• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.2
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• pp.127-132
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• 2013

Traumatic injuries to immature permanent teeth are common and the results can be destructive. Although Hertwig's epithelial root sheath is usually sensitive to trauma, it may resist damage from trauma thereby retaining its vitality and continuing to calcify a root under favorable conditions. This case report describes two cases of trauma to immature permanent incisors. The first case presents an avulsed maxillary central incisor which has been replanted. The other case shows completely avulsed mandibular central incisors which have not been replanted. However, both cases subsequently show continued growing roots separated from the main roots. This report highlights the ability of the immature pulp tissue to continue to form dentin and the robustness of Hertwig's epithelial root sheath to initiate root development despite a traumatic injury.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.4
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• pp.399-406
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• 2011

Traumatic injury on tooth occurs frequently among trauma patients, and mainly occurs on tooth with premature roots which influences pulp tissue, periodontal ligament, alveolar bone, and Hertwig's epithelial root sheath. According to the degree of trauma, a number of kinds of healing process can be observed, such as complete re-vascularization of pulp, root canal obliteration, growth suspension of root apex, and invasion of alveolar bone into root canal, and there can be some complications such as necrotic change of inflammatory root resorption and partial pulp necrosis due to pulp necrosis toward complete necrosis. In this clinical case, 3 patients who had traumatic injury showed root growth suspension and alveolar bone invasion into root canal due to proliferation of periodontal ligament cell and osteocyte at the base of extraction socket into pulp chamber because of the injury on Hertwig's epithelial root sheath. If intrusion of alveolar bone into root canal due to injury on Hertwig's epithelial root sheath after having traumatic injury doesn't show any complication, the pulp may be considered to have normal vitality and doesn't need any further treatment, therefore differential diagnosis is very necessary. However, it may be accompanied with suspension of root growth, therefore, additional trauma during the treatment of injured tooth should not be applied.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.701-704
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• 2004

In this case, we would like to discuss about the single rooted deciduous mandibular first molar. The deciduous mandibular molar of a five years old boy was shown to have a single root, bilaterally. Ordinarily, the maxilary molars have three roots and the mandibular molars have two roots. However, when the hertwig's epithelial root sheath do not invaginate properly during tooth development, root fusion can occur from the absence of root separation. Molars with fused roots not only have unfavorable crown to root ratio, but also according to many reports, have higher probability of having multiple congenitally missing teeth or dens invaginatus in the maxillary incisors, consequently requiring preventive dental treatment In addition, disorders such as ectodermal dysplasia, syndactyly, clinodactyly, bluish sclera can also be related to this condition. Root fusion is known to be of autosomal recessive inheritance. Up to date, single rooted molars have been reported several times in permanent dentitions but hardly in deciduous dentition, which is the motive for this paper.