• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.2
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• pp.475-483
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• 1997

Fracture of the crown in a permanent incisor is relatively common. When it occurs with pulp exposure, it presents both restorative and endodontic problems. In the restoration of a fractured incisor, reattachment of the original fragment or restoration with a composite resin is preferred over a temporary crown. If fractured fragment is intact, the tooth can be restored with reattachment of the fragment. An exposed pulp in a young crown-fractured incisor is usually treated with either pulp capping or pulpotomy depending on the size of an exposure and time elapsed since injury. However, in teeth showing vital and/or hyperplastic pulp tissue at the exposure, only superficial layers of the pulp and surrounding dentin should be removed : i.e. partial pulpotomy can be performed in immature as well as mature teeth. This paper reports 2 cases of crown-fractured permanent incisors with pulp exposure that had been treated by reattachment of original fragment followed by partial pulpotomy or partial pulpectomy. The following results are obtained. ; 1. Fragment reattachment is an acceptable semi-permanent restoration of crown fractured young permanent incisor. 2. Partial pulpotomy is recommended as the treatment of choice in crown-fractured permanent teeth with pulp exposure.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.92-97
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• 2004

Traumatic injuries in the young peranent dentition are common, but root fractures, defined as fractures in volving dentin, cementum and pulp, are relatively uncommon. Case 1 is a 9-year-old boy who had a horizontal root fracture of his maxillary right central incisor in the apical third. Root canal therapy was performed in coronal segment and calcium hydroxide therapy was initiated. Six months after treatment, a periapical radiograph showed calcific tissue formation and normal root development. 1 year and 3 months later, the canal was permanently obturated with gutta-percha. Case 2 is a 7-year-old girl who had a vertical root fracture of her maxillary right central incisor. Fractured tooth was intentionally extracted atraumatically, and then the separated fragments are bonded with resin cement. the restored tooth was replanted into the original socket. Recalls up to 8 months showed normal mobility and no periapical pathosis. In these cases, we performed conservative treatment. Clinical and radiographic examination showed no pathosis or abnormality of the teeth and periodontal tissue.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.2
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• pp.288-292
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• 2009

A crown-root fracture is defined as a fracture involving enamel, dentin, and cementum. The fractures may be grouped according to pulpal involvement into uncomplicated and complicated. Generally a vertically crown-root fractured tooth must be extracted. However, it should be mentioned that the cases have been reported where bonding of the coronal fragment has led to consolidation of the intraalveolar part of the fracture. Definitive conservative therapy comprises one of four treatment alternatives; fragment removal only, fragment removal with gingivectomy, orthodontic extrusion of apical fragment, and surgical extrusion of apical fragment. The choice is primarily determined by the exact information on the site and the type of fracture, but the cost and the complexity of treatment can also be decisional factors. On the other hand, intentional replantation of the teeth with vertical root facture reconstructed with resin bonding has emerged as a new promising method in recent years. This case presents an intentional replantation of the crown-root fractured maxillary central incisor reconstructed with resin bonding. However, an obvious increase of radiolucency was observed after 4 months and the tooth was re-fractured after 16 months.

• Progress in Medical Physics
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• v.15 no.4
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• pp.228-236
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• 2004

Retinal ganglion cells transmit visual scene as an action potential to visual cortex through optic nerve. Conventional recording method using single intra- or extra-cellular electrode enables us to understand the response of specific neuron on specific time. Therefore, it is not possible to determine how the nerve impulses in the population of retinal ganglion cells collectively encode the visual stimulus with conventional recording. This requires recording the simultaneous electrical signals of many neurons. Recent advances in multi-electrode recording have brought us closer to understanding how visual information is encoded by population of retinal ganglion cells. We examined how ganglion cells act together to encode a visual scene with multi-electrode array (MEA). With light stimulation (on duration: 2 sec, off duration: 5 sec) generated on a color monitor driven by custom-made software, we isolated three functional types of ganglion cell activities; ON (35.0$\pm$4.4%), OFF (31.4$\pm$1.9%), and ON/OFF cells (34.6$\pm$5.3%) (Total number of retinal pieces = 8). We observed that nearby neurons often fire action potential near synchrony (< 1 ms). And this narrow correlation is seen among cells within a cluster which is made of 6～8 cells. As there are many more synchronized firing patterns than ganglion cells, such a distributed code might allow the retina to compress a large number of distinct visual messages into a small number of ganglion cells.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.237-245
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• 2000

For the purpose of comparing the bond strengths of some tooth adhesive restoration materials on primary enamel and dentin, 4 kinds (7 brands) of restorative materials including a composite resin (Z 100), a conventional glass ionomer cement (Chem-Flex), 2 brands of resin-modified glass ionomer cements (Fuji II LC-I, Vitremer), and 3 brands of compomers(Dyract AP, F2000, Compoglass) were investigated using UTM for measuring the shear bond strengths. Additionally the failure modes were examined by histologically observing the fractured surfaces of each specimen. The following results were obtained. 1. The shear bond strengths of Z 100 to the primary enamel were higher than those of other experimental materials except Fuji II LC-I, which showed significantly higher bond strength than Chem-Flex or Vitremer (P<0.05). 2. The shear bond strengths of Z 100 to the primary dentin were higher than those of other experimental materials except Dyract AP and Fuji II LC-I, both of which showed significantly higher shear strength than Chem-Flex or Vitremer (P<0.05). 3. The shear bond strengths of all restorative materials except Dyract AP showed relatively higher values to enamel surface than to dentin surface. In Dyract AP, the reverse was true significantly. 4. All materials examined showed cohesive failures except some Chem-Flex and Vitremer, which showed adhesive failures.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.267-272
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• 2004

This case report describes an uncommon treatment method for crown-root fractured incisor with immature root. A 7-year-old girl was referred for treatment of crown-root fractured maxillary central incisor. The fracture line extended to 1/2 of the total tooth length with incomplete root formation. The prognosis of crown-root fracture is usually poor and extraction is usually undertaken. But, in the mixed dentition, extraction of maxillary permanent incisor results in many complications, such as resorption of alveolar bone, poor esthetics, pronunciation and mastication. Conservative therapy in the permanent dentition comprises of few treatment modalities; supragingival restoration, gingivectomy, orthodontic extraction of apical fragment, surgical extrusion of apical fragment with or without rotational replantation. However, in this case, these indications are not applicable, so intentional replantation with adhesive resin system is the treatment of choice. The tooth was followed-up for 12 months. Currently, there are no symptoms. Since this modality adopts the respective advantages of both intentional replantation and adhesive treatment, it might be the treatment of choice in cases of vertical crown-root fracture.