Influence of microscale expansion and contraction caused by thermal and mechanical fatigue on retentive strength of CAD/CAM-generated resin-based composite crowns
Influence of microscale expansion and contraction caused by thermal and mechanical fatigue on retentive strength of CAD/CAM-generated resin-based composite crowns
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DOI：
10.1016/j.jmbbm.2018.06.025
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发表时间：
2018-10-01
影响因子：
3.9
通讯作者：
Egusa, Hiroshi
中科院分区：
文献类型：
--
作者：
Ankyu, Shuhei;Nakamura, Keisuke;Egusa, Hiroshi
CAD/CAM生成的树脂基复合冠已被提议作为传统冠的廉价替代品。然而，在临床使用中，人们对牙冠松动表示担忧。因此，本体外研究的目的是评估热循环和机械循环（TC和MC）对CAD/CAM树脂基冠的固位强度的影响，与疲劳引起的微尺度膨胀和收缩有关。使用树脂基复合材料生产了80个标准化模具。使用牙科CAD/CAM系统从树脂基复合材料（n = 40）和玻璃陶瓷块（n = 40;对照）研磨牙冠。将粘结到模具的牙冠经受TC（温度：5和55 ℃，循环：50，000）和MC（载荷：200 N，循环：120万）。疲劳处理后，冠的固位强度进行了评价，通过冠拉脱试验在十字头速度为1 mm/min。热膨胀系数（CTE）和弹性模量（E-模量）的每种材料也进行了分析，以估计在TC和MC的微观膨胀和收缩。TC和MC显著降低CAD/CAM树脂基冠的固位强度，而CAD/CAM陶瓷冠的固位强度仅受TC影响。此外，树脂基冠在TC过程中表现出更高数量的冠松动比陶瓷冠。热膨胀系数和弹性模量的分析表明，树脂基冠在TC和MC过程中比陶瓷冠更容易变形。本研究表明，冠对由热疲劳和机械疲劳引起的微膨胀和收缩的抵抗力在保持固位强度方面起着重要作用。
CAD/CAM-generated resin-based composite crowns have been proposed as an inexpensive alternative to conventional crowns. However, concerns have been raised about crown loosening in clinical use. Therefore, the present in vitro study aimed to evaluate the influence of thermal and mechanical cycling (TC and MC) on retentive strength of CAD/CAM resin-based crowns in relation to microscale expansion and contraction caused by fatigue. Eighty standardized dies were produced using a resin-based composite material. Crowns were milled from resin-based composite (n = 40) and glass-ceramic blocks (n = 40; control) using a dental CAD/CAM system. The crowns bonded to the dies were subjected to TC (temperature: 5 and 55 degrees C, cycles: 50,000) and MC (load: 200 N, cycles: 1.2 million). After fatigue treatment, retentive strength of the crowns was evaluated by a crown pull-off test at a crosshead speed of 1 mm/min. Coefficient of thermal expansion (CTE) and modulus of elasticity (E-modulus) of each material were also analyzed to estimate the microscale expansion and contraction during TC and MC. TC and MC significantly reduced the retentive strength of the CAD/CAM resin-based crowns whereas that of the CAD/CAM ceramic crowns was only affected by TC. In addition, the resin-based crowns showed a higher number of crown loosening during TC than the ceramic crowns. Analyses of CTE and E-modulus indicated that the resin-based crowns would be more deformed during TC and MC than the ceramic crowns. The present study demonstrated that the resistance of crowns to microscale expansion and contraction caused by thermal and mechanical fatigue would play an important role in maintaining retentive strength.