Objectives

This study aimed to evaluate the effects of different firing cycles on surface hardness, fracture toughness, and roughness of lithium disilicate glass-ceramic, as well as their bond strength to resin.

Materials and methods

A total of 320 polished lithium disilicate glass-ceramic plates were assigned to four main groups (n = 60) to receive one, two, three, or four firing cycles, respectively. Ceramic plates of the four groups were conditioned with HF acid followed by silanization. The pre-treated ceramic plates were cemented with composite resin cylinders using conventional or self-adhesive resin cements to build bonded specimens, and submitted to shear-bond-strength (SBS) testing after water storage for 24 h or 3 mo at 37 °C. The ceramic received different firing cycles after polishing or HF etching was observed using a scanning electron microscope, and their surface roughnesses were determined by a profilometer. The surface Vickers hardness, fracture toughness, and related Weibull analysis results of the polished ceramics after undergoing different firing-cycle times were compared.

Results

One sintering significantly increased fracture toughness of lithium disilicate glass-ceramic; however, multiple firing cycles failed to increase it further. Weibull analysis revealed a significant difference in terms of structural reliability among the specimens receiving 0–4 firing cycles. Specimens that received no firing cycle showed the highest surface hardness. Multiple firing cycles had no significant influence on the surface Vickers hardness and surface roughness. HF etching increased surface roughness, and the roughened surface improved the resin SBS of lithium disilicate glass-ceramic. Multiple firing cycles had no significant effect on surface roughness. Furthermore, multiple firing cycles and 3-mo water storage had no significant effect on the SBS.

Conclusions

The mechanical properties of lithium disilicate glass-ceramics would be partially affected by multiple firing cycles, while their resin bonding would not be.

中文翻译：

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多次烧成对二硅酸锂玻璃陶瓷力学性能和树脂结合性能的影响

目标

这项研究旨在评估不同烧成周期对二硅酸锂玻璃陶瓷表面硬度，断裂韧性和粗糙度以及它们与树脂的结合强度的影响。

材料和方法

总共将320个抛光的二硅酸锂玻璃陶瓷板分配给四个主要组（n = 60），分别接收一个，两个，三个或四个烧结周期。将四组陶瓷板用HF酸处理，然后进行硅烷化处理。使用常规或自粘树脂胶粘剂将预处理过的陶瓷板用复合树脂圆柱体胶粘以构建粘结试样，并在37°C下储水24 h或3 mo后进行剪切粘结强度（SBS）测试。使用扫描电子显微镜观察陶瓷的抛光或HF蚀刻后的烧成周期，并通过轮廓仪测定其表面粗糙度。表面维氏硬度，断裂韧性，

结果

一次烧结显着提高了二硅酸锂玻璃陶瓷的断裂韧性。但是，多个点火周期未能进一步提高它。威布尔（Weibull）分析显示，在接受0–4次烧成的试样中，结构可靠性存在显着差异。没有经过焙烧循环的样品显示出最高的表面硬度。多次焙烧循环对表面维氏硬度和表面粗糙度没有显着影响。HF蚀刻增加了表面粗糙度，并且粗糙化的表面改善了二硅酸锂玻璃陶瓷的树脂SBS。多次烧成对表面粗糙度没有显着影响。此外，多次燃烧循环和3-mo储水对SBS没有明显影响。

结论

二硅酸锂玻璃陶瓷的机械性能会受到多次烧成周期的部分影响，而它们的树脂结合不会受到影响。