Epidermal growth factor receptor distribution in pericoronal follicles: relationship with the origin of odontogenic cysts and tumors

A Comparison of Immunohistochemical Expression of Epidermal Growth Factor Receptor and Human Epidermal Growth Factor Receptor 2 in Dental Follicles with Different Radiographic Sizes

Background

Odontogenic cysts and tumors develop from the dental follicle of asymptomatic impacted teeth. Odontogenic tissues express the epidermal growth factor receptor family (EGFR), which mediates cell proliferation, survival, and neoplastic differentiation. The present study aimed to compare the immunohistochemical expression of EGFR and human epidermal growth factor receptor 2 (HER2) in the dental follicle of impacted wisdom teeth with normal and abnormal radiographic size.

Methods

In this analytical study, immunohistochemical staining of EGFR and HER2 was performed on 30 normal and 30 abnormal follicles of impacted third molars. Follicles with a width of <2.5 mm were considered normal, whereas those with a width of ≥2.5 mm were regarded as abnormal. The immunoreactive score (IRS) was used to report the expression levels of EGFR and HER2. The obtained data were analyzed using SPSS software. Age and sex were compared in normal and abnormal groups with independent t test and Chi square test, respectively. P<0.05 was considered statistically significant.

Results

The EGFR and HER2 overall expression was high in all normal and abnormal follicles. The comparison of the percentage of stained cells and intensity of EGFR and HER2 staining in normal and abnormal follicles were not significantly different (P=0.73, P=0.63, P=0.95, respectively).

Conclusion

Due to the high expression of EGFR and HER2 in normal and abnormal follicles, as well as the lack of significant differences in these two groups, the radiographic size of dental follicles might not indicate the potential capabilities of their cells, and more research in this field is recommended.

Significance of EGFR investigation in odontogenic keratocyst: a narrative review

BACKGROUND

The recent classification of odontogenic keratocysts (OKSs) recognized them as benign neoplasms, although previous findings have revealed their aggressive nature. Immunohistochemical and molecular analyses have investigated OKSs, but the role of epidermal growth factor receptor (EGFR) has not been fully investigated, despite the importance of this oncogene in the process of carcinogenesis in tumors of epithelial origin. The EGFR protein is usually overexpressed, and the EGFR gene is mutated or amplified.

AIMS OF STUDY

This brief review aims to emphasize the importance of EGFR detection in these types of cysts.

METHODS AND RESULTS

It was revealed that the majority of the studies examined EGFR protein expression using immunohistochemical methods; however, considering EGFR gene variants, mutations were less explored in the previous period from 1992 to 2023. Although EGFR gene polymorphisms are clinically important, they were not identified in the present study.

CONCLUSIONS

In light of the current significance of EGFR variants, it would be beneficial to examine them in odontogenic lesions. This would enable resolving of discrepancies about their nature, and potentially enhance classifications OKCs in the future.

Expression of epithelial growth factors and of apoptosis-regulating proteins, and presence of CD57+ cells in the development of inflammatory periapical lesions

The mechanisms that stimulate the proliferation of epithelial cells in inflammatory periapical lesions are not completely understood and the literature suggests that changes in the balance between apoptosis and immunity regulation appear to influence this process.

Surgical ciliated cyst after a mandibular surgery: a particular case report and review of the literature

Background

Surgical ciliated cyst is a rare clinicopathological lesion that appears in patients who undergo maxillofacial surgery. In this report we present a particular mandibular case and we discuss the etiopathogenesis and clinicopathological features of this pathology after reviewing the current literature, as well as the origin of its respiratory epithelial profile.

Case presentation

The patient is a 67-year-old male with an irregular radiolucency in a previously tooth extracted area of the mandible. The histopathological study revealed a cystic lesion with a connective wall with chronic inflammation, partially lined by a ciliated pseudostratified epithelium. PAS and CK19 stains showed the respiratory characteristics of this epithelium and confirmed the final diagnosis of mandibular surgical ciliated cyst.

Conclusions

Surgical ciliated cyst is an uncommon entity associated with maxillofacial surgical procedures with bone and nasal cartilage grafts. In our case, treatment with growth factors present in platelet-rich plasma could explain the respiratory changes observed in the cystic epithelial lining.”

Revisiting the human dental follicle: From tooth development to its association with unerupted or impacted teeth and pathological changes

Dental follicles are involved in odontogenesis, periodontogenesis, and tooth eruption. Dental follicles are unique structures, considering that their remnants can persist within the jawbones after odontogenesis throughout life if the tooth does not erupt. Pathological changes may occur in these tissues as individuals age. The changes range from benign to life threatening. Thus, the assessment of age-related changes in dental follicles associated with unerupted teeth is of paramount importance. In this review, we summarize the physiological roles and changes in dental follicles in odontogenesis, tooth eruption, and aging, in addition to the pathological changes associated with these structures. We encourage investigators to consider this peculiar tissue as a unique model and explore its potential to clarify its importance from the viewpoints of developmental biology, tissue physiology, and pathology.

Changes in Cellular Regulatory Factors before and after Decompression of Odontogenic Keratocysts

Decompression followed by enucleation, which is one of the treatments used for odontogenic keratocysts (OKCs), is frequently used in OKC lesions of large sizes. This method offers the advantage of minimizing the possibility of sensory impairment without creating a wide-range bone defect; moreover, the recurrence rate can be significantly lower than following simple enucleation. This study aimed to assess the changes in histology and expression of proliferation markers in OKCs before and after decompression treatment. A total of 38 OKC tissue samples from 19 patients who had undergone decompression therapy were examined morphologically and immunohistochemically to observe changes in proliferative activity before and after decompression. The markers used for immunohistochemistry (IHC) staining were Bcl-2, epidermal growth factor receptor (EGFR), Ki-67, P53, PCNA, and SMO. The immunohistochemistry positivity of the 6 markers was scored by using software ImageJ, version 1.49, by quantifying the intensity and internal density of IHC-stained epithelium. The values of Bcl-2, Ki-67, P53, proliferating cell nuclear antigen (PCNA), and SMO in OKCs before and after decompression showed no significant change. No correlation between clinical shrinkage and morphologic changes or expression of proliferation and growth markers could be found. There was no statistical evidence that decompression treatment reduces potentially aggressive behavior of OKC within the epithelial cyst lining itself. This might indicate that decompression does not change the biological behavior of the epithelial cyst lining or the recurrence rate.

Detection of MAPK/ERK pathway proteins and KRAS mutations in adenomatoid odontogenic tumors

OBJECTIVE

This study aimed to assess the frequency of KRAS mutation and its association with the presence of the MAPK/ERK signaling pathway proteins in adenomatoid odontogenic tumors.

STUDY DESIGN

Paraffin-embedded tissue samples from nine cases of adenomatoid odontogenic tumor were used. Genomic DNA was extracted from each sample; in one case, genetic mutations in 50 cancer-associated genes were examined by next-generation sequencing. Hotspot mutations in the RAS family were analyzed by Luminex assay using the remaining eight cases. Subsequently, immunohistochemistry for KRAS, CRAF, BRAF, EGFR, ERK, MEK, and BRAFV600E was performed.

RESULTS

A KRAS G12D missense mutation was detected in the DNA sequence of the tumor cells, but it was not detected in the stromal tissue. KRAS G12V and KRAS G12R mutations were detected in two and four cases, respectively. For immunohistochemistry, all the cases were EGFR, KRAS, BRAF, CRAF positive, one case was ERK negative,and one case was MEK and ERK negative, all the other remaining cases were MEK and ERK positive.

CONCLUSION

KRAS mutation at codon 12 and the presence of MAPK/ERK pathway proteins were detected suggesting their association with tumorigenesis of adenomatoid odontogenic tumors.

Association between tooth impaction and odontogenic lesions: A matched case-control study

Background: Impacted tooth is common in dental practice. Dentists usually remove them if they are associated with any pathologic sign or symptom. The challenge is whether to extract the asymptomatic tooth or not. This study was conducted to determine the association between developmental odontogenic cysts and tumors and impacted and unerupted teeth, if left untreated. Methods: In this matched case-control study, 262 participants were recruited in case and control groups to evaluate the association between the presence of odontogenic cyst and tumors and unerupted and impacted teeth in patient records in the School of Dentistry, Shahid Beheshti University of Medical Sciences during 2000-2002. The controls referred to a dental radiology center for routine OPG. We also recorded the data on age, gender, the involved jaw, and type of lesion. All patients' records were reviewed by the research director and an oral pathologist separately. The variables that were matched as confounders were age, gender, and the site of the involved jaw. Results: Results of conditional logistic regression analysis showed that the presence of odontogenic lesions was associated with impacted teeth (OR = 6.9), and not associated with the involved jaw and unerupted teeth. Conclusion: Impacted teeth could be considered as a potential risk factor for the presence of odontogenic lesions.

EGFR is not amplified in ameloblastoma

OBJECTIVE

The aim of this study was to investigate alterations in the EGFR gene and its protein expression for a better understanding of the biologic behavior of ameloblastoma.

STUDY DESIGN

Twenty-five samples of ameloblastoma were selected, and dual-color fluorescence in situ hybridization assay was performed. The results of the assay and immunohistochemistry reaction for EGFR and Ki67 were associated with clinicopathologic features and recurrence.

RESULTS

All analyzed cases presented disomy without any gene polysomy or amplification. With regard to EGFR immunoexpression, 3 cases (12%) were considered negative, and 22 (88%) were positive, of which 13 (52%) were weak and 9 (36%) were strong. All samples presented low positivity for Ki67. There was no association between EGFR expression and clinicopathologic features or recurrence (P > .05). In some cases, EGFR immunoexpression was observed without gene amplification.

CONCLUSIONS

Ameloblastoma development, progression, or recurrence does not appear to be related to EGFR amplification or polysomy.

Primary intraosseous squamous cell carcinoma arising in dentigerous cyst: Report of 2 cases and review of the literature

Dentigerous cysts are one of the most common odontogenic cysts of the oral cavity. Odontogenic cysts can give rise to a variety of neoplasms. Carcinoma arising in a dentigerous cyst is extremely rare, with a review of literature showing near 30 cases. The present report describes 2 cases of primary intraosseous squamous cell carcinoma originated from a dentigerous cyst. The first one refers to a 57-year old female with a persistent lesion in the left retromolarregion and diagnosed with squamous cell carcinoma originated fromthe incomplete excision of the lower third molar follicle during its surgical extraction. The second case describes the case of an 18-year old male with an impacted upper canine with previous history of infection and swelling of the oral cavity. The histopathological study revealed the malignization of the follicle surrounding the dental crown. These two cases confirmed the importance of the histopathological study of all the tissue samples obtained from surgical procedures. Although the development of a malignant lesion from a dentigerous cyst is rare and its clinical-radiological features are apparently innocuous, this entity should be considered as a differential diagnosis.

Key words:Dentigerous cyst, odontogenic cyst, squamous cell carcinoma, primary intraosseous squamous cell carcinoma, odontogenic carcinoma.

Expression of Bcl-2 and epithelial growth factor receptor proteins in keratocystic odontogenic tumor in comparison with dentigerous cyst and ameloblastoma

Background:

Keratocystic odontogenic tumor (KCOT) is a developmental odontogenic cyst on which various investigations have been focused due to its biological activities, high tendency to recur and different growth mechanisms in comparison with other cystic lesions. Previous studies have shown different biological and proliferative activities for the lining epithelium of KCOT. The aim of this study was immunohistochemical evaluation of Bcl-2 and epidermal growth factor receptor (EGFR) expression in KCOT compared with dentigerous cyst and ameloblastoma.

Materials and Methods:

Formalin-fixed and paraffin-embedded tissue sections of 16 cases of KCOT, 16 cases of dentigerous cyst and 16 cases of ameloblastoma were immunohistochemically analyzed to determine Bcl-2 and EGFR proteins’ expression. Biotin-Stereotavidin method was used. It was observed by two oral pathologists separately, and the data were analyzed by Mann–Whitney and Kruskul–Wallis. P < 0.05 was considered as significant.

Results:

Regardless of staining intensity, all cases of ameloblastoma and KCOT except dentigerous cases were positively stained for Bcl-2. Expression of Bcl-2 was higher in the peripheral layer of ameloblastoma and basal layer of KCOT. Furthermore, all cases of ameloblastoma and dentigerous cysts except KCOT samples were positively stained for EGFR. Expression of EGFR was higher in the peripheral layer of ameloblastoma and basal layer of dentigerous cysts.

Conclusion:

According to the expression of — Bcl-2 in ameloblastoma and KCOT, and no expression of EGFR in KCOT, it can be concluded that the biological activity and growth mechanisms of KCOT are different compared with other cystic lesions. However, the aggressive potential of KCOT is not as severe as that of a neoplasm such as ameloblastoma.

The importance of histopathologic analysis of pericoronal follicles for the early identification of ameloblastomas

The objective of this study was to discuss the importance of performing histopathological examination of pericoronal follicles as a routine procedure, so as to enable the early identification of odontogenic lesions. We describe two clinical cases with histopathological diagnoses of ameloblastomas who did not show clinical or radiographic signs of disease before microscopic examination.

Quantitative and qualitative analysis of epidermal growth factor receptor expression in pericoronal follicles in predicting proliferative potential

OBJECTIVE

The odontogenic epithelium in pericoronal follicles (PFs) are known to proliferate to form cysts and tumors. This epithelium is mostly composed of the reduced enamel epithelium (REE) and odontogenic rests (OR). The objective of the present study was to evaluate the epidermal growth factor receptor (EGFR) immunoexpression in these PFs to assess their proliferative potential.

STUDY DESIGN

The immunoexpression of EGFR in 30 PFs were assessed by two independent observers for intensity, percentage and the location of the EGFR staining.

RESULTS

EGFR immunoexpression was noted in 100% of the follicles. A greater proportion of the follicles showed strong intensity (70%). It was noted that nearly 54% of the follicles demonstrated more than 50% of cells with EGFR immunolabelling. EGFR showed combined cytoplasm and membrane staining (40%) and cytoplasm only staining (37%). The analysis of the REE and OR individually for the above-mentioned parameters did not show statistical significance.

CONCLUSION

The increased intensity and overall positivity of the epithelium in follicles shows that odontogenic epithelium is responsive to EGFR mediated growth factors. The predominant combined staining pattern is suggestive of increased potential for the epithelium to undergo cystic or neoplastic proliferation.

Analysis of the proliferative potential of odontogenic epithelial cells of pericoronal follicles

AIM

To evaluate the proliferative potential and the cell proliferation rate of odontogenic epithelial cells.

MATERIALS AND METHODS

Forty-two cases of pericoronal follicles of impacted third molars were submitted to silver impregnation technique for quantification of argyrophilic nucleolar organizer regions (AgNOR) and immunohistochemical staining for EGFR and Ki-67. For AgNOR quantification, the mean number of active nucleolar organizer regions per nucleus (mAgNOR) and the percentage of cells with 1, 2, 3 and 4 or more AgNORs per nucleus (pAgNOR) were quantified. Ki-67 immunolabeling was quantified, whereas for EGFR, a descriptive analysis of staining patterns (membrane, cytoplasm or membrane + cytoplasm positivity) was performed. We evaluated the reduced epithelium of the enamel organ and/or islands of odontogenic epithelium present in the entire connective tissue.

RESULTS

mAgNOR were 1.43 (1.0-2.42) and were significantly different among pericoronary follicles from upper and lower teeth (p = 0.041). Immunostaining of Ki-67 was negative in all cases. EGFR immunolabeling was found mainly in the cytoplasm and was more intense in islands and cords when compared to reduced epithelium of the enamel organ.

CONCLUSION

Odontogenic epithelial cells of some pericoronal follicles have proliferative potential, suggesting their association with the development of odontogenic lesions.

CLINICAL SIGNIFICANCE

The authors suggest that nonerupted, especially of the lower teeth, should be monitored and if necessary removed.

Analysis of the immunoexpression of Ki-67 and Bcl-2 in the pericoronal tissues of impacted teeth, dentigerous cysts and gingiva using software image analysis

BACKGROUND

Pericoronal tissue is the soft tissue located between the bony crypt and the impacted tooth, which is histologically composed of fibrous connective tissue and is usually lined by the reduced enamel epithelium. Increased epithelial cell proliferation in the pericoronal tissue is associated with pathological changes such as development of an odontogenic cyst or an epithelial odontogenic tumor. This study is an attempt to evaluate and compare the proliferative index in the epithelium surrounding the impacted third molar teeth, dentigerous cysts, and gingiva.

MATERIALS AND METHODS

A case control study on pericoronal tissues and dentigerous cysts was carried out using immunomarkers. Forty pericoronal tissues were obtained from asymptomatic impacted third molars with pericoronal radiolucency less than 2.5 mm. Samples of 20 dentigerous cysts and normal gingiva were also included. Routine hematoxylin and eosin and immunostaining for Ki-67, a cell proliferation marker and Bcl-2, an anti apoptotic protein were performed on sections of pericoronal tissues, dentigerous cysts, and gingival tissues. The percentage of Ki-67-positive cells and Bcl-2 positive areas was found using the DigiPro™ version 4.0 Image analysis software. Bcl-2 immunopositivity and Ki-67-Li were analyzed using the Chi-square test and paired t-test. P- values of less than .05 were considered to indicate statistical significance.

RESULTS

The immunohistochemical analysis revealed overexpression of Bcl-2 in the pericoronal tissues with squamous metaplasia, which was comparable to the dentigerous cyst. Ki-67 Li of the pericoronal tissue with squamous metaplasia was equal to the proliferative index of the dentigerous cyst. The expression of Ki-67 Li and inflammatory cells were highly significant (P < 0.0001).

CONCLUSIONS

The results of this study indicate that the pericoronal tissues of asymptomatic impacted third molars may be actively proliferating and normal pericoronal radiolucency cannot serve as an indicator for the differentiation potential.

The relation of pericoronal third molar follicle dimension and bcl-2/ki-67 expression: An immunohistochemical study

Background:

Most common impacted teeth are the mandibular third molars and decision about extraction of them is usually controversial. The presence of pericoronal pathologic changes is an acceptable reason for removal of impacted teeth. Differences in the proliferation rate and apoptosis of odontogenic epithelial cells may influence on the formation of odontogenic epithelial lesions. Therefore, the aim of the present study is to evaluate the immunohistochemical expression of the bcl-2 apoptosis-inhibiting protein and the cell-cycle-related ki-67 antigen in pericoronal follicle of impacted third molars with ≥2.5 mm and <2.5 mm radiolucency.

Materials and Methods:

This was a cross-sectional study that 20 follicles with <2.5 mm radiolucency and 20 follicles with ≥2.5 mm radiolucency were selected by a professional radiologist in digital panoramic radiographs and then referred to a surgeon. Formalin fixed paraffin-embedded tissues were immunohistochemical analyzed for immunoreactivity of bcl-2 protein and ki-67 antigen. The data was analyzed using logistic regression, Spearman correlation coefficient and t-test and Mann-Whitney. P<0.05 was considered significant.

Results:

The findings showed correlation between size of the third molar's follicles and expression of bcl-2 protein (P < 0.001, r = 0.556) but there was no correlation between size of third molar's follicles and staining with ki-67 antigen (P = 0.546, r = 0.098). The follicles with radiolucency ≥2.5 mm showed increased immunoreactivity for bcl-2 protein.

Conclusion:

The results of study suggest that impacted third molars with radiolucency ≥2.5 mm may be associated with deregulation of cell death, indicated with increased expression of the anti- apoptotic protein bcl-2, while cell proliferation (ki-67) does not seem to play a significant role.

Pericoronal follicles of asymptomatic impacted teeth: a radiographic, histomorphologic, and immunohistochemical study

Objective. To associate radiographic and histopathological features of pericoronal follicles (PFs) of asymptomatic impacted teeth and evaluate cell proliferation and apoptosis in the epithelium. Study Design. Epithelium and mesenchyme of radiographically normal (NPF ≤ 2.5 mm) and hyperplastic (HPF 2.6 to 5 mm) PF (n = 140) were studied histologically. Cell proliferation (PI) and epithelial apoptosis were evaluated by Ki-67 and bcl-2 expression in 14 NPFs and 10 dentigerous cysts (DCs). Results. Radiographically, 127 were NPFs and 13 were HPFs; 87.8% of total PFs exhibited epithelium on the surface. Reduced enamel epithelium was observed in 78 (61.4%) NPFs and 6 (46.2%) HPFs, squamous metaplasia in 17 (13.4%) NPFs and 4 (30.8%) HPFs, and cystic epithelium in 15 (11.8%) NPFs and 3 (23%) HPFs. Mean PI was 1.97 ± 1.25 and 7.97 ± 1.74 in the epithelial component of NPF and DC, respectively; bcl-2 positive expression was observed in 9 (64.3%) NPFs and 7 (70%) DCs. Conclusion. The scant epithelial remnant proliferation could imply low risk for development of odontogenic pathologies in the absence of an additional stimulus.

Immunohistochemical expression of p63, epidermal growth factor receptor (EGFR) and notch-1 in radicular cysts, dentigerous cysts and keratocystic odontogenic tumors

The aim of this study was to assess the immunohistochemical expression of p63 protein, epidermal growth factor receptor (EGFR) and Notch-1 in the epithelial lining of radicular cysts (RC), dentigerous cysts (DC) and keratocystic odontogenic tumors (KOT). For this study, 35 RC, 22 DC and 17 KOT were used. The clinical and epidemiological data were collected from the patient charts filed in the Oral Pathology Laboratory, University of Ribeirão Preto, Brazil. Immunohistochemical reactions against the p63, EGFR and Notch-1 were performed in 3-µm-thick histological sections. The slides were evaluated according to the following criteria: negative: <5% of positive cells, low expression: 5-50% of positive cells, and high expression: >50% of positive cells. Moreover, the intensity of EGFR and Notch-1 expressions was also evaluated. Fisher's exact test and Spearman's correlation coefficients were used for statistical analysis, considering a significance level of 5%. Almost all cases demonstrated p63, EGFR and Notch-1 expressions. The p63 expression was significantly higher in KOT (p<0.001). Positive correlation between these immunomarkers was observed. These findings suggest the participation of p63, EGFR and Notch-1 in the development, maintenance and integrity of cystic odontogenic epithelial lining, favoring lesion persistence. The high expression of p63 in KOT suggests that it may be related to their more aggressive biological behavior and marked tendency to recurrence.

Collagen and elastic fibers in odontogenic entities: analysis using light and confocal laser microscopic methods

Dentigerous cyst (DC) and keratocystic odontogenic tumor (KOT) are odontogenic lesions arising from epithelial elements, such as those observed in dental follicles (DF), that have been part of the tooth forming apparatus. These lesions show different clinical and histological characteristics, as well as distinct biological behavior. This study aimed to qualify and quantify collagen and elastic fibers by means of histochemical techniques with light and confocal laser microscopic methods in three odontogenic entities. Eleven DF, 13 DC (n=10 with inflammation, n=3 without inflammation) and 13 KOT were processed to the following techniques: Hematoxylin and Eosin, Masson’s Trichrome, Picrosirius, Direct Blue, and Orcein. DF and DC without inflammation exhibited collagen with similar characteristics: no parallel pattern of fiber orientation, thick fibers with dense arrangement, and absence of distinct layers. A comparison between DC with inflammation and KOT revealed similar collagen organization, showing distinct layers: thin collagen fibers with loose arrangement near the epithelium and thick fibers with dense arrangement in distant areas. The only difference found was that KOT exhibited a parallel collagen orientation in relation to the odontogenic epithelia. It may be suggested that the connective tissue of DC is a reactive tissue, inducing an expansive growth associated with fluid accumulation and inflammatory process, which in turn may be present as part of the lesion itself. In KOT, loosely arranged collagen may be associated with the behavior of the neoplastic epithelium.

Odontogenic epithelium: immunolabeling of Ki-67, EGFR and survivin in pericoronal follicles, dentigerous cysts and keratocystic odontogenic tumors

The aim of this study was to evaluate the biological profile of odontogenic epithelium by immunolabeling of epidermal growth factor receptor (EGFR), Ki-67 and survivin in keratocystic odontogenic tumors (KOT), dentigerous cysts (DC), and pericoronal follicles (PF). Immunohistochemical analysis was performed in 13 KOTs, 14 DCs and 9 PFs. Immunolabeling was analyzed in the basal and suprabasal layers of KOTs and DCs, and in the islands of odontogenic epithelium and/or reduced enamel epithelium of PFs. KOTs showed the highest proliferation rate among the three groups, mainly in suprabasal layers. EGFR immunolabeling was observed mainly in the cytoplasm in basal and suprabasal layers of KOTs and in the suprabasal layer of DCs. Immunolabeling in both membrane and cytoplasm was greater in PFs. In PFs, membrane-only staining was observed. Survivin immunolabeling showed a greater percentage of positive cells (scoring +++) in the suprabasal layer of KOTs. In DCs, both layers showed similar percentages of cells scoring +++; PFs showed the highest percentage of these cells. In KOTs, epithelial cells showed stimulus-independent neoplastic proliferative characteristics, suggesting the presence of a suprabasal proliferative compartment, maintained by inhibition of apoptosis. In DCs, the basal layer seemed to proliferate in response to stimulus. Although PFs showed low proliferative activity, the expression of EGFR indicates that some cells have a high capacity to respond to stimuli, which could probably explain the origin of odontogenic lesions.

Pathological changes and immunoexpression of p63 gene in dental follicles of asymptomatic impacted lower third molars: an immunohistochemical study

OBJECTIVE

The aim of this study was to examine the pathologic changes and immunoexpressivity of p63 gene in dental follicles (DFs) of asymptomatic partially and completely impacted lower third molars.

STUDY DESIGN

Clinical and radiologic examinations included 50 DFs with no signs of abnormal radiolucency (follicular space <2.5 mm), taken from 50 patients.

RESULTS

Histopathologic examinations of the specimens revealed 47 normal dental follicular tissues, 1 ameloblastoma, and 2 dentigerous cysts. p63 Immunoexpressivity was stronger in the DFs of the group with completely impacted teeth (64%),than it was in the case of DFs of the group with partially impacted teeth (40%).

CONCLUSIONS

Stronger p63 gene immunoexpression in the group with completely impacted teeth might be a consequence of bigger number of stem cells than it is in the case of the group with partially impacted teeth. This study also supports prophylactic removal of impacted teeth because of the development of pathologies associated with them.

Determination of potential cellular proliferation in the odontogenic epithelia of the dental follicle of the asymptomatic impacted third molars

PURPOSE

The aim of this study is to determine the proliferative potentials of dental follicles (DF) of radiographically asymptomatic impacted third molar teeth by using Ki-67 and mini-chromosome maintenance protein 2 (MCM-2) proliferation markers, and to discuss whether there is any necessity for the removal of all impacted third molars by detecting the potential of the developing cysts and tumors of its DF.

MATERIALS AND METHODS

This study involved 59 DF of 54 patients referred for clinically and radiographically asymptomatic lower impacted third molars. Thirteen healthy gingiva tissues obtained during the impacted third molar operation in 13 patients served as a control group. DF widths on periapical radiographs below 2.5 mm were included in the study. The epithelial and mesenchymal components of DF were examined histologically. All specimens were stained with periodic acid Schiff, Alcian blue, and mucin for the evaluation of mucous cell prosoplasia. Epithelial cell proliferation was determined by using immunohistochemical labeling.

RESULTS

The histologic examinations showed 11.9% mucous cell prosoplasia, 55.9% squamous metaplasia, 15.3% glandular epithelium, and 33.9% inflammation. Ki-67 expression was found to have higher values than MCM-2 expression in controls 6.15 (3.18) and 10.53 (5.77) and in DF 4.46 (1.39) and 5.89 (2.89), respectively. The expression of both proliferation markers in the basal epithelial cells, mucous, and squamous epithelium and inflammatory cells were statistically significant (P < .01).

CONCLUSION

The results of this study indicate that the odontogenic epithelium in DF of asymptomatic impacted third molars might be actively proliferating and may be an indicator for the differentiation potential of DF. It would also seem that the inflammation observed in the mesenchymal components of DF up-regulate the cell turnover of odontogenic epithelium and lead to proliferation. Based on these observations, we support prophylactic removal of impacted third molars.