• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.203-211
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• 2008

Minimizing damage to anatomical structure is a prerequisite for skeletal anchorage system to install a miniscrew. This research has focused on evaluating the stability and safety of installation in the maxillary molar buccal area, in which most miniscrews are installed clinically and initial fixation is weak. CT (computerized tomography)images were taken for surveying the possibility of damaging to adjucent teeth in accordance with installation angle. If we install a mini-screw($1.2{\times}6.0mm$) in the maxillary molar buccal area, it would be located generally in the 5~8mm upper of CEJ and 3~5mm inner of the cortical bone surface. We has measured the space between roots And comparison has been made for gender and the space between roots in accordance with the 3 different angles of installation(30 degree, 40 degree, 60 degree) in 3 categories. Category 1 : between 1st molar and 2nd molar Category 2 : between 1st molar and 2nd premolar Category 3 : between 1st premolar and 2nd premolar The result are as follow; 1. The space for category 1 was significantly small. 2. For the installation angle, it was safer to install with steeper angle in category 1 and category 2, but not in category 3. According to these results, the installation a miniscrew in category 2, 3 is safer than in category 1. And it is safer to install with steeper angle in category 1 and category 2.

• Journal of Periodontal and Implant Science
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• v.27 no.1
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• pp.61-78
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• 1997

PDGF-BB has been recognized as a highly potential growth factor for guided tissue regeneration in periodontal defect. This study carried out histologic and histometric evaluation of $200ng/cm^2$ PDGF-BB loaded bioresorbable membrane made from polyglycolic and polylactic acid. It was tested for its biocompatibility, ability to prevent epithelial downgrowth and amount of periodontal regeneration. Without membrane and PDGF-BB unloaded bioresorbable membrane were used as control. Healthy six beagle dogs were used. Each dog was anesthetized and buccal flaps were reflected in the mandibular and maxillary premolar areas. Buccal alveolar bone between the mesiobuccal and distobuccal line angles was surgically removed on the lower 2nd and 4th premolar in mandible, 2nd premolar in maxilla, to a level 4mm apical to the cementoenamel junction with creating a Class II buccal furcation defect for available space. Care was taken not to remove the root cementum layer and rubber impression materials were placed over each surgically created defect. Flaps were repositioned and sutured. Reconstructive surgery was performed 1 month after defect preparation. PDGF-BB loaded membranes and controls were randomly placed on maxillary 2nd premolars and mandibular 2nd and 4th premolars. Plaque control regimen was instituted with daily brushing with a 0.1% chlorhexidine digluconate during experimental periods. The animals were sacrificed 2 and 5 weeks after surgery and undecalcified specimens were prepared for histologic evaluation. The degree of coronal regrowth of new bone, new cementum and the amonut of new bone areas formed on the defected area of the PDGF-BB loaded membrnae turned superior to without membrane and drug unloaded membrane. Experimental membrane could prevent the epithelial downgrowth irrespective of drug loaded or not and showed good biocompatiblity, These results implicated that PDGF-BB loaded bioresorbable membrane could be highly useful tool for guided tissue regeneration of periodontal defects.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.1
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• pp.99-107
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• 2017

In the management of ankylosed primary molars, early diagnosis, proper treatment, and thorough follow-ups are very important. Untreated infraocclusion due to ankylosis has a negative impact on normal occlusal development, and may cause problems. There are many treatment options on infraoccluded deciduous molars, such as periodic observation, conservative method, restoration, and space regaining via extraction of the teeth. In this case report, two 6-year-old girls were diagnosed with ankylosed maxillary second primary molar and displaced tooth germ of the second premolar. Early surgical removal of the ankylosed primary molar was considered as a treatment approach. The long-term follow-up shows normal eruption of a succeeded permanent premolar.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.825-836
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• 1998

The intention of this study was to investigate the preventive effect of chlorhexidine varnish on enamel demineralization. The sample consisted of 57 first premolars scheduled to be extracted for orthodontic purposes. The control group (N=10) was left untreated and the experimental groups were worn with specially designed stainless steel orthodontic bands on premolar for plaque accumulation. The group 1 (N=9) was worn band only, the group 2 (N=19) was applied with chlorhexidine varnish for one time, and the group 3 (N=19) was applied with chlorhexidine varnish for 3 times once a week. After 4 weeks of experimental periods, every specimen were examined by SEM and Vickers hardness test to evaluate and compare the degree of enamel decalcification. The results were as follows: 1. Although SEM revealed various degree of enamel demineralization in every experimental groups, the group 1 showed more severe demineralizations than the group 2 and 3. 2. The mean Vickers Hardness Numbers measured in this study seemed to reveal that there was a statistically significant difference between the control goup and the group 1 (P<0.05), and also a significant difference between the group 1 and the group 2, 3 (P<0.05). And there was no significant difference between the group 2 and the group 3 (p>0.05). 3. The results of VHN did not deemed to show a statistically significant difference between maxillary premolar and mandibular premolar in both group 2 and group 3 (P>0.05).

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.2
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• pp.265-275
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• 1993

The purpose of this study was to compare the interpretation results of the panoramic radiographs with those of intraoral radiographs in evaluation of alveolar bone loss. All radiographs were obtained from 100 patients who had visited the Dental Infirmary of Kyungpook National University Hospital for periodontal state evaluation. The results were as follows: The percentages of interpretable sites were 95.9%(94.6% in maxilla, 97.4% in mandible) on the intraoral radiographs, and 90.7%(84.0% in maxilla, 97.3% in mandible) on the panoramic radiographs. The concordance of interpretation scores of marginal bone loss between intraoral and panoramic radiographs was 66.3%(65.6% in maxilla, 66.8% in mandible). And according to the site, the highest concordance was in the distal surface of the mandibular 2nd premolar at 82.0%, and the distal surface of the mandibular 1st premolar(76.8%), the distal surface of the maxillary central incisor(75.8%), the mesial surface of the 2nd premolar (75.0%) in descending order of frequency. According to the interpretation scores of the marginal bone loss, the percentages of concordance between intraoral and panoramic radiographs were the highest on the score 10 at 76.4%, and the lowest on the score 8, 9. And the percentages of concordance were inverse proportional rate from the score 5 to the score 9. Number of the observed sites of the furcation involvement in bitewing and panoramic radiographs were 268 sites, and the percentage of interpretable sites was 92.9% in bitewing radiographs and 86.6% in panoramic radiographs. And the concordance rate of interpretation was 79.5%.

• 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.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.61-71
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• 2009

Anchorage control is important in orthodontic treatment. Recently miniscrew is widly used as maximum anchorage in orthodontic treatment, and then it is important to install miniscrew safely without damaging adjacent anatomic structure. In a view of Miniscrew's stability, maxilla is unfavorable than mandible, and moreover maxillary soft buccal bone has disadvantage on stability. so palatal area comes into notice for installation area. We measured distance between palatal roots and bone thickness at midpalatal area using 3D computed tomography, and have found following results. 1. On the comparison of distance between palatal roots, the distance between 2nd premolar and 1st molar was significantly longest and the distance between premolars was significantly shortest. 2. Going toward lateral area from midpalatal suture and posterior area from zero point, bone thickness significantly became shorter and shorter. And 5.0mm palatal sagittal plane has more significance decrease of bone thickness than 2.5mm palatal sagittal plane. According to these results, we can conclude that the palatal installation of miniscrew between 2nd premolar and 1st molar is safest. And it is more safe that comes closer to midpalatal suture and to anterior area in regard to incisive canal.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.275-285
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• 1991

The clinical and radiographic features of 655 congenitally missing teeth were studied with full mouth periapical radiograms and/or pantomograms from 368 persons visited the Department of Oral Radiology, Infirmary of Dentistry, Kyung Hee University during January 1981 to December 1989. The obtained results were as follows: 1. The prevalence of congenitally missing teeth was revealed to be 8.75% in total examined persons, and there was a higher prevalence in females (9.5%) than in males (8.0%). 2. The most frequently missing teeth were mandibular second premolars (24.6%), followed by mandibular lateral incisors (21.7%), maxillary second premolars (16.2%), and maxillary lateral incisors (11.5%). 3. There was a higher prevalence in the mandible (60.3%) than in the maxilla (39.7%), and no significant differences between right (49.65%) and left (50.35%) side. 4. In number of congenitally missing teeth per person, 54.6% had one missing tooth, and 32.9% had two missing teeth. 5. In persons with one or two congenitally missing teeth, the most frequently missing tooth was mandibular lateral incisor, and the second premolar was the tooth most frequently missing in those persons with more than three congenitally missing teeth.

• The Journal of the Korean dental association
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• v.48 no.11
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• pp.819-828
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• 2010

Activator is a removable functional appliance used for correcting the skeletal Class II malocclusion in children with the mandibular deficiency. Berlin standard activator modified from Andresen activator has following characters; do not cover the palatal surface for tongue space, relief on lingual surface of mandibular incisors and resin capping 1/3-1/2 of crown height on mandibular incisors for preventing labioversion of mandibular incisors, L-hook between maxillary lateral incisor and canine for anterior high pull headgear, relief on mandibular posterior bite block for differential eruption of posterior teeth. Two cases presented here had a mandibular deficiency and slight maxillary protrusion. First case (an 11-year-old girl) treated with Berlin standard activator and anterior high pull headgear for 13 months followed by fixed orthodontic appliance for another 29 months. Second case (a 12-year-old boy) treated with Berlin standard activator for 6 months followed by fixed appliance for another 24 months. Treatment results showed a significant improvement in sagittal skeletal and occlusal relationship without premolar extraction. Mandibular condyles were concentric in TMJ [ossa, and masticatory muscle activities were normalized after treatment. In the retention period facial harmony and occlusal stability was maintained.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.319-326
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• 1993

The purpose of this study was to evaluate the frequency of congenital missing teeth and supernumerary teeth in cleft patients. The subjects were divided into bilateral cleft lip and palate(BCLP), unilateral cleft lip and palate(UCLP) and cleft palate alone(CP alone) groups. 97 cleft patients(BCLP 15, UCLP 70, CP alone 12) between 6-20 years old were evaluated. Panorama film, Orthodontic chart and initial intraoral photogram were employed for this research. The obtained results were as follows. 1. The incidence of congenital missing teeth in total cleft samples was $57.7\%$, and the incidence of supernumerary teeth was $26.8\%$. Each incidence was higher than non-cleft. 2. The incidence of congenital missing teeth was the highest in BCLP and the lowest in CP alone. 3. The number of congenital missing teeth per perso was usually one, and the frequency was higher in the maxillary lateral incisors$(67.8\%)$, and maxillary second premolar$(14.9\%)$ than other teeth. 4. Most of tooth number anomalies in cleft patients were found in maxilla, especially adjacent region to the cleft site.