The physical properties of dental amalgams / by the late Thomas B. Hitchcock. The physical properties and pathological action of dental amalgams ; by E.A. Bogue. Read before the New York Odontological Society at the special meeting, December 14th, 15th, 16th, 1874 : and the discussions which followed.

  • Hitchcock, Thomas Barnes, 1839-1874.
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: The physical properties of dental amalgams / by the late Thomas B. Hitchcock. The physical properties and pathological action of dental amalgams ; by E.A. Bogue. Read before the New York Odontological Society at the special meeting, December 14th, 15th, 16th, 1874 : and the discussions which followed. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    that we may readily obtain and make use of tliem ; or, in other words, can we obtain uniform results of a desirable nature? In considering the subject, let us look first to the condition in which we find teeth which have been filled with amalgam. Examination of a considerable number of teeth filled with amalgam, proves that their further decay may often be prevented by its use, though oftener we shall find a defective joint between the filling and the enamel, sometimes limited to one or two places, at others extend- ing entirely around the filling. If, in these cases, we remove the filling, the cavity is generally found discolored and carious throughout. This could not occur, provided the cavity was properly packed, if the filling was moisture-tight, and we are obliged to conclude, that either the filling was improperly introduced, or, what is more probable, its shape has changed after being placed in the cavity. It has for some years been well known that many of the dental amalgams contracted while hardening, and the statement has also been made that some expand. Until recently, however, no attempt has been made to ascertain the relative amount of change which occurred in the several preparations. The first experiments in this direction of M'hich I find the record were in 1861, by Mr. John Tomes.* These consisted in making fillings in holes in slips of ivory, similar to the glass slides which are used for mounting microscopical objects. When used, the ivory slips were clamped firmly upon another piece of ivory, so that a well-shaped cavity was formed. After introducing the amalgam, and allowing it to harden, the clamp was removed, and the slip, with the filling in it, was put under the microscope. Of seven experiments with various alloys, six showed contraction of the amalgam, while the remaining one, which was a compound of pure copper and mercury, was very much superior to any of the others. Two of the six were of Sullivan's cement, which is said to be largely composed of copper. One of the simplest experiments, and one which we can all try, was first suggested to me by Mr. Thos. Fletcher, of Warrington, England, It consists in making a filling in one end of a glass tube, care being taken not to touch the end of the tube holding the plugs, for fear of false results from the action of the heat of the hand. After the filling is completed, partially fill the tube with a colored fluid,—blue ink is very suitable for the purpose. If the filling contracts, the ink will penetrate between it and the wall of the tube, and can readily be ob- served. Experiments made in this manner show that nearly all the , amalgams contract. The same change in bulk has been shown by Mr. ' Chas. Tomes,t by means of the specific gravity tests. The amalgam * Transactions of Odontological Society of Great Britain, vol. iii. f On the Clicmical and Physical Properties of Amalgams, Transactions of Odontological Society of Great Britain, March, 1871-2, vol. iv., New Scries.