. A manual of mechanical dentistry and metallurgy . Where deep undercuts are present, one of two processesmay be adopted. They are well described in the late Beales article in the American System of Den-tistry, where he says: First, the plaster in the lower FLASKING, VULCANIZING AND FINISHING. 47 section may he made to cover the wax rim within half aHne of the porcelain gnms. This will protect the cast, sothat it will not he fractured when parting the flask or whenpacking the rubher. This method is represented in Or, the base of the cast may be so trimmed that theundercut wil
. A manual of mechanical dentistry and metallurgy . Where deep undercuts are present, one of two processesmay be adopted. They are well described in the late Beales article in the American System of Den-tistry, where he says: First, the plaster in the lower FLASKING, VULCANIZING AND FINISHING. 47 section may he made to cover the wax rim within half aHne of the porcelain gnms. This will protect the cast, sothat it will not he fractured when parting the flask or whenpacking the rubher. This method is represented in Or, the base of the cast may be so trimmed that theundercut will approach as nearly as possible the perpendic-ular, as seen in Fig. 23. When the latter plan is adopted Fig. the flask, before opening, should be moderately heated inwater to about a temperature of 120° F. Allow it to re-main in the water for a few minutes, so that the heat maypenetrate to and soften the wax. Then remove the flaskand separate the two sections carefully. If these directionsare followed, the wax will generally part readily from theteeth and plaster. If any adheres to the pins, it should becarefully washed out with boiling water. The necessity for removing every particle of wax is dueto the fact that its presence destroys the integrity of therubber and interferes with its vulcanization. It is better,therefore, in all cases, to direct upon the cast a stream of 48 MECHANICAL DENTISTRY AND METALLURGY. Ijoiling water, with the liask placed as such an angle thatany particles of wax will be readily carried off. Outlet Grooves or Gates.—The next step is to makegrooves or gates which will act as receptacles for theexcess of rubber. Tliis is clone by cutting a groove aroundthe cast,
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