Department of Prosthetic Dentistry, Faculty of Odontology, Malmö University, Malmö, SE-205 06, Sweden.
Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Malmö, Sweden.
Dent Mater. 2019 Mar;35(3):486-494. doi: 10.1016/j.dental.2019.01.015. Epub 2019 Jan 25.
To measure and compare the size of the cement gap of wax and polymer copings and final glass-ceramic crowns, produced from conventional and digital workflows, one additive and one subtractive.
Thirty wax copings were made by conventional manual layering technique and modeling wax on stone models with spacer varnish simulating a cement spacer. The wax copings were embedded and press-cast in lithium disilicate glass ceramic. Thirty wax copings were produced by milling from a wax blank, i.e. subtractive manufacturing, and thirty polymer burn-out copings were produced by stereolithography, i.e. additive manufacturing. These copings were embedded and press-cast in lithium disilicate glass ceramic in the same manner as the conventional group. The fit of the wax/polymer copings and subsequent crowns was checked using an impression replica method. Mean values for cement gap for marginal, axial, and occlusal areas were calculated and differences were analyzed using Student's t-test.
There were significant differences in mean values for accuracy/production tolerance among different manufacturing techniques for both production stages: wax and polymer copings and final pressed glass-ceramic crowns. In general, crowns produced from a digital additive workflow showed smaller mean cement gaps than crowns produced from a conventional workflow or a digital subtractive workflow. Additive polymer copings showed significantly smaller cement gaps than milled wax copings (p≤.001) and conventional wax copings (p≤.001) in the axial area. In the occlusal area, both additive polymer copings and conventional wax copings showed significantly smaller cement gaps than milled wax copings (p=.002 and p≤.001 respectively). Crowns produced from conventional manual build-up wax copings showed significantly larger mean cement gaps than crowns produced from milled wax and additively manufactured polymer copings in the marginal and axial areas (p≤.001). Among the crowns with smaller cement gaps, crowns produced from additively manufactured polymer copings showed significantly smaller mean cement gaps than crowns produced from milled wax in the marginal and axial areas (p≤.001). In the occlusal areas, the differences in mean cement gaps were only statistically significant between crowns produced from conventional manual build-up wax copings and crowns produced from milled wax where the latter ones showed smaller mean cement gaps (p=.025).
The present study suggests that an additive manufacturing technique produces smaller mean cement gaps in glass-ceramic crowns than a conventional or subtractive manufacturing technique.
测量和比较传统和数字工作流程中蜡和聚合物修复体以及最终玻璃陶瓷冠的水泥间隙大小，其中一个是加法制造，另一个是减法制造。
通过常规手动分层技术和在带有间隔剂清漆的石模型上对模型蜡进行造型，制作 30 个蜡修复体，模拟水泥间隔剂。蜡修复体通过嵌入和加压铸造在锂硅玻璃陶瓷中。通过从蜡坯进行铣削制作 30 个蜡修复体，即减法制造，通过立体光刻制作 30 个聚合物烧蚀修复体，即加法制造。以与常规组相同的方式将这些修复体嵌入和加压铸造在锂硅玻璃陶瓷中。使用印模复制法检查蜡/聚合物修复体和随后的冠的拟合度。计算边缘、轴向和咬合区域的水泥间隙的平均值，并使用学生 t 检验分析差异。
在蜡/聚合物修复体和最终压制玻璃陶瓷冠的两个生产阶段，不同制造技术的准确性/生产公差的平均值存在显著差异。一般来说，数字加法工作流程生产的冠的平均水泥间隙比传统工作流程或数字减法工作流程生产的冠小。在轴向区域，加法聚合物修复体的水泥间隙明显小于铣削蜡修复体（p≤.001）和常规蜡修复体（p≤.001）。在咬合区域，加法聚合物修复体和常规蜡修复体的水泥间隙明显小于铣削蜡修复体（p=.002 和 p≤.001）。通过常规手动堆积蜡修复体生产的冠的平均水泥间隙明显大于通过铣削蜡和加法制造聚合物修复体生产的冠的平均水泥间隙，在边缘和轴向区域（p≤.001）。在水泥间隙较小的冠中，通过加法制造聚合物修复体生产的冠的平均水泥间隙明显小于通过铣削蜡生产的冠，在边缘和轴向区域（p≤.001）。在咬合区域，只有通过常规手动堆积蜡修复体生产的冠和通过铣削蜡生产的冠之间的平均水泥间隙差异具有统计学意义，后者的平均水泥间隙较小（p=.025）。
本研究表明，加法制造技术生产的玻璃陶瓷冠的平均水泥间隙小于传统或减法制造技术。
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