Technical Tips for Improved Retention and Stabilization of a Unilateral Removable Partial Denture

Unilateral removable partial dentures (RPDs) have been suggested for the restoration of short-span, bounded edentulous spaces. An advantage of this restoration is the avoidance of an extensive palatal or lingual major connector; however, the design provides no cross-arch stabilization, which can result in easy dislodgement1 and additional complications.2 Consequently, an RPD with a cross-arch stabilization3 or an implant-retained fixed partial denture (FPD) is generally preferred.4 Limited residual anatomy and close proximity of the maxillary sinus may not allow ideal location or number of implants to support FPD, and the patient may be unable or unwilling to undergo implant site development procedures in the form of grafting or augmentation to allow placement of an adequate number of ideally located implants.5^,6 

The creation of posterior implant support for a removable prosthesis would appear to be an obvious improvement over the conventional distal extension base.7 A dental implant can convert a distal extension RPD base from a tooth- and tissue-supported prosthesis to a tooth- and implant-supported and retained prosthesis. A posterior implant with a resilient frictional abutment complex that is retentive and provides a definitive stop can provide stability and virtually eliminate problems often associated with a tooth- and tissue-supported distal extension RPD.8 Another advantage of an implant-retained prosthesis is that the extension of the base can be reduced, because the implant provides the same stability as a terminal abutment would in a Kennedy Class III situation.7 

The degree of prosthesis retention and stability is based on attachment type, design, alignment, and position.9 Stud attachments have been successfully used to stabilize and retain implant-supported RPDs.7^,8^,10 

This report describes technical tips for creating an implant-retained unilateral RPD with an extracoronal attachment on terminal abutment of the adjacent residual tooth.

1. After preparation of abutment teeth, place the impression coping (Zimmer Dental, Carlsbad, Calif) onto the implant (Tapered Screw-Vent, Zimmer Dental). Make the impression with an elastomeric material (Speedex, Coltene/Whaledent, Altstatten, Switzerland) using a putty-wash technique and a stock tray. Make the impression of mandibular arch (CA37, Cavex Holland BV, Haarlem, Netherlands). Pour the casts in Type IV stone (Bego, Bremen, Germany). Select the proper alignment correction abutment (ERA, Sterngold, Attleboro, Mass) on the implant.

2. Mount the casts prepared from preliminary impressions into a semiadjustable articulator (Dentatus ARH, Stockholm, Sweden) using a face-bow and the centric relation record.

3. Wax up crowns and use a surveyor (Bego) to mill their palatal surfaces for stability and retention. Place the attachment (Snap-riegel, Servo-dental, Hagen, Germany) on the distal surface of the crown wax-up using a surveyor (Bego) (Figures 1a and b) and cast in a base-metal alloy (Kera N, Eisenbacher Dentalwaren GmbH, Noerth, Germany). Verify the fit intraorally. After completing the metal-ceramic restoration (Omega 900, VITA Zahnfabrik, Bad Sackingen, Germany), evaluate esthetics and occlusion intraorally. Make a secondary impression on both the ceramometal restoration and the impression coping on the implant (Impregum, 3M ESPE, St Paul, Minn). Pour the impression with Type III stone (Moldano Dental Stone, Bayer Co, Leverkusen, Germany).

4. Mount the maxillary cast onto the semiadjustable articulator (Dentatus ARH) using a face-bow and new centric relation record.

5. Cast the RPD framework in a base-metal alloy (Biosil-F, Degussa, Hanau, Germany) (Figure 2). Verify the framework fit intraorally. Arrange the teeth (Major, Major Prodotti Dentari, Torino, Italy). After completing the denture (Figure 3), cement the ceramometal restorations with polycarboxilate cement (Durelon, 3M ESPE) and verify proper occlusion. Transfer the direct abutment with attachment (ERA) onto the implant intraorally. Block out attachment undercuts with glove material. Place a metal housing with processing plastic element onto the attachment.

6. Place the unilateral RPD in the mouth (Figure 4), pour autopolimerizing acrylic (Meliodent, Heraeus Kulzer, Wehrhein, Germany) from the opening of RPD. Remove the denture from the mouth (Figure 5). Put self-curing cement (Alpha-Dent, Dental Technologist Inc, Lincolnwood, Ill) into the abutment base to fix the determined position of alignment correction piece to the base of the abutment and cement them to each other by placing the denture into the mouth on the proper occlusion.

7. Remove the denture and clean excessive cement and acrylic resin. Replace the processing plastic element with proper retentive element (Figure 6).

This article describes an alternative treatment option to add retention and stability to a unilateral RPD through the use of an extracoronal attachment and posterior implant support.