the University of Michigan-had the conviction to demand of its students that apply at their door for admission, that they have such qualifications as tend to impress the learner with the importance of a thorough comprehension of the underlying laws and principles on which alone can a solid superstructure be erected.

So, gentlemen, I conclude by saying that I think we cannot have the spirit of ethics which is sure to be stamped into our character by that training the college gives, too strongly diffused in our midst, and while the mere attending college will not make an ethical man out of one who by instinct is unethical, yet the high tenor of thought assimilated by such association cannot fall short of having an elevating effect on the man who is capable of being elevated.-Dental Register.

THE EVOLUTION OF THE MODERN DENTURE.

BY THOMAS D. Dow, '00.

EVEN in studying the science of dentistry which we have been taught to consider one of the modern sciences, we find verified the old adage, "There is nothing new under the sun.”

However, up to the advance was made The materials used

We find it spoken of as an art practiced in Egypt 500 years before Christ. It is also mentioned in the ancient books of the Hindoos, and even in the tombs of the old Etruscans have been found more or less modern looking dentures. latter part of the eighteenth century, very little over the dentures constructed by the ancients. previous to this time were ivory, teeth of animals, and of human beings. The ivory was used for the plate, or for the whole denture, both teeth and plate being carved from one block. When other teeth were used, they were rivited to the ivory plate. Ivory, by absorbing the secretions of the mouth, soon rendered the breath quite offensive. Of course very imperfect adaptation was attained, and this necessitated the use of ligatures or springs for the retention of the denture. No attention was given to restoring the contour of of the face and mouth. A notable example of this was George Washington, all of whose later portraits are spoiled owing to the unnatural expression given to his face by the denture he wore.

The first notable improvement in artificial dentures was the introduction into France of mineral or porcelain teeth. This was a

substance that, although crude in shape and very imperfect in color, was aseptic and consequently free from the objectionable features of extracted teeth.

These porcelain teeth were first manufactured in America by Dr. A. A. Planton about 1819. After him came a great number of experimenters and imitators who had varying successes in this line. In 1825 S. W. Stockton began the manufacture of artificial teeth on a small scale, his business grew to large proportions, and was finally taken up by his nephew, Samuel S. White, better known by his initials, S. S. W. Under his management the business grew to enormous proportions and the product has reached a perfection that seems to allow of no further improvement.

About 1800 Mr. James Gardette made a discovery which revolutionized the making of dentures. This was that plates could be retained, without springs, by atmospheric pressure and by involuntary motions of the facial muscles. It is said that he made this discovery accidentally while fitting a denture to a lady's mouth.

In the latter part of the eighteenth century and the early part of the nineteenth we find gold, silver, and platinum used to some extent as base plates. The gold of course was within the reach of the wealthy only, while silver was used by those who had to consider expense, Platinum was used but little for the same reason. About 1866 a cast aluminum plate was invented by Dr. J. B. Bean. This plate has never become popular owing to the corrosive effects of the fluids of the mouth in many instances. Among other metals that have been used as a base with more or less success, we may mention iridium, palladium, rhodium, and tin.

In 1851 Nelson Goodyear patented a method of vulcanizing or hardening rubber. This was a material that was plastic, easily finished, and that made a plate that allowed very close adaptation to the mouth. For some time it was sold only under the Goodyear patent and so owing to its cost was not used as extensively as its value to the profession would warrant. Lately, however, it has been much improved in quality and reduced in price, so that now it is universally used for dentures.

Shortly after the patenting of the Goodyear process of vulcanizing, a method of preparing collodion was discovered which gave a rather desirable base, this was called celluloid. This material was quite extensively used by dentists while the Goodyear patent was in

force but was generally discarded for vulcanite at the expiration of

the patents.

The introduction of vulcanite into dentistry has, on the whole, lowered the standard of workmanship, as a less degree of mechanical skill is necessary for its manipulation than is required for metals. However, the tendency of the last few years is back to the metals again and a consequent raising of the standard.

The last few years have also shown a marked increase in the number of continuous gum dentures. These are acknowledged to be the most perfect plates made and they mark the highest triumph of prosthetic dentistry. It is gratifying to our patriotic feelings to note that, almost without exception, the improvements along this line have been made by Americans, and that today American dentists are welcome in all parts of the world.

AN EASY AND QUICK WAY TO MAKE A SOLDERED CROWN WITHOUT A DIE PLATE.

C. H. LEBERT, '98.

One of the greatest mistakes made in crown and bridge work by dental students and young practitioners is that they work too much on models instead of on the patient's mouth.

A die made from modelling compound or even a plaster impression is never, even if the greatest care be taken, an entirely unchanged and true reproduction. On the other hand a plaster model

to which a gold band is fitted is too easily injured by the rubbing off of small particles by trying on, and very often the result is, that a gold band, which fits

the model very well indeed, is found too small when

put on the root of the tooth in the patient's mouth.

To make a die in the Melottes or any other metal involves quite a little time and certainly does not help to make an exact reproduction of the model, as there are at least three opportunities where small errors may be made:

1. In taking impression with modelling compound, plaster or any other substances.

2. In pouring up the plaster model.

3. In pouring up the die in metal.

The following seems to the writer to be the best method for

making a good durable crown which when placed in position must fit, even in cases of difficult articulation.

At first sight the process seems to be a complicated one, but after having gone through with it several times, the making of a crown will not require any more labor or time than any other method, in fact will prove to be a gainer as the crown can be put in place immediately, as no fitting is required; this tedious operation being avoided.

With the aid of a Dentometer the measurement of the prepared root is taken in the usual way and a band of gold plate-22 karat, 24 Brown & Sharpe's guage preferable of the indicated length cut out and bend with a pair of round pliers to fit the root. Before

soldering, the band is tried in the patient's mouth and seen that it fits well. After soldering, the band is cut to fit the curves of the gums and the height of band determined. A piece of bee's wax is pressed into the open band and patient requested to bite. After having removed the band with care all unsecessary wax is trimmed off and the respective tooth, in our case a bicuspid, imitated, without disturbing the impression made by the articulating opposite teeth. We have now a crown, the band of which is gold, the cusp, wax, (fig. 1). The crown is now dipped into plaster of Plaster, care should be taken that no bubbles of air are formed. After hardening of plaster the crown is removed, if necessary by heating slightly and so softening the wax. Two or three small nitches are cut into the plaster model, surface smoothed and cut round to fit a rubber ring, (fig. 2). Melottes metal just melted enough so that it will flow poured

into it.

After cooling, the die is held over an illuminating gas flame until covered with carbon and then a counterdie made, (fig. 3). A piece of gold plate is sweaged into the counter die, first by using some lead or still better some vulcanite rubber and the die Band and cusp are soldered and the crown finished in the usual way.

BLEACHING DEVITALIZED TEETH WITH PYROZONE.

CAL.

BY J. P. PARKER, D D.S., SANTA CRUZ, CAL.

This is a subject less written about than practiced, which I think it well to bring before the profession for discussion, that ideas may be brought to light, giving us all the benefit of them.

the

Why should we bleach a discolored tooth? Nature gives us our teeth with a uniformity of color. With the death of a pulp comes a change, more or less discoloring the affected tooth, and in some instances making it very noticeable to the casual observer and objectionable to the possessor. For instance, when we meet a person with nice, clean, white teeth, we observe nothing wrong, eye not being attracted to any special feature; but let there be one decidedly dark tooth in the front of the mouth, and the eyes are so involuntarily fixed as to require an effort on the part of the observer to refrain from gazing offensively. So, to have all the features in harmony, the teeth must be harmonious.

When should we bleach? It has been the practice of many of of our best operators to rid themselves and their patients of a badly discolored tooth by removing the natural crown and replacing it with an artificial one, thus making it expensive, and giving the patient a .ooth which will never be quite as perfect in strength and harmony as Nature gave, for there are few instances when the artificial becomes an improvement over the natural.

The time consumed and the inconvenience to the patient in bleaching, as a rule, is less than in crowning. In bleaching, the tooth and root are made more aseptic, thus improving the sanitary conditions of the mouth, and thereby lessening the chances of pericemental inflammation. In bleaching with pyrozone we remove septic matter that we would not if we were only crowning. A tooth should always be bleached instead of crowned, unless the crown will look better and be stronger.