Biocompatibility is important for the 3D printing of resins used in medical devices and can be affected by photoinitiators, one of the key additives used in the 3D printing process. The choice of ingredients must be considered, as the toxicity varies depending on the photoinitiator, and unreacted photoinitiator may leach out of the polymerized resin. In this study, the use of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) as a photoinitiator for the 3D printing of resin was considered for application in medical device production, where the cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical/physical properties were evaluated. Along with TPO-L, two conventional photoinitiators, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), were considered. A total of 0.1 mol% of each photoinitiator was mixed with the resin matrix to prepare a resin mixture for 3D printing. The specimens were printed using a direct light processing (DLP) type 3D printer. The 3D-printed specimens were postprocessed and evaluated for cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical properties in accordance with international standards and the methods described in previous studies. The TPO-L photoinitiator showed excellent biocompatibility and colour stability and possessed with an acceptable dimensional accuracy for use in the 3D printing of resins. Therefore, the TPO-L photoinitiator can be sufficiently used as a photoinitiator for dental 3D-printed resin.

Various materials have been introduced for the three-dimensional (3D) printing of dentures. In this study, the color stability and surface and physicochemical properties of 3D-printed denture base resins with four types of nanofiller particles were evaluated. Al₂O₃, ZnO, CeZr, and SiO₂ nanofillers were added to a 3D printable denture base-resin matrix and subjected to digital light processing. The specimens were immersed in Coke, coffee, black tea, or distilled water for 6 days. For the assessment of color differences, 6 samples were analyzed using a spectrophotometer. In a separate investigation, surface properties of 10 samples were examined, while a different set of 6 samples was used to analyze water sorption and solubility. All experimental groups exhibited higher color stability in Coke than the control group. However, the groups containing ZnO and CeZr had lower color stability in coffee and black tea than the control group. Moreover, they had agglomerated nanofillers and lower gloss than the control group. Compared with that of the control group, the contact angle of the CeZr group and microhardness of the ZnO group were not significantly different. Water sorption was higher in the Al₂O₃ group, whereas the solubility of the experimental and control groups was not statistically significant. The results demonstrated the significant effect of ZnO and CeZr nanofillers on the color stability of the dentures when exposed to discoloring beverages. These results will facilitate the development of fillers that enhance the resistance of 3D printed denture base resins to discoloration in the oral environment.

The aim of this study was to investigate the element composition and grain size of commercial dental instruments used for ultrasonic scaler tips, which are composed of stainless-steel materials. The differences in mechanical properties and wear resistances were compared. The samples were classified into 4 groups in accordance with the manufacturer, Electro Medical Systems, 3A MEDES, DMETEC and OSUNG MND, and the element compositions of each stainless-steel ultrasonic scaler tip were analyzed with micro-X-ray fluorescence spectrometry (μXRF) and field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS). One-way ANOVA showed that there were significant differences in shear strength and Vickers hardness among the stainless-steel ultrasonic scaler tips depending on the manufacturer (p < 0.05). The mass before and after wear were found to have no significant difference among groups (p > 0.05), but there was a significant difference in the wear volume loss (p < 0.05). The results were then correlated with μXRF results as well as observations of grain size with optical microscopy, which concluded that the Fe content and the grain size of the stainless steel have significant impacts on strength. Additionally, stainless-steel ultrasonic scaler tips with higher Vickers hardness values showed greater wear resistance, which would be an important wear characteristic for clinicians to check.

This in vitro study evaluated how 3 sterilization methods-autoclaving, ethylene oxide (EO) gas, and hydrogen peroxide gas plasma-affect the mechanical, physical, and dimensional properties of 3-dimensional (3D) printed implant surgical guides. These techniques are widely used in dental practice but differ in mechanism and limitations. Twenty specimens were fabricated using a digital light processing printer and divided into 4 groups (n = 5): non-sterilized control, autoclaving (121 °C, 15 minutes), EO gas (55 °C, 60 minutes), and hydrogen peroxide gas plasma (<57 °C, 18 minutes). Mechanical tests evaluated flexural strength, modulus, and Shore D hardness while translucency and dimensional stability were also assessed. Shape deviation and implant positioning accuracy were compared before and after sterilization. Data were analyzed with one-way analysis of variance and Tukey's post hoc test. All sterilized groups maintained internal fit deviations within clinically acceptable tolerance (±120 μm), showing no significant differences in overall dimensional accuracy. Implant placement precision was preserved, with implant-tooth distances ≥2 mm. EO sterilization significantly increased the flexural strength (122.49 ± 10.10 MPa) and modulus (3477 ± 161 MPa) compared with controls whereas autoclaving showed the lowest strength (92.40 ± 15.06 MPa). Shore D hardness exceeded 90 HS in all groups, with autoclaving producing the highest values. Only EO treatment significantly reduced translucency. Sterilization method influenced the mechanical and optical properties of 3D-printed surgical guides without compromising dimensional accuracy. The findings provide evidence-based guidance for clinicians to select sterilization protocols that preserve the functionality of 3D-printed surgical guides and ensure precision in implant placement.

Hye-Bin Go, Jun-Hyuk Choi. J Dent Hyg Sci 2026;26:10-9. https://doi.org/10.17135/jdhs.2026.26.1.10

본 연구의 목적은 치주 조직의 유도 재생에 사용되는 3D 프린터로 제작된 흡수성 차폐막의 물리적 및 생분해성특성을 비교하는 것이었다. 세 가지 유형의 3D 프린터로 제작된 흡수성 차폐막(β-TCP가 함유되지 않은 제품 2종과 β-TCP가 함유된 제품 1종)이 고려되었다. 3D 프린터로 제작된 흡수성 차폐막의 형태와 성분 구성은 EDS (energy-dispersive X-ray spectroscopy)와 함께 주사 전자 현미경(FE-SEM)으로 분석되었다. 기공도 및 기공 크기는 Micro-CT를 사용하여 측정하였다. 또한 인장 강도, 생분해성 시험이 수행되었다. 통계적 분석은 인장 강도에서 일원배치분산분석 (one-way ANOVA)을 시행하였고, 사후분석으로 Tukey’s test를 시행하였다(p0.05). EDS 분석을 통한 SEM 이미지의 결과는 모든 그룹에서 C, O가 존재하는 격자 구조의 선형 층을 보여주었다. 일부 그룹에서는 Ca, P에서 약간의 차이가 있었다. 인장 강도는 모든 그룹에서 유의한 차이를 보였으며(p0.05), 생분해성은 β-TCP를 함유한 그룹이 가장 빠른 분해율을 보였다. 따라서, 본 연구의 결과는 3D 프린터로 제작된 흡수성 차폐막이 임상 사용을 위한 다양한 물리적 및 생분해성 성질을 가지고 있으며, 이러한 정보는 관련 제품의 향후 개발 및 제품의 임상 적용을 위해 고려되는 사항으로 유용할 것이라고 사료된다.