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invariably gives you the result of a principle upon which you may depend, nor is satisfaction to be found in the use of a process, which upon one occasion gives you practical results and at another impractical, as begetting a universal doubt of all until tried.
Struck plates are, and ever must be, of this kind, the decided differences in the various dies used, the invariable unequal shrinkage of metals used in dies, the undirected yet imperative change produced in swedging, the great law of expansion and contraction under heat of unknown temperatures, the various manipulations struck plates undergo in these formations, are a few reasons why it is utterly impossible to obtain a perfect fit from struck plates.
Carving bases are attended by equally great obstacles, and perhaps are not as capable of perfection in this particular as may be found in swedged plates.
Silicious compounds fused upon certain counter impressions are still worse, as the unequal contraction of all fluxable materials in cooling is such as to yield intense labour to overcome, at all times attended by a much greater want of fit than any other. · The expansion and contractility of all gummy materials when parting with and receiving heat, the application of great pressure, the wonderful difference found in the shrinkage of this material when over or underdone, and the impossibility of a perfect equality of subjected heat found in the hard rubber, together with the great difference in the material itself, some being elastic, brittle, some soft, and again hard, are a few reasons why perfection in fit is not a reliable result with it. But we would prefer that these reasonings should be carried out in detail by each one interested, as we do not wish to be thought assuming an invidious position, or of making unjust comparisons, fully satisfied with the ability of all to judge who will do so candidly.
The adaptation of a plate to the mouth in cheoplasty is always as perfect as the impression taken has been correct, for the treatment of this impression does not allow of any chance product. A reliable principle always gives you the same result in one case as the other, and in this process you are brought to the greatest possible amount of certainty that your plate when finished will be a perfect fit to the model from the impression, which if correct will be the best fitting plate that any process yet known can obtain. The composition used for the matrices is subjected to certain low heat, which it is fully capable of bearing without alteration by warping or shrinkage. The metal itself is also as free from shrinkage as a metal can be made whose melting point is of any moment, and whose mechanical and chemical qualities are sufficiently pure to be used as dental plates, so that in all pieces in which the alveolus is not projecting, or in a case of ordinary smooth-, ness, a set thus made will fit as perfectly an exact duplicate model which has not been used as it will the one upon which it has been made, showing by the equal accuracy that in such a case the most desirable result has been obtained. Differing from all other processes, you thus reach an invariable principle, from the fact that the metal is always melted at a precise given temperature, and that it always becomes solid at another ; that it obeys this law of its liquid and solid condition under all circumstances alike. From its comparative nonshrinkage a given surface, as may be found in the most irregular palatal, or alveolar surface, for which a plate may be made fitting perfectly at all points whose accuracy presents the possibility of unequal pressure, and consequeutly must be worn with ease and comfort, as the edges may be formed round and smooth, as is so much admired in bone pieces. It has been much urged, from a superficial and careless view of the principle involved in the retention of atmospheric plates, that weight is a great obstacle. To a badly fitting piece this is true; to a process which is incapable of bringing to bear this principle of atmospheric pressure, every grain of increased substance proves a sufficient objection to its use in many cases, but to one in which this principle is made fully applicable, all the weight possibly involved in any piece for the mouth is not in the slightest degree perceptible to the wearer, so that it is the errors of the method used which proves objectionable, and not the weight.
A perfectly adapted plate is retained by its own attachment, and not by any volition of the patient. Voluntary power must be exercised before a perception of responsibility in the use of that power can be appreciated, as may be instanced in the enormous power employed in the heart's functions, which is entirely imperceptible until derangement takes place, and its principles of action violated. Could utter perfection be reached in a process, many pounds' weight might be sustained in the mouth without perceptible inconvenience, except to the muscles of the neck, for this is the only part capable of receiving impressions of fatigue or distress.
Too many errors exist in not tracing difficulties to their legitimate sources, and, in attributing them to incorrect causes, we often run into still greater error and difficulty.
Too much importance cannot be given to this subject of weight which in the process under consideration must be carefully separated from bulkiness, clumsiness, and inconvenience.
To some methods it is indispensable that you make all these faults to obtain sufficient strength, and in many pieces more recently examined an entire disregard to comfort, use, symmetry, and skill bas been had to obtain a sufficient degree of strength and durability, and even then an absolute failure of this has been the result.
In Cheoplasty this artistic construction of a piece is never necessarily violated, for you can always secure a surplus amount of strength with out in the least marring the symmetry and entire naturalness of the palate surface.
The very exact form of the teeth themselves can be scrupulously imitated, the useful corrugations of the palate can be given, and the planes and curves required in perfect articulation can all be preserved without encroaching upon bulk or clumsiness.
Of course this involves the highest degree of art which can be employed in mechanical dentistry, and we do not wish to be understood as saying that all these high accomplishments are attained by the mere use of this process only, but as stating that with cheoplasty it is alone possible to reach these ends without defeating the grand points in a perfect fit, unquestionable strength, usefulness, and beauty.
That it supplies skill we know too well to the contrary, from hundreds of clumsy pieces we have seen made and worn, but that it offers the best vehicle in which to display the highest attainment of our art we do not think for a moment can be questioned, because it is a modelling process, and because, with whatever manipulation is had in its construction, the adaptation of the piece to the mouth remains unaffected, for with a correct impression a cast plate of the characteristics of this metal must fit.
It will be easily seen that it is also best adapted for the construction of pieces used in reducing all kinds of irregularity either from within or without the arch, because it enables you always to employ the elastic force of soft rubber, the action of which is best suited to these ends employed as ligatures or blocks.
A regulating plate made by this process is so cast as to press only and at once effectively at such points as are desired, spaces being left for the irregular tooth to assume its desired position in the arch, and the pressure applied by ligatures through the front band, or blocks held from behind forcing the tooth forward, the attachment of the plate being by means of clasps or ligatures, or by perfect fit, as the case may be. The application of this process is almost universal, depending solely on the fact of the possibility of a correct impression.
As to its atmospheric powers, we have briefly stated, the formation of
clasps when these are used is most simple and effective, because they are cast as they are required, fitting the teeth so employed with the greatest accuracy and strength, the plate must rest firm and motionless in its position, and can be made as employing a less amount of palate surface than is used by any other method, at the same time giving a means of a perfect restoration of lost form.
The economy of this process is a point upon which I feel more dis-, posed to dwell from recent strictures, did time permit, feeling assured that our whole Profession, as well as the great world at large, fully appreciates its great importance.
Briefly, we would state that in time it occupies about the one-fourth of any other process, referring to absolute time employed, which amount decreases in proportion to the number of teeth to be mounted, as the grinding of teeth is the great majority of time expended, and even in this much less than is common to other processes, as the accuracy of fitting the alveolus is not required, being mostly lateral, as the metal is run about them forming a perfect base.
In expense it is about the one-eighth of gold, thus enabling the liberal professional man to accommodate the wants of rich and poor without material reduction of his own profits, giving at the same time the best product of his art.
We do not urge these two last qualifications simply because it saves time and money, which is profit, but because true economy in all things is the perfection of art and the product of high civilisation, and because with these great qualities it has equal merit, to say the least, with those processes which so often consume time and money fruitlessly.
If there are those who are unfortunate enough to have expended large sums in the effort to reach a higher perfection in their ability, it is folly to desire the rest of their professional brethren to make a simi. lar error for the sake of equality of misfortune. That because a process is expensive in its preparation and in its detailed expenditures, and because it is often attended by great failures in its mechanical or chemical workings, that many imperfections attend its results. For these reasons it is not necessarily a process best to be adopted, as is indirectly reasoned by some, or because of its uncertain character it should be commended for conservative reasons, which smack strongly of a vulgar love of profit, without a love for the Profession generally, or for the wants of suffering humanity. As a most worthy gentleman has remarked, “ True economy resides in using that which is best, as expense and trouble can be no indication of merit.” So true merit when
cheapest is the best. At least I imagine the world will ever come so to consider.
Indeed a little survey of the history of the practice of medicine will prove that the great expense of some remedial agents has greatly restricted their use. We can refer at the present time to many preparations of gold whose efficacy in some diseases are unquestioned, yet from their great expense are almost totally in disuse, substitutes having been discovered of a much less expensive character.
There is a strange anomaly exhibited in the objection of the use of a metal in the mouth, and even of a compound, by many who are daily in the habit of using amalgams, which, to say the least, are confessedly the most easily acted upon by various agents eliminated in the buccal secretions, a combination is claimed by such to be best suited to contact with the most highly vitalised structure of the hard tissues, and that under a diseased condition, and this combination under these circumstances lasting at times ten, twenty, or even thirty years, and yet object to use the purest combination under the most favourable cir. cumstances.
Such a position is hard to reconcile with the claims of consistency, receiving it in whatever light may be thought proper, yet still believing that such take this ground more from want of thought upon this point than from any course of reasoning, and that in a little time their own interests will become more perceptible in recognising the true merit of a subject; for if one is at all good, the other for precisely the same reasons must of necessity be much better.
It may not be improper to state, in conclusion, that the teeth manufactured for this process are being improperly used by some few individuals in connection with other processes. It were well to understand the claims held by the person owning the patent, desiring that no one should run into difficulties blindly. I beg to state that the patent claims the so forming of teeth by means of holes, grooves, and dovetails as can be retained by means of a fusible material, which covers the ground effectually. Those which have been vended in this country were absolutely made for cheoplasty, and modelled mostly by myself, and should most certainly be so accredited.
Dr Blandy having concluded his paper, said he thought it better not to extend his paper to a greater length, but would be happy at a future time to go more fully into the details of the subject if agreeable to the members.
Mr Matthews : Do we understand that you never use clasps ?