Ciliated epithelium–lined radicular cysts

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Vol. 94 No. 4 October 2002

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY ENDODONTICS

Editor: Larz S. W. Spångberg

Ciliated epithelium–lined radicular cysts P. N. Ramachandran Nair, BVSc, DVM, PhD,a Gion Pajarola, DMD,b and Hans-Ulrich Luder, DMD,c Zurich, Switzerland UNIVERSITY OF ZURICH

Objective. This report describes 3 cases of ciliated epithelium–lined radicular cysts among 256 apical periodontitis lesions and also illustrates the occurrence of an Actinomyces-infected periapical cyst. Study design. Serial and step serial sections of 256 plastic-embedded root apices with attached apical periodontitis lesions that were prepared for a previous investigation were reviewed for the presence of ciliated epithelium–lined radicular cysts. The lesions that were found to have such epithelial lining were examined in a transmission electron microscope to elaborate the fine structure of the ciliated cells. Results. A total of 3 ciliated columnar epithelium–lined cysts was found among the 256 apical periodontitis lesions examined. Two of the lesions also contained stratified squamous epithelium. All 3 lesions affected maxillary premolars. One of the lesions was a true cyst, and the other 2 were periapical pocket cysts. The lumen of 1 of the latter revealed the presence of typical “ray-fungus” actinomycotic colonies. Conclusion. Although the stratified squamous component of the epithelia that lined the radicular cysts reported here may be derived from the cell rests of Malassez, the ciliated epithelial cells may be of sinus origin. Microbial agents from diseased root canals can advance into radicular cysts, particularly in pocket cysts, with the possible threat of such infection in upper posterior teeth spreading into the maxillary sinus. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:485-93)

Radicular or periapical cysts are usually lined by stratified squamous epithelium1,2 that is presumably derived from the odontogenic epithelial rests of Malassez.3 Rarely, however, periapical cysts have also been found to be lined partially or predominantly by ciliated columnar or mucosecretory cells that may have respiratory origin.4-10 The purpose of this communication is to report on the structure and fine structure of ciliated epithelium–lined radicular cysts among human apical periodontitis lesions and to highlight the presence of actinomycotic colonies in the cyst lumen of a lesion.

a

Senior Scientist, Department of Oral Structural Biology, Center of Dental and Oral Medicine, University of Zurich. b Group Leader, Oral Surgical Polyclinic, Center of Dental and Oral Medicine, University of Zurich. c Group Leader, Department of Oral Structural Biology, Center of Dental and Oral Medicine, University of Zurich. Received for publication Sep 26, 2001; returned for revision Nov 6, 2001; accepted for publication Jan 21, 2002. © 2002, Mosby, Inc. 1079-2104/2002/$35.00 ⫹ 0 7/15/123862 doi:10.1067/moe.2002.123862

MATERIALS AND METHODS The material used for this report belonged to a previous study11 on the prevalence of radicular cysts among human apical periodontitis lesions. The clinical background, collection of extracted teeth with attached periapical lesions, and processing of the specimens have been described in detail.11 In brief, most of the teeth were extracted for indications such as extensive caries and coronal damage, breakdown of the marginal periodontium, and nonstrategic value of the teeth. However, all the marginal periodontitis-influenced periapical lesions were excluded from the original study. The teeth on extraction were fixed by immersion in a solution consisting of glutaraldehyde and paraformaldehyde.12 The apical thirds of the affected roots with the lesions were severed with a diamond-coated disc operated on a custom-made miniature lathe. The specimens were decalcified in 0.25 mol/L ethylenediamine tetraacetic acid, subdivided in the axial plane into about 0.5-mm–thick pieces, postfixed in 1.33% omnium tetroxide, dehydrated in ascending grades of ethanol, and embedded in Epon (Fluka, Buchs, Switzerland). Onemicrometer–thick to 2-␮m–thick survey sections from 485

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each Epon block and serial sections from selected blocks were prepared with glass or histodiamond knives (Diatome AG, Biel, Switzerland) and the Reichert Ultracut E microtome (Leica, Glattbrugg, Switzerland). The sections were stained in periodic acid–Schiff and methylene blue-Azur II13 and photomicrographed, and suitable areas in the Epon blocks were determined for ultrasectioning. Thin sections were prepared with diamond knife (Diatome AG) and an LKB Ultratome Nova (LKB, Stockholm, Sweden), double contrasted with lead and uranium salts,14,15 and examined in a Philips 201 transmission electron microscope (Eindhoven, The Netherlands). RESULTS A total of 3 ciliated columnar epithelium–lined cysts was found in the 256 apical periodontitis lesions reviewed. Although 1 of the lesions was lined completely by ciliated columnar cells, the other 2 also contained stratified squamous epithelium in the cyst lining. The clinical data and the histopathologic diagnosis of the lesions are presented in the Table. All 3 lesions with ciliated epithelium originated from the maxilla. On the basis of the established histopathologic criteria reported previously,11,16,17 2 of the lesions were categorized as periapical pocket cysts and 1 as a periapical true cyst (Table). Specimen CF-165 This lesion affected the right maxillary second premolar of a 36-year-old woman (Table). Histologically, the lesion revealed a distinct radicular cyst (Fig 1). The roof of the cyst lumen was lined with simple ciliated columnar epithelium, and the luminal wall immediately lateral to the apical foramen was lined with stratified squamous epithelium. The latter formed a collar-like epithelial attachment to the root surface surrounding the apical foramen. The 2 epithelia showed a sharp and distinct boundary (Fig 1, B, C). Axial section (Fig 2, A) passing through the plane of the apical foramen revealed that the root canal opened into a large cystic lumen that contained necrotic cells (Fig 2, B). A bacterial mass could be clearly observed with light microscopy in the apical portion of the root canal (Fig 2, C); facing that was a dense wall of polymorphonuclear leukocytes (PMNs) in various stages of disintegration. Specimen CF-169 This radicular cyst was attached to the root apex of the right first maxillary premolar of a 48-year-old woman (Table). The lumen of the cyst was predominantly lined by ciliated columnar and, to a lesser extent, by stratified squamous epithelia (Fig 3 A, B). The latter

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY October 2002

revealed proliferating arcades of epithelial strands that extended into the surrounding granulomatous tissue (Fig 3, B), which was infiltrated predominately with lymphocytes and plasma cells. Serial sections of the lesion revealed continuity of the infected root canal with the lumen of the cyst. The latter contained a dense collection of PMNs in various stages of disintegration and necrotic cells. An outstanding feature of this lesion was the presence of distinctly separate clusters of bacterial colonies with actinomycotic features (Fig 3 A, B). The colonies were positive with periodic acid–Schiff and showed needle-shaped peripheral filaments that gave the so-called “star-burst” or “ray-fungus” appearance (Fig 3, C). A few layers of PMNs were observed around the bacterial colonies. Specimen CF-173 This lesion affected the left maxillary second premolar of a 34-year-old man (Fig 4). Histopathologically, the lesion was categorized as a periapical true cyst without any continuity of the root canal space into the cystic lumen. The latter was completely lined with simple ciliated columnar epithelium. Two diverticula of a narrow and slit-like lumen could be observed in individual sections (Fig 5). The rest of the lesion that surrounded the tortuous lumen consisted of solid collagenous granulomatous tissue infiltrated predominantly with lymphocytes and plasma cells. The ciliated epithelium The ciliated epithelium in all 3 specimens gave a pseudostratified appearance in light microscope (Figs 5 and 6). However, simple columnar ciliated cells could be observed in random axial ultrasections of the cells (Fig 7). Each cell revealed a euchromatin-rich basally placed nucleus and numerous mitochondria and rough endoplasmic reticulum in the cytoplasm. The luminal border of the cells revealed well organized and distinct cilia that were cut in all possible directions. Numerous PMNs were observed in the intercellular spaces of the ciliated epithelium (Fig 7). They appeared slender and thinly stretched along the long axis of the columnar cells, apparently in the process of transmigration from the subepithelial tissue into the cyst lumen. DISCUSSION Ciliated columnar epithelium does not generally line radicular cysts. This communication is a histopathologic and ultrastructural report on 3 periapical cysts that were lined by ciliated columnar epithelium. Further, 1 of the lesions provided convincing morphologic evidence for the possible occurrence of infected radicular cysts that have significance in clinical endodontics. The 3 lesions reported here originated from a total of

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Table. Clinical data of specimens Specimen CF-165 CF-169 CF-173

Tooth*

Gender

Age (years)

Histopathology

5 4 13

Female Female Male

36 48 34

Apical pocket cyst Apical pocket cyst Apical true cyst

*Tooth 5 is maxillary right second premolar; tooth 4 is maxillary right first premolar; and tooth 13 is maxillary left second premolar.

Fig 1. Photomicrograph of periapical pocket cyst (A) that affected right second maxillary premolar (radiographic inset) of 36-year-old woman. Rectangular demarcated area in A is magnified in B. Note that lumen (LU) is lined with epithelia revealing ciliated columnar (CEP) and stratified squamous (SEP) characteristics. Demarcated junction of 2 epithelia (B) is magnified in C. Original magnifications: A, ⫻20; B, ⫻60; C, ⫻360. D, Dentin.

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Fig 2. Light microscopic view of axial section (A) passing through plane of apical foramen of lesion shown in Fig 1, A. Demarcated areas of apical foramen in A and B are magnified in B and C, respectively. Note massive amount of bacteria (BA) in apical root canal, which is open and continuous with lumen (LU) of apical pocket cyst. Latter is lined with ciliated epithelium (CEP). Original magnifications: A, ⫻20; B, ⫻60; C, ⫻120. D, Dentin.

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Fig 3. Photomicrograph of periapical pocket cyst lined with ciliated columnar (CEP) and stratified squamous (SEP) epithelia that affected right maxillary first premolar (radiographic inset). Rectangular block in A is magnified in B. Demarcated colony in B is magnified in C. Note 2 black arrowheaded distinct ray-fungus type of actinomycotic colonies (AC) within lumen (LU). Original magnifications: A, ⫻20; B, ⫻60; C, ⫻210. D, Dentin.

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Fig 4. Panoramic radiograph of dental status of patient CF-173. Note extensive carious damage of crown of left maxillary second premolar (25) and possible rarefaction (arrowhead) of sinus floor as result of apical periodontitis of tooth.

Fig 5. Photomicrograph of axial histologic section of radiographic lesion arrowheaded in Fig 4. Note apical periodontitis (AP) showing 2 diverticula of cystic lumen. Rectangular demarcated area in A is magnified in B. Lumen (LU) of cyst is lined with distinctly columnar epithelial cells (EP). Demarcated area in B is magnified in Fig 6. Original magnifications: A, ⫻45; B, ⫻120. D, Dentin.

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 94, Number 4

Fig 6. Magnified view of rectangular block shown in Fig 5, B. Note brush-like cilia (CI) on columnar epithelial cells (EP) lining cystic lumen (LU). Original magnification, ⫻330.

256 apical periodontitis lesions, of which 39 were periapical cysts. Several reports exist on the occurrence of ciliated epithelium in radicular cysts.4-10 The reported frequency of ciliated epithelium–lined cysts among ra-

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dicular cysts varies from 0.8% (n ⫽ 88) to 10% (n ⫽ 200) of such lesions.6,8 Most of the studies on ciliated epithelium-lined radicular cysts are based on paraffin embedding and light microscopy. To our knowledge, only 1 investigation exists in which the ciliated epithelial lining of such lesions was examined in a transmission electron microscope.10 Except for the observation by these investigators of some “abnormal cilia” that also existed among a great majority of “normal cilia”, the fine structure of the ciliated cells in our material is in agreement with that of the previous study. About 52% of all apical periodontitis lesions contain epithelial cells11 that are generally believed to be derived from the odontogenic epithelial rests of Malassez. They have been assumed to serve as the source cells of the stratified squamous epithelium that usually lines the cavities of radicular cysts. However, the origin of ciliated columnar epithelium in radicular cysts has not yet been satisfactorily clarified. There have been 3 explanations8 for the presence of ciliated columnar cells in radicular cysts: (1) migration of such cells from the maxillary sinus or the nasal cavity; (2) metaplasia of the stratified squamous epithelium; and (3) differentiation of pluripotent cells within the jaw. All 3 lesions reported here were affecting maxillary teeth. The close anatomic proximity of the inflammatory lesion to the maxillary sinus may result in rarefaction of the sinus floor and perforation into the sinus cavity.5,18 Such periapical inflammation is reported to be a cause of maxillary sinusitis.19-21 The lumen of a periapical cyst in the region may even communicate with the sinus cavity (Fig 8), as has been convincingly shown in photomicrographs by Kronfeld.5 Once direct communication is established, a developing periapical cyst may become lined partially or completely with ciliary epithelium of sinus origin. These observations strongly support the assumption that the 3 inflammatory cysts reported here had rarefied the bony plate and grown into the sinus, although this could clearly be appreciated in the radiograph of CF-173 only (Fig 4). Although the stratified component of the cyst epithelia reported here may be derived from the cell rests of Malassez, the ciliated columnar cells may be of sinus origin. An incidental but clinically important observation was the presence of ray-fungus type of bacterial colonies in the lumen of 1 of the lesions. This presence strongly suggests actinomycotic infection of the cyst. Because the lesion happened to be a periapical pocket cyst, the infectious organisms could have advanced from an Actinomyces-infected root canal into the lumen of the cyst where they established themselves into colonies with typical star-burst appearance. Actinomyces are common in necrotic un-

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Fig 7. Composite transmission electron micrograph of ciliated columnar epithelial cells (CEP) lining cystic lumen of lesion presented in Fig 5. Note distinct cilia (CI) and neutrophilic granulocytes (NG) in process of transmigrating through interepithelial cell space into cyst lumen. Original magnification, ⫻3510. FI, Fibroblast.

Fig 8. Photomicrograph of mesiodistal section through posterior part of maxilla showing first, second, and third molars. Huge radicular cyst that perforated into maxillary sinus is visible at apex of second molar. Note continuity of cyst lumen with sinus space. Reprinted from Kronfeld R. Histopathology of the teeth and their surrounding structures. Philadelphia: Lea & Febiger; 1939. p. 210-1.5

treated root canals of carious teeth22,23 and are also among the frequently reported bacteria of teeth with asymptomatic postendodontic apical periodontitis lesions.24-27 Typical actinomycotic colonies have been found within the body of human periapical granulomas.28-31 In experimental infections of animals, Actinomyces israelii, the primary etiologic agent of human periapical actinomycosis, has been shown to establish in host tissues.32-34 Therefore, the ability of Actinomyces to survive in periapical granuloma and radicular cysts has clinical significance because the presence of such recalcitrant extraradicular infection can adversely affect the outcome of conventional orthograde root canal treatment. Further, the occurrence of such extraradicular infection of posterior maxillary teeth can result in sinusitis as a result of the infection spreading into the maxillary sinus. We thank Mrs Susy Mu¨ nzel-Pedrazolli for excellent technical assistance.

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19. Berry G. Dental caries in paranasal sinus infections. Arch Otolaryngol 1929;8:698-706. 20. Stevensson W. Chronic maxillary sinusitis. Arch Otolaryngol 1931;13:505-31. 21. Martensson G. Dental Sinusitiden. Dtsch Zahna¨ rztl Z 1952;7: 1417-27. 22. Hylton RP, Samules HS, Oatis GW. Actinomycosis: is it really rare? Oral Surg Oral Med Oral Pathol 1970;29:138-47. 23. Sakellariou PL. Periapical actinomycosis: report of a case and review of the literature. Endod Dent Traumatol 1996;12:151-4. 24. Sundqvist G, Reuterving CO. Isolation of Actinomyces israelii from periapical lesion. J Endod 1980;6:602-6. 25. Happonen RP. Periapical actinomycosis: a follow-up study of 16 surgically treated cases. Endod Dent Traumatol 1986;2:205-9. 26. Bystro¨ m A, Happoneen RP, Sjo¨ gren U, Sundqvist G. Healing of periapical lesions of pulpless teeth after endodontic treatment with controlled asepsis. Endod Dent Taumatol 1987;3:58-63. 27. O’Grady JF, Reade PC. Periapical actinomycosis involving Actinomyces israelii. J Endod 1988;14:147-9. 28. Browne RM, O’Riordan BC. Colony of Actinomyces-like organism in a periapical granuloma. Br Dent J 1966;120:603-6. 29. Samanta A, Malik CP, Aikat BW. Periapical actinomycosis. Oral Surg Oral Med Oral Pathol 1975;39:458-62. 30. Nair PNR, Schroeder HE. Periapical actinomycosis. J Endod 1984;10:567-70. 31. Happonen RP, So¨ derling E, Viander M, Linko-Kettungen L, Pelliniemi LJ. Immunocytochemical demonstration of Actinomyces species and Arachnia propionica in periapical infections. J Oral Pathol 1985;14:405-13. 32. Brown J, von Lichtenberg F. Experimental actinomycosis in mice. Arch Pathol 1970;90:391-402. 33. Behbehani M, Jordan H. Comparetive pathogenicity of Actinomyces species in mice. J Med Microbiol 1982;15:465-73. 34. Figdor D, Sjo¨ gren U, Sorlin S, Sundqvist G, Nair PNR. Pathogenicity of Actinomyces israelii and Arachnia propionica: experimental infection in guinea pigs and phagocytosis and intracellular killing by human polymorphonuclear leukocytes in vitro. Oral Microbiol Immunol 1992;7:129-36. Reprint requests: Dr P. N. R. Nair, BVSc, DVM, PhD Department of Oral structural Biology Plattenstrasse 11 CH-8028 Zurich Switzerland