EPI-I

The Journal of Prosthetic Dentistry

287November 2009

Tran et alTran et al

A round-rest, distal depression clasp is suggested as an esthetic alternative to a conventional clasp for maxillary anterior teeth serving as abutments for a removable partial denture. A lingual round rest provides support for the prosthesis, and a mesiolingual reciprocating plate is present. A split minor connector engages a distal depression for retention. The facial surface of the abutment displays no metal and provides an esthetic result. (J Prosthet Dent 2009;102:286-289)

A removable partial denture using an esthetically designed round-rest distal clasp on maxillary anterior abutment teeth: A clinical report

Chi Tran, DDS,a Eugene LaBarre, DMD, MS,b and Howard M. Landesman, DDS, MEdc

The Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, Calif

aAssistant Clinical Professor, Department of Restorative Dentistry.bAssociate Professor and Chair, Department of Prosthodontics.cClinical Professor, Department of Prosthodontics.

Circumferential clasps on maxillary anterior teeth may not be esthetically acceptable to patients who require removable partial dentures1 (RPDs). Extracoronal and intracoronal preci-sion attachments can be esthetic, but are of greater expense and are more difficult to fabricate and maintain.2 A mesial rest, proximal plate, and I bar (RPI) clasp,3,4 and mesial rest, proxi-mal plate, and Akers (RPA) clasp5 can be used for maxillary anterior teeth, but may present unacceptable esthet-ics for patients with high lip lines or high smile lines. A modification to the RPA clasp has been described6 using a cast gold clasp engaging an undercut at the distofacial line angle of the maxillary canine and soldered to the partial denture framework, but fabrication of this clasp assembly is expensive and complex. A wrought wire clasp engaging a proximal un-dercut and soldered to the partial denture framework is an esthetic al-ternative.7 Plunger attachments en-gaging a distal depression have been used8; however, there may not be ad-equate space to place denture teeth. Rotational path designs for partial dentures9,10 can achieve excellent es-thetic results for anterior teeth abut-

ments, but they are difficult to adjust and are seldom used for distal exten-sion RPDs.11 Tooth-colored polymer clasps, featuring acetyl and thermo-plastic resins, are used because of ease of fabrication and esthetics, but are not readily adjustable and have not demonstrated durability. Lingual retention and the elimination of the visible facial clasp arm have been pro-posed for premolars12,13; however, ca-nines may require the fabrication of a crown with milled surfaces providing a deep rest and mesial lingual reten-

tive area.14 A maxillary canine retainer with mesial groove reciprocation, me-siolingual rest, and distofacial depres-sion retention has been described,15 but it may not be applicable to maxil-lary incisors.

A round-rest, distal depression clasp (RRDD) (Fig. 1) is presented as an esthetic alternative to a con-ventional clasp for maxillary anterior teeth serving as abutments for a re-movable partial denture. The RRDD clasp design was developed specifi-cally for maxillary incisors or canine

1 RRDD clasp: support is provided by lingual round rest. Me-sial reciprocating plane and distal guide plane are prepared as shown. Distal depression is placed for retention. Denture tooth is placed against distal proximal contact.

abutments for RPDs when esthetic demands are high, conventional and polymer clasps are unacceptable, and the patient lacks the financial capa-bilities for an intra- or extracoronal clasp-retained RPD. If the edentulous residual ridge is distal to a maxillary incisor or canine, the RRDD clasp consists of a round rest seat located near the cingulum, a mesiolingual reciprocating plate, and a split mi-nor connector engaging a distal de-pression for retention (Fig. 2). If the edentulous ridge is mesial to a max-illary incisor or canine, this clasp de-sign is no longer called an RRDD; it becomes a round-rest mesial depres-sion (RRMD). The RRDD and RRMD are alternatives to a rotational path design.

The purpose of this clinical report is to describe a method of eliminating the display of metal on the labial sur-face of maxillary anterior teeth used as abutments for an RPD by using a round-rest, distal depression clasp.

CLINICAL REPORT

A patient with a missing maxil-lary left canine due to root fracture presented to the Arthur A. Dugoni School of Dentistry, University of the Pacific Dental Clinic (Fig. 3). The premolars and first molar had been previously lost, and the patient did not want implant-supported restora-tions. Financial considerations were a major concern. The patient also did

not want to display any metal clasp on the anterior teeth. Three options for an RPD were presented: a conven-tional RPD with infrabulge clasps, a rotational path design, and an RRDD design. The patient chose the RRDD design for esthetic reasons and for ease of placement.

The diagnostic casts were surveyed and a maxillary RPD was designed with a broad palatal strap as major connector, occlusal rests and cast cir-cumferential clasps on all molars, and an RRDD clasp on the maxillary left lateral incisor. A round cingulum rest was prepared with a round bur (No. 4, 014, 1/10 mm; Brasseler USA, Sa-vannah, Ga) to a depth of 0.75 mm. The reciprocating plane on the me-siolingual surface of the incisor was prepared with a thin parallel chamfer tip carbide bur (H283.31.010: Bras-seler USA) from the mesiolingual line angle, and stopped just short of the mesial proximal contact. The guiding plane on the distolingual surface of the tooth was prepared from the dis-tolingual line angle to stop just short of the distal proximal contact area. In the middle of this surface, a distal de-pression, 0.5 mm deep, was prepared with a No. 4 round bur (Brasseler USA), 1 mm above the gingival mar-gin, and 1 mm lingual to the proximal contact (Fig. 1). A ball burnisher (T-Ball 34; Suter Dental Mfg Co, Chico, Calif ) was placed in the round rest seat and distal depression to verify adequate preparation.

After completion of mouth prepa-rations, an addition-reaction silicone impression (Aquasil; Dentsply Intl, York, Pa) was made. The definitive cast was prepared and surveyed. The minor connector and mesiolingual plate of the RRDD were 3 mm wide mesiodistally and 0.5 mm thick occlu-sogingivally, respectively, to provide adequate rigidity. Distal to the minor connector, a 1- to 1.5-mm-wide split was placed in the casting. A smaller minor connector, 2 mm wide tapering to 1 mm, engaged the distal depres-sion. This small minor connector had a length of 10 mm from the major con-nector to the center of the depression to allow adequate flexibility (Fig. 2). The flexibility of the minor connector engaging the distal depression can be altered by increasing its length or by thinning the dimensions of the arm. A cast chrome (Vitallium; Dentsply Austenal, York, Pa) RPD framework was fabricated (Fig. 4). The frame-work was evaluated intraorally and adjusted. The retentive values of this clasping design were comparable to a cast circumferential clasp or wrought wire.16-18 After maxillomandibular jawrelation records were completed, denture teeth (Bioblend; Dentsply Trubyte, York, Pa) were arranged and evaluated intraorally. Prior to denture base processing, a rubber separat-ing medium (Rubber Sep; Kerr Corp, Orange, Calif ) was used generously on the minor connector flexible arm so that it could flex without bind-ing from the processed acrylic resin denture base. The denture base was processed and finished. A round bur (No. 1; Brasseler USA), sandpaper, or emery-coated discs (Moore’s discs; E.C. Moore, Dearborn, Mich) were used to remove excess acrylic resin to prevent interference with the flexible arm (Figs. 5 and 6). The denture was inserted and the patient was recalled twice each year for 7 years. The pa-tient was pleased with the functional and esthetic results (Fig. 7).

2 As framework is seated or removed, split minor connector flexes. When RPD is completely seated, split minor connector should be passive.