These are only some of the abuses of crown work, to say naught of teeth which could be properly filled, that are sacrificed for crowns which can never take the place of teeth properly filled.
Bridge work has taken the place of gold plates to a certain extent. Still, however good a thing it may be, it also is greatly abused. In my mind, a bridge is not a practical dentiture when it has to span the entire arch supported only by three or four roots, or, say teeth. It has no superiority over a gold plate in such a case, because the latter can be kept clean, while the former can not, and the best of bridges must be removed at times to be reset. The chief objection to a full case of bridge is its becoming loose, which is no doubt caused by the unbalanced movement of the roots, as pressure or weight cannot be brought to bear upon three spans surmounting four pieces at the same time; one piece will surely give way to the undue strain.
The abusive use of open-face crowns must not be overlooked. These classes of crowns for bridge work should never be used, as they are simply not practical. We have yet to see one which will last any length of time. They have no strength nor durability. One of their weak points is the band around the labial surface of the tooth which in course of time cracks. Another is the free access which the secretions have to do their work upon the cement which holds the crown in place.
We are taught that a cement filling is not a permanent one, and especially should not be used below the gum border; but we are advised to use open-face crowns and to set them on with cement. If cement will not last when put into a cavity of a tooth at the gum line, we should hardly imagine that it would last very long when only protected by a thin gold band placed below the gum line, where secretions have continual play at it.
Another class of bridge work which should be done away with is what is called pin bridges, where places are bridged over, getting the necessary support by drilling cavities into sound teeth to insert the pins necessary to support the bridge. This is a class of work which simply will not last, owing to the lack of proper strength required to support a dentiture of that sort. If a good tooth must be sacrificed, why not crown the necessary teeth and get something from the start that will be of lasting service?
In my mind it is far better to have a bridge rest fully upon the gum instead of having a shelf-like projection over the ridge. It is said that the advantage gained from this class is its cleanliness, as there is no way for the food to become lodged during the process of mastication, as is the case with the shelf-projecting bridge. One would naturally imagine that food could find its way underneath, between the gum and the teeth, but strange to say, there is very little that ever finds its way to those places.
In closing, I will offer a suggestion which may, or may not, be new to you. It is this:
For investing material, I recommend common moulding sand, in proportion of one-half plaster and one-half sand. After allowing the mass to set hard, trim it down to suit the case invested, and then with a hair-brush paint the upper surface with a solution of borax water. The advantage of the use of sand as an investing material is that from the change of the color of the mass from a deep yellow to a lighter shade you can perceive the exact moment at which your case is thoroughly dried out. The borax has the property of preventing the mass from splitting. Its greatest qualities are its strength and non-contractible properties, it having an advantage in this respect to pumice, asbestos and other materials generally used for this class of work.
