1.Force and moment analysis of clear aligners: Impact of material properties and design on premolar rotation
Dong-Woo KIM ; Hyun-Jun LEE ; Ki Beom KIM ; Sung-Hun KIM ; Seong-Sik KIM ; Soo-Byung PARK ; Youn-Kyung CHOI ; Yong-Il KIM
The Korean Journal of Orthodontics 2025;55(3):212-223
Objective:
To quantitatively analyze and compare the forces and moments generated by thermoformed polyethylene terephthalate glycol (PETG) and direct-printed TC-85 clear aligners (CAs), with various margin designs, during premolar rotation.
Methods:
In total, 132 CAs were fabricated and divided into four groups (n = 33 per group). Group C consisted of thermoformed PETG aligners with a 2 mm gingival margin. Group E comprised direct-printed TC-85 aligners with equi-gingival margin, whereas Group G utilized direct-printed TC-85 aligners with 2 mm gingival margins.Finally, Group T featured direct-printed TC-85 aligners with an additional 1 mm thickness at the mesial embrasure. The forces and moments were measured using a 6-axis force/moment transducer at 2°, 3°, and 4° of rotation. All measurements were conducted at 37°C to simulate intraoral conditions. Forces were measured in the buccolingual, anteroposterior, and vertical directions, while moments were measured in the mesiodistal, buccolingual, and rotational planes.
Results:
The PETG aligners (Group C) showed significantly increased buccal and posterior force across the rotation angles (P < 0.05), whereas the intrusive force remained consistent. In contrast, the TC-85 aligners maintained consistent forces across all rotation angles.Direct-printed aligners demonstrated significantly lower intrusive forces than PETG aligners (P < 0.001). Group T exhibited reduced unwanted forces while maintaining effective rotational moments. Furthermore, all direct-printed aligners showed more predictable force delivery patterns than thermoformed aligners.
Conclusions
Direct-printed TC-85 aligners demonstrated superior force consistency and reduced unwanted side effects compared with traditional PETG aligners. Although marginal design modifications did not significantly improve rotational efficiency, they effectively reduced unwanted intrusive forces.
2.Virtual Reality-Based Cognitive Behavior Therapy for Major Depressive Disorder: An Alternative to Pharmacotherapy for Reducing Suicidality
Miwoo LEE ; Sooah JANG ; Hyun Kyung SHIN ; Sun-Woo CHOI ; Hyung Taek KIM ; Jihee OH ; Ji Hye KWON ; Youngjun CHOI ; Suzi KANG ; In-Seong BACK ; Jae-Ki KIM ; San LEE ; Jeong-Ho SEOK
Yonsei Medical Journal 2025;66(1):25-36
Purpose:
Cognitive behavioral therapy (CBT) has long been recognized as an effective treatment for depression and suicidality.Virtual reality (VR) technology is widely used for cognitive training for conditions such as anxiety disorder and post-traumatic stress disorder, but little research has considered VR-based CBT for depressive symptoms and suicidality. We tested the effectiveness and safety of a VR-based CBT program for depressive disorders.
Materials and Methods:
We recruited 57 participants from May 2022 through February 2023 using online advertisements. This multi-center, assessor-blinded, randomized, controlled exploratory trial used two groups: VR treatment group and treat as usual (TAU) group. VR treatment group received a VR mental health training/education program. TAU group received standard pharmacotherapy. Assessments were conducted at baseline, immediately after the 6-week treatment period, and 4 weeks after the end of the treatment period in each group.
Results:
Depression scores decreased significantly over time in both VR treatment and TAU groups, with no differences between the two groups. The suicidality score decreased significantly only in VR group. No group differences were found in the remission or response rate for depression, perceived stress, or clinical severity. No adverse events or motion sickness occurred during the VR treatment program.
Conclusion
VR CBT treatment for major depressive disorder has the potential to be equivalent to the gold-standard pharmacotherapy in reducing depressive symptoms, suicidality, and related clinical symptoms, with no difference in improvement found in this study. Thus, VR-based CBT might be an effective alternative to pharmacotherapy for depressive disorders.
4.Clinical Characteristics and Visual Prognostic Biomarkers in Pericentral Retinitis Pigmentosa: A Study in a South Korean Cohort
Su Ho BAE ; Seung Woo CHOI ; Chang Ki YOON ; Un Chul PARK ; Kyu Hyung PARK ; Eun Kyoung LEE
Korean Journal of Ophthalmology 2025;39(2):157-169
Purpose:
To investigate the clinical characteristics of South Korean patients with pericentral retinitis pigmentosa (RP) and to identify clinical biomarkers associated with rapid visual acuity decline based on baseline factors.
Methods:
This retrospective study included 59 eyes of 31 patients diagnosed with pericentral RP. Comprehensive ophthalmological examinations and genetic sequencing were conducted to assess the baseline characteristics. For biomarker analysis, eyes were categorized into two groups based on the annual rate of change in visual acuity. The clinical findings of the two groups were evaluated to identify the biomarkers associated with rapid loss of visual acuity.
Results:
Patients with pericentral RP in this study exhibited a mean best-corrected visual acuity of 0.17 ± 0.23 in logarithm of the minimum angle of resolution. The visual field test showed annular or semicircular scotoma with relatively preserved periphery and 27 eyes (45.8%) exhibited no macular complications in optical coherence tomography. Genetic analysis identified genes associated with previous typical and pericentral RP studies but also highlighted that many genetic causes of pericentral RP remain unidentified. Of the 55 eyes for which the rate of visual acuity change could be estimated, 18 exhibited an annual decline of ≥10%, whereas 37 showed an annual decline of <10%. Male sex and prolonged b-wave latency on dark-adapted 0.01 electroretinogram correlated with rapid visual acuity decline in the multivariate analysis.
Conclusions
South Korean patients with pericentral RP exhibited a milder phenotype compared to typical RP patients reported in previous studies. Genetic analysis revealed heterogeneity, with mutations in some genes commonly associated with milder forms of RP. Male sex and prolonged b-wave latency on dark-adapted 0.01 electroretinogram were significant biomarkers for predicting rapid visual acuity decline. Monitoring initial b-wave latency is important for predicting visual decline, particularly in male patients with pericentral RP.
5.Objective Changes in the Contralateral Eye after Unilateral Cataract Surgery
Seung Hyeun LEE ; Kyoung Woo KIM ; In Ki PARK ; Yeoun Sook CHUN
Korean Journal of Ophthalmology 2025;39(1):48-56
Purpose:
This study evaluated the objective changes in the contralateral eye after unilateral cataract surgery.
Methods:
The study was designed as retrospective observational study. It included 44 patients who underwent unilateral cataract surgery. Collected data were uncorrected and corrected visual acuity, spherical equivalent, intraocular pressure, contrast sensitivity (CS), stereoacuity, and anterior segment optical coherence tomography parameters. Data were collected preoperatively, and 1 week and 1 month postoperatively for each eye.
Results:
Following unilateral cataract surgery, the pupil size of the fellow eye decreased from 3.46 mm to 3.17 mm (postoperative week 1, p = 0.003) and 3.08 mm (postoperative month 1, p < 0.001). Anterior chamber depth of the fellow eye increased significantly from 3.16 mm to 3.27 mm (postoperative week 1, p = 0.005) and 3.26 mm (postoperative month 1, p = 0.001). Uncorrected distance visual acuity (UDVA) of the fellow eye improved significantly at postoperative week 1 (p = 0.042) and postoperative month 1 (p = 0.044). Change of UDVA of the fellow eye at postoperative month 1 was significantly correlated with that of the treated eye (p = 0.039).
Conclusions
Anterior chamber structures changed and UDVA improved in the contralateral eye after unilateral cataract surgery in our cohort. Because fellow eyes were positively affected by monocular cataract surgery, it would be good information if planning for unilateral cataract surgery due to inevitable reasons.
6.Comparison between Suture-Button Technique with Syndesmotic Repair and Screw Fixation Technique for Complete Ankle Syndesmotic Injury: Biomechanical Cadaveric Study
Hong Seop LEE ; Sung Hwan KIM ; Ki Won YOUNG ; Woo Jong KIM ; Dong-Il CHEON ; Sung Hun WON ; Sang Heon LEE ; Seung Jin CHOI ; Young Koo LEE
Clinics in Orthopedic Surgery 2025;17(2):324-330
Background:
The tibiofibular syndesmosis is essential for preserving the stability of the ankle. Acute syndesmotic injuries with evident or latent instability usually warrant surgical interventions. This cadaveric study examines and compares biomechanical characteristics between the following treatments for syndesmosis injuries: suture-button fixation plus syndesmotic repair and screw fixation.
Methods:
The lower extremities of 10 cadavers disarticulated at the knee joints were used, yielding 20 feet. Ten feet underwent surgery using the suture-button fixation with syndesmotic repair, while the remaining 10 feet underwent surgery using screw fixation. Before surgical treatment of syndesmosis injuries, each cadaveric lower limb underwent preliminary physiological cyclic loading, which was followed by a series of postfixation cyclic loading tests after the surgical procedure.
Results:
Our principal finding is that suture-button fixation with syndesmotic repair provided torsional strength comparable to that of screw fixation. The mean failure torque did not differ between the 2 groups, but the rotational stiffness was significantly lower in the suture-button fixation/augmentation group.
Conclusions
Suture-button fixation/augmentation facilitates flexible (physiological) syndesmosis movement and may be a useful alternative treatment for ankle syndesmosis injury.
7.Study Protocol of Expanded Multicenter Prospective Cohort Study of Active Surveillance on Papillary Thyroid Microcarcinoma (MAeSTro-EXP)
Jae Hoon MOON ; Eun Kyung LEE ; Wonjae CHA ; Young Jun CHAI ; Sun Wook CHO ; June Young CHOI ; Sung Yong CHOI ; A Jung CHU ; Eun-Jae CHUNG ; Yul HWANGBO ; Woo-Jin JEONG ; Yuh-Seog JUNG ; Kyungsik KIM ; Min Joo KIM ; Su-jin KIM ; Woochul KIM ; Yoo Hyung KIM ; Chang Yoon LEE ; Ji Ye LEE ; Kyu Eun LEE ; Young Ki LEE ; Hunjong LIM ; Do Joon PARK ; Sue K. PARK ; Chang Hwan RYU ; Junsun RYU ; Jungirl SEOK ; Young Shin SONG ; Ka Hee YI ; Hyeong Won YU ; Eleanor WHITE ; Katerina MASTROCOSTAS ; Roderick J. CLIFTON-BLIGH ; Anthony GLOVER ; Matti L. GILD ; Ji-hoon KIM ; Young Joo PARK
Endocrinology and Metabolism 2025;40(2):236-246
Background:
Active surveillance (AS) has emerged as a viable management strategy for low-risk papillary thyroid microcarcinoma (PTMC), following pioneering trials at Kuma Hospital and the Cancer Institute Hospital in Japan. Numerous prospective cohort studies have since validated AS as a management option for low-risk PTMC, leading to its inclusion in thyroid cancer guidelines across various countries. From 2016 to 2020, the Multicenter Prospective Cohort Study of Active Surveillance on Papillary Thyroid Microcarcinoma (MAeSTro) enrolled 1,177 patients, providing comprehensive data on PTMC progression, sonographic predictors of progression, quality of life, surgical outcomes, and cost-effectiveness when comparing AS to immediate surgery. The second phase of MAeSTro (MAeSTro-EXP) expands AS to low-risk papillary thyroid carcinoma (PTC) tumors larger than 1 cm, driven by the hypothesis that overall risk assessment outweighs absolute tumor size in surgical decision-making.
Methods:
This protocol aims to address whether limiting AS to tumors smaller than 1 cm may result in unnecessary surgeries for low-risk PTCs detected during their rapid initial growth phase. By expanding the AS criteria to include tumors up to 1.5 cm, while simultaneously refining and standardizing the criteria for risk assessment and disease progression, we aim to minimize overtreatment and maintain rigorous monitoring to improve patient outcomes.
Conclusion
This study will contribute to optimizing AS guidelines and enhance our understanding of the natural course and appropriate management of low-risk PTCs. Additionally, MAeSTro-EXP involves a multinational collaboration between South Korea and Australia. This cross-country study aims to identify cultural and racial differences in the management of low-risk PTC, thereby enriching the global understanding of AS practices and their applicability across diverse populations.
9.Clinical Characteristics and Visual Prognostic Biomarkers in Pericentral Retinitis Pigmentosa: A Study in a South Korean Cohort
Su Ho BAE ; Seung Woo CHOI ; Chang Ki YOON ; Un Chul PARK ; Kyu Hyung PARK ; Eun Kyoung LEE
Korean Journal of Ophthalmology 2025;39(2):157-169
Purpose:
To investigate the clinical characteristics of South Korean patients with pericentral retinitis pigmentosa (RP) and to identify clinical biomarkers associated with rapid visual acuity decline based on baseline factors.
Methods:
This retrospective study included 59 eyes of 31 patients diagnosed with pericentral RP. Comprehensive ophthalmological examinations and genetic sequencing were conducted to assess the baseline characteristics. For biomarker analysis, eyes were categorized into two groups based on the annual rate of change in visual acuity. The clinical findings of the two groups were evaluated to identify the biomarkers associated with rapid loss of visual acuity.
Results:
Patients with pericentral RP in this study exhibited a mean best-corrected visual acuity of 0.17 ± 0.23 in logarithm of the minimum angle of resolution. The visual field test showed annular or semicircular scotoma with relatively preserved periphery and 27 eyes (45.8%) exhibited no macular complications in optical coherence tomography. Genetic analysis identified genes associated with previous typical and pericentral RP studies but also highlighted that many genetic causes of pericentral RP remain unidentified. Of the 55 eyes for which the rate of visual acuity change could be estimated, 18 exhibited an annual decline of ≥10%, whereas 37 showed an annual decline of <10%. Male sex and prolonged b-wave latency on dark-adapted 0.01 electroretinogram correlated with rapid visual acuity decline in the multivariate analysis.
Conclusions
South Korean patients with pericentral RP exhibited a milder phenotype compared to typical RP patients reported in previous studies. Genetic analysis revealed heterogeneity, with mutations in some genes commonly associated with milder forms of RP. Male sex and prolonged b-wave latency on dark-adapted 0.01 electroretinogram were significant biomarkers for predicting rapid visual acuity decline. Monitoring initial b-wave latency is important for predicting visual decline, particularly in male patients with pericentral RP.
10.Objective Changes in the Contralateral Eye after Unilateral Cataract Surgery
Seung Hyeun LEE ; Kyoung Woo KIM ; In Ki PARK ; Yeoun Sook CHUN
Korean Journal of Ophthalmology 2025;39(1):48-56
Purpose:
This study evaluated the objective changes in the contralateral eye after unilateral cataract surgery.
Methods:
The study was designed as retrospective observational study. It included 44 patients who underwent unilateral cataract surgery. Collected data were uncorrected and corrected visual acuity, spherical equivalent, intraocular pressure, contrast sensitivity (CS), stereoacuity, and anterior segment optical coherence tomography parameters. Data were collected preoperatively, and 1 week and 1 month postoperatively for each eye.
Results:
Following unilateral cataract surgery, the pupil size of the fellow eye decreased from 3.46 mm to 3.17 mm (postoperative week 1, p = 0.003) and 3.08 mm (postoperative month 1, p < 0.001). Anterior chamber depth of the fellow eye increased significantly from 3.16 mm to 3.27 mm (postoperative week 1, p = 0.005) and 3.26 mm (postoperative month 1, p = 0.001). Uncorrected distance visual acuity (UDVA) of the fellow eye improved significantly at postoperative week 1 (p = 0.042) and postoperative month 1 (p = 0.044). Change of UDVA of the fellow eye at postoperative month 1 was significantly correlated with that of the treated eye (p = 0.039).
Conclusions
Anterior chamber structures changed and UDVA improved in the contralateral eye after unilateral cataract surgery in our cohort. Because fellow eyes were positively affected by monocular cataract surgery, it would be good information if planning for unilateral cataract surgery due to inevitable reasons.

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