• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.759-765
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• 2004

The NCS inhibited the activity of glucosyltransferase which was produced by Streptococcus mutans JC-2, and the rate of inhibition at $100\muM<$ and $200\muM$ were 74.0% and 99.8%, respectively. It was stable in alkali condition, but unstable in acid condition. It was also stable up to $80^{\circ}C$. The kinetic study of the inhibition by NCS was carried out by Lineweaver-Burk plot and Dixon plot. It was non-competitive inhibition, determined by the two plots and $K_i$ and $K_i$ values were $15\muM$ and $19.3\muM$ respectively. The NCS did not show cytotoxicity against human gingival cells at $K_i$ ($15\muM$, $150\muM$, $1,500\mu$ M) concentrations. It had less cytotoxicity than chlohexidin, which has usually been used as the agent of anticaries. To evaluate the industrial applicability of the NCS, human pluck tooth was used. The inhibitory rates of tooth calcification and calcium ion elution by the NCS were 41 % and 2.5 times, respectively. These results suggested that NCS from Bacillus sp. S-1013 is an efficient anticaries agent.

• Imaging Science in Dentistry
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• v.33 no.1
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• pp.59-62
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• 2003

Ameloblastic fibro-odontoma is an extremely rare odontogenic tumor composed of proliferating ectodermal and mesenchymal components of odontogenic tissue, containing hard tooth structure. It occurs predominantly in children and young adults. The mandibular molar-ramus area is the most frequently observed location, presenting radiographically as a well-circumscribed and radiolucent-radiopaque tumor. A case involving a 24-year-old woman presenting with a large ameloblastic fibro-odontoma of the posterior mandible is reported. This case is of radiologic interest because two distinct calcification patterns were observed.

• Imaging Science in Dentistry
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• v.50 no.4
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• pp.377-384
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• 2020

This report presents 2 cases of sinus fungus ball and describes the characteristic radiographic features of fungus ball in the maxillary sinus. Two female patients, aged 62 and 40 years, sought consultations at a dental hospital for the treatment of dental implants and tooth pain, respectively. Panoramic radiography and small field-of-view(FOV) cone-beam computed tomography (CBCT) did not provide detailed information for the radiographic diagnosis of fungus ball due to the limited images of the maxillary sinus. Additional paranasal sinus computed tomographic images showed the characteristic features of fungus ball, such as heterogeneous opacification and intralesional calcification of the maxillary sinus. The calcified materials of the fungus balls were located in the middle and superior regions of the maxillary sinus. It is necessary to use large-FOV CBCT for the detection of calcified materials in the upper maxillary sinus to confirm the diagnosis of fungus ball.

• The korean journal of orthodontics
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• v.21 no.2 s.34
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• pp.341-351
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• 1991

Dental maturity is one of the index of physiological maturity indicators. To investigate the relationship between dental maturity and chronological age, the author took the orthopantomograms of 984 students, aged 7 through 17 years, having normal occlusion. The orthopantomograms were examined and calcification degree of each tooth on the left side was rated according to the method described by Demirjian. On the basis of findings of this study, the following results were obtained. 1. The root completion periods of mandibular permanent teeth were as follows; Central Incisor M $8.32{\pm}1.03\;years$ F $7.96{\pm}1.04\;years$ Lateral Incisor M $9.40{\pm}1.30\;years$ F $9.01{\pm}0.90\;years$ Canine M $12.81{\pm}1.24\;years$ F $11.42{\pm}0.94\;years$ 1st Premolar M $12.76{\pm}1.74\;years$ F $12.19{\pm}1.33\;years$ 2nd Premolar M $13.31{\pm}1.88\;years$ F $12.88{\pm}1.49\;years$ 1st Molar M $9.60{\pm}1.69\;years$ F $9.30{\pm}1.16\;years$ 2nd Molar M $14.38{\pm}1.73\;years$ F $13.96{\pm}1.63\;years$ 2. Sexual differences in same age group at given calcification stage were not significant statistically. 3. The developmental order in mandibular permanent teeth was as follows; a) central incisor, b) lateral incisor, c) 1st molar, d) canine and 1st premolar, e) 2nd premolar, f) 2nd molar.

• Journal of Oral Medicine and Pain
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• v.25 no.2
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• pp.253-263
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• 2000

We collected age determination cases which were done at Yonsei university dental hospital, department of oral medicine from 1976 to 1999 to analyze it's tendency among Koreans. We analyzed 435 clients cases which were stored by age estimation program from January 1993 to December 1999. The results are as follows: 1. There were no significant difference in the sexual distribution (male : 52.0%, female : 48.0%) and more than half percent (51%) were 20's and 30's. 2. Among the age determination clients, those who wanted to decrease their age (50.3%) and those who wanted to increase their age (49.7%) shows similar in number. And the former case were predominant in the female clients, but the latter case in the male clients. Also the clients below six years of age were predominant in the former case, but the clients more than sixty were predominant in the latter case. 3. The purposes of age correction showed different distribution for ages: job or employment for 20's and 30's, marriage for 20's, registration for school for below six, welfare and other social services for 50 and older. 4. Age was estimated by Nolla's growth stage for 12 and under, calcification of the second and third molar for 12~20, and for 20 and over, Takei's tooth abrasion model was used. 5. The alleged age was in accordance with the documents and other information given by clients, but in the 20.6% of the estimation cases, the alleged age was discarded. In the results of the analysis of age determination cases in Koreans, many of the cases resulted from our historical turbulence and social distinctiveness, causing an increase in the necessity for age correction in each age group. For more accurate determination for each age group, further studies with Koreans must be done continuously.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.2
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• pp.138-146
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• 2017

The aim of this study was to estimate time of biomineralization in developmental stages of rat lower incisors. Eruption length was measured. Four stages of incisor development were identified on histologic and microscopic computerized tomography (micro-CT) sections: (1) preodontoblast, (2) dentin matrix secretion, (3) enamel matrix secretion, and (4) enamel calcification. The overall eruption rate of the rat lower incisor was $600{\pm}70{\mu}m/day$ ($mean{\pm}SD$; n = 12). The length of the enamel secretion was $4.59{\pm}0.75mm$ in histologic section, was $3.64{\pm}0.63mm$ in radiographic section, which converts to $180.4{\pm}30.0hours$, $145{\pm}25hours$ respectively (n = 24). These findings suggested that the four biomineralizing developmental stages of the rat incisor took only several days. The significance of this animal study was to provide understanding for the rapid biomineralization process of developing rat tooth germ by analysis of tooth forming period.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.369-373
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• 2001

The congenital missing of mandibular second premolars is among the common dental anomaly in children. When a second premolar is diagnosed as congenitally missed, we should consider many factors influencing the treatment plan such as patient's age, states of roots of 2nd primary molar, degree of crowding, skeletal growth pattern, facial profile, procumbency of the incisor and lower facial height, etc. The mineralization of the second premolars begins in the majority of cases at the age of $2\sim2\frac{1}{2}$ years, but this period varies more widely than those for other permanent teeth. Also, mandibular second premolars show the greatest variations in differentiation and calcification. For this reason, aplasia of this group of teeth cannot be diagnosed at early age and with the same degree of certainty. From the clinical studies with 2 cases and some literature review on late development of second premolars, it could be summarized as follows : 1. The 2 cases showed marked delay in the development of mandibular second premolars. 2. After the crypt formation, the speed of calcification seemed nearly normal, suggesting that the delay was due to differentiation rather than calcification. 3. When one is encountered with similar conditions, it would be desirable to consider the possibility of delayed tooth development.

• Journal of the korean academy of Pediatric Dentistry
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• v.11 no.1
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• pp.131-143
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• 1984

150 rats weighting about 150gm were devided into control group of 80 and experimental group of 70. Control group was subdivided into the irradiated vitamin D injection group and X-ray irradiated group. Experimental group was given 2.0mg ergocalciferol by four intramuscular injection prior to X-ray irradiation with single 800 rads and 1,500 rads respectively. Experimental animals from each group was sacrificed after 1, 3, 7, 14, and 28 days and their incisors were investigated by histopathological examination. The results were as follows; 1. In the irradiated groups, it showed dentin hypoplasia and formation of dentinoid substance caused by degeneration of odontoblast at the early stage. Especially, 1,500 rads group which was severely effected showed formation of osteoid dentin at the apical portion and severe injuries of dental papilla at the first week. 2. In the vitamin D2 administration group, it showed thinned dentin layer at the early stage but, taking time, predentin and dentin layer was thickened. At the fourth week, dentin was chiefly composed of interglobular dentin, especially in the lingual portion. 3. Using in combination of overdose vitamin D2 administration and X-ray irradiation, it effected severely odontoblast, undifferentiated mesenchymal cells around tooth germ and pulp tissue. At the early stage, dentin layer was thinned but, taking time, it was thickened and composed of interglobular dentin caused by calcification of predentin layer. 4. In 800 rads irradiation after the overdose vitamin D2 administration, it showed formation of osteoid dentin in the lingual portion at the first week. In the 1,500 rads irradiation after the overdose vitamin D2 administration, it showed formation of osteoid dentin and degeneration of ameloblast in both buccal and lingual portion at the first week, and enamel hypoplasia caused by edema and loss of polarity of ameloblasts at the second week. 5. By the entire experiment, the overdose vitamin D2 administration and X-ray irradiation effected severely odontoblasts, undifferentiated mesenchymal cells of dental papilla, and primitive cells of tooth germ among the dental tissue. Especially using combination of overdose vitamin D2 administration and X-ray irradiation also effected ameloblasts, resulting in enamel hypoplasia.

• Imaging Science in Dentistry
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• v.48 no.3
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• pp.201-212
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• 2018

Purpose: The aim of this study was to compare cone-beam computed tomography (CBCT) and digital panoramic radiography (DPR) for the detection of pulp stones. Materials and Methods: DPR and CBCT images of 202 patients were randomly selected from the database of our department. All teeth were evaluated in sagittal, axial, and coronal sections in CBCT images. The systemic condition of patients, the presence of pulp stones, the location of the tooth, the group of teeth, and the presence and depth of caries and restorations were recorded. The presence of pulp stones in molar teeth was compared between DPR and CBCT images. Results: Pulp stones were identified in 105 (52.0%) of the 202 subjects and in 434 (7.7%) of the 5,656 teeth examined. The prevalence of pulp stones was similar between the sexes and across various tooth locations and groups of teeth (P>.05). A positive correlation was observed between age and the number of pulp stones(${\rho}=0.277$, P<.01). Pulp stones were found significantly more often in restored or carious teeth (P<.001). CBCT and DPR showed a significant difference in the detection of pulp stones(P<.001), which were seen more often on DPR than on CBCT. Conclusion: DPR, as a 2D imaging system, has inherent limitations leading to the misinterpretation of pulp stones. Restored and carious teeth should be carefully examined for the presence of pulp stones. CBCT imaging is recommended for a definitive assessment in cases where there is a suspicion of a pulp stone on DPR.

• Imaging Science in Dentistry
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• v.41 no.2
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• pp.59-62
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• 2011

Purpose : This study was performed to evaluate the changes of jaw bone density around the dental implant after placement using computed tomography scan (CT-Scan). Materials and Methods : This retrospective study consisted of 30 patients who had lost 1 posterior tooth in maxilla or mandible and installed dental implant. The patients took CT-Scan before and after implant placement. Hounsfield Unit (HU) was measured around the implants and evaluated the difference of HU before and after implant installation. Results : The mean HU of jaw bone was 542.436 HU and 764.9 HU before and after implant placement, respectively (p<0.05). The means HUs for male were 632.3 HU and 932.2 HU and those for female 478.2 HU and 645.5 HU before and after implant placement, respectively (p<0.05). Also, the jaw bone with lower density needed longer period for implant procedure and the increased change of HU of jaw bone was less in the cases which needed longer period for osseointegration. Conclusion : CT-Scan could be used to assess the change of bone density around dental implants. Bone density around dental implant was increased after placement. The increased rate of bone density could be determined by the quality of jaw bone before implant placement.