Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/112

 occurrence; while the views advanced with reference to the pathology and treatment of such cases, suppositional or otherwise, are equally various and conflicting. The probable solution of the difficulty seems to be that, while evil consequences may in certain instances be traceable to dentition, the frequency and importance of such cases is very much exaggerated.

Extraction.—This constitutes the most important opera tion of a surgical nature falling under the care of the dentist, and is chiefly called for where the condition of the tooth, from disease or injury, precludes the possibility of saving it by stopping or other means. The operation is also frequently resorted to where the teeth are too crowded in the jaw, or where they are irremediably misplaced, or where super numerary members of the series exist and occasion incon venience. In order to extract any tooth successfully, there is demanded a knowledge of what its configuration normally ought to be, and of the proper instrument to use; and, along with these, the condition to which decay or other disease may have reduced the tooth must be kept in mind while proceeding with the operation.

In seizing a tooth in order to its extraction the part upon which the hold is taken should be sufficiently sound and strong to withstand the force necessary for dislodging the fangs ; and to obtain such a hold it is necessary to thrust the grasp of the instrument as far as possible beyond the spot affected by decay. It should then be detached from the walls of its socket in that direction where least resistance is likely to be met. This must be judged of according to circumstances, but in general is indicated by an acquaintance with the anatomy of the structures concerned. After being thus loosened it has merely to be lifted from the jaw to complete the operation. Sometimes a tooth is so firmly secured in the jaw that its own tissue will give way before it will separate from the alveolar cavity in which it is fixed. This is particularly the case in friable teeth ; and frequently even in the strongest teeth the root or fangs may be malformed or bent, or secured in such a manner as renders their extrac tion extremely difficult or altogether impossible by any ordinary means.

The instruments employed in extraction may be divided into those which grasp the tooth between their blades and literally extract or draw it out, such as forceps, and those which apply the dislodging force by acting as a lever in the manner of a crow bar, such instruments being termed elevators. The key, an instrument of great power, but now very properly almost disused, partakes in a measure of the properties of both these instruments, but that in a very imperfect and disadvantageous manner. In some rare cases, however, it may be found of much service when used with circumspection. It is impossible here to enter into detail regarding the different forms of forceps, elevators, and other instruments required in dental surgery; but one great principle may be laid down with respect to all of them, which applies especially to forceps, and that is that their form should be as simple as possible consistently with fitting and grasping securely the particular tooth they are intended to remove, and with conveniently reaching that part of the mouth in which it is situated.

Regulation of Teeth.—In the extraction of teeth for the purpose of affording space in cases of dental irregularity from overcrowding, it often becomes necessary to remove a healthy organ, and before doing so among the permanent teeth certain questions present themselves for consideration. Unless there be a fair probability of such a step being sue cessful it endangers the loss of two teeth should the originally misplaced one be so objectionable and so unyield ing to treatment as to require this. In the temporary set the principal disadvantage connected with the removal of any of their number is when to make room for one per manent tooth two or more temporary ones would require extraction, as of course space is thus provided at the expense of the second permanent tooth, for which one of the two temporary ones was keeping a place. In this set, however, the objection to removal of any of its series is greatly obviated by the fact that, while the teeth are very soon to be lost at all events, the jaw is increasing in size and progressively affording more and more, room itself for the incoming second set. Along with extraction, in the great majority of instances pressure requires to be applied to the misplaced teeth in order to effect their regulation. This has generally to be continuously kept up for a con siderable period, and in many cases requires to be main tained after the teeth have been restored to their natural position in order to keep them there until they seem settled in the new locality. Various forms of what are called regulating plates are used for the purpose of applying pres sure in this manner, and may be said generally to consist of a framework fitted and fixed to the adjoining teeth something in the same manner as an artificial set, and cal culated to afford a fixed point or fulcrum from which to act on the tooth to be moved.

In disease of the dental tissues it is not always necessary to remove the affected organ ; such an extreme measure as this is only called for when other remedial means have failed, or appear hopeless. The chief of all dental diseases demanding the dentist s care is, as has been already stated, that known as caries, or decay. It is this affection directly or indirectly that leads to by far the larger number of extractions performed; but it by no means follows that extraction is the only remedy at our command. Many teeth are extracted which might be saved, and the principal method by which this can be effected is by what is termed stopping, or plugging, or filling the teeth.

Stopping.—The operation of stopping a decayed tooth consists in cleaning out the carious cavity and removing all the softened or disintegrated tissue, and shaping and trim ming it so as to reduce it to a form fit for receiving and retaining the material with which it is to be filled up. Along with these proceedings it in general becomes necessary to diminish the sensitive condition in which the interior surface of the prepared cavity is left, to remove or destroy any of the vascular and highly nervous pulp which may be protruding into it, and to subdue any inflammation and arrest any discharge which may have been going on in the fang. Various applications and other remedial measures are resorted to for these purposes, the most common being the applying for a time some of the more convenient escharotics on a plug inserted into and left within the cleaned-out cavity till this end is achieved. &quot;When thus prepared, the cavity is ready to be filled with whatever substance has been selected to replace the lost tissue, and as nearly as possible to restore the contour of the tooth. The substances employed as permanent stop pings are generally metallic. Gold in the form of foil, or in that condition known as sponge gold, tin in the form of foil, and amalgams, composed of various metals either in a simple or compound condition combined with mercury, are the principal materials in use as stoppings. The oxychlorides, from their being capable of insertion in a plastic state, and quickly acquiring a density and hardness approaching that of tooth bone, are also favourites with many as serviceable fillings ; and various preparations of gutta-percha, gum resins, sulphur, and other matters have long been known as valuable, though not very durable, when employed in certain cases.

Dexterity in the insertion of a gold or other foil filling is a matter which can be acquired by experience alone. The general principles are that, the cavity being prepared and