• The korean journal of orthodontics
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• v.49 no.6
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• pp.349-359
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• 2019

Objective: The aim of this study was to analyze three-dimensional (3D) changes in maxillary dentition in Class II malocclusion treatment using arch wire with continuous tip-back bends or compensating curve, together with intermaxillary elastics by superimposing 3D virtual models. Methods: The subjects were 20 patients (2 men and 18 women; mean age 20 years 7 months ${\pm}$ 3 years 9 months) with Class II malocclusion treated using $0.016{\times}0.022-inch$ multiloop edgewise arch wire with continuous tip-back bends or titanium molybdenum alloy ideal arch wire with compensating curve, together with intermaxillary elastics. Linear and angular measurements were performed to investigate maxillary teeth displacement by superimposing pre- and post-treatment 3D virtual models using Rapidform 2006 and analyzing the results using paired t-tests. Results: There were posterior displacement of maxillary teeth (p < 0.01) with distal crown tipping of canine, second premolar and first molar (p < 0.05), expansion of maxillary arch (p < 0.05) with buccoversion of second premolar and first molar (p < 0.01), and distal-in rotation of first molar (p < 0.01). Reduced angular difference between anterior and posterior occlusal planes (p < 0.001), with extrusion of anterior teeth (p < 0.05) and intrusion of second premolar and first molar (p < 0.001) was observed. Conclusions: Class II treatment using an arch wire with continuous tip-back bends or a compensating curve, together with intermaxillary elastics, could retract and expand maxillary dentition, and reduce occlusal curvature. These results will help clinicians in understanding the mechanism of this Class II treatment.

• The korean journal of orthodontics
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• v.51 no.2
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• pp.77-85
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• 2021

Objective: To evaluate the accuracy of a multi-stage convolutional neural network (CNN) model-based automated identification system for posteroanterior (PA) cephalometric landmarks. Methods: The multi-stage CNN model was implemented with a personal computer. A total of 430 PA-cephalograms synthesized from cone-beam computed tomography scans (CBCT-PA) were selected as samples. Twenty-three landmarks used for Tweemac analysis were manually identified on all CBCT-PA images by a single examiner. Intra-examiner reproducibility was confirmed by repeating the identification on 85 randomly selected images, which were subsequently set as test data, with a two-week interval before training. For initial learning stage of the multi-stage CNN model, the data from 345 of 430 CBCT-PA images were used, after which the multi-stage CNN model was tested with previous 85 images. The first manual identification on these 85 images was set as a truth ground. The mean radial error (MRE) and successful detection rate (SDR) were calculated to evaluate the errors in manual identification and artificial intelligence (AI) prediction. Results: The AI showed an average MRE of 2.23 ± 2.02 mm with an SDR of 60.88% for errors of 2 mm or lower. However, in a comparison of the repetitive task, the AI predicted landmarks at the same position, while the MRE for the repeated manual identification was 1.31 ± 0.94 mm. Conclusions: Automated identification for CBCT-synthesized PA cephalometric landmarks did not sufficiently achieve the clinically favorable error range of less than 2 mm. However, AI landmark identification on PA cephalograms showed better consistency than manual identification.

• The korean journal of orthodontics
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• v.52 no.1
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• pp.42-52
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• 2022

Objective: This study compared soft tissue changes after extraction of the four premolars followed by maximum retraction of the anterior teeth according to the type of anterior teeth movement: tipping and translation. Methods: Patients who had undergone orthodontic treatment involving the extraction of four premolars were retrospectively selected and divided into either the tipping (n = 27) or translation (n = 26) groups based on the retraction of the incisor root apex and the axis changes of the incisors during the treatment period. Lateral pre- and post-treatment cephalograms were analyzed. Results: There were no significant differences between the tipping and translation groups before treatment. The retraction amounts of the root apex of the upper and lower incisors in the tipping group were 0.33 and 0.26 mm, respectively, and 5.02 and 5.31 mm, respectively, in the translation group (p < 0.001). The posterior movements of soft tissue points A and B in the tipping group were 0.61 and 1.25 mm, respectively, and 1.10 and 3.25 mm, respectively, in the translation group (p < 0.01). The mentolabial sulcus angle increased by 5.89° in the tipping group, whereas it decreased by 8.13° in the translation group (p < 0.001). Conclusions: An increased amount of retraction of the incisor root apex led to the increased posterior movement of soft tissue points A and B, and this appeared more distinct in cases involving the lower incisor and lower lip.

• The korean journal of orthodontics
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• v.52 no.4
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• pp.268-277
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• 2022

Objective: Poor experience with Invisalign treatment affects patient compliance and, thus, treatment outcome. Knowing the potential discomfort level in advance can help orthodontists better prepare the patient to overcome the difficult stage. This study aimed to construct artificial neural networks (ANNs) to predict patient experience in the early stages of Invisalign treatment. Methods: In total, 196 patients were enrolled. Data collection included questionnaires on pain, anxiety, and quality of life (QoL). A four-layer fully connected multilayer perception with three backpropagations was constructed to predict patient experience of the treatment. The input data comprised 17 clinical features. The partial derivative method was used to calculate the relative contributions of each input in the ANNs. Results: The predictive success rates for pain, anxiety, and QoL were 87.7%, 93.4%, and 92.4%, respectively. ANNs for predicting pain, anxiety, and QoL yielded areas under the curve of 0.963, 0.992, and 0.982, respectively. The number of teeth with lingual attachments was the most important factor affecting the outcome of negative experience, followed by the number of lingual buttons and upper incisors with attachments. Conclusions: The constructed ANNs in this preliminary study show good accuracy in predicting patient experience (i.e., pain, anxiety, and QoL) of Invisalign treatment. Artificial intelligence system developed for predicting patient comfort has potential for clinical application to enhance patient compliance.

• The korean journal of orthodontics
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• v.52 no.3
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• pp.182-200
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• 2022

Objective: This study aims to examine the effectiveness of miniscrew assisted rapid palatal expansion (MARPE) treatment in late adolescents and adult patients using cone-beam computed tomography (CBCT). Methods: Literature search was conducted in five electronic databases (PubMed, Embase, Scopus, Web of Science, and Cochrane Library) based on the PICOS keyword design focusing on MARPE. Out of the 18 CBCT screened outcomes, only nine parameters were sufficient for the quantitative meta-analysis. The parameters were classified into three main groups: 1) skeletal changes, 2) alveolar change, and 3) dental changes. Heterogeneity test, estimation of pooled means, publication bias, sensitivity analysis and risk of bias assessment were also performed. Results: Upon database searching, only 14 full-text articles were qualified from the 364 obtained results. Heterogeneity test indicated the use of the random-effects model. The pooled mean estimate were as follows: 1) Skeletal expansion: zygomatic width, 2.39 mm; nasal width, 2.68 mm; jugular width, 3.12 mm; and midpalatal suture at the posterior nasal spine and anterior nasal spine, 3.34 mm and 4.56 mm, respectively; 2) Alveolar molar width expansion, 4.80 mm; and 3) Dental expansion: inter-canine width, 3.96 mm; inter-premolar width, 4.99 mm and inter-molar width, 5.99 mm. The percentage of expansion demonstrated a skeletal expansion (PNS) of 55.76%, alveolar molar width expansion of 24.37% and dental expansion of 19.87%. Conclusions: In the coronal view, the skeletal and dental expansion created by MARPE was of the pyramidal pattern. MARPE could successfully expand the constricted maxilla in late adolescents and adult patients.

• The korean journal of orthodontics
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• v.52 no.3
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• pp.210-219
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• 2022

Objective: The purpose of this study was to examine the effectiveness and mechanism of clear aligner therapy for the correction of anterior open bite in adult nonextraction cases. Methods: Sixty-nine adult patients with anterior open bite were enrolled and classified into Angle's Class I, II, and III groups. Fifty patients presented with skeletal open bite (mandibular plane angle [MPA] ≥ 38°), whereas 19 presented with dental open bite. Fifteen cephalometric landmarks were identified before (T1) and after (T2) treatment. The magnitudes of planned and actual movements of the incisors and molars were calculated. Results: Positive overbite was achieved in 94% patients, with a mean final overbite of 1.1 ± 0.8 mm. The mean change in overbite was 3.3 ± 1.4 mm. With clear aligners alone, 0.36 ± 0.58 mm of maxillary molar intrusion was achieved. Compared with the Class I group, the Class II group showed greater maxillary molar intrusion and MPA reduction. The Class III group showed greater mandibular incisor extrusion with no significant vertical skeletal changes. Conclusions: Clear aligners can be effective in controlling the vertical dimension and correcting mild to moderate anterior open bite in adult nonextraction cases. The treatment mechanism for Class III patients significantly differed from that for Class I and Class II patients. Maxillary incisor extrusion in patients with dental open bite and MPA reduction with mandibular incisor extrusion in patients with skeletal open bite are the most significant contributing factors for open bite closure.

• The korean journal of orthodontics
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• v.52 no.5
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• pp.324-333
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• 2022

Objective: The aim of this study was 1) to investigate the prevalence and pattern of dental anomalies (DAs), 2) to compare DAs according to the type of malocclusion, and 3) to investigate the correlation between tooth impaction and other DAs in the Korean orthodontic population. Methods: A total of 3,240 orthodontic patients were classified as Class I, Class II, or Class III malocclusion groups. The presence and location of common DAs, including impaction, microdontia, agenesis, supernumerary tooth, transposition, and fusion, were identified by examining diagnostic records. Furthermore, samples were classified as Group 1 without impaction or Group 2 with impaction. The prevalence of other DAs concurrent with impaction was investigated and compared to Group 1. Results: Impaction was the most prevalent DA, followed by microdontia, agenesis, and supernumerary. Class I and Class III groups showed the same order of prevalence, but agenesis was more frequent than microdontia in the Class II group. The prevalence of the four DAs was lowest in the Class III group. Overall, 8.6% of patients were classified into Group 2. The incidence of DAs other than impaction and the prevalence of multiple concurrent DAs were significantly higher in Group 2. Impaction showed a significant relationship with supernumerary tooth, transposition, and fusion. Conclusions: The prevalence and pattern of DAs varied depending on the type of malocclusion. As there was a higher risk of other DAs in patients with impacted teeth, early detection of the impacted tooth and a detailed diagnosis of other possible DAs may be essential.

• The korean journal of orthodontics
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• v.53 no.1
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• pp.26-34
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• 2023

Objective: The purpose of the present study was to compare the root positions in virtual tooth setups using only crowns in a simulated treatment with those achieved in the actual treatment. Methods: Pre- and post-treatment intraoral and corresponding cone beam computed tomography (CBCT) scans were obtained from 15 patients who underwent orthodontic treatment with premolar extraction. A conventional virtual tooth setup was used for the treatment simulation. Pre- and post-treatment three-dimensional digital tooth models were fabricated by integrating the patients' intraoral and CBCT scans. The simulated root positions in the virtual setup were obtained by merging the crown in the virtual setup and root in the pre-treatment tooth model. The root positions of the simulated and actual post-treatment tooth models were compared. Results: Differences in root positions between the simulated and actual models were > 1 mm in all teeth, and statistically significant differences were observed (p < 0.05), except for the maxillary lateral incisors. The differences in the inter-root angulation were > 1° in all teeth, and statistically significant differences were observed in the maxillary and mandibular canines. Conclusions: The virtual tooth setup using only crown data showed errors over the clinical limits. The clinical application of a virtual setup using crowns and roots is necessary for accurate and precise treatment simulation, particularly in extraction treatment.

• The korean journal of orthodontics
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• v.53 no.4
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• pp.232-240
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• 2023

Objective: This study aimed to evaluate the zygomaticotemporal suture (ZTS) maturation, analyze the age distribution patterns of ZTS maturation stages, and investigate the relationship between ZTS and cervical vertebral maturation (CVM). Methods: A total of 261 patients who underwent cone-beam computed tomography (112 males, mean age, 13.1 ± 3.3 years; 149 females, mean age, 13.7 ± 3.1 years) were examined to evaluate the ZTS stages. The ZTS stages were defined based on a modified method from previous studies on zygomaticomaxillary sutures. Differences between groups and correlations between indicators were analyzed using the Spearman correlation test, intraclass coefficient of correlation (ICC), one-way analysis of variance and rank sum test. Statistical significance was set at p < 0.05. The diagnostic value of CVM stages in identifying ZTS maturation stages was evaluated using positive likelihood ratios (LRs). Results: A positive relationship was found between the ZTS and CVM stage (r = 0.747, ICC = 0.621, p < 0.01) and between the ZTS stage and chronological age (r = 0.727, ICC = 0.330, p < 0.01). Positive LRs > 10 were found for several cervical stages (CSs), including CS1 and CS2 for the diagnosis of stage B, CS1 to CS3 for the diagnosis of stages B and C, and CS6 for the diagnosis of stages D and E. Conclusions: The ZTS maturation stage may be more relevant to the CVM stage than to the chronological age. The CVM stages can be good indicators for clinical decisions regarding maxillary protraction, except for CS4 and CS5.

• The korean journal of orthodontics
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• v.53 no.4
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• pp.241-253
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• 2023

Objective: To evaluate the following null hypothesis: the skeletal and dentoalveolar expansion patterns in the coronal and axial planes are not different with two different types of microimplant-assisted rapid palatal expansion (MARPE) systems. Methods: Pretreatment (T0) and post-MARPE (T1) cone-beam computed tomography (CBCT) images of 32 patients (14 males and 18 females; mean age, 19.37) were analyzed. We compared two different MARPE systems. One MARPE system included the maxillary first premolars, maxillary first molars, and four microimplants as anchors (U46 type, n = 16), while the other included only the maxillary first molars and microimplants as anchors (U6 type, n = 16). Results: In the molar region of the U6 and U46 groups, the transverse expansion at the midnasal, basal, alveolar, and dental levels was 2.64, 3.52, 4.46, and 6.32 mm and 2.17, 2.56, 2.73, and 5.71 mm, respectively. A significant difference was observed in the posterior alveolar-level expansion (p = 0.036) and posterior basal-bone-level expansion (p = 0.043) between the groups, with greater posterior skeletal and alveolar expansion in the U6 group. Conclusions: Compared with the U46 group, the U6 group showed greater posterior expansion at the alveolar and basal-bone levels, with an almost parallel split. Both groups showed a pyramidal expansion pattern in the coronal view.