vary glands. The teeth should be kept free from all deposits and accumulations of whatever character; for, though some of these may not affect the teeth directly, yet they induce disease of the surrounding parts, and thus indirectly exert a pernicious influence. upon them.

The foregoing remarks, however, refer rather to the prevention of decay than to its treatment after it actually exists. Yet they are on that account none the less important, since here, as elsewhere, prevention is better than remedy. But they apply to such prevention as well after decay has commenced as before, if the ultimate object is preservation of the teeth. After the first attack the teeth are more vulnerable and less capable of resistance.

When decay has attacked a tooth, the treatment indicated depends upon the nature and extent of the disease. Rapid decay requires more prompt and energetic treatment than that of slow progress. Remedies appropriate and efficient in the one are quite inapplicable to the other. The persistence of caries is not always in proportion to its rate of progress. We sometimes find teeth in which the decay is not advancing rapidly, and thence are led to conclude that it may be easily arrested; the affected part, if superficial, is easily removed, and the dentine thoroughly polished; and yet, after a time, decay again attacks the tooth at the same point. Or, where

the caries has penetrated the tooth, so that it requires filling, though it is skilfully done, and the plug and tooth carefully polished, yet in many instances the dentine soon softens about the border of the filling.

The extent and nature of the decay will suggest the mode of treatment. Superficial caries on some parts of the teeth may be remedied and removed by cutting away the portion implicated in the disease, dressing with a fine file, polishing with Arkansas, Scotch, or rottenstone till the file-marks disappear, and then applying the buff with rouge or oxide of tin, very thoroughly to the entire surface operated upon. Afterward, the most careful attention to cleanliness is requisite, to prevent a recurrence of the attack. This treatment is applicable to decay upon proximate surfaces; but in the depressions of the masticatory and buccal surfaces of the molars, it is not practicable.

Sometimes the dentine, at points where it is exposed, gives warning, by acute sensitiveness, of threatened decomposition, before there are any other indications of it, thus evidencing the presence of some very irritating agent promotive of decay. Such points should receive prompt and strict attention, and the increased sensitiveness be immediately subdued; as it may be by the use of some preparation that will counteract the exciting influence-some dentifrice or lotion containing an alkali; or rubbing the sensitive surface with a steel burnisher will in

many cases effect this object, and prevent the development of decay. Nitrate of silver is sometimes used for this purpose, and occasionally proves very efficient; but its general use for such cases is of doubtful propriety, and when used, it should be with discrimination and caution.

It has been suggested that the character of caries may be modified by the local application of therapeutic agents-that the rapid decay may be changed to the slow, and this, too, without regard to the attendant circumstances, such as the condition of the secretions of the mouth, the causes producing the disease, etc. For this purpose various agents have been proposed. It is held that by an application of the nitrate of silver, the white, rapid decay being changed to that of a dark color, is arrested in its progress. But there is no very palpable principle on which this agent can be supposed to operate to arrest caries. It is generally conceded to be injurious to a healthy tooth; how, then, it becomes beneficial to one decayed, it is not easy to perceive. The notion may have originated in the fact that after the application of nitrate of silver, the dentine to which it has been applied turns dark, or black; and this color being naturally associated with the slow form of decay, it may have been concluded that it might be thus associated by artificial means. This conclusion, however, is fallacious; for the coloring matter being the oxide

of silver, deposited on the walls of the cavity, is wholly foreign, and holds no necessary relation to the kind of decay, or to the agent producing it. The deposit may possibly serve as a temporary shield to the dentine beneath, but only temporary; whereas, on the other hand, it will be remembered that nitric acid is liberated by the decomposition of the nitrate, and operates destructively upon the tooth-bone. An ethereal solution of the terchloride of gold has also been suggested as a preventive application. Its operation would be much the same as that of the nitrate of silver, and equally inefficient. Preparations to neutralize and counteract the effects of deleterious agents upon the teeth have been recommended as topical applications. These are such as possess alkaline properties. But anything of this kind would require frequent application; indeed, it would be necessary to keep the affected part constantly under its influence, as long as the surrounding conditions continued to favor decay.

Though nothing of this kind can be relied upon permanently to arrest caries, yet, in many instances, much benefit is to be derived from local treatment. Alkaline topical applications will in many cases alleviate the most acute sensitiveness of the dentine, accomplishing this, no doubt, by their neutralizing influence upon the irritating agents. Many operators employ simply the bicarbonate of soda for this

purpose, with the happiest results. As another class of topical applications to check or modify caries, those have been suggested which will form an insoluble compound with the gelatinous or animal portion of the tooth; such as tannin, creosote, and some of the essential oils. The only effect of these, however, is to form a shield or protection over the structure beneath there is, of course, no change effected in the conditions or agents which produce decay.