數位方式製作全口活動義齒咬合面準確度之比較-體外實驗

Abstract

實驗目的: 本研究目的在檢測數位化技術包含3D列印以及CAD/CAM切削製作全口活動義齒於咬合面(occlusal surface) 準確度(accuracy) 之差異性。 材料與方法: 將上下顎全口無牙標準模型翻模後製作石膏模型，在上顎以及下顎依照平均值製作咬合蠟堤(occlusal wax rim)，作為後續實驗的參考模型。以3D桌掃機 (E3 3D scanner, 3shape, Copenhagen, Denmark)掃描上下顎石膏模型以及咬合蠟堤並以牙科設計軟體(Exocad DentalCAD 2.4 Plovdiv, Exocad GmbH, Darmstadt, Germany)設計上下顎全口假牙之外型包含咬合面、組織面以及光滑面作為數位假牙設計檔CAD model，後續以CAD/CAM切削 (POLYWAX組)以及3D列印 (NextDent組)方式進行數位全口義齒之製作，3D列印組透過改變列印角度(build angle) 90度以及45度以及在石膏模型上進行後固化(post-curing) 分成四組，每組上下顎各製作10個 (共計90個)。義齒咬合面再現性之測試方式為：1. 掃描各組之義齒咬合面並與數位義齒設計檔CAD model影像疊合分析咬合面 (cameo surface)。2. 使用游標尺測量以及數位軟體距離測量方式測量義齒咬合面參考點之間距離，測量距離包含：大臼齒間寬度(intermolar width)，犬齒間寬度(intercanine width)，前後距離(anterior posterior distance), 垂直距離(vertical distance)，並計算與數位義齒設計檔CAD model之間的差距。統計方式使用以Kruskal-Wallis Test先進行分析，並以Tukey法進行事後比較檢定 (post-hoc test) ，有意義水準設於p≤0.05。 實驗結果: 根據數位影像疊合方式檢測的結果，不論上下顎均顯示：咬合面的再現度在十個參考位置的比較來看，CAD/CAM切削相較於3D列印方式顯示出較高的準確度(accuracy)(變化量0.0115 ~ 0.0719mm)，在3D列印方式的各組當中，改變列印角度顯著影響尺寸準確度，透過在石膏模型上進行後固化可以降低後固化時造成的收縮，進而提高咬合準確度。 根據游標尺測量以及數位軟體距離測量方式測量義齒咬合面參考點之間距離，並計算與數位義齒設計檔CAD model之間的差距，結果顯示在3D列印方式的各組當中，改變列印角度顯著影響尺寸準確度，透過在石膏模型上進行後固化可以降低後固化時造成的收縮，進而提高咬合面準確度。 結論: 在本實驗有限的條件下，對於全口義齒在咬合面再現度檢測的結果，使用游標卡尺以及數位測量方式測量參考點之間距離大小，CAD/CAM切削方式不論是在上顎或下顎，產生的距離差都小於3D列印方式。3D列印方式在上顎以及下顎的表現，改變列印角度以及後處理在模型上進行後固化，可以降低各參考點之間距離誤差。使用數位影像疊合方式檢測下，CAD/CAM切削方式製作義齒在咬合面有較高的真實度，而3D列印方式改變列印角度以及後處理在模型上進行後固化可以提高咬合面準確度。

Objective: This in vitro study was to compare the reproducibility of the occlusal surface and dimensional accuracy of complete dentures fabricated with digital approaches (CNC milling and Rapid prototyping) . Material and methods Two maxillary and mandibular edentulous models (EDE1001-UL-UP-FEM, Nissin Dental Products Inc., Japan) were mounted on semi-adjustable articulator (Stratos 200, Ivoclar, Liechteinstein) using a technique based upon average values. Then, the models and wax rim were scanned by 3Shape E3 scanner (3Shape, Copenhagen, Denmark) and designed with software (Exocad DentalCAD 2.4 Plovdiv, Exocad GmbH, Darmstadt, Germany). The complete dentures were fabricated by two different manufacturing techniques: CAD/CAM milled (CORITEC 250i, imes-icore GmbH, Eiterfeld, Germany) and 3D printing (NextDent Denture base, NextDent, Soesterberg, The Netherlands). The 3D printing group was divided into 4 groups according to printing angles (45 and 90 degrees) and post-curing modifications (post curing on cast or not). The dimensional accuracy was evaluated by: 1) intercanine width 2) intermolar width 3) anteroposterior plane 4) Vertical plane All the specimens were scanned by optical scanner (3Shape E3, Copenhagen, Denmark) and outputting an STL file for each denture’s intaglio and cameo surface. The STL file of each denture was superimposed with the corresponding pre- processing cast using surface matching software (Geomagic Control 2014; 3D Systems) at selected points for each of the 40 dentures using an overlay guide to verify the location of the measurements. Results In both arches, The CAD/CAM milled technique had the least deviation on the reference area. Meanwhile, the 3D printing group showed larger deviaiton than the CAD/CAM milled group. According to digital superimposition, the overall results showed that there was significant difference in the accuracy and precision of the occlusal surface between CAD/CAM milled and 3D printing groups. In the 3D printing groups, printing angle at 90 degrees and post cured on the cast showed the greater accuracy and precision. Conclusions Within the limitation of the study, the conclusions are 1. The CAD/CAM milled denture process presented with higher dimensional accuracy. 2. For complete denture fabrication with 3D printing technique, the building orientation affected the dimensional accuracy. Meanwhile, post-curing modifications (post-curing on master cast) can improve the adaptation of tissue surface of the denture, resulting in less distortion of the occlusal surface