植牙手術目前已普遍被使用於缺牙治療上，一個成功的植牙手術不僅須考量到植體與齒槽骨的骨整合外，對於術後假牙的美觀性也越來越被重視。而植牙導引板的使用可以輔助臨床牙醫師快速、精確、傷口小地情況下完成植牙手術，透過術前電腦斷層影像的評估與植牙位置規劃，牙醫師只需依照植牙導引板上的導引孔洞即可取得最佳的植牙位置。然而，植牙導引板的製作通常為使用3D列印方式完成，但3D列印方式所產生的植牙導引板容易因電腦斷層影像筏值的人為設定及3D列印機的加工誤差造成植牙準確度不穩定，且3D列印的植牙導引板通常製作成本也較高，也因此，能夠精準、快速、低成本的取得植牙導引板仍然一直是臨床上所需要的。
本研究使用幾何轉換法(GCM)將植牙規劃位置進行投影量測，並將此投射資訊轉移至標準板上，最後搭配鑽孔機即可完成植牙導引板製作。為了驗證準確度，本研究分別以體外及體內試驗進行幾何轉換法完成之植牙導引板驗證。於體外試驗中，GCM手術導引板與3D列印導引板於缺牙模型 (缺牙位置:32 36 45 46 )上進行植牙模擬試驗，並比較兩種方法於實際植牙位置與規劃之誤差，結果顯示GCM植牙導引板與3D列印導引板於植牙角度偏差量上無顯著的差異(p>0.05)。GCM植牙偏差量於植體頭部位置為0.65±0.39mm、植體尖端位置為0.81±0.33mm及整體角度偏差為0.76°±0.51°。3D列印導引板之植牙偏差量於植體頭部位置為0.44±0.22mm、植體尖端位置為0.66±0.37mm及3D角度偏差為0.58°±0.32°。於體內試驗中，9位缺牙患者以GCM導引板進行植牙手術，結果顯示GCM植牙導板之偏差量於植體頭部位置可達1.03±0.27mm、植體尖端位置1.17±0.24mm及3D角度偏差1.37°±0.21°。本研究提出之幾何轉換法已證明其精確度，並且可有效地將拍攝用導引板轉換成植牙手術導引板。

Dental implants are widely used in the restoration of missing teeth. Successful implant surgery not only considers osseointegration between implant and bone but also places considerable emphasis on the esthetic appearance of the restored tooth. A dental surgical guide is used to help the dentist place the dental implant quickly, accurately, and with minimal invasion. Through preoperative evaluation and virtual implant planning in the edentulous region, dentists can place an implant in the optimal position by following the guide holes in the surgical guide. The guide is generally fabricated through three-dimensional (3D) printing. However, the stability of a 3D-printed guide is sensitive to, and influenced by, the threshold value setting in the image process software and errors in the 3D printing procedure. Moreover, the cost of a 3D-printed guide for clinical applications is high. Thus, an accurate, fast, and low-cost method for producing surgical guides remains a clinical requirement.
To this end, this study proposes a geometric conversion method (GCM) to measure the planned implant position in projection planes. Using this conversion information, the planned implant positions can be transformed into a surgical guide using a drilling machine. In vitro and in vivo tests were designed to validate the GCM guide. The in vitro test was applied to compare the accuracy of the GCM guide and the 3D-printed guide by employing edentulous models (implant sites: 32, 36, 45, and 47). The in vitro test revealed no significant differences (p > 0.05) in the planned and placed angulations between the GCM guide and the 3D-printed guide. In the GCM guide, the deviation between the planned and placed implants was 0.65 ± 0.39 mm in the implant head, 0.81 ± 0.33 mm in the implant apex, and 0.76° ± 0.51° in 3D angulation. In the 3D-printed guide, the deviation between the planned and placed implants was 0.44 ± 0.22 mm in the implant head, 0.66 ± 0.37 mm in the implant apex, and 0.58° ± 0.32° in 3D angulation. For the in vivo test, nine edentulous patients were selected to receive GCM-guided surgery. The results indicated that GCM guide could achieve the 3D offset deviations of 1.03±0.27mm and 1.17±0.24mm at the implant head and apex, respectively and 1.37°±0.21°for the 3D angulation. These results evidence the accuracy of the GCM, and it is therefore a feasible method for transforming a radiographic guide into a surgical guide.

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