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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.

The study investigated the effects of temperature and centrifugation time on the efficacy of removing uncured resin from 3D-printed clear aligners. Using a photo-polymerizable polyurethane resin (Tera Harz TC-85, Graphy Inc., Seoul, Korea), aligners were printed and subjected to cleaning processes using isopropyl alcohol (IPA) or centrifugation (g-force 27.95 g ) at room temperature (RT, 23 °C) and high temperature (HT, 55 °C) for 2, 4, and 6 min. The control group received no treatment (NT). Cleaning efficiency was assessed through rheological analysis, weight measurement, transparency evaluation, SEM imaging, 3D geometry evaluation, stress relaxation, and cell viability tests. Results showed increased temperature and longer centrifugation times significantly reduced aligner viscosity, weight ( P  < 0.05), and transmittance. IPA-cleaned aligners exhibited significantly lower transparency and rougher surfaces in SEM images. All groups met ISO biocompatibility standards in cytotoxicity tests. The NT group had higher root mean square (RMS) values, indicating greater deviation from the original design. Stress relaxation tests revealed over 95% recovery in all groups after 60 min. The findings suggest that a 2-min HT centrifugation process effectively removes uncured resin without significantly impacting the aligners’ physical and optical properties, making it a clinically viable option.

Medical plastic-appliance-based healthcare services, especially in dentistry, generate tremendous amounts of plastic waste. Given the physiological features of our mouth, it is desirable to substitute dental care plastics with viscoelastic and antimicrobial bioplastics. Herein, we develop a medical-grade and sustainable bioplastic that is viscoelastic enough to align the tooth positions, resists microbial contamination, and exhibits recyclable life cycles. In particular, we devise a molecular template involving entanglement-inducing and antimicrobial groups and prepare a silk fibroin-based dental care bioplastic. The generated compactly entangled structure endows great flexibility, toughness, and viscoelasticity. Therefore, a satisfactory orthodontic outcome is accomplished, as demonstrated by the progressive alignment of male rabbit incisors within the 2.5 mm range. Moreover, the prepared bioplastic exhibits resistance to pathogenic colonization of intraoral microbes such as Streptococcaceae and Veillonellaceae . Because the disentanglement of entangled domains enables selective separation and extraction of the components, the bioplastic can be recycled into a mechanically identical one. The proposed medical-grade and sustainable bioplastic could potentially contribute to a green healthcare future. Medical plastic-appliance-based healthcare services, especially in dentistry, generate large amounts of plastic waste. Here, the authors address this issue by developing a medical-grade and sustainable bioplastic that is viscoelastic enough to align the tooth positions, resists microbial contamination, and exhibits recyclable life cycles.

This study aimed to compare the effectiveness of microcurrent-emitting toothbrushes (MCTs) and ordinary toothbrushes in reducing the dental plaque index (PI) and dental caries activity among orthodontic patients. The evaluation was performed using a crossover study design involving 22 orthodontic patients randomly assigned to the MCT or ordinary toothbrush groups. The participants used the designated toothbrush for 4 weeks and had a 1-week wash-out time before crossover to the other toothbrush. PI (Attin’s index) and dental caries activity were measured at baseline and at the end of each 4-week period. Additionally, patients completed questionnaires to assess patient satisfaction for “freshness in mouth” and “cleansing degree.” The results showed that the MCT group had a significant reduction in PI (p = 0.009), whereas the ordinary toothbrush group did not (p = 0.595). There was no significant difference in the dental caries activity between the two groups (p > 0.05). Patient satisfaction assessment revealed that 65% patients in the MCT group had more than “fair” experience of freshness, in contrast to 50% of patients in the ordinary toothbrush group. Satisfaction with cleansing degree was similar in both groups. Overall, these findings suggest that MCTs are more effective in reducing dental PI than ordinary toothbrushes.

We aimed to evaluate root parallelism and the dehiscence or fenestrations of virtual teeth setup using roots isolated from cone beam computed tomography (CBCT) images. Sixteen patients undergoing non-extraction orthodontic treatment with molar distalization were selected. Composite teeth were created by merging CBCT-isolated roots with intraoral scan-derived crowns. Three setups were performed sequentially: crown setup considering only the crowns, root setup-1 considering root alignment, and root setup-2 considering the roots and surrounding alveolar bone. We evaluated the parallelism and exposure of the roots and compared the American Board of Orthodontics Objective Grading System (ABO-OGS) scores using three-dimensionally printed models among the setups. The mean angulation differences between adjacent teeth in root setups-1 and -2 were significantly smaller than in the crown setup, except for some posterior teeth ( p  < 0.05). The amount of root exposure was significantly smaller in root setup-2 compared to crown setup and root setup-1 except when the mean exposure was less than 0.6 mm ( p  < 0.05). There was no significant difference in ABO-OGS scores among the setups. Thus, virtual setup considering the roots and alveolar bone can improve root parallelism and reduce the risk of root exposure without compromising occlusion quality.

Background In patients with skeletal Class III malocclusion, additional genioplasty is frequently required to enhance lower facial esthetics after orthognathic surgery. This study aimed to evaluate soft tissue thickness changes in the lower face before and after bimaxillary surgery with advancement genioplasty in patients with skeletal Class III malocclusion. Methods Ninety-four patients were included: 57 patients underwent bimaxillary surgery alone (Group N), and 37 patients underwent bimaxillary surgery with advancement genioplasty (Group G). Changes in hard tissue landmarks and soft tissue thickness before and after surgery were analyzed from reconstructed three-dimensional cone-beam computed tomography (CBCT) images. CBCT images were taken pre-surgery (T0) and at least 6 months post-surgery (T1). Within- and between-group changes were tested with paired and independent t -tests; Pearson correlations assessed associations between skeletal advancement (Pogonion and Menton) and soft tissue thickness. Results After surgery, soft tissue thickness at Pogonion (Pog–Pog’) increased in Group N but decreased significantly in Group G (− 1.90 ± 3.93 mm; p  = 0.006), with a significant intergroup difference ( p  = 0.014). In contrast, soft tissue thickness at Menton (Me–Me’) did not change significantly in Group N but increased significantly in Group G (3.14 ± 8.87 mm; p  = 0.038), with a significant intergroup difference ( p  = 0.034). Pearson correlation analysis indicated that skeletal advancement was negatively associated with Pog–Pog’ ( p  < 0.05) and total chin soft tissue thickness ( p  < 0.01), whereas B–B’ and Me–Me’ showed no significant correlations. Conclusions In skeletal Class III patients undergoing bimaxillary surgery with advancement genioplasty, soft tissue thickness decreased at Pogonion and increased at Menton; Pogonion thinning scaled with skeletal advancement. While genioplasty can counteract mandibular setback-related thickening, excessive advancement risks over-thinning. Clinicians should anticipate these responses, calibrate advancement magnitude, and consider selective adjunctive soft tissue procedures.

Poly(methyl methacralyate) (PMMA) has long been used in dentistry as a base polymer for dentures, and it is recently being used for the 3D printing of dental materials. Despite its many advantages, its susceptibility to microbial colonization remains to be overcome. In this study, the interface between 3D-printed PMMA specimens and oral salivary biofilm was studied following the addition of zwitterionic materials, 2-methacryloyloxyethyl phosphorylcholine (MPC) or sulfobetaine methacrylate (SB). A significant reduction in bacterial and biofilm adhesions was observed following the addition of MPC or SB, owing to their protein-repellent properties, and there were no significant differences between the two test materials. Although the mechanical properties of the tested materials were degraded, the statistical value of the reduction was minimal and all the properties fulfilled the requirements set by the International Standard, ISO 20795-2. Additionally, both the test materials maintained their resistance to biofilm when subjected to hydrothermal fatigue, with no further deterioration of the mechanical properties. Thus, novel 3D-printable PMMA incorporated with MPC or SB shows durable oral salivary biofilm resistance with maintenance of the physical and mechanical properties.

Highlights Two-dimensional mono- and few-layered Ti 3 CNT x MXene nanosheets with extremely high nitrogen content were synthesized. Better performance for hydrogen evolution reaction (HER) than Pt/C catalyst in acidic, neutral and alkaline solutions. Exceptional performance of HER in both acidic and alkaline solutions. A large current density (> 500 mA cm −2 ) has been achieved for HER. Transition metal carbides, known as MXenes, particularly Ti 3 C 2 T x , have been extensively explored as promising materials for electrochemical reactions. However, transition metal carbonitride MXenes with high nitrogen content for electrochemical reactions are rarely reported. In this work, transition metal carbonitride MXenes incorporated with Pt-based electrocatalysts, ranging from single atoms to sub-nanometer dimensions, are explored for hydrogen evolution reaction (HER). The fabricated Pt clusters/MXene catalyst exhibits superior HER performance compared to the single-atom-incorporated MXene and commercial Pt/C catalyst in both acidic and alkaline electrolytes. The optimized sample shows low overpotentials of 28, 65, and 154 mV at a current densities of 10, 100, and 500 mA cm −2 , a small Tafel slope of 29 mV dec −1 , a high mass activity of 1203 mA mg Pt −1 and an excellent turnover frequency of 6.1 s −1 in the acidic electrolyte. Density functional theory calculations indicate that this high performance can be attributed to the enhanced active sites, increased surface functional groups, faster charge transfer dynamics, and stronger electronic interaction between Pt and MXene, resulting in optimized hydrogen absorption/desorption toward better HER. This work demonstrates that MXenes with a high content of nitrogen may be promising candidates for various catalytic reactions by incorporating single atoms or clusters.

Graphitic carbon nitride (g‐C3N4) has attracted enormous attention as a photocatalyst due to its appropriate bandgap, high chemical stability, and visible light response. However, it is still challenging to synthesize highly crystalline g‐C3N4, favoring the separation of photogenerated electron–hole pairs and promoting improved photocatalytic activity. Herein, we report a novel approach to achieve highly crystalline g‐C3N4 by simply pressing sodium chloride and carbon nitride into a pellet followed by heat treatment, which is different from conventional molten salt methods. The resulting g‐C3N4 has an optimum band structure that benefits enhanced light absorption and charge separation efficiency. The intimate contact between sodium chloride and carbon nitride in the pressed pellet facilitates the diffusion of sodium ions and increases the material's resistance to high annealing temperatures, leading to improved crystallinity. The photocurrent response of this highly crystalline material under visible light irradiation is approximately four times higher than that of its bulk counterpart, resulting in a hydrogen production rate of up to 650 μmol g−1 h−1 (10% TEOA). This work paves a new path in designing novel carbon nitrides with enhanced photoelectrochemical and photocatalytic performance. Carbon nitride mixed with sodium chlorine is pressed into a pellet with a subsequently heat treatment. The obtained carbon nitride achieves improved crystallinity and enhanced hydrogen evolution reaction.