• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.580-585
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• 2009

Pediatric dentists often meet children with abnormal in number of tooth. Presence of supernumerary teeth is frequent cause of malocclusion. Etiology for supernumerary teeth is not yet clearly defined, but it is thought to be caused by excessive proliferation of dental lamina by hereditary and environmental factors. Supernumerary teeth occur in the maxilla nine times more frequently than in the mandible. Most common supernumerary tooth is the mesiodens in the maxilla, and some are observed in the maxillary molar and mandibular premolar. It occurs rarely in the mandibular incisor region with the incidence of 1-2% among all supernumerary teeth. A six-year old boy visited the department of the pediatric dentistry, Yonsei University Dental Hospital, with the chief complaint of crowded supernumerary teeth on the mandibular incisor region. Clinical and radiographic examinations revealed six permanent mandibular incisors similar in size, shape, and length. Further investigation using computed tomography(CT) was proceeded on the mandible to measure and compare morphologic features and positions of the six incisors. Then, we decided to remove two incisors which were already erupted. Periodic check-up was followed to monitor the dental development and spontaneous positional enhancement of the remaining four incisors in the mandible.

• The korean journal of orthodontics
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• v.23 no.1 s.40
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• pp.47-55
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• 1993

This study was designed to recognize the factors which can affect the normal eruption of the lower third molar and the eruption rate of the lower third molar in the cases of non-extraction and the extraction of first premolar. The sample consisted of 214 cases of extraction of first premolar and 119 cases of non-extraction, and all of these cases were divided into erupted and impacted lower third molar groups and were analized according to the pantomogram. The results of the study were as follows : 1. The eruption rate of the touter third molar was $54.67\%$ in the group of extraction of the first premolar and $35.29\%$ in the non-extraction group. 2. The early inclination of the erupting lower third molar has significant effect in the eruption of it. 3. In the orthodontic treatment, the extraction of first premolar is one of the factors infuencing the nomal eruption of lower third molar. 4. The available space for the normal enruption of lower third molar was greater in first premolar extraction case than in non-extraction case.

• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.493-501
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• 1993

It is the aim of this study to determine the impacts of radicular development of lower third molars on its eruption/impaction and to grope the prediction for eruption and/or impaction in advance. Three hundred and thirty cases of orthopantomogram were employed and classified as mesial root-dominant group, distal root-dominant group and Identical group according to the radicular development of lower third molars. This presentation has carried out the incipient mesial inclination, radicular development, impaction/eruption rate and changes of mesial inclination of the very teeth. Consequently the following summary and conclusions were drawn; Radicular development dominated mesial root than the distal and dominant mesial root invited higher potentialities for normal eruption. The mesial or honzontal impactions were detected on the distal root-dominant group. This analysis has been suggested the potential eruption/impaction of lower third molars were dependent upon the radicular development and the incipient mesial inclination.

• The korean journal of orthodontics
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• v.34 no.1 s.102
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• pp.1-11
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• 2004

Predicting the arch length discrepancy by simply comparing the available arch perimeter with tooth materials is merely a 2-dimensional analysis of the teeth movement. However, the real teeth movement takes place 3-dimensionally and is affected by various factors such as, the arch fen the curve of Spee and the axis of the incisors. The purpose of this study is to clarify the relationship between the decrease in the arch perimeter and the horizontal positional change of the incisors after extraction of the 1st bicuspids, for more analytic evaluation of the arch length discrepancy at pre-treatment model analysis stage. In addition to that to evaluate the effect of the curve of Spee, teeth axis to the basal plane, and the incisional crowding to the treatment outcome. All patients were treated at the department of orthodontics, dental hospital, Yonsei university. Inclusion criteria for patients selection were as follows. $\cdot$ Angle classification I malocclusion with bialveolar protrusion $\cdot$ Extraction of 4 1st bicuspids $\cdot$ No tooth anomaly or prosthesis $\cdot$ No abnormal attrition $\cdot$ No ectopically erupted teeth $\cdot$ Angle classification I canine and molar relationship $\cdot$ Less than 3mm of crowding Model analysis of the above patients was performed and the following conclusions were obtained. 1. When the intercanine distance was maintained, the available space for the distal movement of the mandibular incisors after the extraction of the 4 1st bicuspids was larger than the space provided by the extraction of the 4 1st bicuspids. However the difference was less than 1mm. The more tapered the anterior arch form, the larger the difference. 2. Compared to the situation in which the intercanine distance was maintained, when the intercanine distance was expanded to meet the width of the Posterior teeth, the incisors could move about 3mm more distally. 3. The positional difference of the incisal tip was insignificant whether the central incisors were moved by tipping or bodily movement. 4. When the anterior crowding was solved without changing the intercanine distance, the larger the anterior arch length was, the more the anterior movement of the incisors. 5. When the curve of Spee was levelled, the increase in the arch perimeter was less than half of the deepest curve of Spee.

• The korean journal of orthodontics
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• v.35 no.6 s.113
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• pp.451-458
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• 2005

Cephalometric superimposition is unable to evaluate tooth movement along the occlusal plane and the errors of photographing and superimposition of the occlusogram is also inevitable. The purpose of the present study was to evaluate the rotational movements of the maxillary posterior teeth following space closure after extraction of maxillary first premolars. using 3D dental images. In 19 adult females. analysis of rotational movements of the maxillary posterior teeth was performed between the initial and final 3D dental images superimposed on the maxillary hard palate. The results showed a diversity of rotational movements of posterior teeth. The causes of various rotational movements may be different rotation of molars in each case at the beginning of treatment. individual characters of the dental arch and tooth morphology. The results of the study indicate that accurate evaluation of rotational movements of posterior teeth following space closure after extraction of premolars using 3D dental images can be obtained through the subdivision of tooth movement during the initial aligning, space closure and finishing stages.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.343-351
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• 1998

The purpose of this study was to investigate the pretreatment and posttreatment dentofacial characteristics of non-extraction patients with Class I malocclusion. And to compare this result with matched non-orthodontic normal occlusion and Class I premolar extraction patients. Such comparison might help identify morphologic characteristics of the non-extraction patients. Initial and final cephalometric evaluation were compared in a sample of 22 patients with Class I malocclusions treated in non-extraction manner with edgewise appliance and MEAW The mean age of the total population was 14 years 9 months and the average treatment time was 2 years 8 months. 32 landmarks were located and digitized on each cephalogram. From these landmarks, 24 linear and angular dimension were obtained. Student's t-test were used to compare the pretreatment - posttreatment results, Nonextraction - Normal groups, and nonextraction Extraction groups. Significance was predetermined at $p{\leq}0.05$. The results were as follows. 1. Before treatment, the mean value of the $ODI\;was\;69.9^{\circ},\;APDI\;was\;82.1^{\circ},\;CF\;was\;152^{\circ},\;EI\;was\;152^{\circ}$ in the non-extraction groups. 2. The skeletal pattern of the non-extraction groups were similar with non-orthodontic normal groupsr, but the non-extraction groups had larger interincisal angle. 3. Comparison between groups treated with and without extraction indicated at pretreatment, the extraction groups had more protrusive lips, smaller interincisal angle, and EI. 4. After treatment, there was no significant changes in the skeletal pattern of the non-extraction groups, but uprighting of the maxillary and mandibular first molar and decrease of the interincisal angle were seen.

• The korean journal of orthodontics
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• v.27 no.3 s.62
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• pp.421-430
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• 1997

Alveolar bone grows with development of tooth germs and roots; bone deposition occurs with tooth eruption. Bone components undergoes processes of resorption and deposition, and when the balance between them is disrupted, decrease in alveolar bone height or excessive bone deposition result. It has been hon that repositioning of teeth through orthodontic treatment can cause alveolar bone resorption which result in decreased alveolar bone height, and there have been many studies to evaluate such effects. X-ray films that could be replicated and standardized were chosen in clinical studies, and among them, bitewing films were used for objective evaluation of changes in alveolar bone level. Twenty subjects, 10 to 13-year- old (average 12.2) children with Cl I molar key, healthy oral condition, no congenital missing, no periodontal disease, and pre-and post-orthodontic bitewing films, were randomly selected for comparison of alveolar bone heights. Amounts of tooth and changes in alveolar bone heights were analyzed. The following results were obtained: 1. Amount of tooth movement in canine, premolar, and molar regions, changes in tooth axis, and changes in alveolar bone heights were measured, and the mean and median values were obtained. 2. When pre-and post-orthodontic alveolar bone levels were compared, larger changes were noticed in maxilla than mandible. 3. When mesio-distally compared, larger changes were observed in the distal sides of 3D3 and 4M3, mesial sides of 4M3 and 4D3, distal sides of 4D3 and 5M3, mesial sides of 5M3 and 5D3, md distal sides of 5D3 and 6M3. 4. When the amounts of tooth movements(TX, TY)and changes in tooth axis(A) were compared,34TX, 34TY, 34A of both sides in maxilla were greater, iud changes in alveolar bone level were greater than any other region.

• The Journal of the Korean dental association
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• v.47 no.6
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• pp.364-372
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• 2009

치주 질환으로 인하여 소실된 치주조직을 재생시키려는 여러 술식이 많이 연구되고있다. 그 중 bioactive factor의 적용은 치주조직의 재생에 있어서 우수한 치료법으로 평가되고 있으며, 이를 수용부에 적절히 적용하기 위한 운반체로 생체친화적인 중합체가 이용되고 있다. 본 연구의 목적은 PLGA를 Inorganic filler에 혼합시킨 재료를 성견의 일벽성 골내낭에 적용하여 이 재료의 생체 친화성과 생체 흡수도를 보고자 하는 것이다. 5마리의 비글견에서 제 3 소구치를 모두 발치한 뒤, 8주간의 치유기간이 지나고 제 2 소구치 원심면과 제 4 소구치 근심면에 5mm 깊이, 4mm폭의 일벽성 골내낭을 형성하였다. 좌측 defect에는 PLGA/inorganic filler matrix를 이식하였고 우측에는 아무것도 이식하지 않은 대조군으로 나누어 술 후 8주에 희생하여 치유 결과를 조직학적으로 비교 관찰하였다. 조직학적 분석 결과, 모든 결손부에서 염증의 소견이 관찰되지 않았으며 치근흡수와 유착은 발견되지 않았다. 백악질과 치조골, 치주인대를 포함한 치주조직의 재생에 있어서 대조군, 실험군 간에 조직학적으로 치유양상에 있어 차이를 많이 보이지 않았으며 PLGA/inorganic filler matrix는 8주 내에 완전히 흡수되어 결합조직이나 신생골내에서 그 흔적을 발견할 수 없었다. 이러한 결과는 PLGA/inorganic filler matrix는 생체친화성 및 생체흡수성이 우수한 재료로서 치주 조직의 재생 치료에 있어서 신체활성인자의 scaffold로 사용될 수 있는 가능성을 보여주었다.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.459-464
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• 2003

Dentigerous cyst is a cyst arising by tissue fluid accumulation between the enamel and the residual enamel epithelium. It includes the crown of the impacted tooth and excludes the root. The treatments of the dentigerous cyst are enucleation, marsupialization, decompression, surgical excision and etc. In these cases children were evaluated for the chief complaints of the remained mandibular primary second molar. Each cases showed swelling on the buccal side of the primary secondary premolar. In the radiologic evaluation a radiolucent lesion including the crown of the mandibular secondary premolar was found, and it was diagnosed as dentigerous cyst. And the histopathologic examination showed the same result. Marsupialization was operated through alveolar socket and the alveolar socket was protected with vaseline gauze, the obturator combined with space maintainer was followed by the operation. After the operation, the impacted permanent tooth was showing faster eruption speed than the other normal teeth.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.8-19
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• 2009

The purpose of this study was to investigate the effects of four restorative materials under various occlusal loading conditions on the stress distribution at the CEJ of buccal. palatal surface and central groove of occlusal surface of endodontically treated maxillary second premolar, using a 3D finte element analysis. A 3D finite element model of human maxillary second premolar was endodontically treated. After endodontic treatment, access cavity was filled with Amalgam, resin, ceramic or gold of different mechanical properties. A static 500N forces were applied at the buccal (Load-1) and palatal cusp (Load-2) and a static 170N forces were applied at the mesial marginal ridge and palatal cusp simultaneously as centric occlusion (Load-3). Under 3-type Loading condition, the value of tensile stress was analyzed after 4-type restoration at the CEJ of buccal and palatal surface and central groove of occlusal surface Excessive high tensile stresses were observed along the palatal CEJ in Load-1 case and buccal CEJ in Load-2 in all of the restorations. There was no difference in magnitude of stress in relation to the type of restorations. Heavy tensile stress concentrations were observed around the loading point and along the central groove of occlusal surface in all of the restorations. There was slight difference in magnitude of stress between different types of restorations. High tensile stress concentrations around the loading points were observed and there was no difference in magnitude of stress between different types of restorations in Load-3.