• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.3
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• pp.427-432
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• 2009

The aim of this study was to compare the shear-peel strength and the fracture site of 5 commercially available orthodontic band cements. One hundred molar bands were cemented to extracted human 3rd molars. The specimens were prepared in accordance with the manufacturer's instructions for each cement. After storage in a humidor at $37^{\circ}C$ for 24 hours, the shear debonding force was assessed for each specimen using an universal testing machine with crosshead speed of 2 mm/minute. Maximal failure stress was converted to mean shear-peel strength, MPa. The predominant site of band failure was recorded visually for all specimens as either at the band/cement or cement/enamel interface. Mean shear-peel strength of Ormco was the highest(2.44${\pm}$0.57), followed by Fuji $Ortho^{TM}$(2.24${\pm}$0.50), $Ketac-Cem^{TM}$(2.10${\pm}$0.57), 3M $Unitek^{TM}$(1.82${\pm}$0.43), $Band-Lok^{TM}$(1.73${\pm}$0.28). There were statistically significant differences between Ormco and $Band-Lok^{TM}$, Ormco and 3M $Unitek^{TM}$, and Fuji $Ortho^{TM}$ and $Band-Lok^{TM}$(p<0.05). The predominant site of bonding failure for bands cemented with the Ormco was at the band/cement interface, whereas bands cemented with Ultra $Band-Lok^{TM}$ failed predominantly at the enamel/cement interface. There was no significant difference among the other cements(Fuji $Ortho^{TM}$, 3M $Unitek^{TM}$, $Ketac-Cem^{TM}$).

• Journal of the Korean Academy of Esthetic Dentistry
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• v.24 no.1
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• pp.4-12
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• 2015

Purpose: Due to the presence of various muscles around lips, variety of facial expression can be made and changes from aging process such as wrinkles can develop on the facial skin by the action of multiple muscles. In animals, skin and muscles are developed in the entire body. On contrast, they are well developed only in the face and just one is present in the neck and the palm. Alar band was defined as outer wrinkle formed by zygomaticus minor muscle, which is common in Koreans. This study aimed to investigate clinical prevalence of alar band. Materials & Methods: Subjects were chosen from 780 new patients who visited private clinic in Gyeonggi province for orthodontic treatment. Presence of alar band was examined from the smile extraoral photos. Correlation among skeletal form, lip protrusion, gender, and age were evaluated. Results: Prevalence of alar band was higher in women (27.9%) than in men (18.5%) with statistical significance (p<0.05). With respect to age, prevalence of alar band was 19.4% in age 0-9 y, 16.9% in age 10-19 y, 31.2% in age 20-29 y, 39.5% in age 30-39, 56.5% in age 40-49. Prevalence was gradually increased from patients in their 20s to patients in their 40s and statistical significance was found (p<0.001). Concerning SN_NP, prevalence was 26.2% in normodivergent facial type, 22.0% in hyperdivergent facial type, and 32.2% in hypodivergent facial type. Hypodivergent facial group had higher prevalence but statistical significance was not observed. Statistically significant difference was not found regarding upper lip. However, prevalence of the alar band was 26% in patients with normal lower lip, 14.7% in patients with pretruded lower lip, and 33.3% in retruded lower lip. The prevalence was higher in patients with retruded lower lip with statistical significance (p<0.05). Conclusions: 27.8% on previous anatomical study and this study showed 27.8% prevalence of alar band in clinical smile photographs. Clinical photograph study showed that alar band was more prominent in women, older people, and people with retruded lips with statistical significance. This will provide valuable diagnostic information for esthetic consideration.

• The korean journal of orthodontics
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• v.26 no.1 s.54
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• pp.83-94
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• 1996

Substance P is one of the neuropeptide which presents highly in tension site of periodontal ligament during the orthodontic tooth movement. It has bnn also hon as one of the neuropeptides which cause neurogenic inflammation in various tissues and organs. However, there is no report about the effect of substance P on major extracellular matrix protein, collagen production. The purpose of this study was to evaluate the collagen production by substance P in human periodontal ligament cell. The collagenase-digestion method was used to evaluate collagen production and also used Northern blot hybridization for the evaluation of collagen mRNA level. This study also Included in terms of prostanglandins and gelatinase production with respect to collagen production. For the collagen degradation, zymography was used to estimate denatured collagen degradation. Dose-dependent effect of substance P on noncollagen protein, collagen, and percent collagen was that substance P increased noncollagen protein synthesis, but decreased collagen sytnsis. So the percent collagen, which determined by relative collagen production against total protein production, w3s decreased from $7\%\;to\;3.6\%$. This inhibitory effect of substance P on collagen production was disappeared when cells were treated concomitantly with indomethacin. It means that substance P-induced inhibitory effect on collagen production was due at least in part to the production of prostaglandins. To evaluate whether substance P-induced inhibitory effect on collagen production is correspond to the steady-state levels of procollagen mRNA, Northern blot hybridization was performed and it showed that substance P has no effect on the steady-slate level of ${\alpha}1(I)$ procollagen mRNA. It means that the inhibitory effect of substance P on collagen production was due to the change of a certain mechanism after posttranscription. In this context, gelatinase production by substance P in periodontal ligament cells was evaluated by zymography. Zymogram showed that substance P has no effect on gelatinase production in periodontal ligament cells. To explore wheter substance P-induced inhibitory effect on collagen production is selevtive in periodontal ligament cells or not, MC3T3-E1 cells which originated from mouse calvaria was used. It showed that substance P has no effect on collagen production in MC3T3-E1 cells. Taken together, substance P inhibits collagen production in human periodontal ligament cells. This effect was not due to the change of the steady-state level of procollagen mRNA and gelatinase production, but due at least in part to the change of prostaglandins production.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.955-974
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• 1998

The purpose of the present study was to seek bracket-adhesive combinations which have adequate bond strength with no enamel and bracket fracture. The shear bond strengths were measured, the sites of failure and the enamel damage were investigated and the peripheral sealing and adaptation between enamel surface, bonding adhesive and bracket were evaluated. 240 noncarious human premolars were divided into twenty four groups of ten teeth. Shear bond strengths of each group were determined in an universal testing machine after two days passed and the debonded specimens were inspected to determine the predominant bond failure sites. To evaluate peripheral sealing and adaption between enamel surface, adhesive and bracket, each specimen was cut longitudinally into two halves which included the midsection of the bracket, adhesive and enamel and exmined in scanning electron microscope. Six different types of brackets were bonded to the tooth with four different type of adhesives. Six different types of brackets were Image, Plastic, Crystaline, Fascination, Transcend 2000 and metal bracket and four different adhesives were No-mix, Light-Bond, OrthoLC and Superbond C&B. From this study, it may be concluded that (1) The mean shear bond strength varied from a high of 36.58 Kg (410.07 Kg/$cm^2$) with the Fascination-Light Bond combination group to a low of 8.93 Kg (75.51 Kg/$cm^2$) with theImage-OrthoLC combination group. When using OrthoLC as adhesive, the mean shear bond strength was significantly lower than that of other combination groups, (2) Regardless of adhesives, the mean shear bond strength of Fascination brackets was relatively high whereas Plastic and Image brackets had low shear bonding strength. The shear bond strength of Crystaline bracket and Transcend 2m was relatively equal to or lower than that of metal bracket, (3) There was a correlation between bond strength, enamel damage and bracket fracture. As the shear bond strength was increased, the rate of enamel damage and bracket fracture were increased, (4) The combination groups that use OrthoLC as adhesive were debonded in shear stress without enamel fracture and bracket fracture, whereas the combination groups that use Superbond C&B as adhesive experienced a relative high enamel fracture rate and bracket fracture rate, (5) Peripheral sealing and adaptation between enamel-adhesive-bracket were relatively good when using Light-Bond or No-mix as adhesive. Regardless of adhesives, adaptation between bracket-adhesive were relatively good in Ceramic brackets, (6) The combination groups which had adequate bonding strength with no enamel and bracket fracture were Crystaline-No mix, Crystaline-Light Bond, Crystaline-OrthoLC, metal-No mix, metal-Light Bond and metal-OrthoLC combination groups.

• The korean journal of orthodontics
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• v.36 no.3 s.116
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• pp.188-197
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• 2006

Fiber reinforced composite (FRC) is usually used as a connector joining a few teeth into one unit in orthodontics. However, fracture often occurs during the two to three years of the orthodontic treatment period due to repeated occlusal loading or water sorption in the oral environment. We simulated the repair by overlapping and attaching portions of two FRC strips in the middle and performed a three-point bending test to investigate the changes of the repair strength among the different FRC groups. The specimens were grouped according to the overlapping lengths of the two FRC strips, which were 1, 2, 3 and 4 mm (group E1, E2, E3 and E4, respectively) and the control group consisted of unrepaired, intact FRC strips. Each group consisted of 6 specimens and were cured with a light emitting diode curing unit. Group E4 showed the highest maximum loads of 2.67 N, then the control group (2.39 N), group E3 (2.35 N), E2 (2.10 N), and E1 (1.75 N) in decreasing order. Group E4 also showed the highest stiffness, which was 2.32 N/mm, however, the stiffness of group E3 (2.06N/mm) was higher than that of the control group (1.88 N/mm). According to the visual examination, the specimens tended to be bent rather than being fractured into two pieces with an increased length of overlapping portions. The above results suggest that a minimum overlapping length of 3 mm was necessary to obtain an adequate repair of a 10 mm length of FRC connector. In addition, the critical section adjacent to the joint area, where the thickness decreased abruptly, should be reinforced with flowable resin to minimize the bending tendency.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.278-288
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• 2009

Objective: The aim of this study was to investigate the changes in the center of resistance of the maxillary teeth in relation to alveolar bone loss. Methods: A finite element model, which included the upper dentition and periodontal ligament, was designed according to the amount of bone loss (0 mm, 2 mm, 4 mm). The teeth in each group were fixed with buccal and lingual arch wires and splint wires. Retraction and intrusion forces of 200 g for 4 and 6 anterior teeth groups and 400 g for the full dentition group were applied. Results: The centers of resistance were at 13.5 mm, 14.5 mm, 15 mm apical and 12 mm, 12 mm, 12.5 mm posterior in the 4 incisor group; 13.5 mm, 14.5 mm, 15 mm apical and 14 mm, 14 mm, 14.5 mm posterior in the 6 anterior teeth group; and 11 mm, 13 mm, 14.5 mm apical and 26.5 mm, 27 mm, 25.5 mm posterior in the full dentition group respectively according to 0 mm, 2 mm, 4 mm bone loss. Conclusions: The center of resistance shifted apically and posteriorly as alveolar bone loss increased in 4 and 6 anterior teeth groups. However, in the full dentition group, the center of resistance shifted apically and anteriorly in the 4 mm bone loss model.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.300-309
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• 2009

Objective: The purpose of this study was to evaluate the correlation between menton deviation and dental compensation in facial asymmetry. Methods: Tooth axis and distance of first molar and canine to the reference plane were investigated by cone-beam computerized tomography. The subjects consisted of 50 patients with asymmetric mandibles (male 21, female 29, mean age 24.3 years). Control groups were also assessed (male 11, female 9, mean age 25.6 years). Nine measurements (5 linear measurements and 4 angular measurements) were measured in order to evaluate the correlation between menton deviation and the linear and angular difference of first molar and canine in the deviated and none-deviated sides using the defined MPR images. The differences between deviated and non-deviated side, according to menton deviation, were statistically analyzed using stepwise multiple regression analysis. Results: From the result, Menton deviation was negatively correlated with mandibular first molar's angular measurement (${\Delta\angle}LM6$-Mn plane (dev.-ndev.)) and positively with maxillary fist molar's angular measurement (${\Delta\angle}UM6$-FH plane (dev.-ndev.)) (p < 0.01). Two angular measurements (${\Delta\angle}LM6$-Mn plane (dev.-ndev.), ${\Delta\angle}UM6$-FH plane (dev.-ndev.)) explained the variability in menton deviation with a significant $r^2$ value of 0.589. Conclusions: This study suggests that the tooth axis of upper and lower first molars leans towards the deviated side of Menton when there is mandibular asymmetry with Menton deviation.

• The korean journal of orthodontics
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• v.40 no.5
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• pp.314-324
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• 2010

Objective: The purpose of this study was to determine differences of mandibular anterior alveolar bone thickness and symphysial cross sectional area in 9 different horizontal and vertical facial types. Methods: By using the initial cephalometric radiographs of 270 adult patients (male 135, female 135), the authors measured the buccolingual thickness of anterior alveolar bone on the basis of the root axis and symphysial cross sectional distance. Results: The high angle group showed significantly thinner buccolingual alveolar bone width except for the CEJ area and lingual alveolar bone width ($p$ < 0.05). The low angle group and Class I, II average group showed similar or significantly thicker alveolar bone width than the Class I average group ($p$ < 0.05). The Class III average group showed significantly thinner buccolingual and lingual alveolar bone width than Class I and II average groups ($p$ < 0.05). The Class III high angle group showed minimal alveolar bone width in all facial skeletal types. No significant difference was found in the symphysial cross sectional area of the different vertical facial skeletal types ($p$ > 0.05). Conclusions: The results of this study found that Class III high angle patients have thinner mandibular anterior alveolar bone thickness; therefore, more attention will be needed to determine the incisor position during orthodontic treatment for this group of patients.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.18-27
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• 2009

Objective: The purpose of this study was to understand the differences in masseter muscle(MM) between the shifted and non-shifted sides in facial asymmetry patients, and the changes shown by MM after mandibular surgery. Methods: Pre- and post-operative CT scans were performed on 12 Class III patients with facial asymmetry who were treated by intraoral vertical ramus osteotomy and 10 subjects with normal occlusion. Using the V-works 4.0 program(Cybermed, Seoul, Korea), 3-dimensional images of the mandible, and MM were reconstructed, and evaluated. Results: In the asymmetry group, the MM angle between the shifted and non-shifted sides was only significantly different(p<0.05). Compared with normal occlusion, the asymmetry group showed a significantly smaller volume and maximum cross-sectional area in both sides of MM(p<0.05). After mandibular surgery, the angle of MM(p<0.01) and differences in angle between the shifted and non-shifted sides of MM(p<0.05) were significantly decreased. The thickness in the maximum cross-sectional area was significantly increased(p<0.01). After surgery, MM in facial asymmetry patients was similarly changed to those in the normal occlusion group except for widths. Conclusions: MM in facial asymmetry was definitely different from those in normal occlusion. However, this study suggests that MM changed symmetrically in conjunction with the mandible after proper mandibular surgery.

• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.107-120
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• 2001

Nitric oxide(NO) has been reported to be one of the mediators relating to bone remodelling. Nitric oxide is synthesized from L-arguinine by nitric oxide synthetase(NOS), which is largely divided Into two groups. One group which is composed of $NOS_1\;and\;NOS_3$, is dependent of calcium or calmodulin. The other consisted of $NOS_2$, which is independent of calcium or calmodulin. NOS is thought to be a possible intermediate affecting in the course of tooth movement. This study was designed to evaluate the expression of nitrous oxide synthetase(NOS) in periodontal tissue during the experimental movement of rat incisors, by LSAB(labelled streptavidine biotin) immunohistochemical staining for $NOS_2\;and\;NOS_3$. Twenty seven Sprague-Dawley rats were divided into a control group(3 rats), and 6 experimental groups(24 rats), to which 75g of force was applied, with helical springs across the maxillary incisors. Rats of experimental groups were sacrificed at 12 hours, 1, 4, 7, 14 and 28 days after force application, respectively. After that, the tissues of the control group and experimental groups were studied immunohistochemically. The results were as follows: 1. In control group, the expression of $NOS_3$ was rare in gingiva, dentin, periodontal ligament and alveolar bone, and was mild in the capillaries of pulp and intermaxillary suture. And the expression of $NOS_2$ showed similar pattern to that of $NOS_3$. 2. There were no differences in the expression of $NOS_2\;or\;NOS_3$ in dentin, gingiva, cementum, cementoblast and odontoblast, between control and experimental groups, regardless of the duration of the force application. 3. The expression of $NOS_3$ began to increase at 4 days and showed to the highest degree at 7 days after force application, in the apical region of pressure side of periodontal ligament in experimental groups. 4. The expression of $NOS_3$ in alveolar bone was rare until 7 days, after which it increased to mild degree at 14 days through 28 days in experimental group. But there was no difference between pressure and tension side of periodontal ligament. 5. The expression of $NOS_2$ in periodontal ligament was mild from 7 days after force application, regardless of the side of periodontium, which was generally more evident than that of $NOS_3$. 6. The expression of $NOS_2$ in alveolar bone increased to mild degree at 14 days after force application, and it was evident in osteoblasts, osteoclasts and osteocytes. And the expression of $NOS_2$ was little more stronger in the tension side than that of pressure side of alveolar bone.