10. The most common disease of the teeth is caries, or decay, and almost every part of them is liable to be affected by it, but especially the sides of those in front, and the crowns of those on other parts of the jaws.
11. The disease begins its attack either on the enamel or on the bony portion, and gradually extends itself over the tooth, until it reaches the nerves which supply its natural cavity. These having become exposed to the sudden changes of temperature, and to the contact of extraneous substances in mastication, pain and inflammation are produced, and the extraction of the tooth very commonly becomes the only means of relief.
12. All persons are more or less subject to this disease, but some much more than others; and caries of a peculiar character has been so often traced through whole families, from one generation to another, that it is considered hereditary, as much as any other disease to which the system is liable. In many cases, caries seems to be the effect of some serious disease which affected the constitution, while the teeth were in the early stages of formation.
13. Although the teeth of some individuals possess but little durability, and, when caries attacks them, go on rapidly to decay, in spite of all the aid which science and skill can afford, yet, there are comparatively but few instances in which seasonable and judicious treatment will not arrest the progress of the disease.
14. When the teeth are but slightly affected with caries, especially on the sides, a cure may be accomplished by the removal of the decayed portion. This is effected, by the most approved dentists, chiefly with small cutting instruments. Formerly, the file and the saw were employed for this purpose; and, by their indiscriminate and injudicious use, many teeth were ruined, and the art of dentistry itself brought into disrepute.
15. Notwithstanding the injuries which have been inflicted by the improper application of the saw and file, in some instances they are indispensable; and, in the hands of the scientific operator, they need not be feared. They are especially useful in preparing the way for the employment of other instruments; for, in some cases, the affected part can with difficulty be reached by any other means. But filing the teeth for the purpose of improving their appearance, or for rendering the sides more accessible to the tooth-pick and brush, seems to be reprobated by the most intelligent part of the profession.
16. When the caries has penetrated far into the tooth, and, in its removal, a cavity of suitable form and dimensions can be produced, it is filled with some substance, with the view of protecting the bone from the action of extraneous agents. The dentist is careful to remove every particle of the decayed portion, and to render the cavity perfectly dry by repeated applications of lint or raw cotton, before he attempts to fill it.
17. Gold is the only substance which possesses sufficient solidity to withstand the ordinary friction of mastication, and which, at the same time, is capable of resisting the chemical action of the substances that come in contact with it; yet lead and tin are frequently employed; and many have been made to believe that they answer as good, if not a better purpose, than gold itself. The durability of these metals, however, can never be depended upon, and they ought not to be employed, where the tooth is capable of resisting the mechanical force required to fill it properly with gold.
18. The metal is prepared for the use of the dentist by the gold-beater, in the manner described in the article which treats upon the business of the latter. The leaves, however, are not beaten so thin as those designed for the common purposes of the arts. The portion to be applied is cut from the leaf, and, after having been twisted a little, is forced into the cavity. The metal is rendered perfectly solid by means of instruments adapted to the purpose.
19. This operation, properly performed under favorable circumstances, generally renders the tooth as serviceable, to the end of life, as if it had never been diseased. The hopes of the patient, however, are sometimes disappointed by the unskilfulness of the operator, or by the general unhealthiness of the mouth, arising from tartar, other decayed teeth, or want of care in keeping them free from the lodgment of particles of food.