conference on the biology of the human dental pulp (classification of pulpal pathosis)

CONFERENCE ON THE BIOLOGY OF THE HUMAN DENTAL PULP

Classification of pulpal pathosis

Samuel Seltzer, D.D.S.,’ Philadelphia, Pa.

TEMPLE USIVERSITY SCHOOL OF DENTISTRY

Clinical evidence which indicates the presence of severe pulpal pathosis dictates a treatment policy of pulp extirpation and endodontic therapy. In the absence of such evidence, therapeutic management by indirect pulp capping is the preferable regimen. In such cases, efforts should be made to maintain pulp vitality, even though chronic pulp intlammation may persist. The vitality of the pulp should be maintained as long as possible in the absence of evidence that chronic pulp inflammation is harm- ful to the well-being of the organism. The defensive capacity of the pulp is thereby retained.

I n the past, pulp diseases have been classified on a clinical basis by the use of histologic terms. Traditionally, clinical and histopathologic nomenclature has been intertwined, resulting in a mishmash of misleading terms and diagnoses.2*~ 72, w 125 For example, an “acute serous pulpitis” has been taken to mean that the patient has pain (hence the adjective acute), that the pulp is inflamed (pulpitis) and that the character of the inflammation is nonsuppurative (serous). However, the term has also implied that, on a clinical basis, the pulp is overly sensitive to cold and that it reacts more quickly to the electric pulp tester than the pulp of a control tooth.

Other clinical diagnoses, sucl~ as hyperemia, a pathologic entity in which blood vessels are dilated and filled with erythroeytes, have brought the concept of therapy into the classification. With such a diagnosis, thermally sensitive teeth react quickly to the electric pulp tester, but sWymptoms disappear when a sedative dressing is placed in the teeth ; presumably, the pathosis is reversed.

The more modern investigations of Mitchell and Tarplee, Matsumiya and associates,“0 Seltzer and his collcagues,85~ sB Ogilvie and Ingle,63 Pheulpin and co-workers,o* Holz and co11eagues,35 Fiorc-Donno,25 Baumc,” Tyldeslcy and Munlford,*36 and Hes.+ have demonstrated the futility of attempting to mix clinical and histopathologic classifications. Instead, the status of the pulp has been classified on the basis of clinical symptoms plus the results of certain test

*Professor and Chairman, Department of Endodontics.

269

270 Seltzer Oral Surg. August, 1972

proCedures.27v 32, S% 85 Such classifications lead only to a suggestion of treatment procedures. A calculated guess concerning the histologic status of the pulp can be made, but it is only a guess. To prove whether the guess was correct, either the tooth must be extracted or the pulp must be extirpated and processed for histologic examination. Histologic studies of extirpated pulps leave a great deal to the imagination because of the distortion, twisting, and ripping of pulp tissue which necessarily occur during removal of the pulp with a barbed broach.

In most classifications of pulp pathosis, it is implied that the pulp reacts in the same manner to all irritants. As will be shown, such is not the case. Cognizance must be taken of etiologic factors when any classification of pulp diseases is attempted.

A discussion of classification of pulpal pathosis must, therefore, be based on (1) etiology (history), (2) histopathology (laboratory findings), and (3) symptoms (clinical findings).

ETIOLOGY

Changes in the dental pulp, like changes in other connective tissues, may be inflammatory or degenerative. Aside from physiologic aging-the normal “wear and tear” of bodily tissues-such changes are induced by disease processes, such as caries and periodontitis. A significant number of changes are also initiated by various dental manipulative and restorative procedures (dentistogenic) . Before discussing classifications of pulp diseases, it is desirable to examine, briefly, the causes and results of alterations in the dental pulp.

Changes in pulp may be due to aging, dental tissue manipulations (dentisto- genie), disease processes (caries, periodontal disease), and trauma.

Changes due to aging

Aging of human tissues is genetically controlled. It has often been said, jocularly, that living to a ripe old age involves selection of the proper parents. Many theories of the causes of aging have been advanced. According to Shocks7 and to Curtis,Zo among these are the following: (1) The wear-and-tear theory, which simply postulates that the organism wears out with use. Each cell is endowed with specific amounts of vital substances, such as enzymes. When these substances are used up, they are not replaced. Eventually, death of the cells and the organism ensues. (2) Mathematical theories have been postulated in which an empirical mortality curve fits into a formulated equation. (3) The cellular interaction theory is based on the dependence of every part of the body on every other part. For example, all endocrine glands are interdependent for proper functioning, Individual cells in any organ are dependent on, and influenced by, their neighboring cells. (4) The collagen theory postulates that collagen fibers form continuously at a slow rate. The collagen is eliminated slowly or not at all. As more and more collagen is elaborated, the cells of the tissues are gradually choked off. Tissue function is hampered, and eventually cell death ensues. (5) In the waste product theory, the metabolic waste products are not readily excreted from the cells or intercellular fluids. Slowly, function is interfered with and eventually the organism is poisoned. (6) In the endocrine theory, endocrine

Classification of pulpal pathosis 271

functions slowly decrease as the individual gets older. Cell metabolism is gradually affected adversely. (‘7) The calcium theory suggests that aging is caused by a defect in calcium metabolism. According to Selye and Prioreschi,86 large doses of vitamin D or parathyroid hormone in rats cause mineralization of many soft tissues. Such changes resemble those seen in the tissues of the aged. Injury of a tissue results in its calcification (calciphylaxis) , rendering the tissue nonfunctional. (8) In the somatic mutation theory, it is postulated that the somatic cells of the body develop spontaneous mutations. As more and more cells mutate, eventually an appreciable number of cells are mutants. Since all cell mutations are deleterious, eventually the organs become inefficient and senescent. (9) The autoimmune theory suggests that autoimmune reactions develop with aging. Such reactions develop when some of the cells of the body synthesize proteins which differ immunologically from the other bodily proteins. The results are immune and anaphylactic reactions within the body. (10) Circulatory deficiencies increase with age. The consequences are deficient oxidation of cells, eventuating in cell death and replacement by collagen. With increase in collagen deposition, more capillaries are choked off, resulting in more anoxia. Mutations may also be induced in the endothelial cells of the capillary, leading to breakdown of part of the capillary and further deficiency in circulation.

Many of these theories can be applied to concepts concerning retrogressive and age changes in the dental pulp. Among the age changes which have been reported to occur in the pulp are the following : (1) reduction in size and volume of the pulp due to continued dentin deposition, (2) decrease in cellular components, (3) increase in number and thickness of collagen fibers, (4) decrease in number and quality of blood vessels and nerves, and (5) increase in pulp stones and dystrophic mineralizations. Each of these changes will be discussed briefly.

Reduction in size and volume of pulp. With aging, the pulp chambers of all teeth gradually become smaller because of continuous dentin deposition. As a result of this deposition, there is a tendency toward eventual pulp obliteration.

The pattern for the dentin deposition varies somewhat among the different groups of teeth. In molars, dentin is deposited mainly on the floor of the pulp chamber, with lesser deposition on the occlusal and lateral walls.s5y =, go In upper anterior teeth, the greatest dentin deposition occurs on the lingual wall of the pulp chamber as a result of masticating forces,B7-6D with subsequent deposition in the incisal tip and walls of the pulp chamber. By the age of 71 years or more, the pulp canal becomes almost obliterated. The additionally formed secondary dentin is highly irregular, with fewer dentinal tubules.

Decrease in cellular components. The odontoblasts appear to undergo degenerative changes with advancing age. Electronmicroscopic examinations reveal more vacuoles in older odontoblasts. Gradually, the odontoblasts atrophy and disappear over some or all areas of the dental pulp.997 X17 The primary dentinal tubules are also affected. Increases in peritubular dentinI 3o or increased deposit of apatite crysta1s1o2 may occur, The dentinal tubules are ultimately occluded, a condition called “sclerosis” of dentin.

Aging effects a reduction in the number of cells of the pulp,99 possibly .as a consequence of reduced circulation. The regression of older rat pulpal fibroblasts


is characterized by their diminution in size and in the number of cytoplasmic structures associated with fibrogenesis. Most of the intracellular organelles of the older fibroblasts, such as the rough-surfaced endoplasmic reticulum and the mitochondria, are smaller. The Golgi complex is rarely found.lz4 There is also a significant decrease in the number of regenerable cells.71 With increasing maturity, the pulpal fibroblasts exhibit a decreased oxygen uptake.26 However, aging does not result in uniform alteration of the enzymes of the catabolic cycles, either aerobic or anaerobic, of the fibroblasts of the bovine dental pul~.~”

Increase in number and thickness of collagen fibers. In histologic examination of older pulps with the light microscope, there is a relative increase in the number of argyrophilic reticular fibers and in the number and thickness of collagen fibers as compared to young pulps, IX7 This increase is apparent because of a reduction in the volume of the pulp by the continuous deposition of secondary dentin. The increase in the number of collagen fibrils is also actual, as has been shown by electronmicroscopic examinations of the pulps of premolars and molars of normal persons aged 13 and 14 years and of those aged 56 to 62 years.16 Such examinations revealed that in the ground substance of the younger pulps there was a scarce distribution of collagen fibrils about 750 A in diameter. Collagen bundles were embedded in a denser ground substance. In the pulps of premolars and molars of normal persons aged 56 to 62 years, there was a decided increase in the number of collagen fibrils. Near the collagen fibrils, bundles of unstriated small fibrils, about 150 A in diameter, were noted.

Decrease in number and quaZity of bZood vessels and nerves. Aging has an adverse effect on the number and quality of blood vessels supplying the dental p~lp.~ Blood vessels of aged pulps undergo arteriosclerotic changes, resulting in a diminished blood supply to the cells of the coronal portions of the pulp~.~~s ”

Comparisons of the pulpal blood vessels of noncarious teeth from younger persons (less than 20 years of age) with those of older persons (40 to 70 years of age) were made by Bernick. lo Typically, the pulpal arterioles from young teeth consisted of endothelial layers abutting directly on a thin internal elastic membrane. The media consisted of one or two layers of muscle cells, and the adventitia contained collagenous and elastic fibers. PAS-stained sections showed a deep red stain of the internal elastic membrane, whereas the media and adventitia stained pink.

In contrast, the arterioles of the older pulps exhibited hyperplasia of the intima with a resultant narrowing of the vessel lumen. The internal elastic membrane was masked by the deposition of a PAS-positive material. In some older pulps, there was also a hyperplasia of the elastic fibers together with deposition of PAS-positive material. Dystrophic changes in the media and adventitia were also noted. In some instances, deposition of fine mineral deposits was observed to have progressed to complete obliteration of both adventitia and media.

The number of blood vessels supplying the coronal pulp tissue was extensive in younger teeth. Such blood vessel numbers decreased in the older teeth, regardless of whether or not the pulps exhibited mineralizations.

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Classificatio~n of pulpal pathosis 273

Few studies have been made of the age changes of the nerves of human teeth. Armenio and associates2 and Bernickg have indicated that retrogressive changes do occur, probably as a result of progressive mineralization of the radicular nerve sheath and nerve itself. As a consequence, there is a reduction in the nerve branches in the coronal portion of the aged pu1p.O Vacek and PlaEkova106 have noted that, under caries, the pulp nerve fibers become coarsened and irregular and argyrophilic varicosities are formed.

Imrease in pulp stones und dystrophic mineralization. Ground substance alterations in the dental pulp apparently occur on aging. Such alterations result in a decreased reactivity and predominance of highly aggregated, less soluble macromo1ecules.115 Such changes may contribute to cellular degenerations and increased dystrophic mineralizations.

Senescence of the dental pulp is increased by caries and periodontal disease; dystrophic mineralizations apparently increase markedly as a result of aging and disease processes.s~ 7Q, 12Q Atrophic changes of the pulps of fifty-four intact teeth from a sample of 1,000 persons, ranging in age from 61 to 100 years, were noted by Zakson.l14 Concurrently, dystrophic mineralizations were markedly increased. Such findings of increased mineralizations as a result of aging were confirmatory of earlier ones by Thomas,lo3 HilJ3* Euler,Q4 Shroff *O and more recently by Saunders ,78 Such mineralizations suggest that circulatory disturbances may be the initiating factor.

Dentistogenic changes

Operative manipulations, such as cavity and crown preparations, the insertion of restorations, crown and inlay impressions, and cementations cause changes in dentin and pulp. 12g The severity of the reactions varies with the depth of preparation 93, 953 104 use of coolants,22,Q7,9*, 111,112

deniin,O” d egree of pressure exerted on the

rotational speed of the bur,83p I11 and other factors.4QT 5o The reactions are further influenced by the application of various medicaments to the dentin or pulp (as in pulp-capping and pulpotomy procedures) and by the chemical and physical properties of restorative materials. 40, Q6g IQ7 Inasmuch as biologic varia- tions occur among different persons, a direct cause-and-effect relationship cannot always be quantitated. Following operative procedures, such changes as the production of dead tracts and/or an increase in peritubular dentin, occur in the primary dentin. Reparative dentin is subsequently elaborated under the involved dentinal tubules, unless the pulp tissue is so severely damaged that it is rendered necrotic. A calciotraumatic response, visible in histologic sections between primary and reparative dentin, occurs as a result of the injury to the odontoblasts. The injured odontoblasts of rats’ teeth have been examined under the electron microscope. Such electronmicroscopic observations have indicated that the odontoblasts undergo a series of alterations after being cut at 150,000 r.p.m. under a water coo1ant.83 The membranes of the endoplasmic reticulum become fragmented, and the mitochondria degenerate.

Such changes occur after a half-hour and appear to be the result of protein denaturation induced by desiccation, 118p lQ3: 13x heat, and vibration, although the

274 Seltzer Oral Slug. August, 1972

role of heat appears to be controversial. 22, llGl 133 Two days later, Zach and asso- ciates113 found that the odontoblasts were pyknotic and some were displaced into the dentinal tubules.

In human teeth, the immediate response of the odontoblasts is dependent on the severity of the injury. Such changes as a shift of the cytoplasm from the cell body into the odontoblastic process and an increase in cytoplasmic vacuoles and lipid granules occur.95 In severe injuries, the cells are damaged irreversibly.

Should the odontoblast eventually degenerate, it would appear that other cells in the pulp, probably undifferentiated mesenchymal or reserve cells, assume the function of elaborating reparative dentin.83, Q1, II39 126s 131, 134

An acute inflammatory response in the vicinity of the odontoblastic layer follows severe injury of the odontoblasts. According to Langeland, but disputed by Brtinnstriim,118 this response is initiated by displacement of the affected odontoblasts and erythrocytes into the involved dentinal tubules. Chemical mediators, liberated from the injured cells, are responsible for the initiation of the inflammation. The capillaries in the odontoblastic layer, ordinarily obscure or not seen in histologic sections, become visible as a result of dilatation. The lumina of these vessels became packed with erythrocytes. The ensuing edema causes compression of the odontoblasts and separation of these cells from the dentin, resulting in disruption of t,he pulpodentinal membrane.131 In more severe injuries, especially those resulting from chemicals, margination of polymorphonuclear leukocytes along the capillary walls can be observed. Presently, these leukocytes migrate through the vessel walls and infiltrate the odontoblastic layer and the subjacent cell-free zone. Approximately one week later, the predominant cell population consists of lymphocytes and macrophages. Plasma cells may be found occasionally, but not usually. Under ideal circumstances, the granulation tissue is gradually resorbed and repair is completed. The only remaining evidence of the injury is the presence of reparative dentin. In effect, the reparative dentin represents a mineralized scar. Despite the elaboration of reparative dentin, the chronic inflammation may persist for months or years. In many instances, scattered chronic inflammatory cells have been found in the pulp many years after the operative injury has occurred.84, 85 In the absence of granulation tissue, the presence of such inflammatory remnants has been desig- na.ted as a “‘transitional” stage.

Following severe injury, the pulp does not recover. Such severe injuries are usually chemically induced, especially when the chemicals are placed near or directly on the pulp following mechanical pulp exposure. Should an abscess develop, the pulp does not usually heal. W* Instead, chronic inflammation persists, eventually ending in total pulp necrosis. The terminal result in the production of a periapical lesion.

Fig. 1 depicts the dynamic pulp changes which may follow operative manipulations.

Changes due to disease processes

Caries. Dental caries is a slow, intermittent, insidious, microbial disease which gradually causes demineralization of the enamel and dentin as well as proteolytic

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Classificatiov~ of pulpal patkosis 275

Mild or absence of reaction

I Recovery < ywith a restoration-Chronic partial

pulpitis

I +

Chronic total

pulpitis

Chronic apical periodontitis

Fig. 1. Pulp reactions to mechanical, thermal, and chemical irritants.

digestion of the collagen matrix of the dentin. As a result, various chemical changes of the dentin take place. Magnesium and carbonate content are reduced,3a whereas fluorine content is increased. 37 There are various quantitative changes in the amino acid composition of the dentin ; some are increased, whereas others are reduced. In addition, there is a large increase in the content of carbohydrate material, the formation of a brown pigment, an increased resistance to breakdown by collagenase, and a loss or diminution of fluorescence in ultraviolet light.23 The primary dentinal response is an increase in peritubular dentin, also called “sclerosis” of the dentin. 3o Such sclerotic dentin acts as a barrier to the further penetration of bacterial metabolites, isotopes or dyes.5 With large-scale carious breakdown of dentin, the dentinal tubules may either become completely occluded by mineral deposits, remain empty, or become invaded by bac- teria 33, 99, 130

Pulp response to dental caries begins almost with the inception of the carious lesion in the enamel. BrlnnstrGm and Lind14 and Langeland found scattered chronic inflammatory cells in the pulp under the initial carious lesion (transitional stage). The inflammatory response is directly initiated either by the injurious metabolites of the microorganisms involved in the carious process or by antigens of these microorganisms which activate destructive immunologic processes.

When dentin becomes cariously involved, cells of the pulp manufacture reparative dentin which is deposited under the involved dentinal tubules. The quantity of reparative dentin elaborated appears to be equal to the amount of dentin lost due to caries.54 The original odontoblasts degenerate. Reparative dentin is generally lined with an odontoblastic layer only one or two cells in


depth. Therefore, the cells responsible for reparative dentin elaboration appear to be derived from the reserve cells in the pulp. Despite its function of occluding the cariously involved dentinal tubules, reparative dentin is nonetheless perme- able to medicaments and isotopes.50

In deep-seated lesions, when the carious process has involved the reparative dentin, chronic inflammation of t,he pulp is evident.73 When the pulp is finally invaded by microorganisms, an abscess forms opposite the exposed dentinal tubules. According to Massler,j4 the responsible microorganisms generally are pyogenic streptococci, pyogenic staphylococci, and anaerobic gas-forming bacilli. The remainder of the coronal portion of the pulp has by now become converted to granulomatous tissue. The radicular portion of the pulp may remain intact for a long period of time, and yet the blood vessels may appear dilated. Zerlotti’s*15 examinations of sixty-eight pulps from cariously involved, painful teeth revealed that even when the entire coronal pulp tissue was inflamed, the radicular tissues were unaffected. However, even though vital radicular tissue may persist for a long time, the apical periodontal ligament may exhibit chronic inflammation. Thus, under the irritation of dental caries, the classic dynamic change from acute to chronic inflammation, as results from operative procedures, is not evident. Contrasted to the rapid, acute inflammation induced by operative procedures, the slow, intermittent carious process elicits a slowly developing, chronic inflammatory response in the pulp, which never has the identical features of the acute inflammation seen following operative manipulations. Instead, macrophages and lymphocytes predominate originally. In the late stages, both acute and chronic inflammation is visible in cariously involved pulps. Poly- morphonuclear leukocytes are attracted to the regions beneath the cariously involved dentinal tubules. These leukocytes increase in number as the carious process approaches the pulp tissue (Fig. 2).

Histochemical studies115 have indicated that during the acute phases of caries-induced pulpitis, tissue components break down. Argyrophilic and collagen fibers become fragmented and disrupted. Protein-carbohydrate complexes become markedly degraded. Concurrently, tissue synthesis occurs in the chronically inflamed areas. Reaggregation and rearrangement of argyrophilic fibrils and metachromatic ground substance predominate. The fibroblasts are probably responsible for the synthesis of the matrix, since they demonstrate a high content of RNA, as well as granule-containing glycoproteins, acid mucopolysaccha- rides, sialic acid, and proteins bearing free e-amino groups of lysine-hydroxyly- sine.

Breakdown of the pulp results in the formation of an abscess directly beneath the region of the invading microorganisms, perhaps mediated by the release of lysosomal hydrolases from the polymorphonuclear leukocytes.lol In the remainder of the coronal pulp tissue, the chronic inflammatory infiltrate with its rich content of macrophages, lymphocytes, and plasma cells may indicate the presence of an antibody-mediated hypersensitivity reaction. Excessive antigens available in high concentrations from the microorganisms involved in the carious process may cause synthesis of immunoglobulins. The immune antigen- antibody precipitates thus formed may, in the presence of complement, become

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Untreated caries

1 Pulp

1 Intact pulp with scattered chronic inflammatory cells

[transitional stage)

Exposure 1 Acute partial pulpitis t-- Chronic partial pulpitis

Drainage

> --me-----mm----

Blockage ! Chronic total pulpitis I

Acute apical <- 1 I- Pulp-periapical

periodontitis Drainage, Chronic apical periodontitis 1 1 tissue complex

.--------------4

Fig. 8. Pulp reactions to dental caries.

chemotactic for polymorphonuclear leukocytes. lo8p lo9 Phagocytosis of these immune precipitatePo5 may then result in cell degradation with release of lysosomes into the pulp tissue. The liberation of proteasesGo would then result in the formation of a pulp abscess. The rich granulation tissue barrier below the abscess prevents further spread of inflammation into the radicular pulp tissue. Gradually, with repeated episodes of polymorphonuclear leukocyte-mediated reactions of the Arthus type, the immune response reaches into the radicular tissue and eventually into the periapical tissues, where a typical granulomatous lesion develops.

Periodontal disease. Although some controversy exists,57 periodontitis appears to have a degenerative effect on the dental pul~.~~, T61 84$ 85 A number of investigators have demonstrated that the periodontal ligament and the pulp are supplied by the same vessels.17* l*l 21, 42 Thus, it appears reasonable that inflammatory and degenerative lesions of the periodontal ligament affect the blood supply of the pulp. Histochemical studies have demonstrated the presence of increased amounts of enzymes, such as alkaline and acid phosphatases, 5-nucleotidase, glucose-6-phosphatase, and ATPase, in the pulps of periodontally involved teeth as compared to those of normal teeth. Such increased concentrations of enzymes were found especially in the endothelium of the blood vessels.11s Circulatory disturbances result in atrophy of pulp cells, fibrosis of pulp tissue, dystrophic mineralizations within the blood vessels, nerves, and collagen fibers of the dental pulp, as well as inflammatory changes. Should lateral or accessory canals become exposed as a sequel to periodontal inflammation and bone resorption, there is interference with the blood supply to portions of the pulp. Microorganisms may then gain access to the pulp tissue ; there they localize and multiply. The result is the development of a chronic pulpitis, ending in pulp necrosis.

Should the periodontal lesion cause epithelial proliferation and bone resorption near the root apex, an apical pulpitis may be induced. Resorption of bone


and apical periodontal inflammation may also simulate periapical lesions caused by pulp disease. There is also some evidence that root planing may cause permeability changes of the dentinal tubules, resulting in easier passage of irritants between the oral environment and the pulp.“l

Trauma

Accidental trauma. Traumatic insults to the crowns of teeth, with or without root fractures, may cause pulp degenerations due to rupture of blood vessels supplying the pulp. Hard-tissue formation is stimulated; dentin or cementum- like depositions occur within the pulp tissue, possibly with eventual obliteration of the pulp and necrosis of the remaining pulp fragments.3l l1 Such traumatic incidents frequently end with pulp necrosis and root canal infection.4* 13j I91 29y 53p 58

In root-fractured teeth, healing may occur, with connective tissue or mineralized tissue interposed between the segments, or granulation tissue may form and persist between the fragments1

Trauma from occlusion. Trauma from occlusion has frequently been indicted as a cause of pulp inflammation or degeneration, but such findings have not been documented experimentally. 45 However, it is conceivable that long-acting occlusal trauma could eventually lead to pulp damage resulting from compression of the pulp vasculature. Degenerated pulp tissue might then become infected through anachoresis or through the pumping of microorganisms into the pulpal circulation from the gingival crevice. lzo However, those possibilities are con- jectural.

HISTOPATHOLOGY

As has been shown, pulp pathosis may be of degenerative or inflammatory etiology. Histopathologically, therefore, abnormal pulp conditions may be elassi- fied under the headings pulposis (atrophy or degeneration of pulp), pulpitis, (inflammation of pulp), or necrosis (death of pulp).

Pulposis results from normal aging, caries, trauma, periodontal disease, op-

erative procedures and, systemic factors. Histologically, pulposis is characterized by the reduction in the quantity and size of pulp cells (including odontoblasts, fibroblasts, undifferentiated mesenchymal cells), increase in pulp stones, dystrophic mineralization of fibers, vascular and neural elements, increased Sol- lagen deposition, increased peritubular and reparative dentin formation in the coronal and radicular parts of the tooth, and decreased blood and nerve supply.

Pulpitis may be acute or chronic, partial or total.

Acute pulpitis

In acute pulpitis, the inflammatory changes are usually induced by operative procedures on the dentin but may result from mechanical pulp exposure or pulpotomy procedures. The acute pulp inflammation is characterized by inflammatory changes in the odontoblastic layer, directly under the involved dentinal tubules. The inflammation generally does not extend into the deep pulp tissue. Edema causes disruption of the odontoblastic layer and a reduction in the number of odontoblasts. Dilated capillaries, filled with erythrocytes,

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Cla.ssification of pulpal pathosis 279

are evident. Polymorphonuclear leukocytes (neutrophils and eosinophils) are seen both in the capillaries and extravascularly.

Acute inflammations, mixed with chronic ones, are also seen in the pulps of carious teeth directly under heavily infected reparative dentin or under exposures.

Chronic pulpitis

Chronic pulpitis, resulting from mild to moderate irritating operative manipulations, is usually seen in the subodontoblastic layer under the involved dentinal tubules. The cell-rich and cell-free zones are invaded by macrophages, lymphocytes, and, occasionally, plasma cells. These cells are also found, after more severe chemical injuries, in the deeper pulp tissues. Abundant dilated capillaries, new fibroblasts, and reticular and collagen fibers are also present. In the older lesions, abundant quantities of reparative dentin are elaborated, presumably by undifferentiated reserve cells. The odontoblastic layer lining this reparative dentin usually consists of a single layer of flattened, fibroblastic appearing cells. The radicular pulp tissue usually is intact but contains widely dilated blood vessels.

Under dental caries, chronically inflamed pulps are usually densely infiltrated with lymphocytes and plasma cells. Under deep carious dentinal lesions, pulp abscesses develop under the heavily infected or necrotic dentinal tubules. Poly- morphonuclear leukocytes are abundantly present around the liquefaction necrosis. Granulation tissue may involve the remainder of the coronal pulp tissue, but the radicular tissue may remain resistant. However, periapical changes, such as dilated blood vessels, edema, alveolar bone resorption, and scattered chronic inflammatory cells, may be noted.

Huge quantities of amorphous reparative dentin, lined with fibroblast-like cells, are found under the involved dentinal tubules.

Necrosis

In severe pulpitis of operative origin and under deep-seated caries, portions of the coronal pulp undergo liquefaction necrosis (abscess). Such a reaction usually leads eventually to total pulp necrosis. Histologically, partial pulp necrosis exhibits a liquefied zone, surrounded by live, dead, and dying polymorphonuclear leukocytes. Portions of, or the remainder of, the coronal pulp tissue are converted to granulation tissue rich in macrophages, lymphocytes, and plasma cells. It is tempting to consider the presence of lymphocytes and plasma cells as a sign of localized antigen-antibody reaction. In time, the radicular pulp tissue succumbs, and granulation tissue is found in the apical portion of the root canal and also in the periodontal ligament.

In pulposis, a coagulation type of necrosis may be found. The pulp cells are shrunken, and the nuclei are pyknotic or karyorrhectic. Collagen fibers persist, but they may be heavily mineralized. Nerves and blood vessels are also sites for dystrophic mineralizations. Pulp stones are abundant, and the dentinal walls, both coronally and radicularly, are covered with large amounts of reparative, amorphous dentin, tending toward obliteration of pulp and space.


Transitional stage

The pulp of primary dentin under initial carious attack, and occasionally of periodontally involved teeth, exhibits scattered chronic inflammatory cells, macrophages, and lymphocytes in the region of the tubules beneath the carious enamel and dentin. The number of such cells gradually increases as the caries progresses, but chronic inflammation does not develop until the reparative dentin becomes involved.

A transitional stage is also to be found in the pulp under the heavy deposits of reparative dentin elaborated following operative procedures and restorations. Such findings are indicative of pulp recovery from the irritation, but scattered inflammatory cells may persist in the pulp for years, following the insertion of the restoration. Such pulps also exhibit signs of pulposis, presaging poor recovery from subsequently applied irritants.

In summation, the following represents the entire spectrum of histopathologic diagnosis of pulp pathosis :

1. Atrophic pulp 2. Transitional stage 3. Acute partial pulpitis 4. Chronic partial pulpitis

A. with liquefaction necrosis 5. Chronic total pulpitis 6. Total pulp necrosis

SYMPTOMATOLOGY

There is no clinical sign or symptom which designates the histopathologic status of the pulp with certainty. The use of electric, thermal, percussion, and palpation tests helps to establish an empiric diagnosis, but none of the tests are completely reliable. Other clinical findings, such as referred pain, mobility, and x-ray findings, are reliable for some forms of pulp pathosis but not for others.

Classification based on pain

Pain is the most common symptom of a diseased pulp. In the absence of pain, most pulp pathoses remain undetected in vivo. Pain is usually indicative of tissue damage and, to some extent, usually connotes the extent of the damage. However, the psychologic component of pain frequently gives a misleading picture of the severity of the underlying disease process. Fear of dentists and dental procedures frequently causes an exaggerated perception of pain, resulting in an incompatibility of symptoms and pulpal pathosis. Under those circumstances, the severity of pain cannot be correlated with the severity of tissue change. 31, 61, "17, 110

Characteristics of pulpal pain. Various designations, such as sharp, dull, intermittent, continuous, throbbing, diffuse, etc., have been used to describe pulpal pain. Our studies, as well as those of Tyldesley and Mumford, have failed to uncover any correlation between specific pain characteristics and histopathologic status of the pulp. On the other hand, Massler55 has claimed that a differentia-

Clussification of pulpal pathosis 281

tion can be made between dentinal pain, characterized as being of a sharp, lancinating character, and pulpal pain, which has a dull, throbbing quality. Probably, the distinction arises from the fact that in dentinal pain the primary stimulation is of the nerve endings in and around the odontoblastic layer, composed of slowly conducting “c” fibers. On the other hand, in the more severe types of pulp pathosis, the deeper pulp nerves are more likely to be stimulated. The medullated fibers of the deeper pulp tissues are “a” fibers, which are faster.

Intensity (severity) and duration of pain. Severity and duration of pain appear to be partially related to the status of the pulp. Mild to moderate pain is usually associated with less inflamed pulps. Severe pain and pain of long duration appear to be reliable indicators of severe pulpitis and/or pulp necrosis, but occasionally such symptoms are misleading. 5g Severe pain usually indicates the presence of liquefaction necrosis. In the cariously involved teeth, pulp abscesses are usually found under pulp exposures. In restored teeth, pulp abscesses may develop over a long period of time. However, severely inflamed pulps may be painless when drainage is not impeded.

Spontaneity of pain. The occurrence of spontaneous pain appears to be an indication of severe pathosis of the deep pulpal tissues.121 Pain initiated by stimuli, such as cold, heat, and sweets, which disappears within seconds, probably indicates that nerve endings in the odontoblastic layer have been stimulated. Persistence of such pain probabily indicates a more extensive inflammatory involvement.

Thermally induced pain. Pain induced by thermal stimuli, such as heat and cold, which persists after the removal of the stimulus is indicative of pulpitis or pulp necrosis.52 There does not appear to be a correlation between the type (acute or chronic) or severity (with or without liquefaction necrosis) of the pulp pathosis and the type of thermal stimulus. 74 Inflamed or necrotic pulp can react to either, both, or neither of the two stimuli.

Sensitivity, of a short duration, to thermal stimuli is apparently increased in pulposis induced by periodontal disease.85 When pain persists after removal of the stimulus from periodontally involved teeth, pulpitis should be suspected.

Electrically induced pain. Although significance has been claimed by some investigators77 pain elicited by the electric pulp tester is a poor indicator of the status of the pulp. No correlation between the pain perception threshold and the condition of the pulp has been discovered by Mumford,61l 621 132 Reyn- olds,74 Lundy and Stanley,52 and Johnson and co11eagues.3Q, *O However, patho- logically involved pulps appear to react with pain more or less quickly than corresponding control teeth.84> 85 Even necrotic pulps occasionally evince painful responses to the electric pulp tester.

History of prior pain, Recording of a previous history of pain correlates well with the presence of destructive pulpal pathosis. More than 90 per cent of patients in pain, when interrogated, reported that they had experienced pain in the same tooth at some time prior to their present pain experience. In at least 80 per cent of those patients, moderate to severe pulpitis and/or necrosis of the pulp was found.84l 85


SUMMARY

In summation, pain, although not a completely reliable indicator of the status of the pulp, can be used as a guide, together with other signs and symptoms. Clinically, the pain may be classified as mild, moderate, or severe odontalgia. The implications of such categorization are as follows: Mild to moderate odontalgia is usually associated with transitional stages, chronic partial pulpitis, or atrophic pulps. Pain which arises spontaneously or which persists following thermal stimulation, together with a history of previous pain, usually indicates the presence of severe pulp damage, probably irreversible by therapeutic mea- sures. Severe pain in cariously involved teeth usually indicates pulp expo- suress or severe pulp pathosis, probably with liquefaction necrosis.44j 84s 85 Under restorations, pain usually indicates the presence of an irreversible pulpitis or pulp necrosis.

Classification for therapeutic purposes

A diagnosis of the extent of pulpal involvement in pulposis or pulpitis is difficult; it is easier to determine from clinical findings that a pulp is necrotic. Despite the difficulty in correlating clinical and histologic findings, the clinician must make a diagnosis of the status of the pulp, inasmuch as correct diagnosis dictates proper treatment. The diagnosis is a prediction, based on clinical judgment, of the type of pulp treatment indicated and its probable outcome. Such a prediction has led to the following designation of pulp diseases: reversible or irreversible, treatable or nontreatable, pulps indicated for pulp capping or

conservative pharmacotherapy, or pulps indicated for extirpation or root canal therapy. Gs 27* 7o, 135 Such designations are empiric and cannot be proved by presently available investigative modalities. 31 The evaluation of symptoms can only permit an educated guess as to whether or not the pulp can be treated and saved. Correlations between clinical symptoms and histopathology are difficult and fraught with error. Although severe symptoms of pain, swelling, etc. are usually indicative of severe pulp damage, this correlation does not always hold true.

The basic premise of all clinical classifications is that pulps exhibiting no symptoms or mild to moderate symptoms (predominantly pain) are judged to be amenable to therapy with a reasonable chance for recovery. When severe symptoms are present, the pulp is usually judged to be beyond repair.

Our findings have led us to the conclusion that the most significant factor in determining whether or not a pulp can be treated by drugs is the presence of an abscess. Such a determination may usually be made when there has been a history of previous pain, there is no reaction to pulp tests, the results of electric tests differ markedly from those of control teeth, pain is spontaneous, severe, and long lasting, and thermal irritants or tests evoke severe pain which persists after removal of the stimulus. Additional clinical findings, such as tooth elongation, mobility, sensitivity to percussion and palpation, and the presence of swelling and/or a sinus tract are further evidences of severe pulp pathoses which are nontreatable. Thus, the course of treatment is based on clinical judgment, but there is no sure way to determine afterward whether

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that judgment was correct. Even clinically successful pulp therapy, which apparently has vindicated the judgment of the therapist, does not actually confirm that judgment. Should symptoms be relieved and should the pulp remain rela- tively free of symptoms and maintain its vitality, such therapy might be con- sidered to have been successful in resolving pre-existing pulp inflammation. However, there is no sure way of knowing what the condition of the pulp was at the time of treatment. Conversely, should pain or swelling develop subsequent to treatment, the treatment might have been unsuccessful or the diagnosis might have been incorrect; the pulpitis was so severe that it could not be reversed. Actually, there is no way of determining which alternative was the correct one. The pulp may not have been inflamed initially, the inflammation might persist without symptoms, or the pulp might have become necrotic without symptoms. Inflammation may have been induced by the manipulative procedures or medicaments applied, or the pulp may have been subsequently irritated by the development of new or recurrent caries, leaky restorations, or trauma. Thus, unsuccessful pulp therapy which terminates in endodontic treatment or extraction does not necessarily mean that the clinical judgment was incorrect.

Clinical judgment has, therefore, dictated pulp therapy. With respect to the treatment of deep-seated carious lesions, two schools of thought have emerged. One school believes that the cariously involved tooth always has a pulp inflammation. In such cases, caries should be excavated completely, even if pulp exposure results.4g’ lop, lz8 The other school believes that, rather than risk pulp exposure by complete excavation of caries, “indirect pulp capping” is desirable. Such a belief is baaed on findings that the deep layers of carious dentin are sterile and the pulp is not infected or inflamed until almost or actually exposed.55s 73, *I, *8 There is sufficient evidence to support the contentions of both groups.

In my view, the clinical evidence already enumerated, which indicates the presence of severe pulpal pathosis, dictates a treatment policy of pulp extirpation and endodontic therapy. In the absence of such evidence, therapeutic management by indirect pulp capping is the preferable regimen. In such cases, efforts should be made to maintain pulp vitality, even though chronic pulp inflammation may persist. The vitality of the pulp should be maintained as long as possible in the absence of evidence that chronic pulp inflammation is harm- ful to the well-being of the organism. The defensive capacity of the pulp is thereby retained.

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_- -

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I n*

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i -,

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Woods, R. M., and Dilts, W. E.: Temperature Changes Associated With Various Dental Cutting Procedures, J. Can. Dent. Assoc. 35: 311, 1969. Zach, L., Topal, R., and Cohen, G.: Pulpal Repair Following Operative Procedures, ORAL SURG. 28: 587. 1969. Zakson, M. L. : Age’ Specific Changes of Teeth in Aged and Senile Persons, Stomatologiia (Mosk.) 48: 4:29, 1969. Zerlotti, E.: Histochemical Changes in the Connective Tissue of the Dental Pulp During Inflammation. ORAL SURG. 27: 664. 1969. Bhaskar, 5. k., and Lilly, C. E.: Intrapulpal Temperature During Cavity Preparation, J. Dent. Res. 44: 644, 1965. Bhussry, B. R.: Modification of the Dental Pulp Organ During Development and Aging. In Finn, S. B. (editor) : Biology of the Dental Pulp Organ, Birmingham, 1968, University of Alabama Press, pp. 146-165. BrLnnstrGm, M.: The Effect of Dentin Desiccation and Aspirated Odontoblasts on the Pulp, J. Prosthet. Dent. 20: 165, 1968. Brzezinska, B. : Histochemical Investigations of Certain Enzymes in the Dental Pulp in the Course of Periodontal Disease, Czas. Stomatol. 22: 85, 1969. (From Oral Res. Abstr. 5: 207 (No. 1265), 1970.) Grossman, L. I.: Origin of Microorganisms in Traumatized, Pulpless, Sound Teeth, J. Dent. Res. 46: 551. 1967. Guthrie, T. J., McDonald, R. E., and Mitchell, D. F.: Dental Pulp Hemogram, J. Dent. Res. 44: 678, 1965. Hall, D. C. : Pulpal Calcifications-A Pathological Process? In Symons, N. B. B. (editor) : Dentine and Pulp: Their Structure and Reactions. Baltimore. 1968. Williams & Wilkins Company, pp. 266-274.

I I I

Hamilton, A. I., and Kramer, I. R. H.: Cavity Preparation With and Without Water Spray, Br. Dent. J. 123: 281, 1967. Han, S. 5.: The Fine Structure of Cells and Intercellular Substances of the Dental Pulp. In Finn, 8. B. (editor) : Biology of the Dental Pulp Organ, Birmingham, 1968, University of Alabama Press, pp. 103-139. Harndt, R.: Diseases of the Pulp and Their Diagnosis, Dtsch. Zahnaerztl. Z. 24: 389, 1969. Harrop, T. J., and Mackay, B.: Electron Microscopic Observations on Healing in Dental Pulp in the Rat, Arch. Oral Biol. 13: 365, 1968. Hess, J. C. : Iatrogenic Pulp Disease, Rev. Fr. Odontostomatol. 16: 635, 1969. Kriincke, A.: Treatment of Deep Carious Lesions, Int. Dent. J. 20: 238, 1970. Langeland, K., and Langeland, L. K.: Pulp Reaction to Crown Preparation, Impression, Temporary-Crown Fixation, and Permanent Cementation, J. Prosthet. Dent. 15: 129, 1965. Llory, H., and Frank, R. M.: Ultrastructure de la dentine carike, Actual. Odont-Stomatol., NO. 88, pp. 507-522, December, 1969. Marsland, E. A., and Shovelton, D. 8.: Repair in the Human Dental Pulp Following Cavity Preparation, Arch. Oral Biol. 15: 411, 1970. Mumford, J. M. : Thermal and Electrical Stimulation of Teeth in the Diagnosis of Pulpal and Periapical Disease, Proc. R. Sot. Med. 60: 197, 1967. Schuchard, A., and Watkins, C. E.: Thermal and Histologic Response to High-Speed and Ultrahigh-Speed Cutting in Tooth Structure, J. Am. Dent. Assoc. 71: 1451, 1965. Sveen, 0. B., and Hawes, R. R.: Differentiation of New Odontoblasts and Dentine Bridge Formation in Rat Molar Teeth After Tooth Grinding, Arch. Oral Biol. 13: 1399, 1968. Szymaniak, E., and Pankiewicz, H.: Current Views on the Clinical Diagnosis of Pulp Inflammations, Czas. Stomatol. 21: 381, 1968. Tyldesley, W. R., and Mumford, J. M.: Dental Pain and the Histological Condition of t.he Pulp, Dent. Pratt. Dent. Rec. 20: 333, 1970.

Address correspondence to : Dr. Samuel Seltzer Department of Endodontology Temple University School of Dentistry 3223 North Broad St. Philadelphia, Pa. 19140

conference on the biology of the human dental pulp (classification of pulpal pathosis)

Education