EXPEDITING NICKEL-CHROME CASTING FABRICATION

as 5 hours. This can be substantially reduced by placing the invested waxed framework directly into an oven preheated to 1350“ F for 1 to 1% hours.

Cast, finish, and polish the framework in the usual manner.

3.

4.

Sowter B: Dental Laboratory Technology. Chapel Hill, NC, 1968, University of North Carolina, p 180. Terkla LG, Laney WR: Partial Dentures. ed 3. St. Louis, 1963, The CV Mosby Co, p 225. Luebke RJ, Schneider RL: Microwave drying of artilicial stone. J PROSTHET DENT 53:261, 1985.

REFERENCES 1. Ticonium Technique Manual. Albany, NY, 1966, Ticonium

Company, Division of CMP Industries, Inc., p 2. 2. Rudd KD, Morrow RM, Eissmann HF: Dental Laboratory

Procedures. Vol III: Removable Partial Dentures. St. Louis, 198 1, The CV Moshy Co, p 203.

Repmt rqur.rl\ lo. DR. DONALD R. NELSON UNIVERSITV OF NORTH CAROLINA

SCHOOL OF DENTISTRY CHAPEL HILL, NC 27514

Light-activated composite-amalgam copings for overdentures

John Holt, D.M.D.,* Robert Todd, D.M.D.,** and Robert Quinn, D.M.D.*** Oregon Health Sciences University, School of Dentistry, Portland, Ore.

0 verdentures have become a standard mode of treat- ment for many dental patients, and many of these patients have progressed to this dental situation because of their high incidence of caries. The caries problem is not alleviated by the overdenture construction, and a continual recurrence of caries on the treated roots can be expected for many of these patients.

Gold copings have been used extensively to reduce the incidence of.caries,’ however, they are relatively expen- sive and may not prevent caries at the margins. They also create a space problem in the esthetic placement of the denture teeth for some patients. Treatment of the exposed root portion of the retained teeth with fluoride and silver nitrate is effective in reducing caries inci- dence.2 Recent improvements in the light-activated com- posites make this material a viable method of protecting exposed dentin. This article describes an alternate meth- od of treatment that takes some of the beneficial features from both of these procedures.

TREATMENT PROCEDURES

1. Prepare the tooth by reducing the occlusal surface to the shape of a flattened dome extending to the crest of the gingival margin.

*Professor, Department of Removable Prosthodontirs. **Assistant Professor, Department of Removable Prosthodontics. ***Associate Professor, Department of Operative Dentistry.

Fig. 1. Top view, composite-amalgam overdenture tooth coping. A, Cementurn; B, composite; C, amalgam; D, retentive groove.

2. Place a supplemental groove midway between the canal and the cementum margin (Fig. 1). An inverted cone bur (No. 33 or No. 35) of appropriate size is used for this purpose. The groove provides mechanical reten- tion in addition to bonding of the composite to the dentin with a dentin bonding agent.

3. Treat the tooth with the bonding agent and restore it with a thin layer of light-activated composite (Scotch-

THE JOURNAL OF PROSTHETIC DENTISTRY 403

Fig. 2. Cross-section, composite-amalgam overdenture coping. A, Cementum; B, composite; C, amalgam; D, retentive groove.

bond, 3M Dental Products, St. Paul, Minn. or Com- mand Ultrafine, Type II, Sybron/Kerr, Romulus, Mich.).

4. After the composite is fully cured, drill a hole through it into the canal of the tooth and fill it with amalgam alloy.

5. Build up the alloy in a dome shape slightly higher than the composite restoration (Fig 2).

6. Test the denture with pressure indicator paste and

tlOLT, TODD, AND QUINN

relieve all contacts with the retained roots except on the surface of the amalgam dome. This procedure reduces horizontal or torquing forces on the retained root and also decreases the load on the composite restoration.

I 1 New JOURNAL pdicy for i%lagkWiem in color

The $225 charge to authors for each page of color illustrations will be eliminated for all manuscripts received in the JOURNAL office after January 1, 1986.

High-quality 35 mm color transparencies must be submitted, and manuscript length cannot exceed 10 to 12 double-spaced typewritten pages. The Editor and his reviewers have final authority to determine whether color illustrations afford the most effective presentation.

I c

404 MARCH 1966 VOLUME 55 NUMBER 3