Jones Steven P, Cheuk Godwin C Y, Georgiou George, Moles David R
Unit of Orthodontics, UCL Eastman Dental Institute for Oral Health Care Sciences, London, United Kingdom.
Aust Orthod J. 2009 May;25(1):12-8.
To investigate whether fluoridated apatites have a shear bond strength which more closely equates to that of natural enamel than pure hydroxyapatite, making them potentially useful as biomimetic alternatives to natural enamel for ex vivo laboratory bonding studies.
Discs of pure hydroxyapatite, pure fluorapatite and a 1:1 mixture of hydroxyapatite-fluorapatite were produced by cold uni-axial pressing. The discs were sintered at 1300 degrees C, embedded in epoxy resin, ground and polished. X-ray diffraction technique was used to analyse the purity of the apatites. Scanning electron microscopy was employed to investigate the etch patterns of the apatite specimens. Ninely-six upper left central incisor brackets were bonded to each of the three groups of discs. Shear bond strengths were determined by debonding the brackets using a loaded metal jig in an Instron Universal Testing Machine. The sites of bond failure were recorded using the Adhesive Remnant Index. One-way analysis of variance (ANOVA) and Bonferroni post-hoc comparisons were used to determine statistical differences between the mean shear bond strengths of the three specimen groups.
The mean shear bond strength of pure hydroxyapatite (20.44 MPa; SD: 8.03; 95% CI: 18.81, 22.07) was significantly higher than those of fluorapatite (13.13 MPa; SD: 6.76; 95% CI: 11.76, 14.50) and hydroxyapatitefluorapatite (13.62 MPa; SD: 7.03; 95% CI: 12.19, 15.04) (p < 0.001). There was no statistically significant difference in shear bond strengths between fluorapatite and hydroxyapatite-fluorapatite (p > 0.99), and both were below the normal range ascribed to enamel (15-20 MPa). More than 90 per cent of the fluorapatite and the hydroxyapatite-fluorapatite specimens demonstrated bond failure at the substrate-adhesive interface, while only one-third of the hydroxyapatite specimens exhibited bond failure at that interface.
Pure fluorapatite and hydroxyapatite-fluorapatite specimens offer no advantage over pure hydroxyapatite as a suitable artificial substrate for ex vivo bond strength testing.
研究含氟磷灰石的剪切粘结强度是否比纯羟基磷灰石更接近天然牙釉质，从而使其有可能作为天然牙釉质的仿生替代品用于体外实验室粘结研究。
通过冷单轴压制制备纯羟基磷灰石、纯氟磷灰石以及羟基磷灰石 - 氟磷灰石1:1混合物的圆盘。圆盘在1300摄氏度下烧结，嵌入环氧树脂，进行研磨和抛光。采用X射线衍射技术分析磷灰石的纯度。利用扫描电子显微镜研究磷灰石标本的蚀刻模式。将96个左上中切牙托槽粘结到三组圆盘上。使用Instron万能材料试验机中的加载金属夹具使托槽脱粘，从而测定剪切粘结强度。使用粘结剂残留指数记录粘结失败的部位。采用单因素方差分析（ANOVA）和Bonferroni事后比较来确定三组标本平均剪切粘结强度之间的统计学差异。
纯羟基磷灰石（20.44兆帕；标准差：8.03；95%置信区间：18.81，22.07）的平均剪切粘结强度显著高于氟磷灰石（13.13兆帕；标准差：6.76；95%置信区间：11.76，14.50）和羟基磷灰石 - 氟磷灰石（13.62兆帕；标准差：7.03；95%置信区间：12.19，15.04）（p < 0.001）。氟磷灰石和羟基磷灰石 - 氟磷灰石之间的剪切粘结强度无统计学显著差异（p > 0.99），且两者均低于归因于牙釉质的正常范围（15 - 20兆帕）。超过90%的氟磷灰石和羟基磷灰石 - 氟磷灰石标本在基底 - 粘结剂界面出现粘结失败，而只有三分之一的羟基磷灰石标本在该界面出现粘结失败。
作为体外粘结强度测试的合适人工基底，纯氟磷灰石和羟基磷灰石 - 氟磷灰石标本并不比纯羟基磷灰石具有优势。
