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Journal of Prosthetic Dentistry

Fabricating an altered cast to facilitate intraoral processing of the LOCATOR attachment

  • Ju-Hyoung Lee
    Correspondence
    Corresponding author: Dr Ju-Hyoung Lee, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu 41940, REPUBLIC OF KOREA
    Affiliations
    Associate Professor, Department of Predoctoral Clinical Education, Oral Health Center for People with Disabilities, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
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      The LOCATOR attachment (Zest Anchors LLC) has been widely used for implant-retained overdentures (IODs),
      • Kronstrom M.
      • Carlsson G.E.
      An international survey among prosthodontists of the use of mandibular implant-supported dental prostheses.
      ,
      • Bellia E.
      • Audenino G.
      • Ceruti P.
      • Bassi F.
      Clinical assessment of short implants retaining removable partial dentures: 4-year follow-up.
      with several techniques for incorporating the attachment into the IOD proposed.
      • Bidra A.S.
      • Agar J.R.
      • Taylor T.D.
      • Lee C.
      • Ortegon S.
      Techniques for incorporation of attachments in implant-retained overdentures with unsplinted abutments.
      • Drago C.
      • Hsu Y.T.
      A procedure for relieving an existing prosthesis to fit implant abutments.
      • Srinivasan M.
      • Kalberer N.
      • Maniewicz S.
      • Müller F.
      Implant overdentures retained by self-aligning stud-type attachments: a clinical report.
      When the indirect method is used, a strong bond between the matrix and acrylic resin can be achieved, and staining or porosities on the intaglio surface of the IOD are prevented.
      • Bidra A.S.
      • Agar J.R.
      • Taylor T.D.
      • Lee C.
      • Ortegon S.
      Techniques for incorporation of attachments in implant-retained overdentures with unsplinted abutments.
      However, the method requires additional laboratory procedures and expense, LOCATOR impression posts (Zest Anchors LLC) and the LOCATOR analog (Zest Anchors LLC) are needed, and distortion during denture processing may occur.
      • Bidra A.S.
      • Agar J.R.
      • Taylor T.D.
      • Lee C.
      • Ortegon S.
      Techniques for incorporation of attachments in implant-retained overdentures with unsplinted abutments.
      ,
      • Drago C.
      The direct method may avoid limitations of the indirect method.
      • Bidra A.S.
      • Agar J.R.
      • Taylor T.D.
      • Lee C.
      • Ortegon S.
      Techniques for incorporation of attachments in implant-retained overdentures with unsplinted abutments.
      • Drago C.
      • Hsu Y.T.
      A procedure for relieving an existing prosthesis to fit implant abutments.
      • Srinivasan M.
      • Kalberer N.
      • Maniewicz S.
      • Müller F.
      Implant overdentures retained by self-aligning stud-type attachments: a clinical report.
      After the attachment position is transferred to the intaglio surface of the IOD by using an indelible pencil
      • Bidra A.S.
      • Agar J.R.
      • Taylor T.D.
      • Lee C.
      • Ortegon S.
      Techniques for incorporation of attachments in implant-retained overdentures with unsplinted abutments.
      ,
      • Drago C.
      and a silicone material,
      • Hsu Y.T.
      A procedure for relieving an existing prosthesis to fit implant abutments.
      ,
      • Srinivasan M.
      • Kalberer N.
      • Maniewicz S.
      • Müller F.
      Implant overdentures retained by self-aligning stud-type attachments: a clinical report.
      the corresponding area is relieved. However, the procedure increases chair time, and excessive relief may be made, thereby increasing the risk of denture base fracture. This article introduces a technique for fabricating an altered cast to reduce interference between the matrix and the denture base. By using this technique, the disadvantages of the direct technique can be efficiently overcome.

      Technique

      Horizontal space for incorporating the attachment comprises the diameter of the matrix (5.49 mm) and the width of acrylic resin that encircles the matrix.
      • Alsiyabi A.S.
      • Felton D.A.
      • Cooper L.F.
      The role of abutment-attachment selection in resolving inadequate interarch distance: a clinical report.
      ,
      • Ahuja S.
      • Cagna D.R.
      Classification and management of restorative space in edentulous implant overdenture patients.
      Vertical space for incorporation comprises the height of the matrix (2.35 mm) and the resin thickness.
      • Alsiyabi A.S.
      • Felton D.A.
      • Cooper L.F.
      The role of abutment-attachment selection in resolving inadequate interarch distance: a clinical report.
      ,
      • Ahuja S.
      • Cagna D.R.
      Classification and management of restorative space in edentulous implant overdenture patients.
      • 1.
        Make a definitive impression of the tissue and healing abutments. Fabricate a definitive cast. If the healing abutments might fracture when separating the cast from the impression, fabricate resin dies with autopolymerizing acrylic resin (Pattern Resin LS; GC America Inc) and dowel pins (World Dowel Pin; World D&D).
      • 2.
        Using a pencil, draw a cross around the healing abutments to indicate their centers. Draw parallel lines to each axis of the healing abutments on the lateral surfaces of the cast. Prepare grooves on the healing abutments with a laboratory bur (H33.104.012; Komet Dental) (Fig. 1).
        Figure thumbnail gr1
        Figure 1Grooves placed on surface of healing abutment. Note lines on cast to indicate center and axis of healing abutment.
      • 3.
        Cut an 8-mm-diameter straw into 5-mm lengths with scissors (9 Dean Scissors; Hu-Friedy). Place the straw on the cast in accordance with the marks. Inject a transparent polyvinyl siloxane occlusal registration material (Memosil 2; Kulzer GmbH) into the straw with an automix gun (Fig. 2A). After polymerization, remove the straw and excess with a blade (No. 15 Scalpel Blade; Paragon) (Fig. 2B).
        Figure thumbnail gr2
        Figure 2A, Straw filled with transparent polyvinyl siloxane material on cast. B, Altered cast.
      • 4.
        Fabricate the definitive IOD in accorance with conventional prosthodontic principles (Fig. 3).
        • Carr A.B.
        • Brown D.T.
        McCracken's removable partial prosthodontics.
        ,
        • Zarb G.A.
        • Hobkirk J.A.
        • Eckert S.E.
        • Jacob R.F.
        Prosthodontic treatment for edentulous patients.
        Figure thumbnail gr3
        Figure 3Intaglio view of definitive denture. Note that transparent spacer allows sufficient clearance for attachment and polymethyl methacrylate resin.

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