Complete digital workflow for prosthesis prototype fabrication with double digital scanning: A retrospective study with 45 edentulous jaws

Abstract

Purpose To assess the accuracy of fit of complete‐arch printed prosthesis prototypes generated with a digital workflow protocol for completely edentulous jaws. Materials and methods Forty‐five edentulous jaws (35 patients) underwent intraoral complete‐arch digital scans with the double digital scanning (DDS) technique and the generated standard tessellation language (STL) files were superimposed and imported into computer‐aided design software. After STL merging, each master STL file was used for printing a prosthesis prototype. The primary outcome was the accuracy of fit assessment of the printed prototypes on verified master stone casts. Two experienced clinicians tested the accuracy of fit with radiographs and screw‐resistance tests. Secondary outcomes were the effect of the scan body shape and implant number on the accuracy of fit. Results Out of the 45 DDS‐generated prosthesis prototypes, 39 presented with accurate fit on verified master stone casts, yielding an 86.70% accuracy of fit. Cylindrical scan bodies led to 100% accuracy of fit (25/25), whereas polygonal scan bodies presented with 70% accuracy of fit (14/20). Four implant‐supported prostheses yielded 100% accuracy of fit (12/12), compared with 25/29 (86.30%) accuracy of fit for the six‐implant‐supported ones. Fisher's exact test was used to assess the effect of different scan body shapes (p = 0.005) and implant number on accuracy of fit. Chi‐squared test was used to assess the association between the number of implants per arch and the accuracy of fit (p = 0.039). Conclusions Thirty‐nine out of 45 complete‐arch prosthesis prototypes generated with a completely digital workflow presented with clinically acceptable fit. The effect of the scan body design and implant number was statistically significant, favoring cylindrical scan bodies and four‐implant‐supported prostheses.

Reverse scan body: A complete digital workflow for prosthesis prototype fabrication

“…This reduces the number of required appointments and most importantly allows for implant data acquisition in the edentulous mandible which has been reported to be problematic. [3][4][5][6][7][8][9][10] The fact that 44 out of 50 3D-printed prosthesis prototypes presented with acceptable fit highlights the limitations with 3D printing full-arch prototypes that may include the resin being used, the nesting orientation of the STL file, and the post-processing procedures. The same STL files were used for both milling and 3D printing, yet 88% fit was achieved with 3D printing compared to 100% fit with milling.…”

“…Clinical implications from these findings can be drawn that accurately fitting digitally fabricated prosthesis prototypes can be milled after extraoral scanning with reverse scan bodies skipping implant data acquisition with intraoral scanning. This reduces the number of required appointments and most importantly allows for implant data acquisition in the edentulous mandible which has been reported to be problematic 3–10 . The fact that 44 out of 50 3D‐printed prosthesis prototypes presented with acceptable fit highlights the limitations with 3D printing full‐arch prototypes that may include the resin being used, the nesting orientation of the STL file, and the post‐processing procedures.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] Full-arch digital implant scans for completely edentulous patients are techniquesensitive procedures mainly due to the absence of anatomical landmarks such as teeth, making the superimposition of scans with scan bodies and interim prostheses challenging. [1][2][3][4][5][6] The double digital scanning technique with the use of fiducial markers has been introduced for complete digital workflow for prosthesis prototype fabrication. 2 Fiducial markers are used to aid in data acquisition during edentulous jaw intrao-ral scanning and to assist in the merging of multiple digital scans.…”

“…Full-arch digital implant scanning with intraoral scanners (IOS) for the fabrication of prosthesis prototypes and definitive zirconia implant fixed complete dental prostheses (IFCDPs) is gaining popularity. [1][2][3][4][5][6][7][8][9][10][11][12] Full-arch digital implant scans for completely edentulous patients are techniquesensitive procedures mainly due to the absence of anatomical landmarks such as teeth, making the superimposition of scans with scan bodies and interim prostheses challenging. [1][2][3][4][5][6] The double digital scanning technique with the use of fiducial markers has been introduced for complete digital workflow for prosthesis prototype fabrication.…”

Reverse scan body: The scan pattern affects the fit of complete‐arch prototype prostheses

“…Fiducial markers such as radiopaque self‐adhesive markers, anchor pins, and appliances coupled with the double digital scanning (DDS) technique have been used in the complete digital workflow for prototype prosthesis fabrication 7–11 . Even with the use of fiducial markers, intraoral scanning remains challenging especially in the edentulous mandible due to anatomical factors 3–5 …”