The principles and practice of dentistry : including anatomy, physiology, pathology, therapeutics, dental surgery and mechanism / by Chapin A. Harris.

  • Harris, Chapin A. (Chapin Aaron), 1806-1860.
Date:
1906
Catalogue details

Licence: Public Domain Mark

Credit: The principles and practice of dentistry : including anatomy, physiology, pathology, therapeutics, dental surgery and mechanism / by Chapin A. Harris. Source: Wellcome Collection.

    1088/1184 (page 1088)
    union between celluloid and rubber, hence when one of these materials is added to the other, it can only be done by dovetailing or drilling holes. Good, hard-setting plaster should always be used in working celluloid, and it should be well mixed by adding it to the water in such a manner that all is absorbed that it will take up. Care should also be taken not to mix the plaster too thin or to use very fine plaster, as a coarse grade of strong plaster will give better results. Some are in the habit of adding clean white sand or marble dust to the plaster. The following directions are given in the use of the New Mode Heater, which will prove serviceable in the working of celluloid generally: — Always use good plaster, and do not mix too thin; always select a blank which nearly fits the cast, with an excess in every part; always turn the screws as soon as they will yield to the thumb and finger, and always gently ; always followup the rise in temperature with increased pressure; always give the material plenty of time to flow between the turns; always increase the pressure toward the close of the molding; always reduce the temperature of the piece at once after the comple¬ tion of the molding, and keep the plate under pressure until it is stone cold. ZYLONITE. A A modified form of celluloid has been introduced under the name of zyIonite, the working results of which appear to show a great differ¬ ence in quality. Zylonite, like celluloid, is composed of pyroxylin and camphor, but in different proportions, being, it is claimed, a chemical combination, while celluloid is a mechanical mixture. Possessing translucency, the effect of zylonite in the mouth is very pleasing, and, so far as it has been tested, promises to be more dura¬ ble than celluloid, without the tendency to warp or to change color when ordinary care is taken in its manipulation, which is the same as for celluloid. The zylonite blanks are uniform in color, and although this material requires the same amount of pressure to mold, it flows with a more perfect sharpness of outline than celluloid, and apparently does not disintegrate. CHAPTER XVI. PORCELAIN TEETH. As Pharmacy was once a part of Medical Practice, and instrument¬ making a part of Surgery, so the manufacture of porcelain teeth was at one time confined to the dental laboratory. Until within the past forty years a practical knowledge of the Dento-ceramic art was con-