• The Journal of the Korean dental association
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• v.21 no.6 s.169
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• pp.467-472
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• 1983

Thirty seven human maxillary third mooars were injected with china ink, decalcified, cleared, and used in vitro study to determine the number of root canals the frequency and location of lateral canals, canals per root, and frequency of apical deltas. The results were as follows: 1. Less than half of the examined teeth showed 3 roots and 3 canals. 2. The mesiobuccal root was ound to contain a single primary canal in 65.4% of the teeth examined and two canals in 34.6% of the teeth studed. 3. In mesiobuccal roots with two canals, the separated apical foramen appeared 30.8% of the specimen concerned, but no common apical foramen appeared. 4. Of the 106 canals studied, 46.2% of the canals were found to contain lateral canals and these ramifications were mainly located in the apical third of the root.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.4
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• pp.209-215
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• 2006

Recently Permanent Magnet Linear Synchronous Motors(PMLSMs) are widely used for many linear transportation applications. The PMLSM has many advantages such as simple structure, high speed and thrust. However, especially in short primary type PMLSM, there exists very large detent force, which makes the thrust force ripple, undesired vibration and noise. The detent force is composed of the Cogging force and the End force. The Cogging force comes from the interaction between the permanent magnets and interior teeth of the stator. And the End force acts on the exterior teeth of the stator by the permanent magnets. Usually End force is larger than Cogging force, so the detent force is drasically reduced only by reducing the End force. This paper shows the End force is minimized by optimizing the stator length and chamfering the shape of the exterior teeth of the stator.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.583.1-583
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• 2001

One fifth dilution of formocresol is usually used for pulpotomy of primary teeth and emergency pulpotomy of permanent teeth. Recently Depulpin (VoCo., Germany) gains popularity as devitalizing agent during root canal therapy in spite of high concentration of 49% paraformaldehyde. But there are not enough publications about the reaction of dental pulp and periapical tissue caused by Depulpin. Therefore, This study was performed to evaluate the histological changes in pulp and periapical tissue of rat after pulpotomy using formocresol and Depulpin.(omitted)

• Journal of dental hygiene science
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• v.18 no.3
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• pp.194-200
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• 2018

Early childhood caries is a widespread condition that requires attention; however, its treatment remains a challenge in terms of child behavior management. This study describes the usefulness of customized zirconia crowns for the restoration of deciduous teeth through the evaluation of some cases. Three cases are described: a 29-month-old girl who presented with severe early childhood caries affecting anterior tooth, a 50-month-old boy who presented with extensive caries of his anterior tooth, and 70-month-old girl who presented with extensive caries of his primary posterior dentition. These prefabricated, zirconium-based ceramic crowns ($Nusmile^{TM}$ NuSmile) are available in various sizes, shapes and colors. Before the treatment, radiographs and intraoral photographs were taken to evaluate the appropriateness of treatment. Our findings indicate that customized zirconia crowns may be appropriate for restoring the deciduous teeth. Further long-term clinical studies are required to clarify the usefulness of this restorative method.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.1
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• pp.113-120
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• 2023

Restoring composite resins with the optimal shades for all primary teeth is a great challenge for pediatric dentists. A newly developed single-shade composite resin can exhibit a color similar to that of the surrounding tooth structure based on the structural color phenomenon. This study aims to evaluate the color adjustment potential (CAP) of a single-shade composite resin compared to conventional multi-shade composite resins in primary teeth. A single-shade composite resin and two conventional multi-shade composite resins were included in this study. Two types of specimens, a single specimen and a dual specimen, were evaluated. For single specimens, duplications of the primary second molar denture teeth were made using experimental composite resins. For dual specimens, cavities were prepared on the buccal surfaces of extracted primary second molars and restored with experimental composite resins. The L^*, a^*, and b^* values were measured using a colorimeter for the extracted teeth and specimens. The mean ΔE_ab^* values for single and dual specimens and CAP were calculated. Bonferroni post-hoc analysis was performed to confirm the statistical significance between the ΔE_ab^* and CAP values of the experimental resins. Among the single specimens, the single-shade composite resin showed significantly higher ΔE_Single compared to other composite resins (p < 0.0167). There was no significant difference between ΔE_Dual for all experimental resins. The single-shade composite resin showed highest CAP compared to other multi-shade composite resins. A single-shade composite resin exhibited the most prominent color adaptability compared to other conventional multi-shade composite resins for primary second molars. A single-shade composite resin can simplify shade matching and provide esthetic outcomes for the restoration of primary second molars.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.49-54
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• 2005

Shell teeth, a rare dysplastic condition of dentin, was first described by Rushton in 1954. It is characterized by normal enamel, extremely thin dentin, correspondingly large pulp chambers, and shortened roots. This case report is of a male 3 years old. He is refered to the Chosun University dental hospital Pediatric Dentistry because of dental caries and dentin hypoplasia. Intra-oral examination showed attrition of all primary teeth. Radiographic examination showed that the pulps were extremely large with only a shell of surrounding hard tissue. The permanent premolars were missed congenitally. The diagnosis was shell teeth. Because of behavior problem, all dental treatment was undertaken with general anaesthesia. Extration, endodontic treatment and SS crown were performed. The patient has now been wearing the space maintainer and manages it well. The patient is seen intervals for supervision and follow-up care.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.25-35
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• 2020

The purpose of this study is to evaluate the morphological characteristics of the roots and roots canals of primary molar teeth using Cone-Beam Computed Tomography (CBCT). A total of 68 CBCT images of children aged 4 - 5 years was used for this study. A total of 160 molar teeth were analyzed. Various parameters such as the number of roots and canals, length of root and root canal, and the angulation and shape of the roots were analyzed. All maxillary primary molars had 3 roots. The presence of 2 root canals in 1 root was only observed in the mesiobuccal root of maxillary primary second molars. Most mandibular primary molars had 2 roots, and most mesial roots had 2 root canals. Concerning the length of the roots, the palatal root of the maxillary primary molar was found to be longest whereas the distobuccal root was shortest. In mandibular primary molars, the mesial root was longer than the distal root. In maxillary primary molars, the palatal root had the greatest angulation whereas the distal root has the greatest in mandibular molars. The root and root canals of maxillary primary molars were more curved in shape whereas mandibular primary molars were straight.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.272-285
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• 2003

This study was conducted to observe the microscopic structures of cavities formed after ablation of primary teeth, permanent teeth, enamel and dentin in using a bur and cavities formed after ablation using laser and the following results were obtained after comparing the effects of ablation. Using a #330 bur and Er:YAG laser irradiated at 150 mJ, 200 mJ, 250 mJ and 300 mJ all at the frequency of 5 Hz, 1 mm enamel and dentin samples were ablated and the ablation time was measured. In order to measure the surfaces ablated, 5 each of primary teeth and permanent teeth were ablated using a #330 bur and Er:YAG laser at 150 mJ, 200 mJ, 250 mJ and 300 mJ for 1 sec and the cross section and vertical section were observed. The following results were obtained : 1. Cutting time of Er:YAG laser was longer than that of conventinal high-speed bur regardless of teeth type. 2. Cutting on enamel, Cutting time of conventional high-speed bur in deciduous teeth was longer than in permanent teeth(P<0.05). But Er:YAG laser was not showed any difference between the deciduous and permanent teeth(P>0.05). 3. Cutting on dentin, Cutting time of conventional high-speed bur in permanent teeth was longer than deciduous teeth. Er:YAG laser of 150 mJ, 5 Hz in permanent teeth was longer than in deciduous teeth(p<0.05). But laser of other power did not showed mean difference. 4. The cavity surface treated with the convetional high-speed bur revealed a relatively flat appearance, almost covered with a debris-like smear layer. Cavity wall showed striped appearance because of blade of bur. 5. The cavity surface treated by the Er:YAG laser system was irregular or rough surface with the absence charring, carbonization, or cracking of the dentin. In addition, there was an absence of a smear layer. Cavity floor was round and relatively smooth. According to these results, cutting time of Er:YAG laser was almostly same in permanent and deciduous teeth, but more effective in dentin than enamel. Cutting the sample, Er:YAG laser was needed more time than conventional bur. But SEM findings suggested that laser device produced favorable surface characteristic(i.e, no smear layer, irregular surface, cracking).

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.229-236
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• 2000

For the purpose of evaluating the microleakage of compomer restorations in cervical cavities of primary molars according to the length of etching time, an experiment was performed through next procedures. 48 extracted human primary molars were divided into 6 groups according to applied compomers and the etching time of 0, 15, 30 seconds. All the restorations were filled under the manufacturer's direction, and the degree of dye penetration was evaluated with stereomicroscope. The microleakage of etch group was measured and statistically analyzed and obtained the results as follows: 1. Compared with groups without etching, the degree of microleakage was reduced by acid etching the cavities (p<0.05). 2. There revealed similar preventive effects of microleakage when the teeth were etched for 15 seconds and 30 seconds respectively(p>0.05). 3. No significant difference was observed between two compomers examined in this study(p>0.05). It was, therefore, thought acid etching is effective to minimize the microleakage of compomer restorations in primary teeth, and in cases of performing, 15 seconds is adequate for etching.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.1
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• pp.51-55
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• 2011

Supernumerary teeth are dental abnormalies in the permanent dentition and the primary dentition. The etiology is unclear, but it may occur due to dichotomy of the tooth bud or hyperactivity of dental lamina. They occur more in the permanent dentition than in the primary dentition, with the most common site being the premaxillary area. Supernumerary teeth can be classified by morphology and position. Supplemental tooth refers to normal shape tooth. The treatment of supernumerary teeth depends on its shape, position, effect on dentition, and child's physiological condition. In this case, supernumerary primary tooth in the maxillary molar area was revealed by radiographical and clinical examination, but it was difficult to determine which is the supernumerary tooth. The tooth on the mesial side was extracted to induce the formation of adequate space and to prevent excessive space loss, and the result was favorable.