Nam-Ki Choi

Inhibitory effect of Lactobacillus reuteri on periodontopathic and cariogenic bacteria

The interaction between Lactobacillus reuteri, a probiotic bacterium, and oral pathogenic bacteria have not been studied adequately. This study examined the effects of L. reuteri on the proliferation of periodontopathic bacteria including Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Tannerella forsythia, and on the formation of Streptococcus mutans biofilms. Human-derived L. reuteri strains (KCTC 3594 and KCTC 3678) and rat-derived L. reuteri KCTC 3679 were used. All strains exhibited significant inhibitory effects on the growth of periodontopathic bacteria and the formation of S. mutans biofilms. These antibacterial activities of L. reuteri were attributed to the production of organic acids, hydrogen peroxide, and a bacteriocin-like compound. Reuterin, an antimicrobial factor, was produced only by L. reuteri KCTC 3594. In addition, L. reuteri inhibited the production of methyl mercaptan by F. nucleatum and P. gingivalis. Overall, these results suggest that L. reuteri may be useful as a probiotic agent for improving oral health.

Effects of methyl gallate and gallic acid on the production of inflammatory mediators interleukin-6 and interleukin-8 by oral epithelial cells stimulated with Fusobacterium nucleatum

Interactions between periodontal bacteria and human oral epithelial cells can lead to the activation and expression of a variety of inflammatory mediators in epithelial cells. Fusobacterium nucleatum is a filamentous human pathogen that is strongly associated with periodontal diseases. This study examined the effects of methyl gallate (MG) and gallic acid (GA) on the production of inflammatory mediators, interleukin (IL)-6 and IL-8, by oral epithelial cells stimulated by F. nucleatum. In a real-time reverse transcription-polymerase chain reaction and an enzyme-linked immunosorbent assay, live F. nucleatum induced high levels of gene expression and protein release of IL-6 and IL-8. The effects of MG and GA were examined by treating KB oral epithelial cells with MG and GA and stimulating them with F. nucleatum. MG and GA inhibited significantly the increases in the IL-6 and IL-8 gene and protein levels in a dose-dependent manner. These Compounds also inhibited the growth of F. nucleatum. No visible effects of MG and GA on the adhesion and invasion of KB cells by F. nucleatum were observed. In conclusion, both MG and GA inhibit IL-6 and IL-8 production from F. nucleatum-activated KB cells.

Inhibition of mitochondria-dependent apoptosis by 635-nm irradiation in sodium nitroprusside-treated SH-SY5Y cells

Nitric oxide (NO) is a major factor contributing to the loss of neurons in ischemic stroke, demyelinating diseases, and other neurodegenerative disorders. NO not only functions as a direct neurotoxin, but also combines with superoxide (O(2)(-)) by a diffusion-controlled reaction to form peroxynitrite (ONOO(-)), a species that contributes to oxidative signaling and cellular apoptosis. However, the mechanism by which ONOO(-) induces apoptosis remains unclear, although subsequent formation of reactive oxygen species (ROS) has been suggested. The aim of this study was to further investigate the triggers of the apoptotic pathway using O(2)(-) scavenging with light irradiation to block ONOO(-) production. Antiapoptotic effects of light irradiation in sodium nitroprusside (SNP)-treated SH-SY5Y cells were assayed by reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, DNA fragmentation, flow cytometry, Western blot, and caspase activity assays. In addition, NO, total ROS, O(2)(-), and ONOO(-) levels were measured to observe changes in NO and its possible involvement in radical induction. Cell survival was reduced to approximately 40% of control levels by SNP treatment, and this reduction was increased to 60% by low-level light irradiation. Apoptotic cells were observed in the SNP-treated group, but the frequency of these was reduced in the irradiation group. NO, O(2)(-), total ROS, and ONOO(-) levels were increased after SNP treatment, but O(2)(-), total ROS, and ONOO(-) levels were decreased after irradiation, despite the high NO concentration induced by SNP treatment. Cytochrome c was released from mitochondria of SNP-treated SH-SY5Y cells, but not of irradiated cells, resulting in a decrease in caspase-3 and -9 activity in SNP-treated cells. Finally, these results show that 635-nm irradiation, by promoting the scavenging of O(2)(-), protected against neuronal death through blocking the mitochondrial apoptotic pathway induced by ONOO(-) synthesis.

Ultraviolet-C-induced apoptosis protected by 635-nm laser irradiation in human gingival fibroblasts.

OBJECTIVE The purpose of this study was to examine the protection afforded by 635-nm irradiation against ultraviolet (UV)-C-induced apoptosis in primary human gingival fibroblasts (hGFs). BACKGROUND DATA UV irradiation is known to cause photoaging and cellular apoptosis of skin cells and is considered to be one of the leading causes of skin carcinogenesis. MATERIALS AND METHODS To induce apoptosis, UV-C (100 mJ/cm2) was used to irradiate hGFs. To protect them from apoptosis, pretreatment with 635-nm irradiation was performed for 1 h immediately after cell plating 36 or 48 h before UV-C irradiation. The light source used for irradiation was a continuous-wave 635-nm LED laser emitting at 1 mW/cm2. Experimental samples were selected 24 h after UV-C irradiation. To measure the numbers of apoptotic cells, MTT assay and flow cytometric analyses were performed. For histomorphologic findings, Diff-Quick staining was carried out. Also, the activities and mRNA expression of caspase-3, caspase-8, and caspase-9 were measured. RESULTS In the present study, the number of apoptotic cells declined in the cells that were pretreated with 635-nm light irradiation in a time-dependent manner. In addition, the activities and mRNA expression of caspase-3, caspase-8, and caspase-9 were significantly recovered by pretreatment with 635-nm irradiation. CONCLUSION These results suggest that 635-nm visible light irradiation may be used as a protective tool to prevent UV-C-induced apoptosis.

Effect of Lactobacillus reuteri on the proliferation of Propionibacterium acnes and Staphylococcus epidermidis.

While it is generally accepted that Propionibacterium acnes is involved in the development of acne, other bacteria including Staphylococcus epidermidis have also been isolated from the acne lesion. The interaction between Lactobacillus reuteri, a probiotic bacterium, and acnegenic bacteria is unclear. This study examined the effects of L. reuteri on the proliferation of P. acnes and S. epidermidis. Human-derived L. reuteri strains (KCTC 3594 and KCTC 3678) and rat-derived L. reuteri KCTC 3679 were used. All strains exhibited significant inhibitory effects on the growth of P. acnes and S. epidermidis. The proliferation of P. acnes was decreased by 2-log scales after incubation with L. reuteri for 24 h. In addition, the proliferation of S. epidermidis was decreased by 3-log scales after incubation with L. reuteri for 24 h, whereas the growth of L. reuteri was unaffected by P. acnes or S. epidermidis. Among the L. reuteri strains examined, L. reuteri KCTC 3679 had the strongest inhibitory effect on the growth of P. acnes and S. epidermidis, followed by L. reuteri KCTC 3594 and L. reuteri KCTC 3678. Interestingly, reuterin, an antimicrobial factor, was produced only by L. reuteri KCTC 3594. The most pronounced the antibacterial activities of L. reuteri were attributed to the production of organic acids. Overall, these results suggest that L. reuteri may be a useful probiotic agent to control the growth of bacteria involved in acne inflammation and prevent acne.

Myelin basic protein is temporospatially expressed in developing rat molars

Tooth development occurs through a complex and intricate set of gene-expression cascades. Although its early events have been examined extensively, there are fewer reports on the late events, such as dental hard-tissue formation. This study searched for genes involved in the late stages of tooth development. Differential display-polymerase chain reaction revealed myelin basic protein (MBP) mRNA to be expressed differentially in the second molar root stage germs compared with the third molar cap/early bell stage germs. The MBP expressed during hard tissue formation was confirmed to be a 21.5 kDa molecule by Western blotting. Immunoreactivity of MBP in the third molar (cap/early bell stage) germs was barely detectable in the dental papilla and inner enamel epithelia, whereas strong reactivity was noted in the differentiating and differentiated ameloblasts and odontoblasts in a temporospatial pattern. However, after complete formation of the full-thickness enamel, no reactivity was observed in the maturation-stage and protection stage ameloblasts. Myelin basic protein immunoreactive nerve fibers were also observed near the developing molar germs. This is the first report showing the presence of MBP in dental hard tissue cells, and its functional implications should be studied further.

A STUDY ON THE CHANGES IN PATIENT DISTRIBUTION AND PRACTICE PATTERN FOR LAST 8 YEARS IN THE DEPARTMENT OF PEDIATRIC DENTISTRY OF CHONNAM NATIONAL UNIVERSITY DENTAL HOSPITAL

The purpose of this study was to understand the change of demands in young patients and to suggest a directional shift for the pediatric dental practitioners who are facing these changes. This study collected data on new patients who had visited Chonnam National University Dental Hospital, Department of Pediatric Dentistry from 2003 to 2010 and the researchers were able to find out the following information. Total number of dental visits has been increasing since 2009 and 2010, which includes an increase of male patients in the 13~15 years age group showed significant increase and that in the 3~4 years age group showed a significant decrease. December showed the largest number of total dental visits, of which 69.6% of newly visit patients were living in Gwang-ju. Patients who had systemic diseases were 10.7% of total newly visit patients and 19.1% of patients received sedative treatment. Considering the chief complaints of new patients, 36% of patients visited because of dental caries. Regarding the dental treatment of patients, 38.4% had restoration treatment in 2003 and 30.4% had restoration treatment in 2010.

A Retrospective Study of the Pattern and Treatment of Traumatic Dental Injury to Primary and Permanent Teeth

(940 traumatic teeth) were analyzed. The prevalence rate of dental trauma was twofold higher in males versus females. The principal cause of injury, among all participants, was falling (36.5%). The most commonly affected teeth were the maxillary central incisors (66.9%). Subluxation (43.9%) represented the most common trauma for primary teeth, and uncomplicated crown fracture in permanent teeth (30.9%). Only 10% of patients visited the dental clinic within 1 hour of sustaining trauma. The principal treatment provided for primary teeth, during the initial clinical visit, was follow-up (53.2%); for permanent teeth it was root canal treatment (27.3%). The prevalence of root canal treatment for permanent teeth increased commensurate with the time elapsed since injury. These data suggest that delayed checkup following trauma may increase the risk of loss of pulp vitality.

CONSERVATIVE SURGICAL REMOVAL OF COMPOUND ODONTOMA: CASE REPORTS

Odontoma is a mixed tumor formed by the overgrowth of ectodermal epithelial cells and mesodermal cells. It arises during normal tooth development and only grows to a certain level. It is not a true neoplasm and therefore it is considered as hamartomas. Odontomas are classified into compound and complex types based on morphology. Compound odontoma is commonly found in the anterior region of the maxilla, and has a radiopaque lesion that resembles small teeth. Usually, odontoma is treated by conservative surgical removal and there is little probability of recurrence. This paper describes three cases of compound odontoma diagnosed in children with 1 year of follow-up. These case reports present patients having eruption disturbance of primary and permanent teeth due to the presence of compound odontoma. In order to induce spontaneous eruption, conservative surgical removal was performed showing favorable results.

PERIODONTOPATHIC BACTERIA AND ANTIBIOTIC RESISTANCE GENES OF ORAL BIOFILMS IN CHILDREN

항생제 사용에 따라 구강내 세균들이 가지게 되는 내성의 발현이 문제가 될 수 있다. 어린이 치면세균막에서 치주질환의 원인균들과 흔히 사용하고 있는 항생제들에 대한 내성유전자의 출현율을 알아보고자 중합효소연쇄반응을 이용하여 조사하였다. 1. 치주질환 원인균의 출현율은 F. nucleatum 95.4%, T. forsythia 55.2% 이었으며, P. gingivalis 40.2%, A. actinomycetemcomitans 5.7%, T. denticola는 3.4% 순이었다. 2. 항생제 내성유전자의 출현율 조사에서 cephalosporin 분해효소인 cfxA는 100%에서 발견되었으며