roentgenogram taken June 12, 1918, shows eradication of infected apical foci. (Fig. 13.) FIG. 13.

SUMMARY.

Upon the solicitation of the writer, dichloramin-T has been tried by numer

ous practitioners, and it has been extensively employed during the session of 1917-18 by the students in our infirmary. The results obtained therewith have been most satisfactory. Basing his assumptions upon the logical sequence of the above-discussed method of investigation and the clinical results obtained with this compound by him and by fellow practitioners, the writer feels justified in recommending to the profession the use of this agent for the treatment of infected root-canals and their sequelae. On account of its effectiveness, its extreme simplicity of application, and its innoxiousness, dichloramin-T is superior for the above purposes to any other drug so far known.

40TH AND SPRUCE STS.

T

HE attorney who presents his case in

a court of law usually prefaces his argument with a statement of the points which he proposes to make, thus focusing the attention of his hearers on the principal features of his discourse, and showing the relationship between matters which might otherwise seem disconnected. So I, though not an attorney, but as your essayist for this session, shall first present to you briefly the main features of my paper, in the hope that in this manner I may best serve the coherence and force of my argument.

The most important point which I wish to make is that the etiology of periodontoclasia is a mixed etiology-that is, at least two causative factors must combine to bring about the destruction of the supporting tissues of the teeth; and moreover, that factors both for and

against the health of these tissues must be considered. Next comes the distinction suggested by my title, the division of etiological factors into primary and secondary, with the natural focusing of attention on the group of primary factors.

I wish also to call to your attention the accomplishments of present-day periodontia-the elimination of inflammation and infection around the teeth; the elimination of so-called pockets by the vital attachment of gingival tissue to the root surface; the growth of new bone to at least partially replace bone destroyed through periodontal disease. As a corollary to this I request your very serious consideration of the practicability of the prevention of periodontal disease, not by the specialist alone, but by the general practitioner, with particular refer

ence to the responsibility we must all assume for the loss of teeth not attacked by periapical infection.

While this paper is not to deal primarily with the pathology of the periodontal tissues, it is impossible to consider the etiology of periodontoclasia without suggesting a revision of the somewhat vague pathology and classification of periodontal diseases exhibited in most of our current dental writings, for the purpose of bringing the entire group of ailments commonly known as "pyorrhea alveolaris" into an orderly concourse well within the comprehension of the average dental practitioner.

Before embarking on the elaboration of these points I should like to call to your attention the distinction commonly made between a fact and an hypothesis, and the place that each occupies in science. A fact is something which has been proved and can at any time be proved to be true. Naturally in dealing with any of the branches of physical science it is highly desirable that our concepts should be based on facts, or at least be susceptible of proof. An hypothesis is an assumption, which may not have been proved and may not even be susceptible of proof, but which accords with some of the known facts on which it bears. A concept which accords with all known facts may properly be accepted as being true, and may also be taken as a foundation for the formulation of theories regarding various groups of related phenomena. One of the fundamental hypotheses of natural science is that proposed by Avogadro regarding the number of molecules in equal volumes of gases. Avogadro's hypothesis will probably never be proved, yet upon this assumption is erected the towering structure of modern chemistry, because it accords with all known facts of chemical science.

In the course of the development of medical and dental science many hypotheses have been proposed. If they have always tallied with fact, then they were correct. And many hypotheses have been accepted and later proved-as, for instance, the assumption regarding the or

ganism responsible for malaria. On the other hand, many hypotheses have been found to be accordant with only part of the facts, and have had to be rejected, as the assumption that the endamoeba buccalis is the specific cause of dental periclasia. We must always bear in mind, too, that theory must adjust itself to fact, not fact to theory. In other words, if a phenomenon always occurs in the same way and under the influence of the same causative factors, any theory which does not agree with that sequence of events, no matter how plausible it may seem, must be rejected or remodeled to fit the facts.

No one could wish more ardently than your essayist that out of the maze of speculations of the past an orderly proven set of facts might be presented to you regarding the causation of periodontoclasia. Study of the etiology of this group of dental disorders has revealed the interaction of many factors of widely divergent types, making this etiology nearly as complex as, for instance, the parasitology of the mouth-so complex, in fact, as to make its reproduction in the field of animal experimentation very nearly an impossibility, thus making the proving of our hypotheses enormously difficult. It is, however, a wellknown axiom that the successful treatment of disease lies in the removal of the cause; thus an assumption regarding etiology may be considered to be correct if uniformly successful results follow its application. And it is upon this uniform. sequence of diagnosis, treatment, and result, not only in my own hands but in the hands of many others, that the hypotheses I present to you have been built up. The acid test for the correctness of these assumptions lies in the success with which others may apply them in their own practices. This calls for a word of caution. Remember that it is easy even for the specialist to overlook one out of several contributing etiological factors present, hence the great possibility of an incomplete diagnosis by the untrained observer, with the consequent failure to obtain results. Remember also that root surgery, which is involved in practically

all treatment, must be perfect in its execution; this requires temperament as well as an exacting technique on the part of the operator.

The attempt to apply the principles laid down in this paper by the general practitioner will thus be apt to meet with only partial success, especially if he applies them first, as he is very likely to do, in the treatment of his advanced cases. Failures thus encountered do not of course invalidate the hypotheses I propose; on the contrary, these failures may be turned into stepping-stones which, with persistent study and improvement in technique, will lead to the uniformly successful results obtained by others.

(3) Trauma.

(4) Abnormality of tooth surface.
(5) Parasitic invasion.

(6) Abnormal systemic conditions.

The first four are the groups which I call primary, the fifth and sixth being secondary. I have felt it necessary to call these primary and secondary factors, rather than predisposing and exciting, as is the common practice in pathology, and for this reason: There are several factors which are incapable of inaugurating a disease process in the periodontal tissue, yet which are directly concerned with the production of some of the typical phenomena of the disease, and which thus may properly be called exciting causes. For instance, bacteria are incapable of proliferating in a healthy or hypertonic tissue; they accordingly cannot be a primary cause of periodontoclasia. Yet the severing of the pericemental fibers with resulting pocket for

mation does not take place unless bacteria invade this tissue and proliferate within it. Bacteria are thus seen to be a true exciting cause of this type of dental periclasia, the primary factor on the other hand being something which lowers the tone and hence the resisting power of the tissue.

It may be argued that the term predisposing is virtually synonymous with primary. This might be true if a predisposing cause was always a predisposing cause. But we find that the same factor may be a predisposing cause in one case and an exciting cause in another. But a primary cause is always a primary cause. Then again, to use the terms predisposing and exciting usually means that we give our attention principally to the exciting cause, often forgetting that the exciting cause is inoperative except as it is preceded by the predisposing cause. And I think our

medical brethren are occasionally guilty of the same error. To use the term primary on the other hand focuses our attention on the important and determining factor.

Our primary factors in about the order of their importance, are malocclusion, defective operative and prosthetic procedures, trauma and abnormality of tooth surface. We will now consider these groups in detail with their subdivisions.

MALOCCLUSION.

Malocclusion as a factor in dental periclasia has three subdivisions, i.e. traumatic occlusion, defective approximal contacts, and labio-lingual malposition. Traumatic occlusion is a term suggested by Dr. Paul R. Stillman to apply to any form of malocclusion whereby the tooth or teeth are driven beyond the normal limits of movement within their sockets. during contact with their antagonists in closing or in movements of mastication. It is at once the most destructive factor in dental periclasia, and usually the easiest of prevention in any practice in which the teeth are under observation and control from infancy on through adult life. A whole essay could well be

written on traumatic occlusion, but I shall here try to bring out simply the main points regarding this destructive agency. There are three ways in which the periodontal tissues may receive an occlusal trauma, viz, excessive impact on one or more cusps through elongation or rotation; impact at an angle to the long axis of the root through tipping, as after extraction; and a thrust to one side of the socket due to an elongation or closing up of the bite in the incisal region, or inharmony of the inclined planes in the bicuspid and molar region. The commonest causes of traumatic occlusion are malocclusions of the Angle classification, extractions without retention of space, lack of normal wear of cusps with advancing years, and faulty operative and prosthetic restorations. Extraction, unless the space is retained by an orthodontic retainer, denture, or bridge, will result in drifting and tipping of the remaining teeth, and a closing up of the bite, bringing an impact at an angle to the long axis of the tipped teeth and excessive stress on the anterior teeth, to say nothing of the opening up of contacts. A greater variety of traumatic occlusions may be brought about by extractions than through any other one. operation.

Faulty dental operations bring about traumatic occlusion in a surprising number of cases. Fillings are built just a little too high; occlusal surfaces are not carved to retain normal occlusion, thus permitting the teeth to drift; the lingual surfaces of upper anterior crowns are made a little too full. But more particularly is damage done in the much-berated field of crown and bridge work through making occlusal surfaces too high or through failure to plan for the various movements of the mandible. Occlusal trauma thus instituted is 100 per cent. more destructive than ill-fitting bands, the lack of individual movement of abutments, and uncleanliness, to which so much has been charged in the past. Failure to recognize the part played by traumatic occlusion in virtually pounding crowns and bridges out of patients' mouths, is largely responsible for the [VOL. LX. 74]

muddle in which the crown and bridge branch at present finds itself.

Clasps and Gilmore attachments, used for partial dentures, often produce a tipping effect or side-thrust during mastication which constitutes a very serious trauma. Wing bridges and excessive contacts without an occlusal rest on the adjacent tooth do much damage also. Failure to wear down high cusps of the natural teeth with advancing years often means the continuance of a heavy side strain in the movements of mastication to the point where it becomes an actual trauma. Malocclusion according to the Angle classification does not necessarily mean traumatic occlusion, but mouths in which any abnormality of occlusion exists should be carefully scrutinized for the presence of teeth so placed as to meet their antagonists a little to the buccal or lingual of their proper position; teeth tipped labio-lingually or bucco-lingually; rotated teeth; and excessive overlap in the incisal region.

In the case of most causative factors the method of correction will be suggested simply by calling attention to the cause itself. In the case of traumatic occlusion this may not be so obvious. The carborundum stone guided by articulating paper is the agent most often used, elongated teeth and high cusps being shortened, and occluding surfaces being reshaped to give harmony between the inclined planes of the opposing teeth, as for instance the dressing down of the labial surfaces of the lower incisors. In cases where a number of teeth have been lost or there has been excessive abrasion, it may be necessary to open the bite if the above method would entail an excessive cutting of tooth structure. In regard to crown and bridge work let me suggest that the beginning of the traumatic occlusion comes in taking the bite. Inspection of the occlusion of teeth not covered by the wax both before and during the taking of the bite will enable the operator to detect errors in this step. When the bridge is inserted, be sure that the teeth in the mouth occlude the same as before insertion, and be sure that the bite on all the teeth feels natural to the

patient. The final decision on this can only come after the eating of several meals. The bridge that feels like a stone wall in the mouth is one which does not occlude properly.

Damage done by open or improper contacts has been very fully considered in the past, and need not be enlarged upon in this paper. It is well to point out one fact with regard to open contacts not previously emphasized, namely, that damage is done not only by impaction of food, but by the loss of necessary mesio-distal support, thus permitting a movement of the teeth which leads to a real traumatic occlusion.

Labio-lingual malposition when not a cause of traumatic occlusion or of defective contacts between adjoining teeth is a factor in periodontoclasia, because it increases the difficulty of keeping the tooth surface clean. This condition is often found in the lower incisal region due to narrow arches with consequent crowding, and may sometimes necessitate the extraction of one tooth and the realignment of the others to avoid the loss of several.

DEFECTIVE OPERATIVE AND PROSTHETIC

PROCEDURES.

The next group of etiological factors. has to do with the operations performed by the dentist for the restoration of lost tooth tissue. Mention has already been made of the damage done by traumatic occlusion through building occlusal surfaces too high or with an inharmonious arrangement of the inclined planes. Remember that the teeth may meet properly in the ordinary closing of the jaws, yet exhibit a marked traumatic occlusion in the movements of mastication. Open or improperly formed contacts have also been mentioned. Much damage is done by placing fillings or crowns without regaining space lost by the teeth tipping together as a result of interproximal decay. This squeezes out the gum tissue from between the roots, making a splendid lodging-place for deposits of tartar, food, and bacteria, and making it impossible for the septal tissue to be

maintained in a state of health. Let me recommend the Perry separator and base-plate gutta-percha here. Edges of crowns need never go farther than half a millimeter under the gum margin unless unusual strength is required.

The usual taper of the root renders it utterly impossible to make a band which will fit any farther up the root than the root-trimming instruments will go-and they seldom go far enough under the gum to be lost to sight. In many mouths the gums will not tolerate the least contact with a band no matter how well fitted. The trimming of gingival margins of fillings without injury to the gum is difficult. It will usually be best accomplished with delicate files, of which several designs are available. Failure to properly restore the shape of labial and lingual surfaces may subject the gum margin to unaccustomed impact of food passing rootwise over these surfaces in mastication. All restorations must have polished surfaces to permit of proper cleaning. It seems to be little appreciated that the gum tissue immediately around a natural tooth is more sensitive to pressure than the gum tissue over the bony ridge where teeth have been extracted. This requires extra grinding of facings and trimming of dentures where they are to rest against these tissues.

TRAUMA.

Trauma, as distinguished from traumatic occlusion, means an injury effected usually from outside the mouth. Extreme and rapid separation, improper use of clamps and ligatures, and blows may do much damage to the periodontal tissues. Improper or excessive use of the toothbrush may do some harm, though usually slight as compared with that produced by insufficient brushing.

ABNORMALITY OF TOOTH SURFACE.

By abnormality of tooth surface we mean a surface which exhibits a roughened or etched enamel, abnormal form, or presence of hard or soft deposits. Rough enamel may be as irritating to