A secondary
lingual
casting
for removable
partial
dentures
Carl A. Hansen, DDS,a and Terry A. Johnson, CDTb University of Nebraska Medical Center, College of Dentistry, and Dental Designs Laboratory, Lincoln, Neb. This article describes a technique for constructing a nickel chromium alloy lingual casting that reinforces a removable partial denture against heavy anterior occlusion. The metal can be cast into a thin secondary casting, and it is easily etched and bonded to the resin anterior teeth and associated base. This type of lingual casting has the potential to provide a simple and effective solution to the problem of repeated fracture or displacement of anterior teeth in many restorations. (J PROSTHET DENT 1992;67:799-800.)
H eavy anterior
occlusion or detrimental habits may cause recurrent breakage or displacement of anterior denture teeth. Cast lingual surfaces have been used extensively in conjunction with porcelain and plastic-slotted facings for removable partial dentures to prevent these problems. Because the metal backings for facings are cast as an integral part of the major connector, their use must be carefully planned before the framework is constructed. When the cast lingual backings have not been initially provided as part of the framework, they may be added to the prosthesis through the use of a secondary lingual casting. This article presents a technique for constructing and placing these castings. aAssociate Professor and Director of Graduate University of Nebraska C!ollege of Dentistry. bCertified Dental Technician, Lincoln, Neb.
TECHNIQUE 1. Make a jaw relationship record, with the prosthesis in the mouth. Use a silicone rubber occlusal registration material if needed. 2. Pick up the removable partial denture in an impression
Prosthodontics,
10/l/35793
2. Lingual surface of central incisors and denture base resin have been reduced to provide space for metal casting.
Fig.
1. Tooth that has been repeatedly fractured because of opposing occlusal forces.
Fig.
THE
JOURNAL
OF PROSTHE:TIC
DENTISTRY
Fig.
3. Refractory cast of resin base and lingual surfaces
of teeth.
799
HANSEN
AND
JOHNSON
6. Etched chromium-nickel backing ready to be cemented.
Fig.
Fig.
3. 4.
5.
6.
7. 8. 9.
10. 800
5. Wax pattern is luted to refractory cast.
of the entire dental arch and pour the impression with stone. Mount the cast with the prosthesis to a cast of the opposing arch and repair the broken tooth (teeth) (Fig. 1). Reduce the resin base material between the metal finish line and the teeth by approximately 1.0 mm (Fig. 2). If possible, provide two or more parallel holes in the resin for added retention and resistance form. Reduce the lingual surfaces of the anterior teeth approximately 0.4 mm. Make a refractory cast by making an impression of the reduced resin regions and immediately adjoining framework in reversible hydrocolloid. Pour the impression with a casting investment that is compatible with nickel chromium alloy (Fig. 3). Wax the lingual surfaces of the teeth and the other prepared resin regions directly on the prosthesis. Perfect the occlusion at this time (Fig. 4). Remove the pattern from the prosthesis and lute the margins to the refractory cast (Fig. 5). Sprue, invest, and cast the pattern with a nickel-chromium alloy. Finish and polish the metal backing. After cleaning, the backing may be chemically or electrolytically etched on the surface facing the resin base and teeth (Fig. 6). Clean the resin base and teeth thoroughly with a
Fig.
7. Metal backing cemented to resin teeth and base.
detergent and resin monomer. Cement the metal backing with a free-flowing composite resin cement. An opaque cement (Panavia, J. Morita Inc., Tustin, Calif.) may be used if the metal backing affects the shade of the dentures (Fig. 7). In this situation, the metal should not be etched because the set of the cement may be inhibited by creating an aerobic environment. A sandblasted surface finish is sufficient. 11. The teeth opposing the secondary casting may require sl.ight adjustment at the insertion appointment. The thin casting will assure minimal reduction. k-k-printrequeststo: DR. CARL A. HANSON UNMC COLLEGE OF DENTISTRY 40~~ AND HOLDREGE LINCOI,N. NE 68583-0740 JUNE
1992
VOLUME
67
NUMBER
6
lingual
casting
for removable
partial
dentures
Carl A. Hansen, DDS,a and Terry A. Johnson, CDTb University of Nebraska Medical Center, College of Dentistry, and Dental Designs Laboratory, Lincoln, Neb. This article describes a technique for constructing a nickel chromium alloy lingual casting that reinforces a removable partial denture against heavy anterior occlusion. The metal can be cast into a thin secondary casting, and it is easily etched and bonded to the resin anterior teeth and associated base. This type of lingual casting has the potential to provide a simple and effective solution to the problem of repeated fracture or displacement of anterior teeth in many restorations. (J PROSTHET DENT 1992;67:799-800.)
H eavy anterior
occlusion or detrimental habits may cause recurrent breakage or displacement of anterior denture teeth. Cast lingual surfaces have been used extensively in conjunction with porcelain and plastic-slotted facings for removable partial dentures to prevent these problems. Because the metal backings for facings are cast as an integral part of the major connector, their use must be carefully planned before the framework is constructed. When the cast lingual backings have not been initially provided as part of the framework, they may be added to the prosthesis through the use of a secondary lingual casting. This article presents a technique for constructing and placing these castings. aAssociate Professor and Director of Graduate University of Nebraska C!ollege of Dentistry. bCertified Dental Technician, Lincoln, Neb.
TECHNIQUE 1. Make a jaw relationship record, with the prosthesis in the mouth. Use a silicone rubber occlusal registration material if needed. 2. Pick up the removable partial denture in an impression
Prosthodontics,
10/l/35793
2. Lingual surface of central incisors and denture base resin have been reduced to provide space for metal casting.
Fig.
1. Tooth that has been repeatedly fractured because of opposing occlusal forces.
Fig.
THE
JOURNAL
OF PROSTHE:TIC
DENTISTRY
Fig.
3. Refractory cast of resin base and lingual surfaces
of teeth.
799
HANSEN
AND
JOHNSON
6. Etched chromium-nickel backing ready to be cemented.
Fig.
Fig.
3. 4.
5.
6.
7. 8. 9.
10. 800
5. Wax pattern is luted to refractory cast.
of the entire dental arch and pour the impression with stone. Mount the cast with the prosthesis to a cast of the opposing arch and repair the broken tooth (teeth) (Fig. 1). Reduce the resin base material between the metal finish line and the teeth by approximately 1.0 mm (Fig. 2). If possible, provide two or more parallel holes in the resin for added retention and resistance form. Reduce the lingual surfaces of the anterior teeth approximately 0.4 mm. Make a refractory cast by making an impression of the reduced resin regions and immediately adjoining framework in reversible hydrocolloid. Pour the impression with a casting investment that is compatible with nickel chromium alloy (Fig. 3). Wax the lingual surfaces of the teeth and the other prepared resin regions directly on the prosthesis. Perfect the occlusion at this time (Fig. 4). Remove the pattern from the prosthesis and lute the margins to the refractory cast (Fig. 5). Sprue, invest, and cast the pattern with a nickel-chromium alloy. Finish and polish the metal backing. After cleaning, the backing may be chemically or electrolytically etched on the surface facing the resin base and teeth (Fig. 6). Clean the resin base and teeth thoroughly with a
Fig.
7. Metal backing cemented to resin teeth and base.
detergent and resin monomer. Cement the metal backing with a free-flowing composite resin cement. An opaque cement (Panavia, J. Morita Inc., Tustin, Calif.) may be used if the metal backing affects the shade of the dentures (Fig. 7). In this situation, the metal should not be etched because the set of the cement may be inhibited by creating an aerobic environment. A sandblasted surface finish is sufficient. 11. The teeth opposing the secondary casting may require sl.ight adjustment at the insertion appointment. The thin casting will assure minimal reduction. k-k-printrequeststo: DR. CARL A. HANSON UNMC COLLEGE OF DENTISTRY 40~~ AND HOLDREGE LINCOI,N. NE 68583-0740 JUNE
1992
VOLUME
67
NUMBER
6
