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Composition-dependent mechanical properties and viscoelastic behavior of a 3D-printable polyurethane-acrylate soft denture liner

Wed, 01 Jul 2026 00:00:00 GMT

Title: Composition-dependent mechanical properties and viscoelastic behavior of a 3D-printable polyurethane-acrylate soft denture liner Authors: Ham, Sangmin; Min, Jinhong; Lee, Jiho; Park, Young-Bum; Kim, Hoon; Park, Jaehan Abstract: The long-term clinical performance of conventional soft denture liners is limited by microbial colonization, poor adhesion, and plasticizer leaching. This study developed a polyurethane-acrylate soft denture liner enabling moldless fabrication through digital photolithography-based 3D printing. Two urethane-acrylate oligomers with different molecular weights (1K: 12900 g/mol, 2K: 18500 g/mol) were synthesized and mixed in five different ratios to investigate compositional effects on mechanical and viscoelastic behavior. Increasing the proportion of the 2K oligomer enhanced tensile strength and elongation, with compositions >= 1:1 (GR-C) showing mechanical performance comparable to conventional silicone-based soft liners. Dynamic mechanical analysis showed storage modulus values (0.50-0.65 MPa) within the oral mucosal elastic range (0.37-5.93 MPa), indicating damping capacity. Shore A hardness of all compositions remained within the extrasoft range after 30 days, satisfying ISO 10139-2. Under compressive loading, higher 1K content increased resistance to deformation, while GR-C demonstrated intermediate compressive stress at 10-30% strain. In terms of dimensional accuracy, GR-A and GR-D showed greater deviations than the other groups, with higher deviations along the x- and y-axes compared to the z-axis, and group- and axis-dependent patterns were observed. Optical rheometry revealed that increasing the 2K oligomer content reduced the storage modulus while increasing the loss modulus and loss tangent, indicating enhanced viscous behavior. Water sorption (13.1-14.9 mu g/mm3) was within previously reported ranges, whereas solubility (12.3-16.2 mu g/ mm3) was comparatively higher. Near-surface degree of conversion approached 100% after post-polymerization. GR-C was selected as the optimized formulation and showed no cytotoxicity in an L929 cell assay. In the printability assessment using a novel digital workflow, GR-C exhibited a root-mean square (RMS) deviation of 0.619 mm. These results demonstrate that controlled oligomer composition enables tunable tensile, compressive, and viscoelastic properties in 3D-printable polyurethane-acrylate soft denture liners.

Non-surgical treatment of adult skeletal class III patient with severe alveolar bone loss by sequential segmental displacement and third molar extraction: A case report

Mon, 01 Jun 2026 00:00:00 GMT

Title: Non-surgical treatment of adult skeletal class III patient with severe alveolar bone loss by sequential segmental displacement and third molar extraction: A case report Authors: Hong, Hyeon Gi; Nguyen, Hieu; Alkhamees, Amani; Lee, Kee-Joon Abstract: Compromised periodontal conditions pose challenges in orthodontic treatment. In particular, maxillomandibular skeletal discrepancies may require large-scale tooth movement, making it essential to avoid round-tripping movements to minimize dental and periodontal side effects. This case report describes a 49-year-old male patient with skeletal Class III malocclusion and severe alveolar bone loss, particularly affecting the anterior teeth, who sought non-surgical treatment with aesthetic lingual orthodontic appliances. A comprehensive diagnosis and treatment plan were formulated to establish a flat occlusal plane and Class I molar relationship while minimizing round-tripping of the anterior segment. Segmental distalization of mandibular molars, followed by intrusion of the mandibular incisors, was performed with the aid of miniscrews to achieve normal occlusion and an improved facial profile without further alveolar bone loss. This case report highlights the use of segmental archwires and an orthodontic force system based on the centre of resistance to preserve periodontal support in a middle-aged patient with skeletal Class III malocclusion and severe alveolar bone loss.

Methionine challenge test: methyl mercaptan (CH3SH) response in periodontitis

Mon, 01 Jun 2026 00:00:00 GMT

Title: Methionine challenge test: methyl mercaptan (CH3SH) response in periodontitis Authors: Choi, Yiseul; Song, Yoolbin; Kim, Sooyeon; Park, Wonse Abstract: Halitosis, frequently associated with volatile sulfur compounds (VSCs) produced by oral microbiota, affects a large proportion of adults. Among VSCs, methyl mercaptan (CH3SH) is a critical biomarker for periodontitis-related halitosis due to its strong correlation with periodontal pocket depth and attachment loss. This study investigated the utility of a methionine challenge protocol to selectively stimulate CH3SH production and enhance the standardization of oral air-based screening for periodontal disease. Thirty adults were enrolled and divided equally into control and periodontitis groups. Mouth air samples were collected from oral cavity air using a straw-based sampling method connected to a portable gas-sensing device, which continuously monitored VSCs, including CH3SH and hydrogen sulfide (H2S), across eight time points. Participants underwent an 8 h fast prior to baseline oral air collection, followed by standardized toothbrushing. After a 60 min rest period, they swilled with a methionine solution, with oral air samples collected immediately after and at 10 min intervals for 40 min. Both groups showed increased CH3SH levels following methionine stimulation, with the periodontitis group exhibiting a significantly greater increase from pre- to post-stimulation (p < 0.001) and higher cumulative exposure (p < 0.001). In contrast, H2S levels remained consistently elevated in the periodontitis group but did not fluctuate significantly over time. Furthermore, correlations between CH3SH and H2S decreased immediately post-stimulation and gradually recovered in the periodontitis group. These findings indicate that the methionine challenge effectively induces CH3SH production linked to periodontal dysbiosis, supporting its potential as a non-invasive screening and indicator tool for the presence of periodontitis, rather than for staging disease severity. The protocol offers a promising approach to improve diagnostic accuracy while minimizing variability related to oral hygiene. (The study is registered with the Clinical Research Information Service under number KCT0010328.).

Establishment of standardized intraoral implant model in the rabbit edentulous diastema

Mon, 01 Jun 2026 00:00:00 GMT

Title: Establishment of standardized intraoral implant model in the rabbit edentulous diastema Authors: Dai, Xinning; Huang, Xiaoqiong; Deng, Xinwen; Ye, Zhiqian; Liu, Zixiang; Li, Weiran; Li, Yan; Wu, Shuyi; Li, Shujin Abstract: Rabbits have been valued for decades as a model for osseointegration research and biomaterial evaluation, owing to the practical handling, ethical acceptance, and cost-effectiveness. The rabbit model provides an optimal compromise between clinical translatability and practical experimental viability when compared to both large-animal and rodent alternatives. However, rabbit models face inconsistencies across implant site selection criteria, implant geometric configurations, and operative techniques, underscoring the urgent need for standardized experimental frameworks to improve cross-study comparability. The edentulous diastema in rabbit mandible-an anatomical edentulous zone between incisors and premolars-is recognized as a promising intraoral site for implant placement due to its enhanced trabecular bone density and superior volumetric capacity. In contrast to commonly used extragnathic sites (e.g., tibia, femur), which lack a relevant oral microenvironment, the mandibular diastema offers both close anatomical analogy to the human jaw and straightforward surgical access. Herein, we identified an anatomically optimal implant site in rabbit mandibular edentulous diastema utilizing micro-CT-based quantitative analyses and designed a customized implant according to the measured value. Subsequently, we developed a standardized operative workflow for implant placement, and evaluated the osseointegration following 4 weeks and 12 weeks of implantation. Furthermore, we confirmed the applicability of the standardized rabbit intraoral implant model for peri-implantitis modeling. Collectively, we established a workflow for standardizing an intraoral implant model in the edentulous diastema of rabbits which provide highly reproducible, economical, and effective platform for fundamental inquiries into osseointegration, the evaluation of novel implant surface coatings, and the initial screening of biomaterials.