Transferring dentofacial analyzer into analog workflow with CAD digitization: A dental technique

Abstract

With the transition to digital workflows, moving from a digital platform to an articulator for laboratory procedures such as adding porcelain or luting titanium abutments is sometimes required. This report describes a technique to facilitate the transfer of jaw-relation records to a digital mounting template. Once digitally mounted, the casts can be printed with mounting plates attached to the temporomandibular joints in the appropriate orientation. They can then be placed in an articulator and used for layering porcelain or luting titanium abutments for screw-retained restorations.

Digital articulation has been in development for many years. As the technology advances, it is incorporated into more and more dental computer-aided design (CAD) programs. Digital workflows can often be completed without the use of physical casts. This can be accomplished when the entire restoration is fabricated by using computer-aided manufacturing (CAM) technique. However, physically articulated casts are still needed in some clinical and laboratory situations. It is no less important today to have casts, whether digital, cast and articulated, or printed from digital scans, articulated by using appropriate jaw-relation records. Physical casts may also be needed for occlusal adjustments, luting titanium abutments, adding occlusal or incisal porcelain, prosthetic preparation for computer-guided implant surgery, or simply identifying a situation not easily seen on the computer screen.

Methods for digital facebow transfers that incorporate new digital techniques have been identified, but few have adapted the long-standing techniques that are prevalent in dental practice. Many dental design programs incorporate digital articulators, but the authors are unaware of an inexpensive and straightforward way to relate a facebow transfer to the digital articulator without a facial scan or cone beam computed tomography scan. The presented technique offers a way to transfer the casts to a physical semiadjustable articulator for the finalization of restorations and appliances in the laboratory while still being in a proper relationship to the hinge axis.

Technique

Creating a calibrated digital mounting template

  • 1.

    Design mounting plates (123D Design and Meshmixer; Autodesk Inc) ( Fig. 1 ) which can accept a metal insert that allows them to be printed (J750; Stratasys Ltd) and magnetically attached to an articulator (Model PCH Articulator; Panadent Corp). This can be done by designing a plate from scratch by using 123D Design (Autodesk Inc) or a modeling software program (Meshmixer; Autodesk Inc) ( Fig. 1 ).

    Figure 1
    Articulator plates designed and placed relative to each other in estimated position.
  • 2.

    Design and attach calibration geometries to the mounting plates to create calibration plates. The mandibular geometry should be a plane with several smaller geometries attached at the outer edges for later alignment. The smaller geometries can be cubic or spherical. Position the plane so that its maxillary surface matches the height of the Kois Adjustable Platform (Panadent Corp) as closely as possible. The maxillary geometry should be an asymmetric polyhedron that is smaller than the opposing plate in the horizontal axes. Position the maxillary geometry so that it sits slightly above the mandibular geometry (about 3 to 5 mm). Once the calibration geometries are designed, attach them by using Meshmixer to their respective mounting plates by using cylindrical or polyhedral meshes. Print and place the calibration plates on the articulator.

  • 3.

    Make a polyvinyl siloxane (PVS) registration (First Quarter Impression Material; Zest Dental Solutions) of the 2 calibration plates opposing each other on the articulator (record 1) ( Fig. 2 ) and one of the maxillary plates opposing a disposable index tray seated on the adjustable platform (record 2) ( Fig. 3 ). Trim the excess PVS material from the smaller geometries on the outer edge of the mandibular calibration plate and from the incisal tab and posterior corners of the disposable index tray. The PVS records should be left on the disposable index tray and on the mandibular calibration plate respectively for scanning.

    Figure 2
    Registration of opposing calibration geometries.

    Figure 3
    Registration of maxillary calibration geometry to Kois Disposable Index Tray.
  • 4.

    Scan a second unused disposable index tray and both PVS records (D900L Scanner; 3Shape). The scan of record 1 should include not only the PVS material but also the smaller geometries on the edge of the plane. The scan of record 2 should include the PVS material along with the entire disposable index tray.

  • 5.

    Align the digital versions of the calibration plates to each other by using record 1. Then align record 2 to the digital version of the maxillary calibration plate. Finally, align the unused disposable index tray to record 2 and the original mounting plates to the digital versions of the calibration plates (coDiagnostiX; Dental Wings).

  • 6.

    Delete record 1, record 2, and both calibration plates, leaving the original mounting plates and the unused disposable index tray. This will leave the 2 opposing mounting plates and a Kois Disposable Index Tray in the exact positions that correspond to the articulator chosen for use (Model PCH Articulator; Panadent Corp) ( Fig. 4 ). Save this as a master template for use with future treatments.

Jan 12, 2020 | Posted by in Prosthodontics | Comments Off on Transferring dentofacial analyzer into analog workflow with CAD digitization: A dental technique
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