• Maxillofacial Plastic and Reconstructive Surgery
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• v.14 no.4
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• pp.327-339
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• 1992

This study was undertaken to investigate the effect of orthognathic surgery on occlusal force. The maximum bite force was measured in 26 dentofacial deformity patients, aged 14-26(mean age 20.3) years, before surgery and at IMF removal, 3, 6, and 12months postsurgery. To grope the correlation of bite force and skeletal change after orthognathic surgery, the cephalometric headplates were measured, tabulated and statistically analyzed. The results were as follows. 1. The presurgical maximum bite force was 13.7kg in upper first molar(rt. Side 12.7kg, it. Side 14.6kg). There was remarkable difference with that of normal occlusion. 2. The recovery of bite force was very significant in according to the operation method and the duration of IMF that was 7.6kg at IMF removal, 14.2kg at 3 months, 19.7kg at 6 months. 26.1kg at 12 months postsurgery. 3. To fasten the recovery and to increase the bite force after orthognathic surgery, the long IMF time and the injury to the masticatory muscle should be avoided by the internal rigid fixation and early physical exercise. 4. The bite force was positively correlated to the changes of mandibular plane angle, the angle between platatal plane and mandibular plan, the angle between occlusal plane and mandibular plane, and negatively correlated to the changes of mandibular body length in craniofacial structure. 5. There was no correlationship between bit force and mesial inclination of tooth long axis of first molar in this subject. 6. There was no correlation between the changes of bite force and the changes of mechanical advantage of the temporal and masseter muscle.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.807-823
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• 1995

The purpose of this study was to analyze the stress distribution and the displacement happened to the abutment, the prosthesis, and the surrounding structure according to the location of the nonrigid connector, that is, the keyway in the distal of canine and the mesial of the implant in the three unit fixed partial denture. Two-dimensional finite element model ws constructed and analyzed for the stress distribution and the displacement using software ABAQUS(Ver 5.2 Hibbitt, Karisson & Sorenson, Inc., 1992). After finishing the finite element model, the distribution load of 15kg was applied simultaneously to the all cusp tips of the prosthesis and the concentration load of 10㎏ was applied respectively at the each cusp tip of the prosthesis. The following results were obtained : 1. The amount of displacement of the implant was greater in case of the non-rigid connection than the rigid connection, and the more favorable displacement was shown in case of the IKb than the IKa. 2. Without regard to the connection method, the stress represented at the surrounding bone was similar, and the more favorabel stress distribution was shown in case of IKb. 3. The maximum stress was concentrated at the fastening screw and the neck of implant in all experimental groups, and their stress magnitudes were in the order of IKb, IR, and IKa.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.27-34
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• 2011

This study is making a product for the development of one process worm wheel of making a shape for gear for worm wheel without hobbing manufacturing process. Because of removing a hobbing process, plastic worm wheel for increased productivity and equivalent quality is produced in the result. As the result, this product is selling to Hyundai Mobis, Mando, TRW, KOYO/NSK/Showa(Japan), Delphai(America). The core technology and different strategy are as follows. The technology protection for molding of worm whee is currently patent process "Molding process of helical gear(No. 10-2008-0105908). Further patent procedure for "molding system for positioning decision of inserting boss is currently prepared. As gear molding procedure in hobbing machine without gear machining procedure, most of all, core development technology which is making a gear tooth is main topic. So that, in case of currently developed worm wheel, because core and mold base are not developed in the first procedure, gear is machining in hobbing M/C as the second procedure. In the later, patent for mold base structure will be prepared in this study results.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.334-346
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• 1997

Incidence of using esthetic composite resin in the posterior area is increasing but there were lots of inconsistent reports about their microleakage and marginal adaptation. The purpose of this study was to evaluate the differences of microleakage and marginal adaptation according to restorative techniques. 30 cavities with enamel gingival margin were prepared and restored with 3 types of composite resin [Z-100($Scotchbond^{TM}$ MP), AELITEFIL ($Onestep^{TM}$), Her culite XRV(Fuji BOND LC)] in direct technique and another 30 cavities were restored with preformed CR inlays and 3 different modern resin and resin-modified GI cements (Superbond C&B, Choice, Fuji Duet). Samples were chemically stressed in 75% ethanol for 24 hours and were thermocycled (5-$55^{\circ}C$(500 times. The degree of microleakage through proximal and gingival margins was examined by 1 % MB dye and the degree of marginal adaptation by examining the margins via SEM. The following results were obtained ; 1. In direct groups, Herculite XRV [Fuji BOND LC, 35.13 (15.50) %] group showed statistically different, less microleakage than Z-100 [$Scotchbond^{TM}$ MP, 72.91 (16.91 %] group and AELITEFIL [One-step, 93.73 (13.66) %] group (p<0.05). 2. In indirect groups, the degree of microleakage in Mean(S.D.) were: Super bond C & B [39.00 (24.35) %], Choice [57.19 (33.80) %], Fuji Duet [58.22 (40.36) %]. But there was no significant difference. 3. There was no significant difference between resin cement and resin-modified GI cement. 4. There were gaps at the interface with the tooth structure, but no gap was seen at the interface with restoration in all specimens. 5. In direct groups, Herculite XRV(Fuji BOND LC) group made little gap compared with other groups, but 40-$50{\mu}m$ thickness of bonding agent, Fuji BOND LC, looked like a cement used in indirect technique. 6. All indirect groups showed a variety of cement thickness, from less than $20{\mu}m$ to over $100{\mu}m$ and that dimension of buccal/lingual margin was less than that of gingival margin.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.2
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• pp.196-203
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• 2002

Most dentigerous cysts are solitary. Bilateral and multiple dentigerous cysts are rare and occur typically in association with a number of syndromes such as Maroteaux-Lamy syndrome, Hunter's syndrome, Basal cell nevus syndrome, Marfan syndrome, cleidocranial dysplasia. The presented case is of bilateral nonsyndromic, dentigerous cysts associated with mandibular right and left first premolars. A marsupialization procedure may be a choice of treatment for a large sized dentigerous cyst rather than an enucleation. The marsupialization procedure is recommended during the age when the erupting force of the teeth is still strong. We can expect the unerupted tooth to erupt normally. Although most of bilateral or multiple dentigerous cysts which are not associated with syndromes are rare, a bilateral dentigerous cyst without syndrome is seen. Therefore, it is wise to explain a possibility of development of new one to patient / parents in advance.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.2
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• pp.450-457
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• 1998

The $Papillon-Lef\`{e}vre$ Syndrome(PLS), a disease with autosomal recessive inheritance, is characterized by diffuse hyperkeratosis of the palms and soles, mostly prepubertal periodontitis and premature loss of primary and permanent dentition. The etiology of the destruction of periodontal tissues has not been completely clarified. In recent years, two main factors are suggested to be responsible for tooth loss ; firstly, the presence of gram negative microorganisms in the periodontal pockets of the patients. The other factor suggested is cellular deficiency in chemotaxic and phagocytic function of neutrophylic granulocytes. Resent data suggestes that mechanical debridement in conjunction with antibiotic therapy may be successful in periodontal management of $Papillon-Lef\`{e}vre$ Syndrome, particularly if administered early. In this study, a $Papillon-Lef\`{e}vre$ Syndrome patient was studied clinically, radiologically, histopathologically and microbiologically. 5 years female patient with gingival swelling and destruction of periodontal structure on the whole dentition were examined and palmar and plantar hyperkeratosis were can be seen. On microbiological analysis, Actinobacillus actino-mycetemcomitans was performed. Concurrently, the children recieved extraction of maxillary anterior teeth and construction of removable prosthetis. The combination of professional oral hygiene care and antibiotic therapy improved the dermatologic and periodontal condition.

• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.310-316
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• 2012

A new method for early caries diagnosis was proposed and tested through a home-made optical examination system that used quantitative light fluorescence (QLF) and digital imaging fiber optic transillumination (FOTI) (DIFOTI), with light sources across a wide spectral range, from 350 nm to 1,000 nm. The front-illuminated infrared light scattering image (FIR) showed similar diagnostic abilities to that of DIFOTI. The FIR method was invented based on the observation that caries lesions lose the high transmittance and low scattering properties of benign enamel tissue. There are various methods for the early diagnosis of caries, such as visual examination, exploration, X-ray radiography, QLF, FOTI, and infrared fluorescence (diagnodent). Among them, methods based on optical properties are regarded as having the most potential. A comparative study was performed between the FOTI, QLF, diagnodent, optical coherence tomography, and FIR scattering image methods, using 20 extracted teeth samples with early caries. A scale of lesion measurement based on optical image contrast was proposed. The statistical analysis showed a significant correlation between the DIFOTI and FIR methods (r = 0.35, p < 0.05). However, the QLF and diagnodent methods showed little association with FIR images, as they have different detection principles as compared with FIR. Tomographic images obtained by OCT, using 1,330 nm super luminescent LED as a gold standard of tooth structure, verified that the FOTI and FIR results correctly represented the lack of homogeneity in dental tissue. The newly proposed FIR method attained similar diagnostic results to those of FOTI, but with an easier approach.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.459-473
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• 2000

Dental caries is the most common disease in the maxillofacial area. There are many factors contributing to its development, but complete understanding and prevention is not fully known. Since the structure of the coronal and root portion of the tooth is different, the remineralization and demineralization process is also known to be different. In this study, by using a partially saturated buffer solution, we created artificial enamel and dentin caries and evaluated mineral loss. A remineralization solution with four different degrees of saturation (degree of saturation ; group 1, 0.268, group 2, 0.309, group 3, 0.339, group 4, 0.390, PH 4.3, F-2ppm) was used on a demineralized specimen. The mineral precipitating quantity and depth was evaluated by using microradiography. Using an atomic force microscope (AFM), hydroxyapatite crystals of normal, demineralized, and remineralized enamel and dentin were evaluated. The results were as follows: 1. As the degree of saturation of the remineralizing solution increased, the mineral precipitation in the enamel was increased. In group 4, mineral precipitation was limited near the surface. 2. As the degree of saturation of the remineralizing solution increased, the mineral precipitation in the dentin was decreased and it occurred in a deeper portion. In group 4, however, mineral precipitation occurred on the surface and its quantity increased. 3. There was a statistically significant interaction between enamel and dentin mineral content changes on specimens treated with remineralization and demineralization solution (demineralization r=0.44, remineralization r=0.44, p<0.05). 4. Demineralized hydroxyapatite crystals showed central and peripheral dissolving and widening of intercrystal spaces under the AFM. 5. In dentin remineralization small crystal precipitation occurred between the large crystals. We conclude that by adjusting acidulated buffer solution's degree of saturation, we can control enamel and dentin remineralization. In addition, the AFM is highly useful in evaluating changes in remineralized and demineralized hydroxyapatite crystals.

• The korean journal of orthodontics
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• v.21 no.3
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• pp.521-541
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• 1991

The purpose of this study was to investigate the growth changes of the mandible and associated structure in response to postural hyperpropulsion and changes after removal of postural hyperpropulsor. The experimental animals were four-week-old Sprague-Dawley males rats. The animals were worn the postural hyperpropulsor diurnally for 10 hours per day. The animals were sacrified after 1-week, 2-week, 4-week postural hyperpropulsion and 4-week postural hyperpropulsion 4-week removal period. The growth changes of rat mandible and associated structures following postural hyperpropulsion on the growing rat mandible were observed biometrically, radiographically and histologically. The finding were as follows. 1. The angle between the chief axis of the bone trabeculae in the condyle and the mandibular plane of rats observed for 4 weeks after worn the hyperpropulsor for 4 weeks was directed posteriorly as compared with that of control rats. 2. The ratio of mandibular length to maxillary length of experimental rats was higher than that of control rats. 3. The tooth axis of mandibular first molar of rats worn the postural hyperpropulsor for 4 weeks was mesially inclined as compared with control rats. 4. Histologically, the cartilage layer at the superior region of the condyle of rats worn the postural hyperpropulsor for 2 weeks appeared thicker than that of same aged normal rats, and generalized increase of the cartilage layer was shown on the condyle of rats worn the postural hyperpropulsor for 4 weeks. 5. There was no significant histologic difference between rats observed for 4 weeks after worn the postural hyperpropulsor for 4 weeks (8 week experimental rats) and same aged normal rats. 6. The newly formed bone at anterior region of articular fossa of rats worn the postural hyperpropulsor for 2 weeks and 4 weeks was thicker than that of same aged normal rats.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.647-657
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• 2004

A non-carious cervical lesion(NCCL) is the loss of tooth structure at the cementoenamel junction level that is unrelated to dental caries. This study was to evaluate the occlusal and periodontal status of teeth with non-carious cervical lesions. We evaluated 105 teeth with non-carious cervical lesions in 35 subjects aged 38-75 years and characterized them based on the shape and dimension, plaque retention, bleeding on probing(BOP), probing pocket depth(PPD), occlusal status, brushing type, hypersensitivity and wear facet. The results of this study were as follows 1. No significant association was observed between cervical lesions and occlusal contact in lateral excursions. 2. No significant difference occurred in plaque retention, PPD, BOP between teeth with and without cervical lesions. 3. Test teeth had a significantly higher percentage of hypersensitivity and occlusal wear facet than teeth without cervical lesions. 4. Wedge shaped lesions had a significantly higher percentage of plaque than saucer shaped lesions. 5. Teeth with plaque were found to have significantly deeper PPD than teeth without plaque retention in cervical regions. 6. Teeth with occlusal contacts were found to have significantly deeper PPD than teeth without occlusal contacts. 7. No significant association was observed between cervical lesions and PPD independent of plaque retention and occlusal contacts Although more knowledge is necessary, our results suggest that occlusal contact and bacterial plaque may influence on periodontal tissue, but NCCL is not directly associated with periodontal health