Senior Materials Scientist, Department of Prosthodontics, School of Dental Medicine, Martin-Luther-University, Halle, Germany.
Assistant Professor and Head, Department of Prosthodontics, School of Dental Medicine, Martin-Luther-University, Halle, Germany.
J Prosthet Dent. 2018 Apr;119(4):586-592. doi: 10.1016/j.prosdent.2017.04.017. Epub 2017 Jul 11.
The conventional fabrication of removable partial dentures (RPDs) is a complex, error-prone, time-consuming, and expensive process. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) techniques, especially rapid prototyping, promises a more effective method for fabricating RPD frameworks.
The purpose of this in vitro study was to evaluate the fit of RPD clasps fabricated by means of 4 different CAD-CAM-systems and to compare those fittings with that of the conventional lost-wax casting technique (LWT).
A master model of a partially edentulous maxilla with the canines and second molars as the remaining teeth was fabricated. After the model was optically scanned, we designed a quadrangularly supported RPD with 4 clasps and a palatal strap major connector. A standard tessellation language data set was used to fabricate 12 identical RPDs by using 4 different CAD-CAM techniques: indirect rapid prototyping (wax inject printing combined with LWT), direct rapid prototyping (selective laser melting), indirect milling (wax milling with LWT), and direct milling (resin milling [polyetheretherketone]). Three conventionally cast RPDs (LWT) served as the control group. The fit accuracy of the clasps (n=12 for each group) was determined in both the horizontal and vertical dimensions by using light microscopy.
Indirectly milled RPDs (117 ±34 μm horizontal and 45 ±21 μm vertical) and directly milled RPDs (43 ±23 μm horizontal, and 38 ±21 μm vertical) showed significantly better (P<.05) fit than did conventionally fabricated LWT RPDs (133 ±59 μm horizontal; 73 ±25 μm vertical). The worst fit was found for RPDs fabricated using indirect rapid prototyping (323 ±188 μm horizontal and 112 ±60 μm vertical) or direct rapid prototyping (365 ±205 μm horizontal and 363 ±133 μm vertical), which were unstable on the master model, making them unsuitable for clinical use. Most RPDs exhibited smaller vertical measuring distances.
Compared with the LWT, milling techniques enabled fabrication of RPDs with comparable or better fit. However, RPDs fabricated with rapid prototyping techniques showed distinct fitting irregularities.
传统的可摘局部义齿（RPD）制作过程复杂、易出错、耗时且昂贵。计算机辅助设计和计算机辅助制造（CAD-CAM）技术的应用，特别是快速原型制作，有望为 RPD 支架的制作提供更有效的方法。
本体外研究的目的是评估通过 4 种不同 CAD-CAM 系统制作的 RPD 卡环的适合性，并将其与传统失蜡铸造技术（LWT）进行比较。
制作一个带有尖牙和第二磨牙作为剩余牙齿的部分缺牙上颌模型。模型光学扫描后，我们设计了一个具有 4 个卡环和一个腭侧带大连接体的四边形支撑 RPD。使用标准的 tessellation language 数据集，通过 4 种不同的 CAD-CAM 技术制造了 12 个相同的 RPD：间接快速原型制作（蜡注射印刷结合 LWT）、直接快速原型制作（选择性激光熔化）、间接铣削（蜡铣削结合 LWT）和直接铣削（树脂铣削[聚醚醚酮]）。3 个传统铸造的 RPD（LWT）作为对照组。使用光学显微镜测量每组 12 个卡环的水平和垂直方向的适合精度。
间接铣削的 RPD（水平方向 117 ±34 μm，垂直方向 45 ±21 μm）和直接铣削的 RPD（水平方向 43 ±23 μm，垂直方向 38 ±21 μm）的适配精度明显优于传统 LWT RPD（水平方向 133 ±59 μm；垂直方向 73 ±25 μm）。使用间接快速原型制作或直接快速原型制作的 RPD 的适配精度最差（水平方向 323 ±188 μm，垂直方向 112 ±60 μm），因为它们在主模型上不稳定，不适合临床使用。大多数 RPD 的垂直测量距离较小。
与 LWT 相比，铣削技术能够制作适配精度相当或更好的 RPD。然而，使用快速原型制作技术制作的 RPD 显示出明显的适配不规则性。
