医疗和牙科

New study finds 3D printing to be more accurate than milling in the creation of dental crowns

日本的研究人员Tohoku University Graduate School of Dentistryhave found Digital Light Processing (DLP) 3D printing to be a more effective means of producing dental crowns than conventional milling.

在最近的一项研究中,牙医3D从同一数据集中打印和湿磨冠,然后将其预期设计叠加于所得模型。该团队通过几个测试周期说,他们的3D打印牙科修复体显示出“更高的准确性”和“边缘差异更高”,因此,他们将DLP视为永久性冠冕创造的更“有前途的技术”。

在摩尔冠上看到的设计和扫描数据之间的整体偏差的颜色图。图像通过Tohoku University。
在摩尔冠上看到的设计和扫描数据之间的整体偏差的颜色图。图像通过Tohoku University。

是时候从铣削开始了吗?

As the wear-resistance and color stability of dental materials continue to improve, some dentists are turning to milled resin-composite dental crowns over traditional metallic restorations. Using CAD design software and an impression of a patient’s tooth, this approach allows for the development of custom implants, before using a milling machine to grind them from a ceramic block.

但是,Tohoku大学团队说,这些技术面临的问题,例如铣床和材料浪费的恶化。研究人员还强调了铣削如何迫使牙医遵守僵化的准备要求,即使他们坚持使用这些要求,凹槽也可以在皇冠的内表面上发展,从而导致患者不完美。

By contrast, due to the R&D going into new dental 3D printing resins, including those that possess high durability and are capable of dispersing occlusal stress, the team has praised the technology’s potential for creating models, bases and splints.

在研究之前,研究人员还理论上,3D打印以“优越的尺寸精度”产生永久性冠。然而,尽管经常比较3D打印和铣削的牙齿假肢,但牙医声称它“尚不清楚”哪个过程更适合这份工作,因此他们着手进行研究以通过一系列实验确定地发现。

摩尔的STL文件与每个offse冠设计t parameter and whole deviations between un-offset and offset crown. Image via Tohoku University.
STL files of the models used to identify deviations between un-offset and offset crowns. Image via Tohoku University.

Putting crown 3D printing to the test

研究人员的测试标本是通过基于牙齿模型的3D扫描产生的,然后是从混合树脂复合块中铣削的,并使用3D印刷Asiga Max系统分别。准备好后,将这些原型中的每一个与其原始设计模型进行了比较,该模型利用工业3D数字化器,该模型收集了帮助识别任何偏差所需的数据。

Initial results showed a significant difference between crowns designed to adapt to the line angles of the models and un-offset prosthetics, with a gap of 100–200 µm observed. While printed models showed a high trueness of value, this deviation was more pronounced in milled parts, in which the team observed “a definite internal groove,” something they attributed to the crowns’ brittle base material.

Interestingly, the researchers also found their printer’s 62 µm pixel resolution to be smaller than that of the internal cusp area of un-offset crowns. This made the system precise enough to realize accurate models, whereas with milling, they discovered that the grooves it left on crowns’ inner surfaces could lead to an inferior fit, and were a “limitation of the technique.”

However, while the Japanese team concluded that their results support the idea of DLP being better suited to producing crowns than milling, they say further research is needed into different systems and parameters. Likewise, the dentists have called for more studies into the fracture resistance and biocompatibility of 3D printed implants, which they believe could now be used to restore sharp teeth like incisors.

Dental restorations printed with Saremco CROWNTEC resin. Photo via Saremco.
Dental restorations printed with Saremco CROWNTEC resin. Photo via Saremco.

Commercialized dental 3D printing

正如团队在他们的研究中所暗示的那样,3D打印已经在牙科假体生产中建立,而周围发展的行业继续看到引入了新材料,从而增强了其应用。今年早些时候3D Systems partnered with Saremco, in a move that madeCROWNTECresins available for use with the custom crown-3D printingNextDent 5100

随后Desktop Health’slaunch of theEinstein 3D printer and Flexcera Smile Ultra+ resin, products designed to facilitate the production of high-strength, aesthetically-pleasing dental prosthetics. While the former has a similar DLP architecture to the systems of fellowDesktop Metal公司ETEC,它的性能通过“ HyperPrint”提高了,这项技术为其提供了50%的速度提升。

最近,Dentsply Sirona还扩大了其牙科植入物制造产品组合,启动PrimePrint 3D打印机and post-processing unit. Powered by a 385nm light engine, the newly-unveiled printer is designed to enable dentists to easily produce accurate models, guides, provisionals or splints.

研究人员的发现在其论文中详细介绍了“Comparison of the accuracy of resin-composite crowns fabricated by three dimensional printing and milling methods”,由Hiroaki Kakinuma,Kuniyuki Izumita,Nobuhiro Yoda,Hiroshi Egusa和Keiichi Sasaki合着。

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Featured image shows the measurement points on the inner surface of each crown produced for the study. Image via Tohoku University.