• The korean journal of orthodontics
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• v.45 no.3
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• pp.113-120
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• 2015

Objective: This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing. Methods: Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models. Results: Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078). Conclusions: In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.

• The korean journal of orthodontics
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• v.50 no.3
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• pp.216-226
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• 2020

Root resorption can be caused by several factors, including contact with the cortical bone. Here we report a case involving a 21-year-old female with Angle Class II, division 1 malocclusion who exhibited significant root resorption in the maxillary right central incisor after orthodontic treatment. The patient presented with significant left-sided deviation of the maxillary incisors due to lingual dislocation of the left lateral incisor and a Class II molar relationship. Cephalometric analysis demonstrated a Class I skeletal relationship (A point-nasion-B point, 2.5°) and proclined maxillary anterior teeth (upper incisor to sella-nasion plane angle, 113.4°). The primary treatment objectives were the achievement of stable occlusion with midline agreement between the maxillary and mandibular dentitions and appropriate maxillary anterior tooth axes and molar relationship. A panoramic radiograph obtained after active treatment showed significant root resorption in the maxillary right central incisor; therefore, we performed cone-beam computed tomography, which confirmed root resorption along the cortical bone around the incisive canal. The findings from this case, where different degrees of root resorption were observed despite comparable degrees of orthodontic movement in the bilateral maxillary central incisors, suggest that the incisive canal could be an inducing factor for root resorption. However, further investigation is necessary to confirm this assumption.

• Journal of Periodontal and Implant Science
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• v.50 no.4
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• pp.226-237
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• 2020

Purpose: This study was conducted to assess the efficacy of prophylactic gingival grafting in the mandibular anterior labial area for preventing orthodontically induced gingival recession. Methods: Eight mongrel dogs received gingival graft surgery at the first (I1) and third (I3) mandibular incisors on both sides based on the following group allocation: AT group (autogenous connective tissue graft on I1), AT-control group (contralateral side in the AT group), CM group (xenogeneic cross-linked collagen matrix graft on I3) and CM-control group (contralateral side in the CM group). At 4 weeks after surgery, 6 incisors were splinted and proclined for 4 weeks, followed by 16 weeks of retention. At 24 weeks after surgery, casts were made and compared with those made before surgery, and radiographic and histomorphometric analyses were performed. Results: Despite the proclination of the incisal tip (by approximately 3 mm), labial gingival recession did not occur. The labial gingiva was thicker in the AT group (1.85±0.50 mm vs. 1.76±0.45 mm, P>0.05) and CM group (1.90±0.33 mm vs. 1.79±0.20 mm, P>0.05) than in their respective control groups. Conclusions: The level of the labial gingival margin did not change following labial proclination of incisors in dogs. Both the AT and CM groups showed enhanced gingival thickness.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.479-484
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• 2000

The conventional treatment of skeletal class III malocclusion has been focused on the application of orthopedic forrce primarily to the mandible. Thus moderate Class III malocclusions can be corrected by the anterior displacement of the maxilla and maxillary dentition, possibly by restricting the growth of the mandible or by changing its direction. The patients having skeletal Class III malocclusion were treated with removable appliance & fixed appliance for detailed tooth movement and the following results were observed: 1. The anterior crossbite was corrected. 2. The forward and downward growth of the maxillary complex was obtained. 3. The lingual tipping of the mandiblar incisors was performed and the mandible was rotated in the clockwise direction.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.458-464
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• 2004

Anchorage plays an important role in orthodontic treatment especially in the maxillary arch. In spite of many efforts for anchorage control. it was difficult for clinicians to predict the result of treatment because most of the treatment necessitated an absolute compliance of patients, But recently, skeletal anchorage has been used widely because it does not necessitate patient compliance but produces absolute anchorage. In addition titanium miniscrews have several advantages such as ease of insertion and removal. possible immediate leading and use in limited implantation spaces. In this case, a skeletal Class I bialveolar protrusion Patient was treated with standard edgewise mechanics using indirect active P.S.A. (palatal skeletal anchorage). The miniscrews in the paramedian area of the hard palate provided anchorage for retraction of the upper anterior teeth and remained firm and stable throughout treatment This indicates that the PSA can be used to reinforce anchorage for orthodontic treatment in the maxillary arch Consequently, this new approach can help effective tooth movement without patient compliance, when used with various transpalatal arch systems.

• The korean journal of orthodontics
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• v.47 no.3
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• pp.195-206
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• 2017

Facial asymmetry can be classified into the rolling-dominant type (R-type), translation-dominant type (T-type), yawing-dominant type (Y-type), and atypical type (A-type) based on the distorted skeletal components that cause canting, translation, and yawing of the maxilla and/or mandible. Each facial asymmetry type represents dentoalveolar compensations in three dimensions that correspond to the main skeletal discrepancies. To obtain sufficient surgical correction, it is necessary to analyze the main skeletal discrepancies contributing to the facial asymmetry and then the skeletal-dental relationships in the maxilla and mandible separately. Particularly in cases of facial asymmetry accompanied by mandibular yawing, it is not simple to establish pre-surgical goals of tooth movement since chin deviation and posterior gonial prominence can be either aggravated or compromised according to the direction of mandibular yawing. Thus, strategic dentoalveolar decompensations targeting the real basal skeletal discrepancies should be performed during presurgical orthodontic treatment to allow for sufficient skeletal correction with stability. In this report, we document targeted decompensation of two asymmetry patients focusing on more complicated yaw-dependent types than others: Y-type and A-type. This may suggest a clinical guideline on the targeted decompensation in patient with different types of facial asymmetries.

• The korean journal of orthodontics
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• v.49 no.1
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• pp.21-31
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• 2019

Objective: This study was performed to explore the effect of different bracket, archwire, and ligature combinations on resistance to sliding (RS) and rotational control in first-order angulation. Methods: Three types of brackets (multi-level low friction [MLF], self-ligating, and conventional brackets) coupled with four nickel-titanium archwires (0.012, 0.014, 0.016, and 0.018-inch diameter) and two stainless steel ligatures (0.20 and 0.25 mm) were tested in different first-order angulations ($0^{\circ}$, $2^{\circ}$, $4^{\circ}$, $6^{\circ}$, $8^{\circ}$, $10^{\circ}$, $15^{\circ}$, $20^{\circ}$) by using an Instron universal mechanical machine in the dry state at room temperature. RS value was evaluated and compared by one-way ANOVA. Results: Under the same angulation, the RS values showed the following order: conventional brackets > MLF brackets > self-ligating brackets. The RS was the highest for conventional brackets and showed a tendency to increase. The RS for MLF brackets coupled with thinner archwires and ligatures showed a similar tendency as the RS for the self-ligating bracket. In contrast, the RS for MLF brackets coupled with thicker archwires and ligatures increased like that for conventional brackets. MLF brackets showed the greatest range of critical contact angles in first-order angulation. Conclusions: The RS in first-order angulation is influenced by bracket design, archwire, and ligature dimension. In comparison with self-ligating and conventional brackets, MLF brackets could express low friction and rotational control with their greater range of critical contact angles.

• The korean journal of orthodontics
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• v.51 no.2
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• pp.86-94
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• 2021

Objective: This study aimed to investigate the effect of micro-osteoperforations (MOPs) on external apical root resorption (EARR) during the initial orthodontic alignment phase of maxillary anterior crowding. Methods: Thirty patients (25 females, 5 males; mean age, 22.66 ± 3.27 years) who presented with moderate crowding of the upper labial segment and underwent extraction-based fixed appliance treatment were recruited. They were randomly allocated to receive adjunctive therapy with MOPs (n = 15) or treatment with fixed appliances only (control group; n = 15). EARR was measured from long-cone periapical radiographs taken at the start and the sixth month of treatment. A correction factor for the enlargement difference was used to calculate EARR. Data were analyzed with descriptive statistics and repeated-measures analysis of variance. Results: The mean root lengths of 168 teeth were measured and showed no statistically significant difference (p > 0.05) after six months of fixed appliance treatment in the MOP (mean difference [MD] = 0.13 mm; 95% confidence interval [CI] = -0.10-0.35) and control group (MD = 0.14 mm; 95% CI = -0.10-0.37). Most of the roots in the MOP and control groups (42.86% and 52.38%, respectively) showed only mild resorption. Less than 8% of the roots in both groups (7.14% in the MOP group and 4.76% in the control group) showed moderate resorption. Conclusions: Acceleration of orthodontic tooth movement with adjunctive MOPs therapy during the alignment phase does not exacerbate EARR in patients with moderate crowding of the upper labial segment in comparison with controls.

• The korean journal of orthodontics
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• v.51 no.1
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• pp.32-42
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• 2021

Objective: To investigate the three-dimensional forces created by clear aligners on mandibular teeth during differential activation with en-masse retraction and/or intrusion in vitro. Methods: Six sets of clear aligners were designed for differential en-masse retraction and/or intrusion procedures in a first premolar extraction model. Group A0 was a control group with no activation. Groups A1-5 underwent different degrees of retractions and/or intrusions. Each group consisted of 10 aligners. Aligner forces were measured on a multi-axis force/torque transducer measurement system in real-time. Results: In the en-masse retraction groups (A1 and A2), lingual and extrusive forces were observed on the incisors; the canines mainly received distal forces; intrusive forces were seen on the second premolars; and the molars received mesial forces. In the en-masse retraction and intrusion groups (A3, A4, and A5), incisors also received lingual and extrusive forces; canines received distal and intrusive forces; mesial and extrusive forces were seen on the second premolars; and the second molars received distal and intrusive forces. The vertical forces on the incisors did not differ significantly among groups A1, A3, and A5. However, the vertical forces on the second premolars reversed from intrusion in group A1 to extrusion in groups A3 and A5. Conclusions: With clear aligners, the "bowing effect" is seen during en-masse anterior teeth retraction and can be partially relieved by performing en-masse retraction accompanied by anterior teeth intrusion. Vertical control of incisors remained unsolved during en-masse retraction, even when intrusive activation was added to the anterior teeth.

• Imaging Science in Dentistry
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• v.51 no.2
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• pp.155-165
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• 2021

Purpose: This study aimed to evaluate changes of the alveolar bone and interdental bone septum of the mandibular incisors through cone-beam computed tomography (CBCT) after orthodontic treatment of mandibular dental crowding without dental extraction. Materials and Methods: The sample consisted of 64 CBCT images(32 pre-treatment and 32 post-treatment) from 32 adult patients with class I malocclusion and an average age of 23.0±3.9 years. The width and height of the alveolar bone and interdental septum, the distance between the cementoenamel junction (CEJ) and the facial and lingual bone crests, and the inclination of the mandibular incisors were measured. Results: The distance between the CEJ and the marginal bone crest on the facial side increased significantly (P<0.05). An increased distance between the CEJ and the bone crest on the facial and lingual sides showed a correlation with the irregularity index (P<0.05); however, no significant association was observed with increasing mandibular incisor inclination (P>0.05). The change in the distance between the CEJ and the marginal bone crest on the facial side was correlated significantly with bone septum height(P<0.05). Conclusion: Bone dehiscence developed during the treatment of crowding without extraction only on the incisors' facial side. Increasing proclination of the mandibular incisor was not correlated with bone dehiscence. The degree of dental crowding assessed through the irregularity index was associated with the risk of developing bone dehiscence. The interdental septum reflected facial marginal bone loss in the mandibular incisors.