• The Journal of Korean Academy of Prosthodontics
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• v.55 no.4
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• pp.394-402
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• 2017

Purpose: The purpose of this study is to evaluate the displacement of artificial tooth of monolithic complete denture manufactured by milling and 3D printing method in which the denture base and the artificial teeth are simultaneously made. Materials and methods: Twelve upper and lower complete dentures for each were made by milling and 3D printing method. Group Up and Group Lp are a group of upper and lower dentures made by printing, and Group Um and Group Lm are denture groups made by milling. Group Uc and Group Lc are is a group of finally designed upper and lower dentures respectively. Measurements were performed between both central incisors (AB, ab), both canines (CD, cd), both first molars (EF, ef), between an incisor and a first molar (AE, ae), and between incisor and lingual point (AG, ag) for each upper and lower denture. Results: AG and ag value between printed dentures and original ones as well as between milled dentures and original ones showed a statistically significant difference (One-way ANOVA, P<.05) in both lower and upper monolithic dentures. In the lower monolithic ones, ab, cd and ef value revealed a significant difference between Group Lp and Group Lm (One-way ANOVA, P<.05). Conclusion: Dentures made using milling or 3D printers revealed statistically significant difference compared with those of original data. However, it showed clinically very accurate reproducibility.

• Journal of Oral Medicine and Pain
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• v.32 no.2
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• pp.211-218
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• 2007

The purpose of this study was to compare the maximum bite forces between pre- and post-treatment related to specific diagnostic groups of TMD including masticatory muscle disorder (MMD), disc derangement (DD), joint inflammation (JI) and osteoarthritis (OA). Bite force between pre- and post-treatment was compared in 36 patients with unilateral TMD, successfully-managed in the Department of Oral Medicine, Dankook University Dental Hospital, for this study. The ratio of men to women was 7:29 and their mean age of $28.1{\pm}13.7$ years. The patients were categorized, through clinical and radiographic examination, into aforementioned 4 groups; MMD (N=18), DD (N=6), JI (N=5) and OA (N=7). The maximum bite force measurements were done at the antagonizing canines and 1st molars using a bite force recorder. Paired t-test, ANOVA, Multiple Comparison t-tests were used for statistical analysis. The results of this study showed that the maximum bite force before treatment increased after TMD treatment, which was noticeable at the canines (p=0.001 and p=0.000 for the affected and unaffected sides, respectively). In comparison related to the diagnostic groups of TMD, patients with osteoarthritis of TMJ exhibited the lowest strength while those with inflammatory disorder of TMJ had the highest strength on the affected sides. Increase of bite force after treatment was also found in each group. Significant difference between pre- and post-treatment was found at canines on the affected sides in MMD (p=0.045) and DD groups (p=0.009) while on the unaffected sides in OA group (p=0.003). Conclusively, the reduced bite force due to TMD could be recovered by conservative TMD treatment and that the difference of bite forces between pre- and post-treatment was noticeable at the canines.

• The korean journal of orthodontics
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• v.25 no.4
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• pp.403-414
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• 1995

The purpose of this study was to investigate the histologic changes in mandibular periodontium during overbite closure for openbite treatment by continuous arch wires and anterior vertical elastics. Two female monkey(Macaca nemestrina) with permanent dentition were used. Posterior bite block was fixed to each of their maxillae, which made the animal temporary anterior openbite as well as stabilized the whole maxillary anchorage. In each mandible, all the teeth except the second molars which had been extracted, were prepared for cast crowns. 018 inch Standard brackets were welded on these crowns. After cementation, two types of the $016{\times}022$ inch continuous arch wires, the plain ideal arch to the control animal and the MEAW(multiloop edgewise archwire) to the other experimental one were inserted. Then anterior vertical elastics were applied for two weeks. The overbite depth changes in the monkeys and histologic examinations of the mandibular periodontiums suggested the following conclusions. 1. During two weeks of the experimental period, the overbite increased + 0.3 mm in the control and + 1.3 mm in the experimental one. 2. In both the control and the experimental animal, histologic examinations showed that incisors, canines and first premolars were subject to extrusive force and the rest of posteriors were subject to intrusive one. 3. In periodontiums of the extruded incisors of the experimental one, reorientation of the periodontal fiber structures reflected the direction of force and the alveolar bone surfaces including apical and crestal areas which had been subject to tension, were the front of new bone formation. 4. In periodontiums of the extruded incisors of the experimental one, neither excessive hyalinization nor gross root resorption was observed. 5. Alveolar bone remodeling of anteriors and posteriors was more remarkable in the experimental one than the control.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.280-285
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• 2016

Mandible defects could be caused by congenital malformations, trauma, osteomyelitis, tumor resection. If large areas are included for reconstruction, those are primarily due to tumor resection defects. The large jaw defect results in a problem about mastication, swallowing, occlusion and phonetics, and poor esthetics causes a lot of inconvenience in daily life. It is almost impossible to be a part underwent mandibular resection completely reproduced, should be rebuilt artificially. This case is of a patient who was diagnosed with squamous cell carcinoma pT1N0M0, stage I in February 2004 and received surgery (combined mandibulectomy and neck dissection operation (COMMANDO) in oromaxillofacial surgery) in March 2004, by implant assisted removable partial denture. We could obtain good retention and stability through sufficient coverage and implant holding. Follow up period was about four years. Mandibular left third molar regions have been observed to have resorption of surrounding bone, and periodic check-ups are necessary conditions.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.370-377
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• 2018

Although the frequency of composite resin restoration in children is gradually increasing, there are insufficient researches about the rate of composite resin repair in children. The purpose of this study was to evaluate the repair rate of composite resin restorations in the permanent first molar in children under 12 years old. This study retrospectively analyzed 169 children treated with composite resin restoration in the permanent first molar from May 2014 to April 2015. According to the location of the tooth, the repair rate was higher in the mandible than maxilla and in the left than right. In the classification of restoration, the repair rate was the highest in the class II cavity, and the repair rate was the lowest in the restoration of the occlusal surface only. Repair rate in two years was 14.8%, and repair hazard ratio decreased with age. The most common reason of composite resin restoration replacement was the secondary caries (74.1%). Within the limits of study, the repair rate of children was higher than that of adult due to the characteristics of children. Therefore, dentists should understand these characteristics and try to reduce the repair rate of composite resin composite restorations.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.3
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• pp.430-437
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• 2007

The probability table of Moyers and prediction equation of Tanaka and Johnston that have been the most frequently used, cannot produce accurate prediction when used in Korean because they are based on the Caucasian popularity of the Northern European race. The method of Moyers or Tanaka and Johnston predicts sizes of the unerupted canine and premolars on the basis of the sizes of mandibular incisors. However, some of the recent papers raise a question as to whether the mandibular incisors are the best combination to predict the sizes of the unerupted canine and premolars. The purpose of this study is to determine which sum or combination of sums of permanent tooth widths present the best prediction for the unerupted canine and premolars in a Korean sample, to calculate a specific linear regression equation for this population, and to evaluate the clinical significance. A new linear regression equation was calculated based on the data of 178 Korean young adults(70 women, 108 men, mean age 21.63 years) with complete permanent dentitions. Fifty three more children(28 girls, 25 boys, mean age 14.22 years) were used as a validation sample for the application of the multiple linear regression equation. The conclusions were as follows: 1. The combination of the sums of permanent upper central incisors, lower lateral incisors and upper first molars was the best predictor for the unerupted canine and premolars in this sample($r=0.65{\sim}0.80$). 2. The multiple linear regression equation was calculated including sex and arch as additional predictor variables. male, upper: $Y\;=\;0.332{\times}X_0\;+\;6.195$ male, lower: $Y\;=\;0.332{\times}X_0\;+\;5.269$ female, upper: $Y\;=\;0.332{\times}X_0\;+\;5.929$ female, lower: $Y\;=\;0.332{\times}X_0\;+\;5.003$. The determination coefficient of the equation was 64% and a standard error of the estimate was 0.71mm. 3. In about 97% of the validation sample, the estimation of the tooth width sums of unerupted canine and premolars using the new multiple linear regression equation was smaller than 1mm compaired with the actual values.

• Journal of Oral Medicine and Pain
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• v.26 no.3
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• pp.301-308
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• 2001

지금까지 여러 가지 형태의 기기를 이용하여 보고된 사람의 교합력은 그 최대치가 매우 다양하다. 본 연구에서는, 교합력을 측정하기 위하여 새로운 측정기기를 개발하였다. 본 기기를 이용하여 전치부 교합력 측정 시에는 대칭적으로 최대한 물도록 하악을 유도하여 최대 교합력을 측정하였고, 구치부는 편측으로 물도록 하악을 유도하여 최대 교합력을 측정하였다. 교합 시 치아간 수직고경은 15.1mm 였다. 측정기기 내 strain gauge를 사용하여 전기저항의 변화를 힘으로 전환하였다. 마이크로 프로세서가 수치를 계산하면 액정화면에 수치가 표시된다. 실험실 내 기기교정 검사에서는 50kg과 100kg의 부하를 가하였다. 개발된 교합력 측정기기의 임상적 신뢰도를 시험하기 위해 건강한 치과대학 재학생 10명을 대상으로 최대 교합력을 측정 하였다. 이 새로운 측정기기로 측정된 교합력은 이전연구에서 기록되었던 것보다 더 높은 수치가 나왔다. 또한 제1대구치와 전치부에서 최대 교합력을 측정한 경우 실험자 내와 실험자 간에 통계적으로 유의한 신뢰성을 얻을 수 있었다. 본 기기는 안정적이고 조작성이 쉽다고 판명되었다. 그러므로, 본 기기는 더 큰 연구 집단의 선별검사에 매우 유용하게 사용할 수 있을 것이며, 또한 치주질환이 있는 치아나 임플란트, 악관절 장애를 가진 환자의 교합력 측정과 같이 특정된 경우의 교합력 측정에도 유용할 것이다.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.328-334
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• 2009

Statement of problem: Pier abutments act as a Class I fulcrum lever system when the teeth are incorporated in a fixed partial denture with rigid connectors. Therefore non-rigid connector incorporated into the fixed partial denture might reduce the stresses created by the leverage. Purpose: The purpose of this study was to evaluate, by means of finite element method, the effects of non-rigid connectors and supporting alveolar bone level on stress distribution for fixed partial dentures with pier abutments. Material and methods: A 2-dimensional finite element model simulating a 5-unit metal ceramic fixed partial denture with a pier abutment with rigid or non-rigid designs, the connector was located at the distal region of the second premolar, was developed. In the model, the lower canine, second premolar, and second molar served as abutments. Four types of alveolar bone condition were employed. One was normal bone condition and others were supporting bone reduced 20% height at one abutment. Two different loading conditions, each 150 N on 1st premolar and 1st molar and 300N on 1st molar, were used. Results: Two types of FPD were displaced apically. The amount of displacement decreased in an almost linear slope away from the loaded point. Non-rigid design tended to cause the higher stresses in supporting bone of premolar and molar abutments and the lower stresses in that of canine than rigid design. Alveolar bone loss increased the stresses in supporting bone of corresponding abutment. Conclusion: Careful evaluation of the retentive capacity of retainers and the periodontal condition of abutments may be required for the prosthetic design of fixed partial denture with a pier abutment.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.169-179
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• 2004

The purpose of this study was to discriminate clinically and radiographically among the three groups of dentigerous cysts studied. First, Group I, involved area of dentigerous cyst was successive permanent tooth area beneath deciduous tooth. Second, Group II, involved permanent molar area, and the last, Group III involved maxillary anterior supernumerary tooth area. The author observed and compared the clinico-radiographic features of 49 cases of Group I, 36 cases of Group II, and 15 cases of Group III of dentigerous cyst and this observation and comparison had been done by based on the charts and panoramic films. The obtained results were as follows: 1. The cases of Group I were 29 cases and, those of Group II were 36 and those of Group III were 15. 2. The incidence of dentigerous cyst is high in first decade. In Group I, before first decade and early first decade was 87.8%, in Group II and Group III, was discovered more lately. 3. The frequency of dentigerous cyst is 2.5 times higher in male than in female. 4. The sequence of chief complaint was swelling(50%), routine examination(32%), and pain(9%). 5. When considering the type of the cyst, lateral type is many most in Group I (71.4%) and central type is many most in Group II (94.4%) and Group III (100%). 6. The most size of dentigerous cyst was 2 crown size in Group I, 1 crown size in Group II, above of 4 crown size in Group III. 7. Almost involved teeth showed displacement and some tooth of displaced teeth showed delayed root development and dilaceration of root. 8. The most many response of alveolar bone was buccal bone expansion in Group I (67.3%), no bone expansion in Group II(66.7%) and palatal bone expansion in Group III (60.0%). 9. The percentage of involved teeth were as follows : The mandibular third molar was 31% and many most. The mandibular second premolar was 30%. Mesiodens of maxillary anterior area was 15%. The maxillary canine was 8%. The mandibular first premolar was 5%. 10. In the Group I, causes suggesting of dentigeous cyst are pulpotomized deciduous tooth(59.2%), severe dental caries of deciduous tooth, untreated traumatic history on the deciduous tooth etc. 11. The treatment method of dentigerous was marsupialization in 61.2% of cases of Group I and that was enucleation in 61.1% of cases of Group II and in 80.0% of cases of Group III.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.2
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• pp.128-137
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• 2015

Purpose: Most of the former studies about the occlusal contact patterns during the mandibular movement focused on foreigner. The purpose of this study is analyzing the occlusal contacts of young Koreans by using T-Scan system. Materials and methods: The sample size was 87 and the occlusal contacts of each right and left lateral movements were measured from the maximum intercuspation to the 3mm excursive position for three times respectively. All of the occlusal contacts were double checked through the thin metal foil. The results were categorized as two; 1) considering occlusal contact patterns on working side only, 2) considering occlusal contact patterns on working and nonworking sides. Results: The results showed that the nonworking side occlusal contacts play major roles in the lateral mandibular movement. In both cases of considering with and without the nonworking side occlusal contacts, the group function was the most prevalent. In the working side, the contacts were the most frequent in canine and the frequency of contacts was decreased as the distance was increased from canine to molar. In the nonworking side, the contacts were the most frequent in second molar. And the gender factor was statistically significant (${\alpha}$=.05), as females have more nonworking side occlusal contacts in this study. Conclusion: Among the three factors of anterior guidance, the group function was the most dominant factor. The analysis of 87 samples showed that canine contact was the most frequent in the working side and second molar contact was the most common in the nonworking side.