Chang) ； 林俊彬(Chun-Pin Lin)

《中華牙醫學雜誌（中文版）》 1卷2期 (2005/06) Pp. 81-87

https://doi.org/10.7106/CJD.200506.0081

摘要

陶瓷矯正托架主要優點為美觀、強度高，比樹脂矯正托架更能抵抗染色。由於陶瓷矯正托架屬於既硬且脆的物質，其機械性質諸如硬度、彈性模數、斷裂韌度等，攸關其臨床表現與適用性，過去的文獻未曾直接測試陶瓷矯正托架的機械性質，因此本研究目的針對Inspire(上標 ®)單晶陶瓷矯正托架(Inspire(上標 ®) monocrystalline ceramic bracket)，以掃描式電子顯微鏡探討其內部結構及斷裂特徵並以深度感應壓痕技術(depth-sensing indentation technique)測試硬度、彈性模數及斷裂韌度等機械性質。由斷面形態分析顯示單晶陶瓷矯正托架斷裂方式為劈裂斷裂(cleavage fracture)，典型的特徵為流紋，流紋分支平行於施力方向，不利於抵抗裂紋傳播，因此屬於脆性斷裂。其硬度、彈性模數、斷裂韌度的數值分別為7696±1731Kg/平方公厘、449.3±83.9GPa、0.7±0.17MNm^(-1.5)。與人類琺瑯質之性質比較，單晶陶瓷矯正托架之硬度及彈性模數過高而斷裂韌度偏低。

關鍵字

硬度 ； 彈性模數 ； 斷裂韌度 ； 深度感應壓痕技術 ； 斷面形態分析

並列摘要

Ceramic brackets are superior to metal brackets in esthetics and strength. They also perform better than plastic brackets in stain resistance. As ceramics are hard and brittle, their mechanical properties such as hardness, elastic modulus, and fracture toughness are closely related to their clinical performance and applicability. However, these properties of ceramic brackets have never been investigated in the previous literature. Therefore, the purposes of this study were (1) to analyze the microstructure and fracture patterns of a single-crystal ceramic bracket (Inspire(superscript ®)) by scanning electron microscopy (SEM) and (2) to determine the hardness, elastic modulus, and fracture toughness using a depth-sensing indentation technique. From the fractographic analysis, the fracture pattern of the Inspire brackets showed cleavage fractures and river patterns. The branches of the river patterns paralleled the direction of force, and this condition was disadvantageous to resisting crack propagation. Therefore, this type of fracture pattern belongs to brittle fractures. From the depth-sensing indentation technique, the hardness, elastic modulus, and fracture toughness of Inspire were 7696±1731 kg/mm^2, 449.3±83.9 GPa, and 0.7±0.17 MN m^(-1.5), respectively. Compared with the properties of human enamel, both the value of hardness and the elastic modulus of the Inspire brackets were too high, while the fracture toughness was too low. In conclusion, an improved ceramic bracket with a lower value of hardness and a higher value for fracture toughness needs to be further developed.

並列關鍵字

hardness ； elastic modulus ； fracture toughness ； depth-sensing indentation technique ； fractographic analysis