The periodontium and periodontal pathology in the howler monkey

ArchsoralBiol. Vo1.12, pp.359-365, 1967.Pergamon PrwsLtd. Printed in Gt.Britain.

THE PERIODONTIUM AND PERIODONTAL IN THE HOWLER MONKEY

PATHOLOGY

W. B. HALL*, H. E. GRUPE* and C. K. CLAYCOMB? Departments

of Periodontology* and Biochemistryt University of Oregon Dental School, Portland, Oregon, U.S.A.

Summary-One hundred and six forrnalin ftxed and sixty-five defleshed skulls of wild howler monkeys were surveyed grossly for evidence of periodontal disease. Sixteen wet specimens displayed clinically detectable pocket formation. Roentgenograms confirmed the presence of osseous lesions. Similar bone lesions were noted in the dried skulls. Two normal animals were studied microscopically. All areas of gross pathology, periodontal and periapical, were prepared and studied similarly. The periodontal lesions were quite similar to those seen in man, grossly, roentgenographically, and microscopically. No generalized periodontal disease, such as is commonly found in man, was noted. Two dehiscences and one hundred and fifty fenestrations were noted in the dried skulls. The existence of these osseous defects did not appear to be related to periodontal problems. The howler monkey would appear to have distinct advantages for future studies of periodontal disease.

INTRODUCTION

RELATIVELYfew papers concerning the normal and diseased periodontal tissues of non-human primates may be found in the literature. Studies on rhesus, spider and marmoset monkeys are most numerous. Recently, this literature was reviewed by COHENand GOLDMAN(1960). COHEN(1959) studied the skulls of gibbons, orangutans and chimpanzees. He noted little evidence of osseous destruction and “severe attritional patterns in the teeth”. Few reports of periodontal studies of populations of wild monkeys have appeared. COLYER(1936) reported that monkeys and apes are the only animals that suffer much periodontal disease in the wild state and that the incidence of disease increases when the animals are raised in captivity. KAKEHASHI, BAERand WHITE(1963) noted a high incidence of periodontal disease in a wild population of gorillas. Most of the studies of captive monkeys have dealt with the effects of nutritional deficiencies on the periodontium (SHAW, PHILLIPS and ELVEHJEM, I945 ; GOLDMAN,1947). The howler monkey, Allot&z carayu, is a small new world monkey native to the jungles of northern Argentina (Fig. 1). Specimens may attain a tip of the nose to tip of the tail length of 120 cm. Maximum weights for wild males are 10 kg, for females 6.5 kg. The animals are relatively docile and are easily handled in captivity (MALINOW, 1966). Previous reports on the tissues of the howler monkey (SCHULTZ, 359

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C. K. CLAYCOMB

1956, p. 980) discuss the periodontium and periodontal disease only briefly. In the present study, the skulls of 171 howler monkeys, shot in their native Argentine jungles, were examined. MATERIALS AND METHODS The heads of the 171 howler monkeys which were examined represented animals of a wide variety of ages. Several animals had only deciduous teeth and several, mixed dentitions. The great majority, however, had only permanent teeth, which showed varying degrees of occlusal wear, the amount of wear probably being related to the age of the animal (MALINOW,1966). Of the heads, 106 were wet, formalin-preserved specimens while sixty-five were defleshed, dried skulls. Prior to gross examination, the cheeks and masticatory muscles of the wet specimens were resected so that the lower jaw could be lifted free permitting ease of vision and manipulation during the survey. Visual examination was made with the aid of magnifying loupes. Sulcus and pocket depths were measured with the Marquis periodontal probe. All abnormalities were noted, and these specimens were set aside for radiographic and histologic study. Roentgenograms of normal and pathologic areas were obtained by sectioning the heads along the mid-sagittal plane on a high-speed band saw, placing the halves on occlusal-size X-ray film packets and exposing them with a dental X-ray unit. Six adult animals with no clinically evident periodontal or periapical lesions were used as controls. All specimens with suspected periodontal or periapical lesions, fractured teeth or mixed dentitions also were radiographed prior to preparation for histologic study. Clinical photographs were obtained at this time. Two clinically normal animals of intermediate age were selected for comprehensive histologic survey. Blocks of tissue consisting of anterior, canine or posterior teeth were prepared for study in a variety of planes of sectioning. The blocks were decalcified for 4 weeks in formic acid-formalin solution, cut to size and embedded in paraffin. Sections were cut serially at 6-8 p. Each fiftieth and fifty-first section was retained and stained with haematoxylin and eosin or Masson’s trichrome stain, respectively. Some 700 slides were prepared and studied. Sixteen of the 106 wet specimens exhibited pocket formation clinically in one or more areas. Blocks of tissue from areas exhibiting such changes were prepared identically to the normal specimens. Special stains, such as the BROWNand BREN (1931) bacterial stain, were applied to appropriate sections. Some 800 slides were prepared and studied. RESULTS Normal specimens

Monkeys included in this sample were older animals as indicated by the advanced wearing of tooth crowns. Neither wear nor age appeared to be related to periodontal health. In several specimens, crowns were worn below the crest of the free margin of the gingiva, yet the epithelial attachment did not extend apically from the cementoenamel junction.

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THE HOWLER

MONKEY

361

The typical appearance of a normal wet specimen is illustrated in Figs. 2a and b. The gingiva was thin and appeared to follow bone contours closely. Many areas showed evidence of fine stippling. Melanin deposits were a notable feature, especially in older male animals. The free gingiva assumed a knife-edged margin in most areas. Normal gingival sulcus depths ranged from 1 to 3 mm. Interproximal depths were about 3 mm. That these measurements represented normal sulcus depths was confirmed by the microscopic appearance of the sulci. Interdental papillae displayed the characteristic “col” form described by COHEN (1959) whenever adjoining teeth were in contact. In regions where diastemata were present, especially mesial and distal to canine teeth, the interdental gingiva closely stimulated the rounded form of the underlying bone. A clear-cut mucogingival line was observable on all vestibular surfaces and on the mandibular lingual surface. The width of the band of attached gingiva varied from 2 to 4 mm. Heavy deposits of supragingival calculus were present in all specimens. Roentgenograms of clinically normal animals are illustrated in Figs. 3a and b. Bone loss was not apparent in the roentgenograms. A clear-cut lamina dura could be noted around all alveoli. Crestal density of bone was similar to that seen on normal human films. The periodontal ligament appeared thin and of nearly identical width from crest to apex. Heavy bone trabeculae were prominent and numerous. Microscopically, the normal howler periodontium was similar in many respects to that of humans. The epithelium of the attached gingiva was ten to twenty cells in thickness, displayed prominent rete peg formation and was parakeratotic for the most part, with only occasional areas being orthokeratinized. Keratinization was present at the tip of the free gingiva and then decreased rapidly so that the gingival sulcus could be viewed as essentially non-keratinized. The epithelial attachment, which usually extended precisely to the cemento-enamel junction in most sulci, was approximately l-l.5 mm in length. A narrow zone of chronic inflammatory cells, principally plasma cells, extended from the tip of the free gingiva to the apical end of the epithelial attachment (Fig. 4). The “col” was covered by a thin stratified squamous, nonkeratinized epithelium two to six cells in thickness. In the gingival connective tissue, many melanoblasts were seen below the pigmented areas. The superficial connective tissue or lamina propria was of a loose, fibrous type while the deeper portions were dense connective tissue. A thick periosteum covered the bone. Interproximally, a densely organized interdental ligament was present between all teeth. The interdental “COY, in most cases, contained a tent-shaped zone of chronic inflammation extending to this ligament (Fig. 5). The periodontal ligament consisted of heavy bundles of collagen fibres interspersed with loose connective tissue and great numbers of blood and lymphatic vessels. Many prominent epithelial cell rests of Malassez were present close to the cementurn. Such rests were particularly numerous in inter-radicular areas. The cementum was mostly acellular except near the root apices and in inter-radicular areas. Many accessory root canals were present, especially in inter-radicular areas. The alveolar bone consisted of bundle bone surrounding the alveolus with deeper cancellous bone containing fatty marrow spaces. Evidence of bone apposition and resorption were more striking than in human material. Howship’s lacunae, containing

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osteoclasts, were observed in some areas around almost every tooth examined. The greatest activity in bone resorption and apposition was noted in the buccal and lingual walls of the alveoli of posterior teeth and around canines. Several interesting abnormalities were noted in this otherwise normal gingiva. Pieces of a cellulose-like material were observed deeply embedded in gingival connective tissue. Most were walled off by a thickening of connective tissue with occasional foreign body giant cells on the periphery. Similar material was packed into many sulci. In one area, a worm-like parasite surrounded by foreign body giant cells was noted. Pathologic specimens Of the 106 wet specimens examined, 16 or 15 per cent showed evidence of disease

involving the periodontium. Six animals had more than one area of periodontal pocket formation. Ten animals had periapical lesions, canines being most often involved. Twenty animals had other interesting findings such as fractures of crowns, sinus tract formation or supernumerary teeth. Several displayed extreme wear or crowns, so that occlusal surfaces were actually apical to the free margin of the gingiva, without pocket formation. None of the animals exhibited generalized periodontal disease as is frequently found in man. Pocket depths as great as 9 mm were probed in pathologic areas. The deepest measurements were around erupting canines where depths to 15 mm were recorded; however, these measurements did not represent true periodontal pockets but only eruption phenomena. All but one of the true pockets were present between posterior teeth. Food or hair wedging appeared to be associated with many of these pockets. One might assume that the packing of foreign matter into these areas could have been a sequel to the lesions, since such material also had been noted embedded in normal gingiva and packed into normal sulci; however, this remains undetermined. In the sixty-five dried skulls, two dehiscences and 150 fenestrations were noted on molar and premolar roots (Fig. 6). The absence of bone on these roots apparently did not predispose these teeth to periodontal disease. Bone destruction, with crater formation, appeared to characterize the disease process (Fig. 7). Mobility measurements could not be performed meaningfully in fixed specimens. Inter-radicular bone loss was noted in only two cases. Only one lesion was found along the buccal surface of a posterior tooth root, and this was a recession rather than a pocket formation phenomenon. Roentgenographic examination of diseased areas confirmed the presence of bone loss. Figure 8 demonstrates such an area in which calculus and an open contact may also be seen. Several animals had combined periodontal and periapical lesions. Since no pulps were well-preserved, probably due to the method of fixation (immersing the whole animal in Formalin), the assumption was made that periapical inflammation represented the result of pulpal death. In the animal illustrated in Fig. 9, the presence of calculus near the apex of the distal root of the third molar and the poor condition of the pulp made a decision as to the aetiology of the extensive lesion dfficult. Figure 10 illustrates a typical canine periapical lesion.

THE PERIODONTKJM AND PERIOLXNTAL PATHOUMY

IN THl3 HOWLER MONKEY

363

Examination of the histologic sections of teeth with periodontal pockets revealed the presence of bacterial deposits, calculus and plaque. A section from a three-walled infrabony crater is illustrated in Fig. 11. The lesion was much broader apically than occlusally, so that calculus and epithelium appeared apical to some remaining attached interdental ligament fibres in several of the serial sections. The epithelium lining the pockets was only a few cells in thickness in some areas, with numerous strands of cells extending deep into the connective tissue. Higher magnification (Fig. 12) demonstrates the highly inflamed subjacent connective tissue. The infiltrate consisted of small lymphocytes, plasma cells and occasional macrophages, with some polymorphonuclear leukocytes migrating between cells of the thin epithelium. Capillaries and small vessels in the region were engorged and distended. In other cases, gingival recession apparently was coincident with apical migration of the epithelial attachment and bone loss so that no pocket formation resulted. Figure 13 illustrates an area near the apex of a typical periapical lesion on a fractured canine. Extensive necrosis and inflammation were present within the pulp canal and at the apex. Epithelium appeared to have proliferated in an attempt to wall off the lesion. Large numbers of polymorphonuclear leukocytes surrounded this epithelium, while the predominant inflammatory cells in other regions were plasma cells and lymphocytes. A large area of external resorption was present on the root. Multinucleated giant cells were present in the typical scallop-shaped lacunae. In sections stained with the BROWNand BREN(1931) bacterial stain, large numbers of round and coccoidal bacteria were noted within odontoblastic processes subjacent to the area of external resorption. Such bacterial invasion of odontoblastic processes was not found elsewhere. The histologic findings confirmed the presence of periodontal or periapical lesions in each of the areas which were examined. Additional lesions may have been present in other specimens in which the clinical examination of fixed heads did not suggest the presence of sufficient pathology to warrant histologic investigation.

DISCUSSION The normal periodontium of the howler monkey is remarkably similar to that of man. Major differences appear to be the large canines, the presence of diastemata between anterior teeth and the presence of three premolars. An exaggerated interdental “col” is a characteristic of the howler as well as of other monkeys. The finding of clinically evident periodontal pockets in sixteen of 106 wet specimens does not represent a particularly high incidence of periodontal disease in the wild howler population; however, according to COLYER(1936), it represents a significant amount of periodontal disease in wild primates. The lack of generalized periodontal disease in any of the howlers adds further substance to COLYER’Sconclusion that periodontal disease in wild monkeys is most likely related to local disruptive processes such as food and hair impaction. Such debris was packed into most lesions noted in the howlers. Extensive abrasion of the occlusal surfaces of the teeth of older animals was

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CLAYCOMB

not related to the presence or absence of periodontal lesions. SCHULTZ (1956, p. 983) observed that “In many wild monkeys and apes of advanced age, one can observe extreme degrees of dental attrition with little tooth substance left above the gums.” COHENand GOLDMAN(1960) also observed that “In the thirtyfour (gibbon) skulls from the Far East, there were no evidences of bone resorption, despite the severe attritional patterns in the teeth of the adult specimens.” Such findings support the widely held opinion that heavy function of teeth does not cause nor predispose to periodontal disease (BAERet al., 1963). An additional interesting observation was that the presence of a great number of dehiscences and fenestrations, averaging more than two per animal, also did not appear to predispose to periodontal disease. KAKEHASHIet al. (1963), who examined only the defleshed skulls in 292 gorillas, also noted similarly high numbers of dehiscences and fenestrations. They assumed that these bone defects were related to periodontal disease; however, the large number of such defects noted in the dried howler skulls and the absence of periodontal lesions related to such defects in the wet specimens would indicate that dehiscences and fenestrations do not predispose teeth to inflammatory periodontal disease, at least not in the howler monkey. SCHULTZ(1956) observed that “Alveolar abscesses on the canines show a high frequency, probably on account of the fact that these long piercing and holding teeth become quite commonly broken themselves or break their sockets when used as levers.” He also noted that such lesions were more common in males. In the howlers, ten out of 106 animals had one or more broken canines. Seven of these animals were males. Because of its rather benign nature, the similarity of its dentition and periodontium to that of the human, its relatively small size and cost, the howler monkey would appear to have distinct advantages for periodontal studies. The incidence of periodontal lesions in these 106 animals was only 15 per cent; however, a number of studies, such as those of SHAWet al. (1945) and GOLDMAN(1947) indicate that alterations in diet can lead to significant increases in the incidence and severity of periodontal disease when monkeys are raised in captivity. The size of the howler would make it suitable for isotopic studies. Acknowledgements-This study was supported in part by USPHS Research Grant DE-01908-03 from National Institute of Dental Research, NIH, Bethesda, Md. We wish to express our appreciation to Dr. RENE MALINOWof the Oregon Regional Primate Center for providing us with the howler specimens. We also wish to thank Mr. RICHARDPEDERSEN and Mr. RICHARDPARK for technical assistance. R&urn&-Cent six cranes de singes hurleurs sauvages, fixes, et soixante cinq cranes sets,

sont etudies pour la mise en evidence de parodontolyse. Seize specimens humides montrent des culs de sac nets. Les radiographies confirment l’existence de lesions osseuses. Ces dernieres sont aussi visibles sur les cranes sets. Deux animaux normaux sont etudies microscopiquement. Toutes les regions montrant macroscopiquement des lesions parodontales et pbi-apicales ont et6 ttudiees. Les lesions du parodonte sont identiques a celles observkes chez l’homme, macroscopiquement, radiographiquement et microscopiquement. Aucune forme generaliske, telle que celle notee chez l’homme,

THE PERIODONTIUM AND PERIODONTAL PATHOLOGYIN THE HOWLERMONKEY

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n’a Cte observee. Deux pertes de substance et cent cinquante resorptions de la lame alveolaire vestibulaire sont not& dans les cranes sets. L’existence de ces lesions osseuses ne semble pas en rapport avec des maladies parodontales. Le singe hurleur parait presenter certains avantages pour l’btude des parodontolyses. Zusammenfassung-106 Formalin-fixierte und 65 vom Weichgewebe befreite Schldel wilder Briillaffen wurden makroskopisch auf Symptome parodontaler Erkrankungen untersucht. 16 feuchte Objekte weisen klinisch erkennbare Taschenbildung auf. Rontgenaufnahmen bestltigten die Existenz von Knochenllsionen. Ahnliche Lasionen wurden an den getrockneten Schldeln beobachtet. Zwei normale Tiere wurden mikroskopisch untersucht. Alle deutlich pathologisch veranderten Abschnitte im periodontalen und periapikalen Gebiet wurden ahnlich vorbereitet und untersucht. Die periodontalen Lasionen waren den beim Menschen beobachteten makroskopisch, rontgenologisch und mikroskopisch sehr Ihnlich. Es wurde keine generalisierte Zahnbetterkrankung festgestellt, wie sie gewohnlich beim Menschen gefunden wird. Bei den getrockneten Schldeln wurden zwei Dehiszenzen und 105 Knochendurchbriiche beobachtet. Die Existenz dieser Knochendefekte schien nicht mit periodontalen Problemen zusammenzuhlngen. Der Brtillaffe scheint gewisse Vorziige fiir zukiinftige Untersuchungen parodontaler Erkrankungen zu besitzen. REFERENCES BAER, P. N., KAKEHASHI,S., LITTLETON,N. W., WHITE, C. L. and LIEBERMAN, J. E. 1963. Alveolar bone loss and occlusal wear. J. Am. Sot. Periodont. 1,91-98. BROWN, H. J. and BREN, L. A. 1931. A method for the differential staining of Gram-positive and Gram-negative bacteria in tissue sections. Bull. Johns Hopkins Hosp. 48, 69-73. COHEN, B. 1959. Morphologic factors in the pathogenesis of periodontal disease. Br. dent. J. 107, 31-39. COHEN,D. W. and GOLDMAN,H. M. 1960. Oral disease in primates. Ann. N. Y. Acad. Sci. 85,889-909. COLYER,F. 1936. Variations and Diseases of the Teeth of Animals. John Bale, Sons and Danielsson, London. GOLDMAN,H. M. 1947. Periodontosis in the spider monkey-a preliminary report. J. Periodont. 18,34-40. KAKEHASHI,S., BAER, P. and WHITE, C. L. 1963. Comparative pathology of periodontal disease. I. Gorilla. Oral Surg. 16, 397406. MALINOW,R. 1967. The Biology of the Howler Monkey. A monograph. In press. REED, 0. M. 1965. Studies of the dentition and eruption patterns in the San Antonio Baboon Colony. In: The Baboon in Medical Research (Edited by VAGTBORD,H.) p. 167. University of Texas Press. SHAW, J. H., PHILLIPS,P. R. and ELVEHIEM,C. A. 1945. Acute and chronic ascorbic acid deficiencies in the rhesus monkey. J. Nutr. 29, 365-372. SCHULTZ, A. A. 1956. In: Primatologia (Edited by HOFER, H., SCHULTZ,A. H. and STARCK,D.) Vol. 1. Basel.

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FIG. I. An adult howler

PATHOLOGY

monkey,

IN THE HOWLER

Al/or&r

MONKEY

cmrvtr.

PLATE 1 A.O.B.

f.p. 366

W.

B. HALL,

H. E. GRU~E AND C. K.

CLAYCOMB

FIGS. 2a, b. Facial aspect of the maxilla and the mandible calculus, amount of fibrous gingiva and the mucogingival junction.

PLATE 2

showing

dentition,

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PATHOLOGY

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HOWLER

MONKEY

FIGS. 3a, b. Lateral roentgenogram of the maxilla and the mandible of a normal animal showing lamina dura, periodontal ligament space and crestal bone density.

PLATE

3

W. B. HALL, H. E. GRUPE AND C. K. CLAYCOMB

FIG. 4. Gingival sulcus in the normal animal. Surface epithelium is parakeratotic. The epithelial attachment is at the C-E junction. A moderate infiltrate of plasma cells may be noted subjacent to it. Haematoxylin and eosin. Y 80. FIG. 5. Mesio-distal section of thegingival interdental papilla in thenormal animal. Note the chronic inflammatory infiltrate coronal to the transeptal fibres of the periodontal ligament. Haematoxylin and eosin. - 80.

PLATE4

THE PERIODONTIUM

FIG. 6. Facial

aspect

AND

PERIODONTAL

of the maxilla

PATHOLOGY

in a dried

IV THE HOWLER

skull showing

MONKEY

fenestrations

and a

dehiscence. FIG. 7. The

mandible

of a dried

skull

showing

extensive

bone

craters

between

the molars. PLATE 5

W. B. HALL. H. E.

GRUPE

AND

C.

K.

CLAYCOMB

FIG. 8. Roentgenographic view of the left half of a mandible showing calculus, an open contact and bone cratering. FIG. 9. Roentgenographic dontal-periapical bone lesion. PLATE

6

view of a mandibular

molar with a combined

perio-

THE PERIODONTIUM

FIG. lesion.

AND

10. Roentgenographic

PERIODOXTAL

ciew

PATHOLOGY

of a maxillary

IN THE HOWLER

canine

with

MONKEY

a typical

periapical

PLATE 7

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K. CLAYCOMB

FIG. I I. Mesio-distal section through an interdental three-walled infrabony crater. Note the calculus apical to the crest of the interdental septum, migration of the epithelial attachment several millimeters onto cementum and bone resorption resulting in crater formation. Haematoxylin and eosin. s 40. FIG. 12. Higher magnification of the area near the bottom of the infrabony crater illustrated in Fig. 10. The chronic inflammatory infiltrate consists mostly of plasma cells, some lymphocytes and an occasional macrophage. Haematoxylin and eosin. X 120. FIG. 13. Histologic section of an area near the apex of a fractured maxillary canine tooth. The periapical lesion consists of polymorphonuclear leukocytes surrounding proliferated epithelium with plasma cells and lymphocytes in the deeper tissues. Haematoxylin and eosin. \ 480. PLATE8