A textbook of clinical periodontia : a study of the causes and pathology of periodontal disease and a consideration of its treatment

Front matter

^Battel JMpdl

A GIFT FROM

Dr. John S. Stone Clarksburg, W. Va, 1954

Preface

The dissemination of knowledge which will assist our colleagues in the control of periodontoclasia furnishes the underlying motive for the publication of this book. Our ideal is the preparation of a text book from which the dental student may learn, and to which the dental practitioner may refer. It has been found that other methods of instruction such as the reading and publication of essays, the giving of clinics and even class-room instruction, have only partially succeeded in their purpose. These methods are important and valuable. At the same time periodontology has developed into a subject of such breadth that only in a text book, with its opportunities for elaboration can it be presented in a manner which will bring out every phase, and which will tend to maintain clearly the perspective of the subject; furthermore it has the advantage of reaching a greater number of students. It also permits of that deliberate study and reflection necessary to the digestion of new thoughts which are so difficult of attainment in the class-room.

It is to the advantage of periodontology that the struggle against periodontal disease should be more widely discussed, to the end that these pathological conditions may be more perfectly brought under control. Hence, while presenting theories which we believe to be sound, we have no desire to minimize the value of opinions which we do not share ; for attempts to make proselytes for a dogma have never led to progress. Only the truth can in the end prevail.

The authors realize that to many readers this volume will represent largely a disagreement with the views expressed by many investigators of prominence. The difference of opinion does exist, but it is voiced primarily because these dissonant theories have in practice failed to give satisfactory results. The theories which we advance, on the other hand, have given vii viii PREFACE

highly pleasing results, both in our own experience and in that of many others. It is this fundamental and necessary relationship of theory to practice which demands the contradiction of many views put forward in the past.

While the theories which have been advanced in the past have been sharply refuted by the inconsistent results which have attended their application in the clinic, nevertheless each theory has been based upon a part of the truth. Whatever advance has been made has been built upon the careful study of the work of previous investigators, with such rearrangement of their theories as would make them compatible with clinical experience; and while results have been obtained which have satisfied many, only the change from disease to continuing health is to be considered the acceptable ideal.

We realize that the book is incomplete. There are still many phases of this subject which require further investigation but it is our hope that this book may prove an inspiration to other students, who by their investigations may penetrate more deeply into the unexplored regions of this science and thereby carry forward the frontier of knowledge in this field.

The reader will find very frequent allusions to the subject of traumatic occlusion. We do not wish it to appear that we have unduly emphasized this phase of periodontal science. Periodontal disease centres largely around disturbance of function. Other factors may disturb function as much as does traumatic occlusion; and the reader will find them duly credited in these pages. But the fact remains that the traumatic disturbance of function is so constantly found: it so constantly intrudes itself into the field of periodontal pathology, that we can only adequately and fully present this subject by giving this factor the emphasis which it demands. Familiarity with its manisfestations in the clinic will justify this assertion.

In presenting the chapters on Anatomy, Histology, and other subjects dealing with the fundamental sciences concerned, it has been our object to link them to the clinical aspects as far as possible. It is our hope that in this way we may aid the clinician in concentrating his attention on the underlying principles. He

PREFACE ix

should at all times be able to interpret his clinical picture in terms of histology and pathology. Only thus can he fully understand the conditions with which he deals. And only thus will he be able intelligently to modify his treatment to deal successfully with the variations in the conditions which he sees.

It will be noted that Diagnosis has been given a place of prominence and has been made a Section of this book in itself. The reason for this is the important position which this subject occupies in the field of periodontia. It is the foundation of correct practice, yet comparatively few in our profession consciously analyze their cases for the purpose of classifying the pathology.

Modern developments, both in Dentistry and in Medicine have brought Diagnosis into a position whose importance is second to no branch of dental practice. If we have made a contribution of value in this field only, we shall feel repaid for our efforts.

Success in periodontia depends upon clear thinking and unprejudiced logic. The operator must not allow his judgment to be influenced by specious arguments based upon incomplete study. For these arguments may be so clearly and logically presented, and they may seem to the neophyte to be so acceptable as to convince him of their truth. But theorizing1, no matter how plausible, will not carry the decision as to the truth of a hypothesis. It must stand or fall on the success which attends its application in practice. And it is because of consistent clinical results, as well as the essential harmony of these ideas with accepted pathology and histology, that we are convinced of their fundamental truth.

"We find upon a review of this completed book, that we may be accused of having made a very complex matter out of a branch of dentistry which our profession would fain see simplified. It may seem to many readers that where so much material is presented, its application in practice will be difficult. With a full realization of this fact, we can but say, that periodontia is an extremely complex subject, and one which refuses to be simplified. One cannot hope for success in treatment until he x PREFACE

masters these many details. There is no short and easy way to the successful treatment of periodontal disease. Nevertheless it is so important that these disorders be comprehended and controlled, that we have given in this volume all of those facts regarding periclasia which we have confirmed by experience, in the hope that this full presentation may be of real assistance to our confreres.

This book is not intended to be controversial, and for this reason we have omitted references to those theories and hypotheses with which we disagree. We desire nevertheless to acknowledge our indebtedness to the following physicians and dentists but for whose work this book could never have come into being: —

Professor J. G. Adami, Doctor Elmer S. Best, Professor G. V. Black, Doctor M. H. Fletcher, Professor A. C. Fones, Professor A. Hopewell-Smith, Doctor R. G. Hutchinson, Jr., Doctor Austin F. James, Doctor Arthur H. Merritt, Professor F. B. Noyes, Doctor Rodrigues Ottolengui, Doctor James M. Riggs, Doctor D. D. Smith, Doctor W. J. Younger, Professor Hans Zinsser, Doctor E. C. Rosenow, Doctor F. Park Lewis.

In addition we desire to acknowledge our indebtedness to the following, who by suggestion, encouragement and personal service have aided in the making of the book :

Doctor C. F. Ash, Doctor Anthony Bassler, L. E. Cornell, Dr. Gillette Hayden, Doctor Grace Rogers Spaulding, Doctor A. H. Stevenson, Doctor Charles Sutton, Dr. L. M. Waugh.

Notwithstanding our indebtedness to those whose names have just been mentioned, our greatest debt is to Harold Keith Box, L.D.S., D.D.S., Ph.D., F.A.A.P. Doctor Box, through his outstanding ability both as a clinician and pathologist, has contributed so much to every chapter of this book, that we are unable to adequately express to our readers how much of the worth of this volume is due to his constructive criticism and inspiration. In addition we acknowledge our indebtedness for the photomicrographs which give only a faint idea of what Doctor Box has accomplished in the field of histology. While it

PREFACE xi

might be unfair to state that this volume represents Doctor Box *s views upon this subject, it is quite proper to affirm that many of his findings are expressed in its pages.

PAUL R. STILLMAN.

JOHN OPPIE McCALL.

Chatiemac Club,

Warren County, New York.

PART ONE Relation to the Basic Sciences

I Introduction and General Consideration of Periodontoclasia . 3

The Dentist's part in the preservation of human life. Disintegrating forces in the mouth. Variety of theories regarding causes and treatment of dental and periodontal disease. Nomenclature. Diagnosis. Uniformity of results obtainable through the medium of correct diagnosis.

II Nomenclature 8

Necessity and authority for new terminology. Derivation of "Periodontoclasia," ' ' Apoxesis, ' ' etc. Subdivision of Gingivae. "Centric" and "Eccentric Occlusion," "Non-Occlusion," etc.

III Anatomy 13

Gingival Tissues. Enamel Contours. Cusp relations as a cause of Traumatic Occlusion. Inclination of Roots. Anatomy of the Boot Surface.

IV The Cell and the Tissues 20

Definition. Differentiation in form due to differentiation of function. Tissues and organs. The cell body. Spongioplasm. Paraplasm. Motility of protoplasm. Chemotaxis. Nucleus, Nuclear and Cell Division. The Tissues. Intercellular substance.

V Histology 25

Consideration of salient points. Alveolar bone. Marginal gingiva — epithelium, connective tissue, blood supply. Cemental gingiva — epithelium, connective tissue. Crevicular epithelium. Pericementum— attachment to eementum. Absorption of alveolar bone in afunctional and traumatic ulalrophia.

VI Physiology 29

Teeth and periodontium developed to meet functional demands. Function of teeth : Pulp : Marginal gingiva : Cemental gingiva : Transeptal fibers. Functions of pericementum : Principal groups of fibers: tactile sense. Function of eementum: Alveolar process. Saliva.

VII Pathology 38

General Consideration: Periodontal pathology similar to general pathology: Mechanical element in periodontal pathology. Periodontal inflammation : Gingival, Pericemental, Alveolar. Periodontal abscess. Relative toxicity to the system of parietal and periapical infection.

xiii xiv CONTENTS

PART TWO The Causes of Periodontoclasia

VIII Etiology 47

General Consideration: Great variety of causes concerned in etiology: Primary and Secondary causes: Etiology always compound: Biogenetic and Pathogenic forces in Etiology.

IX Etiology (Cont'd): The Etiological Chart: Primary Factors 51 Primary factors nearly all mechanical. Mechanical irritants act

on the entire pericementum, on the alveolar crest structures, or on the gingival tissue.

Traumatic occlusion as an injury to entire pericementum and alveolus and to alveolar crest tissues. Malocclusion; Kestorative Defects; Abnormal tooth form; Habits of Occlusion. Gingival irritants. Deposits; Developmental defects; Impingement of restorations on marginal, cemental, and alveolar gingiva. Extrinsic trauma.

X Etiology (Cont'd) : The Etiological Chart: Secondary Factors 58

Abnormal systemic conditions: Extra-oral disease: Nutritional influences. Diet.

Chemical injurious agents. Bacterial toxins: Decomposing organic material: Inorganic and Organic poisons. Predisposing 'local conditions: Histological and anatomical characteristics. Injurious habits.

XI Etiology (Cont'd): Traumatic Occlusion 63

Centric and Eccentric Occlusion: Traumatic Occlusion defined, a potential or actual Injurious Agent. Occlusal force: Example of variations in force applied to individual teeth: Coordination of teeth in every position of the jaw requisite for normal occlusion : Angle definition of normal occlusion : Line of Occlusion: Traumatic Occlusion after orthodontic treatment. Conditions essential to normality of occlusion: Factors which will produce traumatic occlusion. First tissue change produced by Traumatic Occlusion is in bone: Second change in marginal and cemental gingiva: Third change in pericementum. Pocket formation. Compensation of traumatic occlusion by abrasion. Correction of Traumatic Occlusion: Grinding of tooth surface: Orthodontic treatment: Opening the bite. Detection of traumatic occlusion: Early clinical signs: Discomfort after partial correction. Grinding occluding surfaces a safe procedure.

XII Etiology (Cont'd) : Congenital Non-occlusion 76

Definition: Congenital non-occlusion compared with traumatic occlusion: Comparison of tissue condition, and of reaction to infection.

XIII Prognosis 79

Definition: Factors governing prognosis: Eegeneration of tissue: Limitations to recovery: Pulp Canal Sepsis: Injury to cementum: Inaccessibility of surface to scaling instruments: Collateral factors in prognosis : Cell vitality an important factor. Derangement of nervous system unfavorable: Normality of cementum, dentine and pulp is important: Prognosis frequently depends on collateral factors: Proportion of remaining bone and pericementum requisite: Personal care of the mouth.

CONTENTS xv

PART THREE Therapeutics of Periodontia

XIV The Biologic Element in Periodontoclasia 89

Biogenetic forces aiding in the repair of tissue: Problem of regenerative power and elimination of pathogenic agencies. Analogy of the gardener. Response of Biogenetic forces to surgical operation or relief from injury.

XV Treatment 95

General Consideration : Knowledge of the disease, its pathology

and etiology necessary : Diagnosis of the type of disease an indicator of its etiology : Removal of mechanical factors and stimulation usually required.

Management of Cases. Treatment, a standardized procedure with variations for different types of periclasia: Periodontist must understand periodontal disease and its treatment and also the problem of restoration. Restoration of function essential. Standdardized examination : Usual steps in treatment : Maintenance of health through systematic care of the mouth.

PART FOUR Diagnosis of Periodontal Disease XVI Facts and Factors in Diagnosis 103

Definition: Dentist confused by variety of opinions: Dental examination usually superficial: Importance of detecting incipient lesions: Focal infection and dental diagnosis.

XVII Infection and Resistance 107

Micro-organisms constantly found in the tissues: Their proliferation necessary to establish infection : Immunity, — natural, acquired, artificial. Types of pathogenic bacteria found in the mouth.

XVIII Focal Infection Ill

Definition: Systemic effects of acute infections: Primary and secondary foci and their relationship: Dentist's responsibilty : Tests for presence of metastatic disease: Complement fixation

test : Blood chemistry.

XIX Case Records 116

Importance of recording symptoms and conditions: Factors in a complete diagnosis: Mouth examination, radiographs, study casts, record chart. Diagnostic field of the dentist: Manner of taking case record.

XX Recording of Symptoms 121

Subjective symptoms: Sites of secondary infections: Sites of pain and their diagnosis: Recording findings: Use of diagnostic chart.

xvi CONTENTS

XXI Differential Diagnosis of Parietal and Periapical Lesions 126 Eelative harmfulness of the two groups: Significance of pus: Types of parietal disease: Prognosis of parietal lesions: Prognosis of periapical lesions: Types of teeth showing periapical infection: Eelative responsibility of the dentist and physician

in regard to oral infection: Hazard of root-canal rilling: Factors governing choice between treatment and extraction.

XXII The Normal and Pathological Periodontium as Seen in

the Radiograph 134

Appearance of normal periodontium: Types of tissue alteration and their radiographic appearance : Parietal lesions : Traumatic occlusion and its interpretation in the radiograph : Established infection: Periapical prognosis: Prognosis as indicated in the radiograph.

PAET FIVE

Types of Periodontoclasia

XXIII General Consideration 151

Older conception of periodontal disease: variety of symptoms indicating several pathological processes: Classification of types based on morphology : Secession : Gingivitis : Alveoloclasia : Pericementoclasia: Periodontal Abscess. Pure and fusion types.

XXIV Ulatrophia 155

Definition: Symptomatology: Sub-types: — Ischemic, symptoms, etiology: Afunctional, symptoms, etiology: Calcic, symptoms, etiology: Traumatic, symptoms, etiology. Treatment of all types.

XXV Gingivitis 161

Symptomatology: Sub-types: Simple: Chronic, Symptoms, Etiology. Hypertrophic: Symptoms, Etiology. Indolent: Subacute: Acute: Chronic Exudative. Treatment of all types.

XXVI Phagedenic Gingivitis 167

Terminology: Symptomatology: Pain: Fetor of Breath: Gingival exudate: Phagedenic Gingivitis communicable: Pathology and bacteriology: Etiology: Prognosis. Treatment, medication, surgical and prophylactic treatment.

XXVII Alveoloclasia 179

Symptomatology. Fusion types. Etiology: Treatment: Slow alveolar disintegration.

XXVIII Pericementoclasia 183

Symptomatology: Fusion types: Pathology. So-called "Pus Pocket", — Characteristics, Histology, Exudation, Distribution of epithelium, Absorption of bone. Etiology: Primary and secondary factors. Treatment: Possibility of cure: What constitutes cure: Sequence of remedial measures; Prophylactic treatment to maintain health.

CONTENTS xvii

XXIX Periodontal Abscess 195

Definition: Sub-types: — Periapical: Parietal. Pericemental abscess:— Symptoms, Etiology, Treatment. Gingival abscess: — Symptoms, Etiology, Treatment. Extra-alveolar abscess: — Symptoms, Periosteal elevation, Treatment. Periostitis: — Symptoms, Treatment.

PART SIX Technical Procedures

XXX The Use of Steel Instruments 201

Origin of term "scaler": Nature of substances to be removed

by instruments: Function of instruments: Principles governing their design: Types of scalers: Working parts: Bevel of cutting edge: Comparison of advantages of each type: Principles governing the use of instruments: Finger Rest: Two Point Contact: Angle of application of blade to tooth surface.

XXXI The Use of Splints 209

Object of splint: Indications for use: Methods of fixation:

Silk or linen ligature: platinum bands: Orthodontic appliance.

XXXII Oral Prophylaxis and Prophylactic Treatment . . . 212 Problem of oral prophylaxis: Recognition of early signs of disease: Cleanliness through function the ideal: Explanation of lack

of cleanliness due to interference with functions. Oral prophylaxis is prevention in the broadest sense: Contributed to by normal occlusion; restoration of surface contours; cleanliness; instruction in the care of the mouth; periodic prophylactic treatment.

Prophylactic Treatment: A part of Oral Prophlaxis: Functions of prophylactic treatment. Technic of use of the porte-polisher : Abrasives: Ribbon floss.

XXXIII Personal Care of the Mouth 220

Cleanliness, resistance and function. Tooth-brush the best artificial substitute for nature's method. Methods of using brush. Time required. Method of using flat floss. Dentifrices: essential properties, degree of abrasiveness. Construction of the tooth brush.

Conclusion

XXXIV The Sociologic Aspects of Dental Disease .... 231 Emphasis of the profession in the past has been on reparative work. Responsibilities of the dent'st of to-day. School and oral hygiene work: Its possibilities in public health conservation : Example set by large corporations in establishing dental clinics: Effect of dental disease on the development and mentality of school child. The call to the service of mankind.

"Nothing has been more hazardous in the natural sciences, nothing has more damaged their progress, than premature synthesis, that is, a premature connecting of scientific elements as yet discrepant, a leaping to conclusions without the justification of observed relations."

Virchow.

The Freedom of Science in the Modern State.

Chapter I Introduction

The preservation of life is a fundamental instinct of all living creatures, and health is their inherent birthright. Man, in contradistinction to the lower orders, has a definite sense of his relation to his species, which engenders in him a benevolent disposition toward his kind. It therefore follows that to preserve the health and life of mankind, is the highest corporeal service which may be rendered. Tin' dentist has an important part to play in this scheme of things. He has long proclaimed his jurisdiction over the mouth, the portal of the body. But it has remained for the scientific advances of recent years to reveal the full significance of his claims. The responsibilities of dental practice thus made clear, must be met. The dentist must control infection in his accredited field, if he is to be in very truth a "practitioner of the healing art."

Disintegrating Forces. — Broadly speaking, the tissues of the mouth are subject to two disintegrating forces. One has its inception in caries of the tooth and leads to the death of the pulp, with infection of the periapical tissues as its final stage. The other is an affection of the investing structures of the teeth, tending toward the complete disintegration of the periodontium. The latter class of diseases is of greater prevalence ; and while it has in the past baffled the efforts of many in the profession, it is nevertheless the easier of the two to control, when once its diagnosis, etiology, and treatment are fully understood.

Field of Periodontology. — No branch of dental science has more points of contact in dentistry than has periodontology.

Every operation which the dentist performs, with the exception of full denture prosthesis, has a definite influence upon the health of the periodontium. He may not place the simplest filling without a consideration of the surface contours. To fail in this regard may not induce a recurrence of caries, but it may derange occlusal function, leave a faulty contact, or produce gingival irritation. Prosthetic restorations have even a more obvious influence, as have also incorrect pulp canal operations. Improper or incomplete removal of deposits from the tooth surface are well recognized as causative agencies in periclasia. It therefore follows that dental operations can only be correctly performed by one who possesses a thorough working knowledge of periodontology.

Varying Theories. — No field of dental science has produced so many and so widely differing theories as has the study of periodontology. These theories, together with the misunderstanding regarding the principles involved, have produced a condition which may be mildly described as " confusion worse confounded." The reason for these puzzling differences in the point of view, is the extreme subtlety and complexity of the phenomena concerned in the pathology and etiology of periodontal disease.

Etiology. — That the factors in etiology combine to produce a certain pathological picture in one mouth, while an apparently similar grouping seems to create a dissimilar effect in another, is almost inexplicable to the casual student. With the exception of traumatic occlusion* the factors of periclasial etiology have been known and studied for many years. Various groupings of these factors have been suggested with the emphasis, first upon this one and then on that. Always the results of treatment based upon these theories have been inconsistent.

It has been the misfortune of many clinicians to discover some part of the truth and to be so carried away with its importance as to have their view of the basic principles of periodontology perceptibly distorted.

With the discovery that traumatic occlusion played an im-

* An abnormal occlusal stress which is capable of producing, or has produced, an injury to the periodontium.

INTRODUCTION 5

portant part in etiology, it became possible to explain a large percentage of earlier failures. With its discovery also the other factors began to assemble themselves in their true perspective in the picture.

The clinical results of Biggs demonstrated the part played by calculus in the etiology of periclasia, a discovery whose influence upon treatment is as potent today as it was sixty years ago. Since it was however but a part of the truth, it became necessary to look for other factors. Briefly, this led to the formulation of several theories, among which were the " gouty diathesis" and the "bacterial," with its hopes set upon the value of germicides and vaccines. Each of these had its advocates and its day. Later developments in the realm of instrumentation swung the tide again toward the mechanical element in etiology. This theory is based upon the hypothesis that mechanical irritants have a predominating influence on tissues whose functions are chiefly mechanical. Stated in another way this hypothesis is as follows: — Tissues whose functions are chiefly mechanical, are influenced most markedly by mechanical injurious agencies.

Function and Health. — It has been found that function is the most important factor in the maintenance of health. It follows that interference with function is most frequently the opening wedge for disease. In the mouth, either insufficient or excessive function has been found to be the predominating factor in the production of periodontoclasia. Since excessive function is by far more common than insufficient function, it will seem to some readers to receive an undue emphasis in these pages. When one adds to the significance of functional disturbance the factor of mechanical injury, the emphasis will be found to have been well placed. It thus appears that departures from the normal give the keynote to the etiology and the pathology of periodontal disease. The restoration of normal function then, is the heart of the problem of treatment. Practice based upon this concept has shown Nature to be a receptive ally who needs no coaxing when correctly interpreted. When disturbing factors are completely removed it will be found that Nature 's inherent regenerative impulses will at once assert themselves and in fact may even be effective in the face of minor difficulties. Clinical experience bears out the fundamental soundness of these statements.

Nomenclature. — The diseases which are here considered have been grouped under the general name of Periodontoclasia, a term signifying a breaking down of the tissues around the teeth. While this term is applicable to practically all types of periodontal disease, it nevertheless happens that cases do occur in which the process is metaplastic or hyperplastic in its nature. And even atrophic changes may be challenged if grouped under this generic term. These cases however are so far in the minority in practice, that the terminology herein employed may be accepted as representing the pathology of these conditions with a very fair degree of accuracy. The introduction of more suitable terms must wait upon further research.

It is furthermore to be noted that the term periodontoclasia in its strict sense is inclusive of periapical lesions. Since periapical lesions are most commonly produced through the agency of pulp disease and since the parietal lesions constitute so broad a chapter of this pathologic complex, it has seemed most practical to exclude from this book the consideration of the etiology, pathology and treatment of periapical lesions.

Diagnosis. — Diagnosis of periodontal disease however, requires consideration of both parietal and periapical lesions, since the parietal frequently encroaches upon the periapical. For this reason, and because of the profound bearing of oral health upon general health, the diagnosis of both classes of periodontal disease will be given full consideration.

The pathology and etiology of inflammations elsewhere in the body have been studied and their fundamental facts have been recorded and accepted. In presenting periodontoclasia as a group of diseases all but one of which are inflammatory in their nature, we find it unnecessary to reopen a topic now considered settled. The factors which produce periodontoclasia are precisely those which produce other inflammations, just as the changes which take place in the periodontium are similar to those occuring elsewhere in the body.

Recent Research. — Recent study of the histology of both the

INTRODUCTION 7

tooth and its investing structures justifies the assumption of an optimistic attitude toward the treatment of dental periclasia. Clinicians for many years have maintained the fundamental possibilities in treatment, notwithstanding the fact that eminent histopathologists have assured them that the results which they observed were scientifically impossible.

With the additional evidence of the latest researches in histology we can fearlessly announce the confirmation of the claims of Riggs, made half a century ago. Thus the responsibility of the dentist in this field of practice becomes at once an issue which may not be evaded.

The study of any branch of science is only accurate when based upon a complete assemblage and correct valuation of its various factors. So our hypothesis regarding these disease processes becomes acceptable only with a thorough and orderly arrangement of the pathologic and etiologic facts which are ready to our hand. To recognize these facts in their entirety is to make possible a complete understanding of the rationale of treatment. The uniformity of the clinical results founded upon such knowledge, furnishes a convincing proof of the soundness of the hypothesis.

Chapter II Nomenclature

The nomenclature in any field of science, to be acceptable, must be founded on a comprehensive knowledge of the phenomena relating to that subject. Scientific terms to be of value, must express a definite meaning, and when properly coined, are explanatory of the processes and phenomena to which they apply.

The newer study of periodontology which began with a more complete understanding of the phenomena of cause and effect observed in periodontal disease, brought out very definitely the need of a functioning terminology. All credit should be given to previous investigators for their efforts, on which in great part this work is founded. But the investigations which have led up to the publication of this volume, have compelled the adoption of terms more closely adapted to the description of the various conditions, than were those previously proposed. With the founding of the American Academy of Periodontology, there was established a Committee on Nomenclature. The newer terms employed in this book, are largely those which have been proposed by this Committee.

We are here concerned with the study of a group of disease processes, most of which have in common the feature of causing a breaking down of the supporting tissues of the teeth. A term which is to correctly designate this group of diseases as a whole, must be sufficiently broad to be applicable to the diseases which may affect any or all of these tissues. The nature and the etiology of these disease processes varies to such an extent, that it is unwise to adopt a term descriptive of a single phase of their pathology. The supporting tissues of the teeth may best be grouped under the term "periodontium,"* a word derived from

* Periodontium. — The investing tissues of the teeth, including Gingivae, Pericementum, and Alveolar Process.

NOMENCLATURE 9

the Greek roots, peri — around, odous — a tooth. The breaking down of these tissues will be most simply and broadly expressed by the term "periodontoclasia,"* the suffix being taken from the Greek klasia, a breaking or destruction. As a synonym for this we also use the term "dental periclasia" or simply " periclasia.' r,\ Mention has already been made of the possible desirability of a still broader term, but the term periodontoclasia will still be applicable to the vast majority of types of periodontal disease.

The term periodontoclasia naturally leads to the formation of derivative words such as: "periodontal," "periodontia, "J 1 ' periodontology, " "periodontist," etc., whose meanings are so clear as to require no elaboration.

Older Terms. — With no desire to criticize, it nevertheless seems wise to discuss briefly some of the more commonly used terms which in the past have been applied to this group of diseases. The term "pyorrhoea alveolaris" has been loosely applied to this entire group, and has even been used as a synonym for periodontoclasia. It means a flow of pus from the alveolar process. The entire unsuitability of this term may be recognized when it is understood that periodontal disease frequently occurs without pus formation. And when pus formation does take place, it seldom proceeds from the alveolar bone. The same reasoning may be applied to "alveolitis," "peridentitis," and numerous other designations. Therefore the term periodontoclasia is offered not as a synonym for pyorrhoea alveolaris, etc., but with the idea that it may supplant these terms in the literature of the subject. The term "Riggs' disease" because it is inclusive and makes no reference to pathology, is acceptable for use as a colloquial term.