Epithelial cell proliferation in odontogenic keratocysts: a comparative immunocytochemical study of Ki67 in simple, recurrent and basal cell naevus syndrome (BCNS)-associated lesions

The aim of the present study was to investigate epithelial cell proliferation in the linings of odontogenic cysts, including three different subtypes of odontogenic keratocyst (OKC), namely simple (non-recurrent), recurrent and basal cell naevus syndrome (BCNS)-associated lesions. Ki67 immunoreactivity in OKC (simple, n = 10; recurrent, n = 8; syndrome, n = 9), dentigerous cysts (DC, n = 5), radicular cysts (RC, n = 5) and normal oral mucosa (n = 7) was studied using a biotin-streptavidin-peroxidase method on paraffin sections after microwave treatment. Ki67⁺ epithelial cells were counted manually and related to the length of basement membrane (BM) as determined by TV image analysis. Data were analysed by the Mann-Whitney U test. The number of Ki67+ cells in simple OKC linings (53.1 ± 17.8 cells/ mmBM) was similar to that in oral epithelium (42.5 ± 12.7 cells/mmBM; P>0.2). However, both contained significantly more Ki67+ cells than DC (3.9 ± 1.3 cells/ mmBM) and RC linings (6.7 ±4.8 cells/mmBM; P<0.006). The epithelial distribution of Ki67⁺ cells differed between groups, with the percentage of positive cells in basal layers in OKC linings (7.0 ± 2.1%) being significantly lower than that of oral epithelia (35.9 ± 5.6%), DC (78.4 ± 8.4%) and RC (80.6 ± 7.7%) linings respectively (P<0.003). Comparison of Ki67 expression within the OKC group revealed no significant difference between simple and recurrent lesions (44.0 ± 13.8 cells/ mmBM; P>0.3). However, OKC associated with BCNS contained significantly higher numbers of Ki67+ cells (91.8±35.6 cells/mmBM; P<0.01). There was no difference in epithelial distribution of positive cells between the OKC groups. The results are consistent with OKC having a greater proliferative capacity than DC and RC and that its recurrence is not associated with a subgroup of lesions exhibiting increased proliferation. The increased proliferation in OKC associated with BCNS presumably reflects the underlying genetic defect(s) in this syndrome.     

p53 expression in odontogenic keratocyst epithelium

The expression of p53 protein was studied in odontogenic keratocysts (OKC, 11 solitary, 5 recurrent and 6 NBCCS cysts), radicular (RC, n=5) and dentigerous (DC, n=5) cysts, using a panel of antibodies to p53 (clone BP53-12, clone 1801 and polyclonal CM1) and a sensitive biotin-streptavidin method on paraffin embedded sections. Of the three antibodies tested, clone BP53-12 gave the most intense and consistent nuclear staining pattern. Clone 1801 and polyclonal CM1 stained only 38% and 71% OKC linings, respectively, but not RC and DC linings. However, BP53-12⁺ cells were detected in the epithelial linings of all cyst types. Quantification of BP53-12⁺ cells was performed by manual counting and by relating cell number to unit length of basement membrane as determined by TV image analysis. BP53-12⁺ cell counts in solitary OKC linings (25.5 ± 11.0 cells/mmBM) were significantly greater than those in DC (9.3 ± 4.9 cells/mmBM, P<0.01) and RC (6.7 ±2.6 cells/mmmBM. P<0.01) linings. The epithelial distribution of positive cells in OKC was predominantly suprabasal, which also varied from that of DC and RC linings (P<0.005). There were no detectable differences in BP53-12 reactivity between the different subtypes of OKC (i.e., solitary, recurrent and NBCCS-associated OKC: P>0.1). When data for the NBCCS-related OKC group were excluded, there was a significant correlation (r=0.55. P<0.01) between p53 and Ki67 labelling. To detect the presence of p53 gene mutations, genomic DNA, extracted from paraffin sections of OKC (4 solitary, 2 recurrent and 4 NBCCS cysts). RC (n=3) and normal oral mucosa (n=1), was subjected to a combination of polymerase chain reaction and single-stranded conformation polymorphism (PCR-SSCP) analysis for exons 5-10 of the p53 gene. Exon 4 was not analysed because of compromised DNA quality. No abnormality in banding patterns was found and all samples save results similar to DNA from known, sequenced, normal p53 gene controls. Absence of p53 mutations within exons 5–9 was confirmed by the direct sequencing of 2 fresh frozen OKC samples (1 solitary and 1 NBCCS cyst). These results suggest that over expression of p53 protein in OKC epithelium, detected by immunocytochemistry, is not reflected by alteration of the p53 gene and presumably reflects overproduction and/or stabilisation of normal p53 protein.     

Survivin、Ki67在牙源性囊肿上皮组织中的表达及意义

目的：探讨根端囊肿、含牙囊肿及角化囊肿衬里上皮中Survivin、Ki67的表达及意义。方法：采用免疫组化法检测12例根端囊肿、20例含牙囊肿、22例角化囊肿中Survivin、Ki67表达水平,并加以分析。结果：Survivin在根瑞囊肿中无表达,在含牙囊肿和角化囊肿中表达的阳性率分别为10％、63．6％,角化囊肿OD值显著高于根端囊肿和含牙囊肿（P〈0．05）;Ki67在3种组织中均有表达,角化囊肿中Ki67-ＬＩ显著高于根端囊肿和含牙囊肿（Ｐ〈0．05）;角化囊肿中Survivin阳性表达的Ki67-LI显著高于表达阴性者（Ｐ〈0．05）,且Survivin表达与Ki67表达呈正相关（r=0．452,P〈0．05）。结论：survivin、Ki67在牙源性囊肿中的表达差异显示了它们具有不同的增殖和分化过程。     

The differential expression pattern of BMP-4 between the dentigerous cyst and the odontogenic keratocyst

BACKGROUND: Bone morphogenic protein-4 (BMP-4) is widely expressed in oral cavity and involved in tooth morphogenesis, cellular differentiation and proliferation. The purpose of this study was to compare the difference in expression pattern of BMP-4 in odontogenic keratocysts (OKC) and dentigerous cysts (DC). METHODS: We evaluated 77 cysts, OKC (n = 34) or DC (n = 43). The average age of patients with OKC was 29.5 +/- 14.4 and that of patients with DC was 36.1 +/- 19.4. The male to female ratio was 20:14 for OKC and 27:16 for DC. Ten cases of OKC were recurrences. Expression of BMP-4 was determined by immunohistochemistry and in situ hybridization. RESULTS: The intensity scales were (-) for invisible or trace staining, (+) for visible staining, and (++) for dense, strong staining. OKCs exhibited the following staining patterns: the epithelium in 15/34 specimens and the mesenchymal cells in 17/34 specimens showed (++) stain. In contrast, the staining pattern of DC was (-) for epithelium in 37/43 specimens. The mesenchymal cells showed (-) degree staining in 30/43 specimens. The difference between the groups studied was significant (P < 0.001 in epithelium and mesenchymal cells). When recurrent and non-recurrent OKC were compared BMP-4 was expressed more intensely in the recurrent cases (P = 0.036 in epithelium). The difference in BMP-4 expression in mesenchymal cells was not significant. In situ hybridization demonstrated positive mRNA probes to BMP-4 were localized in epithelium and mesenchymal cells of OKCs and DCs. CONCLUSIONS: BMP-4 was expressed more intensely in OKC when compared with DC, and was more intensely expressed in recurrent cases.     

Scanning electron microscopic study of surface of human oral mucosa

The surface ultrastructure of the healthy oral mucosa of humans was studied using SEM as follows: dorsum of the tongue (10 specimens), buccal mucosa (5), floor of the mouth (3), hard palate (5), and gingiva (10). One part of each formalin-fixed sample was processed routinely using the system of critical point drying for scanning electron microscopy. The other part of the specimen was embedded in paraffin blocks and stained with hematoxylin-eosin for light microscopy. With SEM at low magnification, the surface structure of the oral mucosa at different areas of the oral cavity was smooth with some desquamating cells. Only the tongue mucosa with its papillae formed a specialized mucosa. The hairs of the filiform papillae were covered by microorganisms, whereas on the oral mucosa there usually was little or no colonization by microorganisms. At high magnification, the surface structure of the superficial epithelial cells was pitted or microplicated. On keratinized epithelium the surface structure was pitted, whereas on non-keratinized epithelium it was microplicated. On cell boundaries some variation could also be seen; in keratinized epithelium these boundaries were overlapping and in non-keratinized epithelium they were tight.     

Scanning electron microscopic study of surface of human oral mucosa

The surface ultrastructure of the healthy oral mucosa of humans was studied using SEM as follows: dorsum of the tongue (10 specimens), buccal mucosa (5), floor of the mouth (3), hard palate (5), and gingiva (10). One part of each formalin-fixed sample was processed routinely using the system of critical point drying for scanning electron microscopy. The other part of the specimen was embedded in paraffin blocks and stained with hematoxylin-eosin for light microscopy. With SEM at low magnification, the surface structure of the oral mucosa at different areas of the oral cavity was smooth with some desquamating cells. Only the tongue mucosa with its papillae formed a specialized mucosa. The hairs of the filiform papillae were covered by microorganisms, whereas on the oral mucosa there usually was little or no colonization by microorganisms. At high magnification, the surface structure of the superficial epithelial cells was pitted or microplicated. On keratinized epithelium the surface structure was pitted, whereas on non-keratinized epithelium it was microplicated. On cell boundaries some variation could also be seen; in keratinized epithelium these boundaries were overlapping and in non-keratinized epithelium they were tight.     

KAI-1 protein expression in odontogenic cysts

The KAI-1 tumor suppressor gene is widely distributed in normal tissues and its down-regulation may be correlated with the invasive phenotype and metastases in several different epithelial tumors. The aim of the present study was an evaluation of KAI-1 expression in radicular cysts (RC), follicular cysts (FC), orthokeratinized keratocysts (OOKC), and parakeratinized keratocysts (POKC). Eighty-five odontogenic cysts, 28 RC, 22 FC, and 35 OKC (16 OOKC, 19 POKC) were selected. All the POKC were negative and only four of 16 of the OOKC were positive for KAI-1. On the contrary, all RC and FC cases were positive and immunoreactivity for KAI-1 was detected throughout all the layers of the cyst epithelium. The lack of KAI-1 expression in POKC could help to explain the differences in the clinical and pathologic behavior of OKC and, according to what has been reported for epithelial tumors, could be related to the increased aggressive behavior and invasiveness of OKC.     

Thin-layer chromatographic analyses of lipids in different layers of porcine epidermis and oral epithelium.

Frozen cryosections were cut parallel to the surface of porcine skin and palatal, buccal and floor-of-mouth mucosa so as to provide separate samples representing various epithelial layers. The samples were dried, extracted with chloroform:methanol, and the lipids were chromatographed on silica gel plates in various solvent systems. After charring, lipids were quantified with a scanning densitometer. Overall, greater differences in proportions and distributions of lipid components were evident between keratinized and non-keratinized epithelia than between epidermis and keratinized oral epithelium. For epidermis and palate there was an increase in neutral lipids, including ceramides, from the deeper layers to the surface; ceramides were most abundant in surface layers. In buccal epithelium there was a distinct increase in glycosylceramides toward the surface, and in both non-keratinized regions ceramides were present in only very small amounts. The results suggest that although neutral lipids may be associated with a superficial barrier layer in skin and oral mucosa, there are differences in the composition of this barrier between keratinized and non-keratinized epithelia.     

The Odontogenic Jaw Cysts： Analysis of the Clinical Parameters of 669 Cases

目的分析、比较三型牙源性颌骨囊肿的临床特点.方法收集20年间牙源性角化囊肿(odontogenic keratocyst,OKC)、根端囊肿(radicular cyst,RC)及含牙囊肿(dentigerous cyst,DC)的临床资料,对其性别构成、年龄分布、发病部位及临床表现等进行比较研究.结果1)三型颌骨囊肿的男女之比分别为OKC 1.6∶1,RC 1.4∶1,DC 4.1∶1(χ2检验,P＜0.005).2)除DC未见于70岁以上年龄段外,几乎各年龄段均见三型颌骨囊肿的发生,三型囊肿组间及组内的年龄分布均有显著性差异(χ2检验,P＜0.005).OKC及RC20～29岁年龄段患病人数最多,分别占各年龄段患病人数的27%及20%;DC10～19岁年龄段患病人数最多,占各年龄段患病人数的29%.3)颌骨的任一部位均见三型颌骨囊肿的发生,但发生频率不同,三型颌骨囊肿组间及组内发病部位的分布有显著性差异(χ2检验,P＜0.005).4)OKC有137例合并感染,感染率39%;RC48例合并感染,感染率24%;DC18例合并感染,感染率16%,三型间有显著性差异(χ2检验,P＜0.005).结论1)男性较女性更易发生牙源性颌骨囊肿.2)不同的年龄段,对OKC、RC及DC的易感性不同.OKC及RC发生的高峰期均为20～29岁年龄段;DC发生的高峰期为 10～19岁年龄段.3)不同的颌骨部位,对OKC、RC及DC的易感性不同.OKC好发于下颌磨牙区,其次为下颌双尖牙区;RC及DC则好发于上颌前牙区.4)感染症状的出现,对OKC、RC及DC彼此间的鉴别诊断具一定临床意义.     

A histological and scanning electron microscopy study of the muco-gingival junction in the vervet monkey

Specimens of clinically healthy oral epithelium from the vervet monkey ( Cercopithecus aethiops ) containing gingiva, alveolar mucosa and muco-gingival junction were examined histologically and with the scanning electron microscope.
The gingiva was covered by a stratified squamous keratinized epithelium and the alveolar mucosa by a non-keratinized stratified squamous epithelium. A groove was present between the two epithelia in approximately half the specimens, the floor of which was lined by keratinized epithelium. Non-keratinized epithelial cells were seen to interdigitate with keratinized cells at the base of the alveolar mucosa side of the groove.     

Marsupialization as a definitive treatment for the odontogenic keratocyst.

PURPOSE: We sought to show that marsupialization can be a definitive treatment for the odontogenic keratocyst (OKC). MATERIALS AND METHODS: Ten patients (10 males and 4 females) between the ages of 11 and 64 with biopsy-proven OKC (8 mandibular and 2 maxillary) measuring between 2 and 8 cm were treated by marsupialization consisting of excision of the overlying mucosa and the opening of a 1-cm window into the cystic cavity and, where possible, suturing of the cyst lining to the oral mucosa. Immunohistologic determination of bcl-2 was done for all samples of cyst lining. The cavities were kept open either by vigorous use of a home syringe by the patient or by suturing into place the flange and short length of a nasopharyngeal airway. Once the cyst had largely filled in, histologic material was taken from the base of the residual depression and studied by light microscopy and bcl-2 expression. RESULTS: In the 10 patients, the OKCs completely resolved both clinically and radiographically. The time taken for resolution varied from 7 to 19 months. In all cases, the histologic material obtained after marsupialization showed normal epithelium only, with no signs of cystic remnants, daughter cysts, or budding of the basal layer of the epithelium. At initial biopsy, bcl-2 was expressed in the keratocyst lining, but not in the histologic material obtained after marsupialization. Follow-up time ranged from a minimum of 1.8 years to a maximum of 4.8 years. Teeth at the periphery of the cysts were observed to upright and erupt. CONCLUSIONS: All 10 OKCs resolved completely after marsupialization. Teeth within the cyst were found to be upright and erupt. Marsupialization requires a cooperative patient who will irrigate the cavity and keep it open. It appears that the cyst lining is replaced by normal epithelium during this treatment.     

Expression of transforming growth factor-beta 1 (TGF-beta 1) in odontogenic cysts

AIM: To evaluate the positivity to transforming growth factor-beta 1 (TGF-beta 1) in different types of odontogenic cysts. METHODOLOGY: A total of 30 radicular cysts (RCs), 27 follicular cysts (FCs) and 28 odontogenic keratocysts (OKCs) were evaluated for immunohistochemical analysis of TGF-beta 1. TGF-beta 1 was evaluated in blood vessels, stromal cells (fibroblasts) and pluristratified squamous epithelium. TGF-beta 1 expression was determined by evaluating the number of positive elements. TGF-beta 1 expression was determined by evaluating 1000 cells in the pluristratified squamous epithelium (500 in the basal and parabasal layers, and 500 in the superficial layer) and 500 cells (the fibroblasts in the stroma) for each specimen, and counting the number of positive cells. The number of positive vessels was evaluated in 10 high power fields (HPF). The Chi-square test was used to evaluate differences between the two groups (RC + FC and OKC). A P-value <0.05 was considered to indicate statistical significance. RESULTS: A higher and statistically significant positivity was found in the basal-suprabasal epithelial layers (P=0.0011), superficial epithelium (P=0.053) and stromal cells (P=0.0002) of orthokeratotic and parakeratotic OKC as compared with RC and FC. CONCLUSIONS: These differences suggest that control of the cell cycle may be abnormal in orthokeratotic OKCs. These OKCs may have an intrinsic growth potential not present in other cyst types.     

Human vaginal epithelium and the epithelial lining of a cyst model constructed from it: a comparative light microscopic and electron microscopic study.

The light microscopic features and keratin filament distribution of human vaginal epithelium resemble those of buccal mucosa. We used vaginal epithelium to establish a human cyst model in immunodeficient mice. To strengthen the view that this experimental cyst is a suitable model to study mucosal diseases, we compared specific light microscopic and ultra-structural features of vaginal epithelium and the epithelial lining of the cyst. Nineteen cyst walls and 6 specimens of vaginal mucosa, which had been used to establish the cysts, were examined. We counted the number of cell layers of 17 cyst linings and the 6 vaginal specimens. Surface keratinisation was evaluated on sections stained with the Picro-Mallory method. To demonstrate intercellular lamellae and membrane coating granules 2 cyst linings were examined ultra-structurally. The epithelium lining of the cyst wall was thinner than that of vaginal mucosa but the surface keratinisation and ultra-structural features of the intercellular lamellae and membrane coating granules were similar. We concluded that vaginal mucosa is a useful substitute for oral mucosa in the cyst model.     

The lipid composition of porcine epidermis and oral epithelium

The permeability barrier of mammalian skin has been analysed in terms of its lipid composition whereas that of the oral mucosa is uncharacterized. As there are differences in permeability between different regions of the oral mucosa, and between the oral mucosa and skin, there may be corresponding differences in the nature of the barrier layer. Lipids were identified by thin-layer chromatography after solvent extraction of separated epithelium; their localization was determined in histological sections using standard histochemical stains. Keratinized oral epithelium and epidermis showed a similar pattern of lipid distribution, the majority of neutral lipids being ceramides, localized around the cells of the stratum corneum. The non-keratinized epithelium contained few neutral lipids but polar lipids, particularly cholesterol sulphate and glucosylceramides, were clearly evident. Histochemical staining suggested that these were localized in intercellular regions throughout the epithelium. The differences in the types and distribution of lipids accord well with known permeability differences, which show that keratinized oral epithelium and epidermis have a similar impermeability to water and that non-keratinized regions have greater permeability.     

Dedifferentiation of odontogenic keratocyst epithelium after cyst decompression.

PURPOSE: Cytokeratin-10 expression by cystic epithelium has been shown in the suprabasilar layers of odontogenic keratocyts (OKCs) but not in dentigerous cysts. Cyst decompression and irrigation result in the loss of keratinization. In this study, we used cytokeratin-10 antibody staining to evaluate changes in OKC epithelium to determine if decompression/irrigation treatment results in an epithelial modulation that may be associated with lower long-term recurrence. METHODS: Fourteen OKCs were exteriorized by removal of mucosa and bone. An irrigation port was placed into the cyst for twice-daily irrigations. At 3-month intervals, panoramic radiographs were obtained and cyst-lining cells were sampled and stained for cytokeratin-10. Residual cystectomy was performed when necessary based on clinical and radiographic criteria, and the lining was evaluated by histologic and immunohistochemical examination. RESULTS: There were 6 males and 8 females with a mean age of 32 years. Ten cysts were mandibular, and 4 were maxillary. Average duration of irrigation was 8.4 months (range, 6 to 12 months), and the mean shrinkage of the radiolucency was 65% (range, 5% to 91%). All cytologic samples obtained at 3 and 6 months contained cytokeratin-10-positive epithelial cells. At the time of cystectomy, 9 of 14 cases were cytokeratin-10 negative and no longer showed histologic features of OKCs. Specimens from the remaining 5 patients were histologically consistent with OKC and were cytokeratin-10 positive. Mean treatment time of the cytokeratin-10-positive group was 7 months, and that of the cytokeratin-10-negative group was 9 months. CONCLUSION: Epithelial dedifferentiation and loss of cytokeratin-10 production were observed in 64% of patients treated by cyst decompression/irrigation after a 9-month average treatment time. Longitudinal follow-up of these patients will determine whether this change is associated with lower rates of recurrence than alternative OKC therapy.     

Primary fixation of vervet monkey oral epithelium for ultrastructural investigation-SEM

Vervet monkey attached gingiva and alveolar mucosa was used to investigate the effect of primary fixative composition and osmolarity on the scanning electron microscope appearance and epithelial cell surface feature density. Primary fixation was obtained using 12 different fixatives with osmolarities varying between 320-2010mOsm followed by further standard SEM processing procedures. All primary fixatives investigated produced acceptably fixed oral epithelium for SEM study, showing all the morphologic features characteristic of either keratinized or non-keratinized oral tissue. Point counting revealed that the density of microvilli of attached gingiva epithelial cells when fixed at 2010mOsm was 72 +/- 8% of the cell surface area. This decreased to 40 +/- 5% when fixed at 320mOsm. Similarly the microplication density of the alveolar mucosa epithelial cells decreased from 70 +/- 5% at 2010mOsm to 43 +/- 7% at 320mOsm. Both these differences proved to be highly significant.     

A comparative study of epithelial cell proliferation between the odontogenic keratocyst, orthokeratinized odontogenic cyst, dentigerous cyst, and ameloblastoma

OBJECTIVES: The aim of the present study was to compare the proliferation index of the epithelial cells between odontogenic keratocysts (OKC), orthokeratinized odontogenic cysts (OOC), dentigerous cysts (DC), and ameloblastomas. MATERIALS AND METHODS: The proliferation index, employing a novel cell proliferation marker IPO-38, was studied by the immunohistochemical technique in 10 OKC, seven OOC, eight DC and 10 ameloblastomas. RESULTS: The ameloblastoma had no higher labeling index (LI) of IPO-38 than the OKC (P = 0.910) but had higher LI than the OOC (P = 0.001) and DC (P = 0.000); the OKC had higher LI than the OOC (P = 0.002) and DC (P = 0.000); and the OOC had higher LI than the DC (P = 0.011). IPO-38-positive cells in the OKC and OOC were located principally in the suprabasal cell layers while the ameloblastoma were found in the peripheral portion in particularly, the follicular and plexiform types. CONCLUSION: These findings support previous studies that the proliferation indices are useful in predicting the different biological behavior of the odontogenic lesions and the OKC should be regarded as a benign tumor rather than simply an odontogenic cyst.     

Surface characteristics of cells from different layers of keratinized and non-keratinized oral epithelia

Portions of clinically healthy non-keratinized and keratinized oral epithelia were removed from adult vervet monkeys (Cercopithecus aethiops). The epithelium was separated from the underlying lamina propria by trypsin digestion, following which the epithelial cells were separated from the various epithelial layers. These were examined with the light and scanning electron microscope. Cells from non-keratinized epithelia have surface microplications while those from keratinized epithelia show microvilli and pits. Two distinct types of cell are therefore present. It is suggested that the different surface appearances are related to different types of mechanical adhesion between the cells.     

Evaluation of collagen in connective tissue walls of odontogenic cysts –A histochemical study

J Oral Pathol Med (2011) 40 : 257–262 Background: The purpose of this study was to evaluate the nature of collagen in the connective tissue walls of odontogenic cysts, like the odontogenic keratocyst (OKC), dentigerous cyst and radicular cyst using picrosirius red stained sections. Furthermore, it was intended to assess if the capsular connective tissue can affect the nature of overlying epithelium, thus emphasizing the role of epithelial–mesenchymal interactions in biological behaviour of the cysts. Materials and method: The material for the study included 51 formalin‐fixed paraffin‐embedded tissue blocks (15 odontogenic keratocyst, 15 dentigerous cysts, 15 radicular cysts and four normal mucosa and two dental follicular tissue as controls), retrieved from the Department of Oral Pathology and Microbiology, MCODS, Manipal. Tissue blocks were sectioned at 5‐μm thickness, stained with picrosirius red stain and observed with polarization and light microscopy. Results: Few sections of OKC and dentigerous cyst exhibited greenish‐yellow birefringence in sub‐epithelial region, whereas others showed a yellowish‐orange birefringence under polarization microscopy. Most radicular cysts had yellowish‐orange to orange birefringence. Shift in colour in case OKC and dentigerous cyst was attributed to the presence of inflammation in those sections. These regions also exhibited either a change in phenotype or thickness of overlying epithelium. Conclusion: This technique can be used to study the nature of collagen fibres in odontogenic cyst walls. Further studies with an increased sample size and using various epithelial and mesenchymal markers and ssDNA antibodies should be carried out to confirm the effect of epithelial–mesenchymal interactions on the nature of epithelium of odontogenic cysts.     

CD1a-positive cells in odontogenic cysts

Langerhans cells (LC) are bone marrow-derived cells that have a CD1a-positive immunophenotype and are an important portion of the cell-mediated immune response. The aim of this study was an immunohistochemical evaluation of CD1a positive cells in different types of oral cysts. Fifty-five cysts were studied: 18 odontogenic keratocysts (OKC), of which five were orthokeratotic and 13 parakeratotic; 19 radicular cysts; and 18 dentigerous cysts. Positive LC was 80% for orthokeratotic OKC, 33% for parakeratotic OKC, approximately 35% for radicular cysts, and approximately 20% for dentigerous cysts. The results show that OKC with well-differentiated epithelial linings presented a greater number of LC than the other cysts. However, when the cyst wall was inflamed there were no differences in LC expression in the different types of cysts. The data confirm that LC distribution seems to be associated with the degree of differentiation of the epithelia.