• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.55-58
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• 2000

Spectacle diopter of age related changes during 5 years examined 360 eyes(male 79, women 81) who visited optical shop every year. Increasing refractive error of Myopia obviously appeared in young generation which term was elementary school, and then middle and high school. In this study, we concluded that term of correction spectacles should be 4 months in elementary school, 6 months in middle school, and every year in high school.

• The korean journal of orthodontics
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• v.35 no.2 s.109
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• pp.116-126
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• 2005

The object of this study was to evaluate how friction that occurs during the sliding movement of an orthodontic archwire through orthodontic brackets is differently affected by variant designs and ingredients of brackets and archwires and bracket-archwire angles. In order to simulate the situations which could occur during orthodontic treatment with fixed appliances, 4 types of brackets (Gemini, a stainless steel twin bracket, Mini Uni-Twiu. a stainless steel bracket with a single bracket design and narrow mesio-distal width; Clarity, a metal-reinforced ceramic bracket; Transcend, a ceramic bracket) and 3 types of orthodontic archwires $(0.016',\; 0.016{\times}0.022'\;stainless\;steel,\;0.016'\;Nitinol)$ were used and the bracket-archwire angles were controlled as $0^{\circ},\;3^{\circ}\;6^{\circ},\;and\;9^{\circ}$ Gemini significantly show and the lowest static and kinetic frictions (P<0.001) Clarity showed the highest static and kinetic frictions with a bracket-archwire angle of $0^{\circ}$. and Transcend at $6^{\circ}\;and\;9^{\circ}$ (P<0.001). An $0.016{\times}0.022'$ stainless steel rectangular archwire significantly showed the highest static and kinetic frictions (P<0.01). The lowest static and kinetic frictions were observed when the bracket-archwire angles were $0^{\circ}\;and\;3^{\circ}$ with 0.010' stainless steel round archwires (P<0.01), and $6^{\circ}\;and\;9^{\circ}$ with 0.016 Nitinol (P<0.001). The static and kinetic frictions were increased as the bracket-archwire angles were increased (P<0.001)

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.587-592
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• 1995

The purpose of this study was to observe the pattern of bone remodellings in the periodontal ligament of dog, in which experimental tooth movement was performed A control and 5 experimental dogs, one and half year in age, were studied. Light force (50-75g) was applied by placing open-coil spring between left mandibular premolars ; heavy force (250-300g), between right mandibular premolars. Experimental dogs were sacrificed at 12 hours, 1, 3 ,7 and 14 days after force application, respectively. And soft X-ray films were obtained and read on the sectioned periodontal tissue around mandibular premolars. The results were as follows. 1. New bone formation began to be observed in tension side at 7-day and increased at 14-day , No difference was observed between light force group and heavy force group. 2. Bone resorption was observed as a shape of destruction of lamina dura at 3-day and increased gradually at 7-day, 14-day.

• The korean journal of orthodontics
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• v.36 no.4
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• pp.242-250
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• 2006

Objective: Periodontal ligament fibroblasts have an ectomesenchymal origin and are thought to play a crucial role for not only homeostasis of periodontal tissues but also bone remodeling, wound healing and regeneration of tissues. Recently, it has been reported that UNC-50 is not expressed in gingival fibroblasts but in PDL fibroblasts. The purpose of this study was to examine the expression of UNC-50 and osteocalcin in the periodontium after application of intermittent force. Methods: Twelve rats had 40 grams of mesially-directed force applied at the upper molar for 1 hour/day. Four rats were sacrificed at 1, 3 and 5 days. Immunohistochemical localization of UNC-50 and osteocalcin antibody was carried out. The results showed apposition of new cellular cementum and a slight increase in periodontal space at the tension side. Results: Strong UNC-50 expression was observed in the differentiating cementoblasts close to PDL fibroblasts in the tension side whereas it was barely expressed at the compression side. Expression was strong at day 3, and decreased at day 5. Osteocalcin immunoreactivity expression was strong in differentiating cementoblasts at the tension side. Conclusion: It can be suggested that UNC-50 is related to the differentiation of cementoblasts, and may be responsible for the molecular event in PDL cells under mechanical stress.

• The Journal of the Korean dental association
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• v.26 no.7 s.230
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• pp.667-675
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• 1988

• The Journal of the Korean dental association
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• v.25 no.6 s.217
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• pp.588-592
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• 1987

• 대한치과교정학회:학술대회논문집
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• 2005.11a
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• pp.69.2-70
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• 2005

• The korean journal of orthodontics
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• v.36 no.4
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• pp.295-307
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• 2006

Objective: The purpose of this study was to compare the histological and biomechanical characteristics of self-tapping and self-drilling microscrew implants. Methods: 112 microscrew implants (56 self-drilling and 56 self-tapping) were placed into the tibia of 28 rabbits. The implants were loaded immediately with no force, light (100 gm), or heavy force (200 gm) with nickel-titanium coil springs. The animals were sacrificed at 3- and 5-weeks after placement and histologic and histomorphometric analysis were performed under a microscope. Results: All microscrew implants stayed firm throughout the experiment. There was no significant difference between self-drilling and self-tapping microscrew implants both in peak insertion and removal torques. Histologic examinations showed there were more defects in the self-tapping than the self-drilling microscrew implants, and newly formed immature bone was increased at the interface in the self-tapping 5-week group. There was proliferation of bone towards the outer surface of the implant and/or toward the marrow space in the self-drilling group. Histologically, self-drilling microscrew implants provided more bone contact initially but the two methods became similar at 5 weeks. Conclusion: These results indicate the two methods can be used for microscrew implant placement, but when using self-tapping microscrew implants, it seems better to use light force in the early stages.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.2
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• pp.127-134
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• 2019

The aim of this study was to evaluate the compomer cement and resin cement as an orthodontic band cement on zirconia crown. A total of 30 specimens were prepared. Preformed stainless steel crowns and zirconia crowns of upper right second primary molar were used. Orthodontic bands were cemented on stainless steel crowns (Group I, n = 10) and zirconia crowns (Group II, n = 10) with compomer cement. The other bands were cemented on zirconia crowns with resin cement (Group III, n = 10). The tensile loads were applied to band to measure the bond strength. The mean of bond strengths of group I, II and III were 0.79 MPa, 1.09 MPa and 1.56 MPa respectively. Bond strength of group II is significantly higher than group I. There was no significant difference between group II and III. Compomer cement and resin cement containing functional monomers showed favorable bond strength of orthodontic bands.

• The korean journal of orthodontics
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• v.41 no.4
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• pp.268-279
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• 2011

Objective: The purpose of this study was to compare self-drilling orthodontic mini-implants of different surfaces, namely, machined (untreated), etched (acid-etched), RBM (treated with resorbable blasting media) and hybrid (RBM + machined), with respect to the following criteria: physical appearance of the surface, measurement of surface roughness, and insertion pattern. Methods: Self-drilling orthodontic mini-implants (Osstem implant, Seoul, Korea) with the abovementioned surfaces were obtained. Surface roughness was measured by using a scanning electron microscope and surface-roughness-testing machine, and torque patterns and vertical loadings were measured during continuous insertion of mini-implants into artificial bone (polyurethane foam) by using a torque tester of the driving-motor type (speed, 12 rpm). Results: The mini-implants with the RBM, hybrid, and acid-etched surfaces had slightly increased maximum insertion torque at the final stage ($p$ < 0.05). Implants with the RBM surface had the highest vertical load for insertion ($p$ < 0.05). Testing for surface roughness revealed that the implants with the RBM and hybrid surfaces had higher Ra values than the others ($p$ < 0.05). Scanning electron microscopy showed that the implants with the RBM surface had the roughest surface. Conclusions: Surface-treated, self-drilling orthodontic mini-implants may be clinically acceptable, if controlled appropriately.