Byung-Do Lee

Upregulation of heme oxygenase-1 in oral epithelial dysplasias

The expression of heme oxygenase-1 (HO-1), stress-related enzyme, is induced in leukaemia and some cancer tissues, but relatively little is known about the differential pattern of HO-1 expression and proliferation in premalignant lesions of the epithelial oral mucosa. The purpose of this study was to evaluate whether HO-1 expression and proliferation were increased in preneoplastic lesions compared to normal and oral cancer tissues. Immunohistochemical staining was used to examine the expression patterns of HO-1 and proliferating cell nuclear antigen (PCNA) in a series of normal mucosa and mild-to-severe cases of oral epithelial dysplasia (OED) and oral squamous cell carcinoma. Both HO-1 and PCNA are expressed in the basal cells of normal oral mucosa. In patients with OED and carcinoma in situ, immunostaining for PCNA and HO-1 was more intense, and gradually extended into the superficial layers of the mucosa. HO-1 and PCNA expression was correlated with the degree of epithelial dysplasia. Oral squamous cell carcinoma also showed elevated expression of HO-1, but this level was not higher than in severe OED or carcinoma in situ. These results suggest that the up-regulation of HO-1 in premalignant oral lesions is part of an early cytoprotection mechanism against carcinogenesis in the oral mucosa.

Evaluation of the radiopacity and cytotoxicity of resinous root canal sealers

The aim of this study was to evaluate the radiopacity and cytotoxicity of three resin-based (AH 26, EZ fill and AD Seal), a zinc oxide-eugenol-based (ZOB Seal), and a calcium hydroxide-based (Sealapex) root canal sealers. Specimens, 10 mm in diameter and 1 mm in thickness, were radiographed simultaneously with an aluminum step wedge using occlusal films, according to ISO 6876/2001 standards. Radiographs were digitized, and the radiopacity of sealers was compared to the different thicknesses of the aluminum step wedge, using the Scion image software. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the cytotoxicity of each material was determined in immortalized human periodontal ligament (IPDL) cells. The results demonstrated that EZ fill was the most radiopaque sealer, while Sealapex was the least radiopaque (p 0.05). These results indicate that resin-based root canal sealer is more biocompatible and has advantage in terms of radiopacity.

Quantitative Analysis of Endodontic Treatment for Periapical Lesions in Intraoral Radiographs

Intraoral radiographs have been taken to diagnose periapical lesions. Subsequent endodontic treatment needs to be evaluated quantitatively, that is often difficult due to various imaging factors as well as subjective visual interpretation. Therefore, we sought to establish an image analysis based quantitative model to evaluate endodontic treatments (40 effective and 43 noneffective cases). To normalize an image, the dentin area and the background were used as references. In each pair of images representing before and after treatment, the lesion area was manually selected by experts and segmented by tophat operation. Numerous features representing the effective bone healing were calculated. Using relative differences of selected features, an evaluation model was derived by logistic regression analysis. Gray level intensity and textural differences obtained from lesions significantly increased in the effectively treated cases. The model provided the accuracy of 80.7%. Our quantitative model may be helpful to evaluate endodontic treatment in clinical settings and in animal studies.

Glandular odontogenic cyst mimicking ameloblastoma in a 78-year-old female: A case report

Glandular odontogenic cyst (GOC) is a rare, potentially aggressive jaw lesion. The common radiographic features include a well-defined radiolucency with distinct borders, presenting a uni- or multilocular appearance. A cystic lesion in the posterior mandible of a 78-year-old female was incidentally found. Radiographs showed a unilocular lesion with a scalloped margin, external root resorption of the adjacent tooth, and cortical perforation. This lesion had changed from a small ovoid shape to a more expanded lesion in a period of four years. The small lesion showed unilocularity with a smooth margin and a well-defined border, but the expanded lesion produced cortical perforation and a lobulated margin. The provisional diagnosis was an ameloblastoma, whereas the histopathological examination revealed a GOC. This was a quite rare case, given that this radiographic change was observed in the posterior mandible of an elderly female. This case showed that a GOC can grow even in people in their seventies, changing from the unilocular form to an expanded, lobulated lesion. Here, we report a case of GOC with characteristic radiographic features.

Eosinophilic granuloma in the anterior mandible mimicking radicular cyst.

Eosinophilic granuloma is a common expression of Langerhans cell histiocytosis and corresponds with typical bone lesions. The radiographic appearance of eosinophilic granuloma in the jaw is variable and not specific. It may resemble periodontitis, radicular cyst, or malignancies. The purpose of this report is to describe the characteristic radiographic features of eosinophilic granuloma of a 39-year-old male. The lesion in the anterior mandible was first diagnosed as radicular cyst because the radiographic findings were ovoid radiolucent lesion with well-defined border. However, careful interpretation revealed a non-corticated border and floating tooth appearance that were the characteristic radiographic features for the differential diagnosis. Early clinical signs of eosinophilic granuloma can occur in the jaw and a bony destructive lesion might be mistaken for periodontitis or an odontogenic cystic lesion; therefore, careful interpretation of radiographs should be emphasized.

A magnetic resonance imaging study on changes in rat mandibular bone marrow and pulp tissue after high-dose irradiation

Purpose This study was designed to evaluate whether magnetic resonance imaging (MRI) is appropriate for detecting early changes in the mandibular bone marrow and pulp tissue of rats after high-dose irradiation. Materials and Methods The right mandibles of Sprague-Dawley rats were irradiated with 10 Gy (Group 1, n=5) and 20 Gy (Group 2, n=5). Five non-irradiated animals were used as controls. The MR images of rat mandibles were obtained before irradiation and once a week until week 4 after irradiation. From the MR images, the signal intensity (SI) of the mandibular bone marrow and pulp tissue of the incisor was interpreted. The MR images were compared with the histopathologic findings. Results The SI of the mandibular bone marrow had decreased on T2-weighted MR images. There was little difference between Groups 1 and 2. The SI of the irradiated groups appeared to be lower than that of the control group. The histopathologic findings showed that the trabecular bone in the irradiated group had increased. The SI of the irradiated pulp tissue had decreased on T2-weighted MR images. However, the SI of the MR images in Group 2 was high in the atrophic pulp of the incisor apex at week 2 after irradiation. Conclusion These patterns seen on MRI in rat bone marrow and pulp tissue were consistent with histopathologic findings. They may be useful to assess radiogenic sclerotic changes in rat mandibular bone marrow.

Multiscale image analysis for the quantitative evaluation of periapical lesion healings

Intraoral radiographs are used routinely for the diagnosis of periapical lesions and the evaluation of subsequent lesion treatments. However, a reliable and reproductive evaluation is often difficult due to the subjectiveness of visual interpretation and various imaging factors in routine dental radiography. To aid radiographic evaluation of periapical lesion healing, we have developed a multiscale image analysis method based on the change of bone features. Fifty pairs of pre- and post-treatment intraoral radiographs were retrospectively obtained and classified into successful (25 cases) or failed (25 cases) treatments based on the presence of periapical radiolucency. To accurately segment the bone images, an optimal scale was determined at which measured bone thickness reached 95% of the maximum values. Trabecular bone images were segmented in multiple scales to calculate intensity and skeleton features. Texture features were calculated within the user-traced lesion area. Based on relative differences of these features between pre- and post-treatment, several treatment efficacy models were derived and tested by leave one out cross validation. Intensity, skeleton, and texture features were significantly changed after successful treatment (Wilcoxons paired test, p<0.05). Treatment efficacy of periapical lesions was classified at the sensitivity of 96% and the specificity of 92% (logistic regression analysis). We found that healing lesions show not only brighter but also larger, thicker, more branched trabecular bones, while cases of persistent disease have bones with more uniform density. Our model may aid the early intervention for re-treatment of failed lesion healings.

Radiographic analysis of peri-implant trabecular bones after implant placement

Intraoral radiographs are routinely used to assess a bone-implant interface after placement of a dental implant. Unlike marginal bone loss occurring in outer and denser crestal bones, bone resorption in inner and networked trabecular bones has not been thoroughly investigated. In this study, we hypothesize that peri-implant trabecular bones may undergo bone resorption and osseointegration after implant placement. Quantitative image analysis was performed on longitudinal radiographs of implants (n=24). Between 4 weeks and 8 weeks after the implant placement, trabecular bones showed increased intensity (Wilcoxon pairwise signed rank test, p<0.05). However, in 20 weeks, the intensity decreased. Furthermore, trabecular bones become shorter. Thickness of peri-implant bones gradually increased starting from 4 weeks and then decreased toward 20 weeks (quadratic regression, p<0.05). Our results suggest that routinely taken intraoral radiographs may be useful in assessing the status of peri-implant bones after implant placement.