不同種類的車削式義齒設計在黏合過程中對於車削式全口義齒咬合誤差的影響 體外實驗

Abstract

實驗目的： 本研究的目的是討論兩件式車削式全口義齒的不同義齒種類設計在黏合中，相對於單件式車削式全口義齒所產生的咬合誤差的影響及評估。

材料與方法： 本實驗先製備出石膏模去模擬上顎無牙脊的主模(master cast)，將主模和蠟堤(wax rim)及對咬模固定並利用桌掃機(E3; 3Shape A/S)掃描而得到立體結構檔案(STL)，匯入牙科設計軟體(3shape dental manger system )進行上顎全口活動義齒的設計並匯出檔案作為原始設計檔(designed data)，用五軸車削機(Idensol X5P, Toshin Tech.)車削出全口義齒。單件式(one-piece)車削式義齒設計為對照組，車削出6組；兩件式(two-piece)車削式義齒為實驗組，實驗組分成三種義齒設計，分別為T1:整段牙弓、T2:四段三單位牙橋及T3:單顆牙齒，實驗組每組都車削出12組。為標準化定位車削出的義齒與義齒基底床的相對位置，再經由設計軟體(DentalCAD, exocad GmbH ; Meshmixer, Autodesk, Inc.)軟體設計黏合導引板並3D列印出，T1和T2組隨機搭配各3個導引板，T3組隨機搭配這6個導引板用自聚式樹脂(RelyX U200, 3M ESPE)進行黏合。將所有共42組義齒利用桌掃機(E3; 3Shape A/S)掃描並得到掃描檔案(Scanned data)。利用3D疊合軟體(Geomagic Control X, 3D Systems Inc)將原始設計檔和掃描檔案去進行疊合(superimposition)及3維空間分析(3D compare)，以均方根誤差(root mean square)代表誤差大小，用wilcoxon signed rank test 去檢定各組均方根是否和設計檔有差異；利用kruskal-wallis test去比較四組之間的差異，再使用Dwass-Steel-Critchlow-Fligner (DSCF) Test去進行成對比較。另一方面，利用游標尺量測所有實際義齒模型的右上第一大臼齒、右上犬齒、右上正中門牙、左上犬齒及左上正中門牙的咬頭至義齒基底底部的高度並記錄，利用kruskal-wallis test去比較四組之間的差異，再使用Dwass-Steel-Critchlow-Fligner (DSCF) Test去進行成對比較，設定p 值小於0.05時有顯著差異。

實驗結果： 黏著義齒後，實際模型量測部分，右上第一大臼齒、右上犬齒、右上正中門牙、左上犬齒和左上第一大臼齒的在對照組和實驗組(T1.T2.T3)之間四組的平均量測高度有顯著差異。對照組和實驗組有有顯著差異者在右上第一大臼齒處為對照組與T1；右上犬齒處是對照組與T1及T3；右上正中門牙處是對照組與T3；左上犬齒是對照組與T3；左上第一大臼齒是對照組與T2和T3 (p<0.05)。 數位影像疊合分析部分，將對照組與三組實驗組與原始設計檔相比，在右上第一大臼齒、右上犬齒、右上正中門牙、左上犬齒和左上第一大臼齒處的均方根誤差皆與原始設計檔有顯著差異(C: p=0.031;T1.T2.T3: p=0.0005)；而四組相比，T3組在五個量測區域都和對照組有顯著差異；T2組在左上第一大臼齒和對照組有顯著差異；T3組在右上第一大臼齒處有顯著差異。

結論： 在本實驗有限的條件下，推論出以下的結論： 1.單件式車削式義齒和兩件式車削式義齒相比，產生的咬合偏移量是最小的。 2.兩件式車削式義齒中，黏著單顆牙齒的設計會比黏著整段牙弓及黏著四段三單位牙橋的設計在較多咬合面有更大的咬合偏移誤差，且有顯著差異。 3.兩件式車削式義齒中，黏著整段牙弓及黏著四段三單位牙橋的設計產生的咬合偏移誤差並無顯著差異。

Objective: This in-vitro study was to evaluate the effects of different artificial teeth designs of two-piece milled dentures to the teeth displacement compared to the monolithic one under dental-related CAD/CAM software procedures. Material and methods A sample model was prepared and scanned through the desk scanner (E3, 3shape A/S). We used dental CAD/CAM software (3shape dental system, 3shape A/S) to design upper complete denture. We used the same design settings to plan one-piece denture as control group and two-piece denture as 3 tested group with 3 different artificial teeth designs respectively: T1, the full arch design; T2, 4 three-unit bridges design; individual tooth design. The control group had 6 samples and T1, T2 and T3 had 12 samples respectively. After designing, all the three-dimensional structure file (STL files) were exported as designed datas and sent to be milled by 5-axis machine (Idensol 5XP; Toshin Tech.) with the PMMA resin discs (ARDENTA, ARIX CNC MACHINES CO.). We further used STL files of tested groups to create the cementation index through the CAD software (DentalCAD, exocad GmbH.). We used 3D printing technique to print the index. Overall 6 indices were printed and post-processed. All the tested groups were then be cemented with self-adhesive resin cement (RelyX U200 clicker, 3M Espe, USA). After cementation, all the dentures were desk-scanned to get the scanned data. Then we superimposed the scanned data with the control groups and tested groups to evaluate the displacement of the cameo surface of the artificial teeth. Calculating the mean deviation and root measure square to get the data analysis. On the other hand, we used the caliper to calculate the degrees of displacement between one-pieced and two-pieced complete denture over the cusp tip and incisal edge of teeth. Results About the measuring data there was significant difference between the control group and all the tested groups over all the 5 measuring points. The T1 group were significantly higher than the control group over upper right first molar and upper right canine. The T2 group were significantly higher than the control group over upper left first molar area. The T3 group were significantly higher than control group over upper right and left canine, upper central incisor and upper left first molar area. There was significant difference between all the tested groups except the upper left molar area. About the 3D comparison data there was significant difference between the control group and all the tested groups. T3 group had significant difference compared to control group over all the 5 measuring regions. T1 group were significantly higher than the control group over upper bilateral first molar and upper left canine. T2 group were significantly higher than the control group over upper bilateral first molar and upper right canine. Among the 3 tested groups, there no significance difference. Conclusions Within the limitation of the study, the conclusions are: 1.The one-piece denture had the smallest deviations compared to two-pieced denture. 2.Compared the different artificial teeth designs, the individual tooth design had highest occlusal deviations over multiple occlusal measuring surfaces. 3.There is no significant difference between the occlusal deviation of the full arch design and 4 three-unit bridges design.