Journal of Prosthetic Dentistry

Accuracy of digitally fabricated drilling guide to form screw-access channels in cement-retained implant prostheses: A randomized clinical trial

  • Soohyun Bae
    Graduate student, Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
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  • Hang-Nga Mai
    Research Professor, Institute for Translational Research in Dentistry, Kyungpook National University, Daegu, Republic of Korea

    Lecturer, Dental School of Hanoi University of Business and Technology, Hanoi, Vietnam
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  • Du-Hyeong Lee
    Corresponding author: Dr Du-Hyeong Lee, Department of Prosthodontics, School of Dentistry, Institute for Translational Research in Dentistry, Kyungpook National University, 2175 Dalgubeoldae-ro, Jung-Gu, Daegu 41940, REPUBLIC OF KOREA
    Associate Professor, Department of Prosthodontics, School of Dentistry, Institute for Translational Research in Dentistry, Kyungpook National University, Daegu, Republic of Korea
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Published:September 18, 2022DOI:


      Statement of problem

      Accurate intraoral preparation of screw channels in cement-retained implant prostheses could be a treatment challenge for tilted or badly positioned implants.


      The purpose of this randomized clinical trial was to evaluate screw channel accuracy for retrieving cement-retained implant prostheses by using a digitally fabricated drilling guide.

      Material and methods

      Twenty-four participants requiring removal of cement-retained implant prostheses were recruited and consecutively assigned to 1 of 2 groups. In the first group, drilling guides were fabricated by using an intraoral scan, computer-aided design (CAD), and 3D printing to facilitate screw channel preparation (guide group). In the second group, screw channel preparation was based on panoramic radiographs without a drilling guide (freehand group). Screw channel accuracy was evaluated with a 3D analysis and subsequently compared with the ideal shape of the screw channel for linear deviation at coronal and apical levels, angular deviation, surface loss deviation, and volume loss deviation. The ideal shape of the screw-access channel was based on the Ø2.2-mm cylinder image marked along the long axis of the implant. The Mann-Whitney U and Kruskal-Wallis tests were used for statistical analyses (α=.05).


      The drilling guide group showed higher dimensional accuracy than the freehand group for angular deviation (9.45 degrees versus 15.69 degrees; P=.014) and surface loss deviation (7.40 mm versus 9.53 mm; P=.001), especially when the implant was tilted more than 30 degrees. The deviation values of the screw channels were not significantly different according to implant tilt in either group (P>.05).


      Digitally fabricated drilling guides for intraoral preparation of screw channels in cement-retained implant prostheses can improve accuracy and provide a less-destructive screw channel.
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