4. Fit the overlay casting to the implant prosthesis and solder it in place. 5. Reinsert the modified implant prosthesis and make new impressions and jaw relation records for fabrication of the maxillary fixed partial denture (Fig. 4).
Reprint requests to:
Making a provisional crown removable partial denture.
DR. RONALD D. WOODY GRADUATE PROSTHODONTICS BAYLOR COLLEGE OF DENTISTRY 3302 GASTON AVE. DALLAS, TX 75246
of an existing
Boston University, Goldman School of Graduate Dentistry, Boston, Mass.
New crowns are often planned for clasped abutment teeth of an existing removable partial denture. However, maintaining function of the removable partial denture while the new crowns are being made can be a problem if provisional crowns do not incorporate the rest seats, guiding planes, and undercuts needed for clasping. Using a prefabricated provisional crown is ineffective in this situation. Alternatively, a provisional crown can be custommade with a conventional ‘Lblock” technique, but difficulty is encountered in trying to fit it to the clasp. The provisional crown will often be undercontoured, resulting in space between it and the clasp. This article describes an alternate technique for constructing well-fitting provisional crowns under existing removable partial dentures.
1. Lubricate the acrylic resin sections of the existing removable partial denture. 2. Mix tooth-colored acrylic resin as if for a “block” technique for making a provisional crown, place the acrylic resin on the prepared abutment tooth, and seat the existing removable partial denture completely. Have the patient close into centric occlusion (Fig. 1). 3. As the acrylic resin is setting, repeatedly remove and reseat the removable partial denture to prevent the acrylic resin from engaging tooth undercuts adjacent to the preparation. The acrylic resin will attach to undercuts in the removable partial denture. 4. When the acrylic resin has polymerized, grind out 0.5 mm to 1 mm from the inner surface of the acrylic resin mass. Mix additional acrylic resin for relining the planned provisional crown, and place it in the crown. Reseat the removable partial denture completely. Care-
aAssociateProfessor,Department of Prosthodontics. 10/4/38586
Fig. 1. RPD has been seated over acrylic resin block and patient has closed in centric occlusion.
Fig. 2. Excess acrylic resin removed to allow separation of provisional crown from RPD framework.
Fig. 3. Provisional crown separated from RPD framework before final contouring.
fully remove and reseat the removable partial denture while the acrylic resin cures. 5. When the acrylic resin has polymerized, visualize the margin of the crown preparation, mark it with a pencil, and grind off the excesswith a small cylindrical bur. The goal is to remove enough excess acrylic resin to allow disengaging the prosthesis from the crown occlusally, similar to the way the prosthesis will disengage from the crown intraorally. It is necessary to remove acrylic resin that is occlusal to the rest, reciprocal arm, and all except the tip of the retentive arm. In addition, it will be necessary to remove from the crown any acrylic resin contacting the major connector or acrylic resin bases of the removable partial denture (Fig. 2). Note that lubricating the acrylic resin bases of the removable partial denture will prevent bonding of the temporary crowns.
Fig. 4. Completed provisional crown with RPD in place.
6. When the provisional crown has been separated from the removable partial denture, the critical regions (rest seat, guiding planes, contact of reciprocal and retentive clasp arms) can be marked with a pencil to preserve them while the contours of the provisional crown are created and polished (Figs. 3 and 4). 7. If the retentive surface was inadvertently lost during the previous step, it is possible to add acrylic resin with a small brush to recreate the undercut. 8. The provisional crown should be cemented so that it will be sufficiently stable to prevent its dislodgment during normal use. Reprint requests to: MR. RICHARD GORDON 30 ROSE AVE. MARBLEHEAD, MA 01945
the finish of stone dies during
Pontificia kiniversidad Javeriana, Bogota, Colombia
1. Protective wax cap placed over coronal portion of die protects die during trimming. Shallow ditch is carved below finish line.
dental student, Pontificia