Dental Dentures

170 (Partial Dentures: Trimming, Finishing and Polishing)

Units such as the Eltropol SL, with automated movement of the object and a heated polishing bath, should be utilized for electrolytic polishing (Fig. 170 + 171).

171 (Partial Dentures: Trimming, Finishing and Polishing)

Using alligator clamps or a copper hook on the retentive lattice or on the base itself, suspend the chrome-cobalt framework in the electrolytic bath such that the clasp tips are relatively far from the ring cathode. If the tips of the clasps are too close to the cathode, an excessive removal of metal may take place. The most effective polishing occurs at a polishing bath temperature of between 45° and 60°C.

172 (Partial Dentures: Trimming, Finishing and Polishing)

Neither the base nor the inside surface of the clasps should be trimmed or finished (Fig. 172). Before polishing, use a carbide bur to touch up the stippled surfaces of the base.

173 (Partial Dentures: Trimming, Finishing and Polishing)

Boil the wax off of the master model (Fig. 173) Seat the framework on the model. Only the clasp tips of the framework scrape the stone model as they go to place in their respective undercuts.

174 (Partial Dentures: Trimming, Finishing and Polishing)

To prevent distortion of upper arch partial denture frameworks during polishing, prepare an alabaster base, or block, on which the framework firmly sits (Fig. 174).

175 (Partial Dentures: Trimming, Finishing and Polishing)

The blue chrome-cobalt polishing paste is used for polishing and the final high-luster shine. Residual polishing paste is removed in the steam cleaning unit or in an ultrasonic bath.

Expert or novice, all interested dental laboratory technicians are continually called on to reexamine their own technique and adjust to new knowledge. Only this can help to eliminate the vast number of potential errors existing in the manufacture of chrome-cobalt frameworks. The successive use of harmonious materials and equipment in the chrome-cobalt system described here, insure a smooth flow in the sequence of operation and make possible exact fitting, faultless chrome-cobalt frameworks which meet the highest demands of quality (Fig. 175).

165 (Partial Dentures: Trimming, Finishing and Polishing)

The chrome-cobalt framework must be carefully removed from the mold to prevent bending or distortion. Use a hammer on the sprue base only. Remove as much of the investment material as possible before using the blasting unit. Blasting with pure aluminium oxide – 250 µm, such as Korox 250, can be done manually or automatically. When several castings are simultaneously blasted automatically, be sure that they do not become entangled in one another. This could result in areas where an excessive amount of metal has been removed due to impaired rotation of the castings. From time to time the contents of the automatic blasting unit should be checked. (more…)