The significant rise in the use of clear aligners for orthodontic treatment is attributed to their aesthetic appeal, enhancing patient appearance and self-confidence. The aim of this study is to evaluate the aligners’ response to common staining agents (coffee, black tea, Coca-Cola, and Red Bull) in color and chemical stability. Polyurethane-based thermoformed and 3D-printed aligners from four brands were exposed to common beverages to assess color change using a VITA Easyshade compact colorimeter after 24 h, 48 h, 72 h, and 7 days, as well as chemical stability using ATR-FTIR spectroscopy. The brand, beverage, and manufacturing method significantly influence color stability. ATR-FTIR analysis revealed compositional differences, with variations in response to beverage exposure affecting the integrity of polymer bonds. Color change analysis showed coffee as the most potent staining agent, particularly affecting Tera Harz TC85 aligners, while ClearCorrect aligners exhibited the least susceptibility. 3D-printed aligners showed a greater color change compared to thermoformed ones. Aligners with a PETG outer layer are more resistant to stains and chemical alterations than those made of polyurethane. Additionally, 3D-printed polyurethane aligners stain more than thermoformed ones. Therefore, PETG-layered aligners are a more reliable choice for maintaining the aesthetic integrity of aligners.

Background: This study explores how different post-processing methods affect the mechanical properties and degree of conversion of 3d-printed polyurethane aligners made from Tera Harz TC-85 resin. Methods: Using Fourier-transform infrared (FTIR) spectroscopy, the degree of conversion of liquid resin and post-processed materials was analyzed. This investigation focused on the effects of various post-curing environments (nitrogen vs. air) and rinsing protocols (centrifuge, ethanol, isopropanol, and isopropanol + water). The assessed mechanical properties were flexural modulus and hardness. Results: The degree of conversion showed no significant variance across different groups, though the polymerization environment influenced the results, accounting for 24.0% of the variance. The flexural modulus varied considerably, depending on both the rinsing protocol and the polymerization environment. The standard protocol (centrifugation followed by nitrogen polymerization) exhibited the highest flexural modulus of 1881.22 MPa. Hardness testing revealed significant differences, with isopropanol treatments showing increased resistance to wear in comparison to the centrifuge and ethanol rinse treatments. Conclusions: This study conclusively demonstrates the adverse effects of oxygen on the polymerization process, underscoring the critical need for an oxygen-free environment to optimize material properties. Notably, the ethanol rinse followed by nitrogen polymerization protocol emerged as a viable alternative to the conventional centrifuge plus nitrogen method.

Vat photopolymerization 3D printing, including stereolithography (SLA), digital light processing (DLP), and masked SLA (mSLA), has transformed dental device fabrication by enabling precise and customizable components. However, the rheological behavior of photopolymer resins is a critical factor that governs the printability, accuracy, and performance of printed parts. This review surveys the role of viscosity, shear-thinning, and thixotropy in defining the “printability window” of dental resins and explores the relationship between these properties and the formulation and final material performance. Rheological characterization using rotational rheometry provides key insights, with shear rate sweeps and thixotropy tests quantifying whether a resin behaves as Newtonian or pseudoplastic. The literature shows that optimal printability typically requires resins with low to moderate viscosity at shear, moderate thixotropy for stability, and formulations balanced between high-strength oligomers and low-viscosity diluents. The addition of fillers modifies the viscosity and dispersion, which can improve reinforcement but may reduce print resolution if not optimized. Thermal and optical considerations are also coupled with rheology, affecting the curing depth and accuracy. In conclusion, controlling resin rheology is essential for bridging material formulation with reliable clinical outcomes, guiding both resin design and printer process optimization in modern dental applications.

Three-dimensional (3D) printing has emerged as a transformative technology in dental splint fabrication, offering significant advancements in customization, production speed, material efficiency, and patient comfort. This comprehensive review synthesizes the current literature on the clinical use, benefits, limitations, and future directions of 3D-printed dental splints across various disciplines, including prosthodontics, orthodontics, oral surgery, and restorative dentistry. Key 3D printing technologies such as stereolithography (SLA), digital light processing (DLP), and material jetting are discussed, along with the properties of contemporary photopolymer resins used in splint fabrication. Evidence indicates that while 3D-printed splints generally meet ISO standards for flexural strength and wear resistance, their mechanical properties are often 15–30% lower than those of heat-cured PMMA in head-to-head tests (flexural strength range 50–100 MPa vs. PMMA 100–130 MPa), and study-to-study variability is high. Some reports even show significantly reduced hardness and fatigue resistance in certain resins, underscoring material-specific heterogeneity. Clinical applications reviewed include occlusal stabilization for bruxism and temporomandibular disorders, surgical wafers for orthognathic procedures, orthodontic retainers, and endodontic guides. While current limitations include material aging, post-processing complexity, and variability in long-term outcomes, ongoing innovations—such as flexible resins, multi-material printing, and AI-driven design—hold promise for broader adoption. The review concludes with evidence-based clinical recommendations and identifies critical research gaps, particularly regarding long-term durability, pediatric applications, and quality control standards. This review supports the growing role of 3D printing as an efficient and versatile tool for delivering high-quality splint therapy in modern dental practice.

To optimize the therapeutic usefulness of aligners, it is crucial to understand how their mechanical properties alter with time. Specimens from four different brands, including Duran+, CA® Pro, Zendura A, and Zendura FLX, were produced for material testing of thermoplastic orthodontic aligners (TOA) using dimensions measuring 4mm x 10mm. Each brand's 24 samples were split into three groups as follows: G1 being thermoformed, G2 being thermoformed and underwent 500 thermocycles (simulating 7 days), and G3 being thermoformed and underwent 1000 thermocycles (simulating 14 days). Surface roughness, modulus of elasticity in bending, and spectrophotometry were used to assess the effect of aging on TOAs. After 1000 thermocycles, Duran+ had the highest modulus of elasticity and differed statistically from all other groups. The intragroup comparison showed that only Duran+’s elastic modulus significantly changed after 1000 thermocycles in comparison with the control group. Surface roughness values (Ra), did not statistically differ among brands or thermocycling group measures. The change in chemical properties was not significant in any brand. One-layer PETG (Duran+) failed to demonstrate stability after in vitro aging, thus suggesting that clinicians should be aware of the change in mechanical properties when using one-layer PETG (Duran +) in a 2 weeks regime.

Academic stress affects students’ psychological and physiological well-being. Dental undergraduate programs are known for their demanding curriculum, leading to significant stress symptoms. The objective was to determine if salivary cortisol levels were higher in students exposed to academic stress, assess the relationship between stress severity/temperament and cortisol values, and explore relaxation technique effects. Salivary cortisol was measured at two time points for all participants: Before exams and during a relaxation period after summer break. A third measurement was conducted for students with high pre-test cortisol levels who received instructions on progressive muscle relaxation (PMR) before subsequent exams. Additionally, participants completed two questionnaires: Perceived Stress Scale (PSS) and Fisher’s Temperament Questionnaire. The group analysis based on the PSS indicated that 39 participants reported high stress. Women demonstrated significantly higher stress than men (p = 0.042054). A significant difference in stress levels was observed between director and builder temperament types (p = 0.029276). Cortisol levels showed a significant decrease from the first measurement to the second measurement, and the third measurement after implementing PMR. The grade in the “Dermatovenereology” course correlated with stress level according to the PSS (k = 0.578467). Pre-test cortisol levels correlated with the frequency of using PMR guidelines during winter test periods (k = 0.416138). Stress negatively affects the immune system and poses health risks. Implementing stress reduction techniques in dental/medical education could benefit students and the healthcare system.