They maintain that secondary decay about fillings may be, in many cases, the result of incompatibility between filling and tooth bone. The result of conductivity of fillings. And that the successful treatment of many cases require a physiological change in the organ, a course of therapeutic and antiseptic treatment, not "recognised" prior to these investigations. They claim that at certain stages of decay, a metallic filling (we will take "gold," as this is the best conductor) promotes decay, and in many cases it is the prime agent in provoking it. This is the view we are compelled to accept, from a careful, practical observation, in everyday practice.

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When this is manifest, it is shown in that class of poorly calcified teeth, and in those of young subjects, where the "aqueous or vital element is in excess of the mineral constituent. If these teeth are filled with gutta percha or any non-conducting material, though the fillings may soon be worn away by attrition, the decay is absolutely stopped so long as the material remains in a position to protect the walls of the cavity from external causes of decay, such as preventing the ingress of particles of food, and foreign substances in general, even though "dampness" pervade the whole cavity underneath the filling. And there are few cases where guttapercha fillings are water-tight. In this class of fillings, though often imperfectly done, decay in the very poorest quality of teeth is effectually arrested.

Why so? "Because the aqueous element of the tooth, being of the same nature as the solid constituent, has no power to act upon the latter, and cannot cause decay, or dissolution, until the equilibrium is disturbed." "Decay only takes place, when the external fluid is rendered chemically different by confinement in fissures, pits, or cavities, and is thus changed from the other fluids, to which other surfaces of the teeth are exposed." The non-conducting filling being in harmony with the tooth, the aqueous element remains neutral or becomes neutral by contact with this vital fluid. This is the case with leaky non-conducting fillings, consequently there is nothing to excite chemical action. The decay is arrested by external excitants being shut out, such as thermal changes, electrical currents, and decomposing fluids, and nature goes on unmolested in the work of more perfect calcification of the organ.

This, together with the usual antiseptic and disinfectant remedies, is the topical therapeutic treatment that such cases require. And yet, this is not the course that it is best to pursue in all cases. It is often advisable to use a material that is antagonistic and incompatible with the tooth structure.

Under these circumstances we must anticipate future decay, and make calculations accordingly with the idea of refilling or repairing at no distant future. Because if we fill these poor, soft, or imperfectly calcified teeth with gold, we must depend upon it the aqueous element, natural to this class of teeth, is a condition that is liable under many circumstances to work mischief, despite all efforts on our part, not excepting those of even a few of the best operators we have.

In this we mean to show that we have an element to contend with that mere mechanical means will not overcome. Gold is not a "panacea" for all conditions of decay of the teeth, any more than some "patent medicines are for all ills that flesh is heir to. For an example, we will take gold, and fill this class of teeth in such localities as proximate and labial surfaces, and the filling will often exert a deleterious condition. There is a certain class of teeth that we have to operate on that we find affected by decay-sometimes it might be termed erosion more properly-where the lime salts are dissolved out at a line ascribed by the gum, white opaque patches are presented that can often be removed with the thumb-nail, being so soft and chalky, caused by the dissolution of earthy matter occasioned by acid secretions. Now, we must admit that if we prepare a cavity of this sort, and fill with gold, the margins about the fillings seem to fairly melt away, like snow beneath the noon-day's sun. This is not always the result of imperfect manipulation; if these fillings are absolutely water-tight in themselves the result may be the same. Often there is so much of this aqueous element in the organ that it is impossible to dispose of moisture about the fillings for any great length of time, no matter how skilfully the operation may have been performed. For in this class of teeth there seems to be, under some circumstances, a retrograde action that "supersedes" the topical therapeutic treatment that may have been applied to the cavity before filling.

And this is one thing that the opponents of this theory have lost sight of or would not look at squarely in the face, but hang their faith on this peg: that if there is no leakage about a gold filling there can be no electrical action; and if our fillings are water-tight so as to perfectly exclude external moisture, we have accomplished all that is necessary for success. A few have recognised this in a measure, but claim, where this aqueous condition is manifest, it is confined to the dentinal tubuli and not so with the enamel-the latter being of such a dense structure it is devoid of this aqueous element entirely. And that if a filling at the margins be perfectly water-tight, the moisture from the dentinal tubuli

will be inert to act deleteriously upon the tooth, for no electric current can be established.

But this is an error. For it has been shown conclusively by Dr. Abbot (and, I think, others) that, "the enamel is not a crystal, but living tissue endowed with the same vital element as dentine, only to a less degree." Now that this is an established fact, it is our conviction that a filling often becomes a battery in many cases where the operation is "absolutely perfect." And the result is electro-chemical decomposition about the margins of fillings, in spite of our best efforts.

Doubtless many of you have seen discoloration about fillings made with "crystal gold" some years ago of a bluish character, that is generally pronounced "leakage." In fact this gold was discarded by many because of the discoloration that often followed its use. In many cases this was not the result of faulty operations. I have seen many of these fillings, inserted by an eastern gentleman of acknowledged , ability, whose operations with gold are perfection. About many of these fillings there was a "blueness" which was proof positive of chemical action. The acid used in the preparation of this gold had left its mark. The iron had entered the tubuli, and the aqueous element in the tooth was fuel sufficient to feed this chemical fire. In such conditions, with soft teeth, time generally pronounces the verdict of failure. With well calcified ones the power of resistance to such impressions may prove a success.

When we think of the recognised make up of the different classes of teeth, and hear the claim made that gold is the best filling for all teeth, or as good as any, if properly manipulated, it reminds me of something that has been said by Dr. S. B. Palmer on this subject, and it goes to show how absurd it would be to apply this principle of gold in all cases to other matters outside of the mouth, where judgment should govern our operations. He says "In cases of repairing a leaky cistern, wisdom would demand knowledge of the material of which the cistern is composed, and the nature of the repair necessary. Then call a carpenter, plumber, or mason to make the repair. A porous cement cistern would not be benefited by the carpenter or plumber, only by a mason, and the application of a chemical to fill the pores over the entire surface."

And in this class of teeth mere mechanical manipulation of a material that is indestructible in itself cannot be made subservient to meet the requirements of all cases.

Dr. Flagg uses no gold in his own practice at the present day. Yet this is not the teaching of the new theory. He

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says:-"That the New Departure' concedes the use of gold as a filling material whenever and wherever it can be used for the preservation of teeth as successfully as other materials. The new departure begins where gold leaves off, to help gold, if need be, to sustain its exalted reputation, and to furnish a substitute in other materials, in cases where gold is inadmissible."

And he remarked at the outset, in presenting his paper to the Odontological Society, New York, in 1877, which excited so much discussion and comment :-" I do not want to say anything to you of the teeth which you are in the habit of filling successfully, and, as we express it, satisfactorily with gold-teeth of dense structure, whose cavities have walls so strong that you can impact a filling which lasts a lifetime. But I do ask that you will gradually discontinue this packing of gold into teeth that are so poor, so frail, so unsubstantial, that it is, to say the least, doubtful whether the result will be creditable to your profession or satisfactory to your patient."

This is the point I wish to make. And it must be admitted by any intelligent, unbiased Dentist, that many of the non-conducting fillings that we have at our command, meet the requirements of such teeth better, though the filling may be short-lived in itself. But it is really the topical therapeutic treatment that such cases often demand. Who is there, that has practised for some years, that has not seen groups of gold fillings on labial surfaces, one adjoining another, put in at different times, or removed and renewed the whole operation from time to time? We do not

denounce the practice; often we are compelled to choose the least of two evils. If the subject cannot have the case renewed from time to time, when the plastics are used up (for in such localities, gutta percha, oxychlorides, and the like, are soon worn down by friction and attrition), I trust we have something better in the "oxy-phosphates." The latter I have experimented with for two years very satisfactorily. But this is scarcely time enough to determine their durability, and in what class of mouths, and what condition of the secretions, they will do the best service. And when this class of plastic fillings are not admissible in our judgment, according to the varied circumstances that may be presented, we must do the next best thing, which would be to devote much more time to the operation, and increase the expense by a gold filling, often at the expense of the vital organisation of the tooth, instead of having that soothing, antiseptic, and therapeutic condition imparted to the organ by the non-conducting fillings. The latter assists nature in

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the work of perfect development, while the former "sometimes" retards this progress, for under chemical excitement she cannot perform this office.

I recognise gold as superior to all other material in general that we have at our command, if skilfully manipulated. But it must be used with judgment in its proper place. We must acknowledge its conductivity, consequently its inadaptability to meet the requirements of all cases.

The therapeutic effects of English precipitated chalk and lime water would do much to stay the progress of decay in this class of teeth, by counteracting the acid condition of the secretion usually manifested in such cases. A hygienic diet with young subjects would work a great change. But what can we effect in respect to hygiene? But little. People will eat what their appetites crave, even if it is at the expense of teeth. The good advice that we may be inclined to give on this subject will not be heeded by many. The topical treatment, conducted by the Dentist, is about all that will effect much, aside from the beneficial results of ordinary cleaning. This most all will do.

We must depend upon our exertions; success is only accomplished by good judgment on our part, and a thorough knowledge of the requirements that each case demands.

The application of such remedies as carbolic acid, creosote, thymol, oxide of tin, and varnish, will effect much toward making perfect operations in gold a success. By the affinity of the tooth elements for such remedies, the tubuli are sealed up in a measure and the aqueous element disposed of in a degree. Our object should be to prevent chemical action by the application of such remedies as tend very much to dispose of the aqueous element. If this is accomplished, and the gold operations are absolutely first-class, our efforts are generally crowned with success. If we do not succeed in controlling chemical action, non-conducting fillings will usually best meet the requirements. This precaution would often make successful an operation in gold that would otherwise prove a failure. In fact, the application of carbolic acid, or creosote, should never be omitted. For it disinfects the cavity, thereby acts as an antiseptic, obtends sensitiveness, lessens thermal shocks, and imparts general comfort and satisfaction to the patient.

When cavities are deep, it is usually best to line such with some non-conducting material, as a decided benefit will be derived from such a practice. It is plainly shown that a tooth affected with caries does not remain passive and inert to impressions of decay; but, on the contrary, great efforts are made by nature to protect pulps from exposure and from