Ji Suk Shim

This study aimed to fabricate hybrid blocks by infiltrating various resin compositions into pre-sintered porous lithium disilicate (Li₂Si₂O₅) scaffolds and to evaluate their surface characteristics, mechanical properties, and cytocompatibility. Hybrid ceramic–polymer blocks were produced using mixtures of Bis-GMA, UDMA, and TEGDMA monomers, polymerized at 300 MPa and 180 °C. Four groups (BT82, BT55, UT55, UT73) with different monomer ratios were tested. Complete resin infiltration was achieved in all groups. Surface roughness, contact angle, and water sorption showed no significant differences. However, mechanical properties varied depending on resin composition. UDMA-containing groups (UT55, UT73) exhibited higher flexural strength and Vickers hardness, while Bis-GMA-containing groups showed lower values. Flexural strength was maintained after thermal cycling, but hardness decreased in all groups. All formulations demonstrated excellent cytocompatibility. These results demonstrate that optimizing the resin composition enables the fabrication of lithium disilicate-based hybrid blocks with excellent mechanical properties and biocompatibility, suggesting their potential application as chairside Computer Aided Design/Computer Aided Manufacturing dental restorative materials. Graphical Abstract

김윤아, et al. J Korean Acad Prosthodont. 2026 Oct;64(4):351-362. https://doi.org/10.4047/jkap.2026.64.4.351

Purpose: Supports are essential for ensuring dimensional accuracy in 3D printing; however, an excessive number of supports compromises printing efficiency. This study aimed to investigate how a varying number of support arrangements affects the precision and trueness of 3D-printed dentures.Methods: Three denture base printing files were designed, each with different numbers of supports: 40 (group 40), 55 (group 55), and 70 (group 70). Thirty samples were printed and measured across the groups. Accuracy was evaluated by assessing trueness and precision using the root mean square error (RMSE). The error areas in each group were analyzed through micro-computed tomography (micro-CT) 3D imaging.Results: Group 70 showed a significantly lower RMSE for trueness than Group 40 (P < 0.05), but showed no significant difference from Group 55 (P ≥ 0.05). For precision, Group 70 outperformed both Groups 40 and 55 (P < 0.05), which did not differ significantly (P ≥ 0.05). Micro-CT revealed no mismatches in the palatal region. Discrepancies—areas where the supports in Groups 40 and 55 did not accurately align with those in Group 70—were predominantly observed at initiation points of overhangs in thinner sections.Conclusions: Based on these results, this study recommends placing support structures strategically around overhangs and thin-walled areas to enhance the accuracy of 3D-printed denture fabrication. These findings indicate that optimizing support placement, rather than merely increasing the number of supports, is crucial in improving the quality and reliability of 3D-printed dental prostheses.

Purpose: To investigate the remnant cement in the subgingival regions (RCS) of abutments fabricated with different CAD/CAM parameters, including margin curvature radius, convergence angle, top fillet radius, and subgingival abutment shape.Methods: Twelve experimental groups were fabricated to test the following parameters: abutment margin curvature radii of 0.8 mm, 1.2 mm, and 1.6 mm; convergence angles of 4°, 8°, and 12°; top fillet radii of 0.6 mm, 1.0 mm, and 1.4 mm; and subgingival abutment shapes of straight, S-curve, and concave. A constant amount of cement was injected into each crown. Vertical and continuous loads were applied to each specimen using a universal machine. RCS values were measured using a 3D intraoral scanner and an analytical balance. Statistical analysis was performed using one-way analysis of variance followed by post hoc Tukey test (α = .05).Results: Regarding margin curvature radius, RCS values were significantly higher in the order of 1.6 mm, 1.2 mm, and 0.8 mm (P < 0.001). For convergence angle, higher RCS values were observed at 12° > 8° > 4°(P < 0.001). Among subgingival abutment shapes, concave yielded the highest RCS values, followed by S-curve and straight (P < 0.001). No significant differences in RCS values were found among the groups with different top fillet radii (P > 0.05).Conclusions: Within the limitations of this study, a smaller margin curvature radius, smaller convergence angle, and straight subgingival shape were associated with reduced RCS length, surface area, and weight.

Purpose: This study evaluated the cytotoxicity of clinically available dental cements containing resin: conventional adhesive resin cement (ARC), self-adhesive resin cement (SARC), and resin-modified glass-ionomer cement (RMGIC), focusing on their degree of conversion (DC) and effects on cellular responses.Methods: The DC of all the groups was measured over two weeks under light-free conditions. Cell viability, morphology, and apoptosis were assessed in gingival fibroblasts, dental pulp stem cells, and macrophage cells after exposure to extracts from specimens with different DC values. Eluate analysis was performed using attenuated total reflectance-Fourier transform spectroscopy and gas chromatography/mass spectrometry.Results: The DC increased rapidly within 20 min for ARC and SARC, reaching a plateau at 24 h, while RMGIC showed a slower increase. ARC and SARC exhibited significant cytotoxicity at lower DC levels, with improved cell viability as DC increased. RMGIC displayed minimal cytotoxicity across all DC levels. Analysis revealed unreacted monomers and other substances contributing to cytotoxicity, with apoptotic effects correlating to their concentration in the eluates.Conclusions: DC significantly influences the cytotoxicity of resin-containing dental cements, with ARC and SARC showing higher cytotoxic effects at lower DC levels compared with RMGIC. Considering DC levels may guide clinicians in minimizing adverse effects when selecting these cements. Dental cements containing resin can release substances that may affect cell viability.

Axin2 negatively regulates the Wnt signaling pathway, which plays a crucial role in multiple tooth development phases. This study aimed to investigate the effects of Axin2 deficiency on tooth development in zebrafish, which are categorized as polyphyodonts. To investigate the role of Axin2 in tooth formation, we generated Axin2 knockout zebrafish using the CRISPR/Cas9 system. Tooth development in zebrafish was observed in the transgenic line, which specifically emits fluorescence in dental tissues. Micro–computed tomography and field emission scanning electron microscopy were used to evaluate tooth shape. Tooth elemental composition was examined using energy-dispersive spectrometry analysis, and gene expression was determined using quantitative polymerase chain reaction. The results showed that the body length of the Axin2 mutant was significantly lower than that of the wild type. β-Catenin expression increased in the dental pulp of the Axin2 mutant compared with that of Axin2 ^+/+ zebrafish. Confocal imaging showed that initiation and morphogenesis of teeth were sequentially delayed at positions 2V and 1V. Dentin elements, including phosphorus, calcium, carbon, and oxygen, were detected at significantly low levels in Axin2 ^−/− zebrafish. In addition, runx2a , runx2b, sp7, scpp5 , and col1a1a/b expression was significantly reduced in Axin2 ^−/− . The results show that the loss of Axin2 function causes hypomineralization and delayed tooth development in zebrafish and suggest that spatiotemporal regulation of Wnt signaling is necessary for the normal maturation of odontoblasts.

김태완, et al. J Korean Acad Prosthodont. 2025 Oct;63(4):394-405. https://doi.org/10.4047/jkap.2025.63.4.394

남건희, et al. J Korean Acad Prosthodont. 2025 Oct;63(4):384-393. https://doi.org/10.4047/jkap.2025.63.4.384

This study aimed to investigate the effects of crown seating speed, crown seating force, quantity of cement used, and type of implant cement on the amount of remnant cement in the subgingival region (RCS) after cementation. Cement-retained implant crowns were cemented to titanium abutments using the following methods: four types of implant cement (TBN: TEMP BOND NE, NR: NEXUS RMGI, ME: MAXCEM ELITE, and U200: RELYX U200), three quantities of cement (0.02 ml, 0.04 ml, and 0.06 ml), three crown seating speeds (5 mm/s, 10 mm/s, and 15 mm/s), and two crown seating forces (25 N, 50 N). The surface area and length of the RCS were measured using a 3D intraoral scanner. The total RCS weight was measured using an analytical balance. The RCS increased significantly as the seating speed increased, the seating force increased, and the quantity of cement increased (p < 0.05). The RCS values were the highest for TBN, followed by U200, NR, and ME (p < 0.05). The lower seating speed, smaller quantity of cement used, and smaller seating force applied in cement-retained implant restorations minimized the RCS in cement-retained prostheses. The type of cement is a factor that determines the aspects of the RCS.