• The korean journal of orthodontics
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• v.30 no.2 s.79
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• pp.127-142
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• 2000

This study have been carried out to find out the mechnical effect of Multiloop Edgewise Arch Wire(MEAW) making use of the finite element method. The tip back bend of MEAW taken in this analysis is $5^{\circ},\;10{\circ}\;and\;15{\circ}$. In addition, Class II or up & down elastic is applied to find out stress distribution and their values in PDL. A adult male of normal occlusion was selected to create the models of teeth and PDL. And the model of MEAW was also created using commercial finite element code (ANSYS version 5.2). The MEAW is forcibly engaged with a class II or up & down elastic, to determine the initial stress generated in PDL. Comparing the compressive and tensile stress at each reference-planes, following results are obtained. 1. When a MEAW of $5^{\circ},\;10{\circ}\;15{\circ}$ tip back bend was engaged with Class II or up & down elastic, the distribution of compressive, tensile stress in entire PDL is similar in each case. 2. The values of compressive and tensile stress in PDL is higher in $15{\circ}$ tip back bend case than in $10{\circ}\;or\;15{\circ}$ tip back bend case. 3. In the distal PDL of 1st and 2nd molar, compressive stress appears. The compressive area is more wide and its values is higher in PDL of 2nd molar than those in 1st molar. The compressive area and its values become more wide and higher according to the increase of the tip back bend. 4. The values of compressive stress are comparatively smaIIer in PDL of molars than those in premolars. 5. Comparing class II and up & down elastic case, tensile stress values in anterior teeth PDL are smaller md their distribution is more wide in up & down elastic case than class If elastic case. On another hand, there is no difference in distribution and stress values in PDL of posterior teeth between two cases. 6. Comparing the tensile area in PDL of anterior teeth, tensile stress values are maximum in PDL of canine.

• The korean journal of orthodontics
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• v.41 no.5
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• pp.312-323
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• 2011

Objective: This study compared the bone thickness of the palate between lateral cephalogram and 3D model measurements. Methods: The subjects consisted of 30 adults (15 men,15 women) with a normal skeletal pattern and occlusion. The CT images were transformed to a 3D model, and were compared with the cephalometric image. Descriptive statistics for each variable were calculated. Results: In the 3D CT model, the mid-palatal area was the thickest part. It became thinner as the palate tapered laterally. In the male group, the thinnest portion was positioned 6 mm away from the mid-palate, while in the female group the thinnest portion was 8mm away from the mid-palate. Correlation analysis between the lateral cephalometric and 3D CT model revealed a significant correlation except in the mid palatal area and the area 2 mm lateral to the mid-palate in men, whereas there was a significant relationship in every area in the women. In both men and women, the highest correlation appeared in the area 8 mm lateral to the mid palate. Conclusions: Using regression analysis, an actual prediction of the bone thickness between the measured bone thickness of the lateral cephalometric radiograph and 3D model was made. This will provide useful information for mini-implant length selection when inserting into the palate.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.4
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• pp.249-257
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• 2012

Purpose: This study was designed to help to provide the criteria of the esthetic smile in oromaxillary region on twenties, fifties and sixties. Materials and methods: The facial straight photographs of 33 adults (male 15, female 18, mean age 27.2 years old) and 20 seniors (male 7, female 13, mean age 55.6 years old) in resting and smile position were taken. The measurements and proportion of lip-teeth relation during smile were statistically analyzed, and survey of freshmen and seniors who belong to School of Dentistry, Chonnam National University were taken to select the best esthetic smile among the photographs. Results: In the relationship between the upper lip and the teeth, average smile was the most frequent, and mean of smile line ratio was 1.090 in young group and 0.90 in old group. The correlation between the buccal corridor ratio and exposed teeth count was inversed. At smile, most frequently exposed tooth was the second premolar (63.64%) in young gourp and the first premolar (35.00%) in old group. The correlation between the upper lip change ratio and exposed clinical crown length of maxillary central incisor was inverse, but there was no correlation between the lower lip change ratio and exposed clinical crown length of maxillarycentral incisor. Conclusion: In the result of survey, the students selected the case exposed to the first premolar as the most esthetic smile. The most esthetic smile between full facial photograph and the lip only photograph by the freshmen was different, but that by seniors was identical.