• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.321-329
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• 2002

Bending moments results from offset overloading of dental implant, which may cause stress concentrations to exceed the physiological capacity of cortical bone and lead to various kinds of mechanical failures. The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different angulated placement of dental implant in mandibular posterior missing areas. The three kinds of finite element model, were designed according to 3 main configurations: Model 1(parallel typed placement of 2 fixtures), Model 2(15. distal angulated placement of one fixture on second molar area), Model 3(15. mesial angulated placement of one fixture on second molar area). The cemented crowns for mandibular first and second molars were made on the two fixtures (4mm 11.5). Three-dimensional finite element models by two fixtures were constructed with the components of the implant and surrounding bone. A 200N vertical static load were applied to the center of central fossa and the point 2mm apart from the center of central fossa on each model. The preprocessing, solving and postprocessing procedures were done by using FEM analysis software NISA/DISPLAY IV Version 10.0((Engineering Mechanics Research Corporation, USA). Von Mises stresses were evaluated and compared in the supporting bone, fixtures, and abutment. The results were as following : (1) Under the point loading at the central fossa, the direction of angulated fixture affected the stress pattern of implants. (2) Under the offset loading, the position of loading affected more on the stress concentration of implants compare to the angulated direction of implants. The results had a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the placement angulation of implant fixture is placed toward mesial or distal direction. In designing of the occlusal scheme for angulated placement, placing the occlusal contacts axially during chewing appears to have advantages in a biomechanical viewpoint.

• The Journal of the Korean dental association
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• v.23 no.7 s.194
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• pp.625-630
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• 1985

11 years 7 months old female had a reverse object of anterior teeth and class III molar relationship. Maxillary right and left canines were erupted labially and lower left lateral incisor was congenitally missed. She was treated by rapid palatal expansion and full band technique with extraction of maxillary and mandibular second molars. The following results were obtained. 1. Maxilary arch was expanded. 2. Anterior cross-bite and crowding was corrected. 3. Molar relationship was corrected. 4. Profile was somewhat improved.

• Imaging Science in Dentistry
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• v.34 no.4
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• pp.191-194
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• 2004

This report is to show healing process of two cases of buccal bifurcation cyst (BBC) developed from the mandibular deciduous second molars. Extracting the involved deciduous teeth led to marsupialization of the cysts and promoted eruption of the associated successors without orthodontic force. The cyst-associated premolars in the two cases erupted faster than the premolars on the contralateral noncyst side. The cysts were completely filled with normal bone. The monitoring radiographs showed bone healing, root formation, and path of eruption of the associated teeth after marsupialization of BBC.

• Restorative Dentistry and Endodontics
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• v.38 no.3
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• pp.160-166
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• 2013

This case report demonstrates an unnecessary endodontic treatment of teeth with florid cemento-osseous dysplasia (FCOD) due to a misdiagnosis as periapical pathosis and emphasizes the importance of correct diagnosis to avoid unnecessary treatment. A 30-year-old woman was referred to our institution for apicoectomies of the mandibular left canine and both the lateral incisors. The periapical lesions associated with these teeth had failed to resolve after root canal treatment over a 3-year period. Radiographic examinations revealed multiple lesions on the right canine, the second premolar, and both first molars as well as the anterior region of the mandible. Based on clinical, radiographic and histological evaluations, the patient condition was diagnosed as FCOD. The patient has been monitored for 2 years. To avoid unnecessary invasive treatment, accurate diagnosis is essential before treatment is carried out in managing FCOD.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.243-258
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• 2008

The purpose of this study was to investigate the relationship between the stages of calcification of various teeth and skeletal maturity stages among Korean individuals. The study subjects consisted 154 female and 179 male ranging from 7 years to 16 years of age. A total of 333 hand-wrist, cephalo-lateral and panoramic radiographs were obtained and analyzed. The tooth development of the mandibular canines, first, second premolars, and second molars were assessed according to the Dermijian's system. Skeletal maturity stages were determined from hand-wrist radiographs by using the SMI system and cephalo-lateral radiographs by using the CVMS, respectively. The results were as follows. 1. The mean ages of each stage of skeletal maturity were consistently younger in female subjects. 2. There was a high correlation between skeletal maturity of hand-wrist and cervical vertebrae in the both sexes. 3. There was a high correlation between skeletal maturity and dental calcification stage of mandibular canines, first premolar, second premolars, and second molar. 4. The mandibular second molar was tooth showing the highest correlation. 5. Percent distributions of the relationship between calcification stages of individual teeth and stages of skeletal maturity were obtained in both sexes. In summary, this suggests that tooth calcification stages from panoramic radiographs might be clinically useful as a maturity indicator of the pubertal growth period.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.122-134
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• 2000

The aim of this study is (1) to establish the baseline information concerning the width of keratinized gingiva, depth of gingival sulcus and width of attached gingiva on the buccal surface of the teeth: and (2) to determine the relationship between the above values and tooth eruption: and (3) to estimate the frequency of mucogingival problems. The results were as follows; 1. The mean width of attached gingiva of the children aged $6\sim12$ proved to be wider in the maxilla than in the mandible. Of the primary teeth, the widest width was found in the areas of maxillary primary lateral incisors and maxillary primary canines(3.50mm and 3.55mm). The narrowest was noted in the area of mandibular first primary molars(1.34mm) In the permanent dentition, the greatest width was found in the areas of maxillary permanent lateral incisors (3.00mm). The narrowest was noted in the area of mandibular first premolars(0.55mm). 2. In the primary dentition, the width of attached gingiva of primary canines and first and second primary molars became wider from the age of six as the age increased. In the permanent dentition of the boys, only mandibular central incisors and maxillary first molars showed the tendency towards increase in the width of attached gingiva with increasing age. In the permanent dentition of girls, central and lateral incisors of both jaws and maxillary first molars showed statistically significant increase in the width of attached gingiva with increasing age(p<0.05). 3. At the age of tooth change, the attached gingiva of primary teeth were almost wider than those of successive permanent teeth (p<0.05). 4. During the period of 6 to 12 years of age, the width of keratinized gingiva and the depth of gingival sulcus of permanent tooth at the age of twelve were larger than those of primary tooth at the age of six (p<0.05). 5. The maximum in the frequency of mucogingival problems was found in the areas of upper and lower first primary molars of primary dentition, and in the upper and lower first premolars of permanent dentition regardless of sex. The frequency was higher in primary teeth than in the corresponding successive permanent teeth These teeth showed tendency towards increase in mucogingival problems with age.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.3
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• pp.253-263
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• 2022

A buccal pit is a prominent point-like depression that appears at the cervical end of the mandibular molar developmental grooves. A defective buccal pit can be defined as a buccal pit in which the continuity of the dentinoenamel junction is broken and the pit extends to the dentinal level. This study aimed to determine the frequency of buccal pits and defective buccal pits in un-erupted mandibular first and second molars using cone-beam computed tomography (CBCT). The analysis was performed on CBCT images taken from 417 Korean children and adolescents who visited the Department of Pediatric Dentistry, Yonsei University Dental Hospital between 2004 and 2020. Based on cross-sectional views of CBCT images, buccal pits were categorized into 4 classes according to the depth of the pits. The expression rate of the buccal pits was 29.1%. The prevalence of defective buccal pits was 7.9%. The buccal pits tended to develop bilaterally. To date, this is the most comprehensive study on the frequency of buccal pits with the largest sample size. This was the first attempt worldwide to analyze the depth of the buccal pit using CBCT images and to define a defective buccal pit worldwide.

• The Journal of Korean Academy of Prosthodontics
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• v.22 no.1
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• pp.109-122
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• 1984

The purpose of this study was to analyze the magnitude and mode of the stress distribution induced in the supporting alveolar bone and periodontal ligament and, to determine the displacement of abutment teeth and telescope denture base by applying chewing force to the telescope denture quantitatively and qualitatively. Two finite element models of telescope denture that were restored the missing mandibular second molar with two abutment teeth which were constructed. In two different models, parallel and tapering type telescope crowns were constructed. These finite element models of two cases used for these experiment were a two-dimensional mesiodistal section of the mandibular second bicuspid and first molar. Chewing force of 25Kg that was devided in the ratio of 45/155 (29%) in bicuspid and 55/155 (35.5%) in molars was applied to telescope denture and abutment teeth respectively. The displacement of the telescope denture base and abutment teeth and the stress distribution in the periodontal ligament and alveolar bone were analized to investigate the influence of chewing force acting on the telescope denture and abutment teeth. The results were as follows: 1. Abutment teeth displaced mesially and the magnitude of displacement of abutment teeth in vertical direction were more than that of horizontal direction in two cases. The displacement of abutment teeth on the telescope denture treated with tapering type telescope crown were less than that of the parallel type crown. 2. The displacement of the telescope denture base that were treated with parallel type telescope crown were less than that of treated with tapering type telescope crown. 3. The stress induced in the alveolar bone and periodontal ligament on abutment teeth that treated with parallel type telescope crown were more than that of treated with tapering type telescope crown and more stress induced in the alveolar bone than in the periodontal ligament. 4. In the telescope denture, the magnitude of displacement of abutment teeth and stress induced in the periodontal ligament and alveolar bone were within physiologic limit.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.399-406
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• 2013

Reports about the intrusion of a natural tooth bounded by implants are very rare, although some concerns have been discussed on the intrusion of teeth connected to implants. A female aged 56 years received an implant (mandibular right first premolar) and post/core onto root rest (mandibular right second premolar) and was restored by single zirconia crown, respectively. Molars were implant restorations. Four month after loading, second premolar was intruded and prominent gap was shown between opposite tooth. Because nonspecific discomfort was expressed, observation was decided after explanation of prognosis of tooth without treatment. Three month later reversal to original position was detected on the periapical radiographs and fully recovered position with intimate contact was completed 11 more months later. Till now 2 years and 3 month observation is being performed. Through the observation of spontaneous recovery of a natural tooth bounded by implants, the cause of intrusion and a mechanism of spontaneous recovery could be estimated.

• Korean Journal of Cleft Lip And Palate
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• v.4 no.2
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• pp.19-27
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• 2001

This study was performed to determine the prevalence of hypodontia and hyperdontia of permanent teeth among Korean schoolchildren, and to compare differences in the prevalence between Korea, other country, and other ethnic groups. The sample consisted of 346 girls aged 6.9～0.3 yr and 375 boys aged 6.8～0.4 yr on whom a panoramic radiograph was taken at Yeonchun-Gun community in Korea. The prevalence of congenitally missing teeth (third molars excluded) was 6.7% in boys and somewhat higher, 9.5% in girls, and 8.0% for both sexes combined. On the average, number of missing teeth per affected child was 1.9 teeth. The most commonly congenitally missing teeth were the mandibular second premolar (32.7%), followed by the mandibular incisor (28.7%), the maxillary second premolar (16.7%), and the maxillary lateral incisors (10.2%). The prevalence of supernumerary teeth was 2.1 % in boys, 1.4% in girls, and 1.8% for both sexes combined. The most common supernumerary teeth were the mesiodens (76.9%), followed by the supernumerary premolar (23.1 %). The affected male-female ratio was 1.6: 1.0. The prevalence of congenital missing teeth in this study was similar to in studies of Japanese, Danish, American and German. The frequency of hyperdontia was lower in this study than in studies of Chinese children, Japanese and American.