Publications by authors named "Ji Man Park"
ARS: AI-Driven Recovery Controller for Quadruped Robot Using Single-Network Model.
Biomimetics (Basel)
December 2024
Legged robots, especially quadruped robots, are widely used in various environments due to their advantage in overcoming rough terrains. However, falling is inevitable. Therefore, the ability to overcome a falling state is an essential ability for legged robots.
View Article and Find Full Text PDFArticle Synopsis
- A study was conducted to examine the accuracy and failure load of 3D printed interim fixed dental prostheses (FDPs) with different wall thicknesses in their hollow pontic designs, focusing on how inward polymerization shrinkage affects fit.
- The investigation involved creating multiple 3D printed specimens with varying wall thicknesses (4 options: solid and 2.5, 2.0, and 1.5 mm) and measuring their fit and strength using advanced imaging and testing techniques.
- Results showed that the 2.0-mm wall thickness provided a better fit and comparable strength to solid designs, while thinner walls led to increased fracture rates, highlighting the importance of wall thickness in prosthetic design.
Article Synopsis
- - The study assessed the mechanical properties and accuracy of zirconia crowns made through additive manufacturing (AM) versus subtractive techniques (CNC), using tests involving autoclaving, strength measurement, and morphology analysis.
- - Results showed that increased autoclave time led to decreased flexural strength in both manufacturing groups, but no correlation was found between the m-phase fraction (a measure of material change) and strength.
- - Additively manufactured zirconia crowns exhibited less precision in their fit compared to those created by subtractive methods, though their overall mechanical properties were found to be comparable, indicating potential clinical applicability.
Article Synopsis
- This study evaluated the accuracy of complete-arch dental casts produced by six different 3D printers, focusing on both horizontal and vertical measurements using low-viscosity resin material.
- Ten casts were printed from a reference design and analyzed for accuracy through multiple deviation metrics, with surface characteristics examined via advanced microscopy techniques.
- Results indicated that LCD printers generally had higher accuracy (trueness) compared to DLPa and SLA printers, with specific variations in dimensions and surface quality noted among the different printer types.
Article Synopsis
- This study compared the accuracy (trueness) and physical properties of zirconia crowns made using five additive manufacturing methods against those made through subtractive manufacturing.* -
- The research found that while differences in trueness were significant among the additive methods, all techniques produced crowns within clinically acceptable levels, although all additive groups displayed greater surface roughness and voids compared to the control group.* -
- Overall, the additive manufactured zirconia crowns maintained typical zirconia characteristics, indicating their potential suitability for dental applications despite some quality concerns.*
Article Synopsis
- This study examined how the shade and translucency of ceramic crowns impact the accuracy of scans done by intraoral scanners.
- Eight resin typodonts with crowns of varying translucencies and shades were tested using two different intraoral scanners, both with and without scan powder.
- Results showed that while crown shade didn't significantly affect scan accuracy, high-translucency crowns were less accurate than low-translucency ones, and using scan powder improved accuracy overall.
Article Synopsis
- 3D printed zirconia materials are compared to milled zirconia, particularly focusing on their flexural strength, with previous studies mostly examining 3Y-TZP, prompting the need for research on 4Y-TZP.
- This study evaluated the flexural strength of four types of zirconia specimens (two 3D printed and two milled) using a standardized testing method and analyzed their crystalline structure through various methods.
- Results indicated that 3D printed 4Y-TZP had significantly higher flexural strength than milled 4Y-TZP, while 3D printed 3Y-TZP exhibited lower strength compared to its milled counterpart, with tetragonal phases confirmed in all
Article Synopsis
- The study aimed to accurately predict the positional coordinates of incisor points using scan data from conventional complete dentures.
- By analyzing STL data from 100 pairs of dentures, researchers calculated the x, y, and z coordinates of incisor points and assessed the prediction accuracy through root mean squared error (RMSE) metrics.
- Results indicated that while the accuracy for predicting the X coordinate was RMSE of 2.22, the Y coordinate accuracy improved significantly by including additional facial measurements, achieving a lower RMSE of 0.73.
Article Synopsis
- The study focused on how fixed implants in toothless areas affect oral health-related quality of life (OHRQoL) in disabled patients, highlighting the lack of research in this area.
- Using the OHIP-14 questionnaires, researchers evaluated 63 disabled individuals and found significant improvements in OHRQoL scores after implant treatment.
- Results indicated that while severity of disability impacted OHRQoL improvements, older patients exhibited lower scores post-treatment, with no significant differences found based on sex or whether the disability was congenital or acquired.
Deep learning-based automated detection of the dental crown finish line: An accuracy study.
J Prosthet Dent
December 2024
Statement Of Problem: The marginal fit of dental prostheses is a clinically significant issue, and dental computer-aided design software programs use automated methods to expedite the extraction of finish lines. The accuracy of these automated methods should be evaluated.
Purpose: The purpose of this study was to compare the accuracy of a new hybrid method with existing software programs that extract finish lines using fully automated and semiautomated methods.
Comparison of Fit and Stability Between 3D-Printed and Milled Implant Abutments with Titanium-6Al-4V and Co-Cr Metal Alloys.
Int J Oral Maxillofac Implants
October 2023
Article Synopsis
- - The study compared the fit and clinical performance of 3D-printed titanium (Ti) and cobalt-chromium (Co-Cr) abutments with traditional CNC-milled abutments using parameters like removal torque values (RTVs).
- - A total of 138 abutments were examined, with various techniques like scanning electron microscopy (SEM) used to assess the fit, and the impact of torque tightening and cyclic loading on the RTVs was measured.
- - Results indicated that 3D-printed Co-Cr abutments fit well with implants, showing comparable RTVs to CNC-milled ones, whereas the fit of 3D-printed Ti abutments was found to be inadequate. *
Article Synopsis
- Researchers investigated how ULK1, a key protein that starts autophagy, behaves at a molecular level during amino acid starvation.
- They discovered that ULK1 forms clusters of up to 161 molecules at the endoplasmic reticulum, which are crucial for forming autophagosomes.
- The study revealed that while ULK1 doesn't need to be active for the initial clustering, its activation is essential for the clusters to grow and interact with other important proteins like Atg14 and LC3B.
Article Synopsis
- In glucose-starved cells, autophagy is crucial for generating energy and supporting cell survival, with AMPK acting as a key energy sensor.
- Traditional views suggest that AMPK activates autophagy by phosphorylating ULK1, the initiator of the autophagy process.
- However, recent findings from our study indicate that AMPK actually inhibits ULK1 activity, challenging the established model and highlighting its role in regulating autophagy and cellular resilience during energy shortages.
Article Synopsis
- Autophagy is a process that helps cells stay balanced when they don't have enough energy.
- The study shows that a protein called AMPK can actually stop another protein, ULK1, from starting autophagy even when cells are low on energy.
- However, AMPK also protects important parts needed for autophagy, which helps cells to recover and get back to normal when they have enough energy again.
Article Synopsis
- The study aimed to evaluate how hemispherical dimple structures affect the retention of cobalt-chromium (Co-Cr) crowns on titanium abutments with varying heights and dimple configurations.
- Researchers prepared 180 different crown and abutment setups, using two different cements, and measured retention forces after thermal treatments.
- Results indicated that dimples significantly improved retention force compared to control groups, and higher 6.0-mm abutments yielded better retention than 3.0-mm ones, with less adhesive failure noted in dimpled groups.
Article Synopsis
- - This paper examines the necessity of a precise motion-tracking system for robotic computer-assisted implant surgery to prevent complications from inaccurate implant placement.
- - The authors categorize key features of the motion-tracking system into workspace, sampling rate, accuracy, and back-drivability, and establish requirements for each to meet performance standards.
- - A new 6-DOF motion-tracking system is introduced, showcasing high accuracy and back-drivability, with experimental results validating its effectiveness for the surgical application.
Article Synopsis
- Polycaprolactone has shown promise as a biomaterial for bone regeneration, particularly in the context of dental implants.
- This report details the first clinical application of a 3D printed polycaprolactone mesh used for alveolar ridge augmentation in two patients who required significant bone enhancement.
- After 2 years, patients experienced bone gains of about 6 mm vertically and 8 mm horizontally, although there was some reduction in ridge dimensions post-surgery, indicating potential effectiveness but also the need for further studies.
Article Synopsis
- Three-dimensional (3D) printers are being evaluated for their accuracy and surface quality in creating dental casts, important for various dental applications.
- This study tested four types of dental casts printed by six different 3D printers using various technologies (FDM, DLP, SLA) to assess both trueness and surface characteristics.
- Results indicated significant differences in trueness across different printers, with SLA printers producing the smoothest surfaces, while FDM printers displayed more visible layering.
Article Synopsis
- - The study aimed to evaluate how the build orientation (45° vs. 60°) and layer thickness (50 µm vs. 100 µm) impact the fit of three-unit resin prostheses created through stereolithography (SLA) printing.
- - Forty resin specimens were produced, and their fit was measured at various points, revealing that the fit was generally better at a 45° angle compared to a 60° angle, while layer thickness did not significantly influence fit.
- - The findings suggest that the area near the pontic had the largest gaps, emphasizing the importance of build orientation in achieving better overall fit, with a 45° orientation being the preferred choice.
Article Synopsis
- The study investigates the clinical performance of two intraoral scanners (IOSs) for creating cast-free zirconia crowns, assessing their marginal and internal gaps through a randomized clinical trial.
- It involves 35 participants and compares crowns made from scans obtained via a confocal microscopy-based IOS and a dual camera triangulation-based IOS, using a replica technique for gap measurements.
- The results indicate that the crowns from the dual camera triangulation IOS have acceptable gap measurements and are comparable to those created with the confocal IOS, suggesting both technologies are viable for clinical use in digital dentistry.
A Digital Workflow for the Fabrication of a Milled Removable Partial Denture.
Int J Environ Res Public Health
July 2022
Article Synopsis
- Complete dentures made using both additive and subtractive methods are common and clinically acceptable, but removable partial dentures (RPDs) face limitations in digital fabrication due to the technique sensitivity of pink resin encasement.
- This article describes a new digital workflow that utilizes the subtractive method to create RPDs, allowing for the milling of both the metal framework and denture base with sockets for teeth.
- The innovative process results in customized artificial teeth and minimizes issues like resin shrinkage, presenting a viable digital alternative to traditional analog fabrication methods for RPDs.
Article Synopsis
- High-speed 3D printing has improved the speed of creating dental materials, but postpolymerization still takes a long time and its effects on material properties are not well understood.
- This study investigated how different postpolymerization methods affect the physical properties and safety of a 3D printed dental material called C&B MFH by testing various devices and measuring metrics like hardness and cytotoxicity.
- Results indicated that the LC device produced the hardest specimens, while the MP group had the least hardness; all tested groups maintained a flexural strength of at least 100 MPa, and all had over 70% cell viability, showing they are non-toxic.
Article Synopsis
- The study assessed the accuracy of automatic vs. manual finish line registration methods in dental CAD, testing various configurations on digital tooth models.
- Results indicated that automatic registration had higher error rates, particularly with more rounded and obtuse edges, and the accuracy varied significantly between different CAD software.
- The findings suggest potential inaccuracies when using automatic methods on unclear tooth edges, highlighting the influence of CAD software choice on registration accuracy.
Article Synopsis
- The study aimed to determine how different methods of registration for cone beam computed tomography (CBCT) and intraoral scans affect accuracy and duration, specifically in relation to the number of dental restorations compared to natural teeth.
- A total of 36 patients were analyzed, and while the accuracy of registration methods was comparable, the time taken varied significantly, with deep learning-based methods being the fastest.
- Results showed that higher ratios of dental restorations lead to decreased accuracy and shorter registration times, emphasizing the impact of restorations on the registration process regardless of the method used.*
Article Synopsis
- A study was conducted to compare 1-year outcomes of immediate loading (IL) versus delayed loading (DL) for dental implants in partially edentulous jaws, using fully guided surgery.
- Out of 72 patients, the DL group had a 100% survival rate for both patients and implants, while the IL group had only 69.4% survival at the patient level and 83.4% at the implant level.
- Despite differences in survival rates, both groups exhibited stable marginal bone levels, with less than 0.1 mm of bone loss.