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Aim: To evaluate the mechanical properties of a newly formulated vinyl polysiloxane (VPS) impression material. Materials and Methods: Experimental, Capture (S&C Polymer), Express, Imprint 3 and Imprint 4 (3M ESPE), Start VPS (Danville), Honigum (DMG), Virtual (Ivoclar Vivadent), Elite HD+ (Zhermack) were evaluated for tear strength, tensile strength, and elongation at break. Un-nicked specimens with a 90° angle on one side (type C) for tear strength were prepared and tested according to ASTM-D624. Dumbbell-shaped specimens (type 1) for tensile strength and elongation at break were prepared and tested according to ISO 37. All tests were carried out at 500 mm/min on a Shimadzu (AGS-X-10 KN-table top) tester. A one-way analysis of variance (ANOVA) was used to analyze the data. Results: Experimental material showed significantly higher or higher tear strength and elongation at break compared to other impression materials for both light body (LB) and heavy body (HB). For tensile strength, Experimental is similar to most impression materials; however, significantly lower than Imprint 3 and Start VPS for LB. This parameter for HB is higher or significantly higher than other impression materials except Start VPS. Tear strength and tensile strength were not correlated for LB but have a weak or moderate correlation for HB. Elongation at break is inversely proportional to tensile strength moderately for LB; however, there is no or very weak relation for HB. Conclusions: Experimental VPS impression material demonstrated a significantly higher tear strength and adequate tensile strength with higher elongation compared to other commercially available VPS impression materials. Adequate mechanical properties can provide accurate impressions for successful clinical fabrication of restorations. Experimental VPS impression material is suitable for use in dental impressions for fabrication of restorations.

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In vat polymerization (VP) 3D printing, there is an urgent need to expand characterization efforts for resins derived from natural resources to counter the increasing consumption of fossil fuels required to synthesize conventional monomers. Here, we apply multiscale mechanical characterization techniques to interrogate a 3D printed biobased copolymer along a controlled range of monomer ratios. We varied the concentration of two dissimilar monomers to derive structural information about the polymer networks. Current research primarily considers the macroscale, but recent understanding of the process-induced anisotropy in 3D printed layers suggests a multiscale approach is critical. By combining typical macroscopic techniques with micro- and nanoscale analogues, clear correlations in the processing-structure-property relationships appeared. We observed that measured moduli were always greater via surface-localized methods, but property differences between formulations were easier to identify. As researchers continue to develop novel sustainable biopolymers that match or exceed the performance of commercial resins, it is vital to understand the multiscale relationships between the VP process, the structure of the formed polymer networks, and the resultant properties.

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The degree of monomer conversion and polymerization shrinkage are two of the main reasons for potential adhesion failure between the tooth structure and the restoration substrate. To evaluate the degree of conversion and polymerization shrinkage of a newly developed self-adhesive resin cement, the degree of conversion (DC) was measured using FTIR under different activation modes, temperatures, and times. Volumetric shrinkage was tested using the AcuVol video imaging method. The experimental cement showed a higher DC than other cements under self-curing. The DC of the experimental cement was higher than that of other cements, except SpeedCem Plus under light curing. The experimental cement had a higher DC than other cements, except SpeedCem Plus in some conditions under dual curing. All self-adhesive cements had a higher DC at 37 °C than at 23 °C under self-curing, and there was no statistical difference between 23 °C and 37 °C under light curing. All self-adhesive cements showed a significantly higher DC at 10 min than at 5 min under self-curing. There was no statistical difference between 5 min and 10 min for most cements under dual curing. All self-adhesive cements statistically had the same volumetric shrinkage under light curing and self-curing. The newly developed self-adhesive resin cement exhibited a higher degree of conversion and similar volumetric shrinkage compared to these commercial self-adhesive resin cements.

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STATEMENT OF PROBLEM: 5Y-PSZ-based zirconia dental restorations exhibit high translucency and good esthetics but have a higher fracture risk compared to 3Y-TZP. OBJECTIVES: To investigate the effect of BruxZir SteelTM treatment on the fracture resistance of zirconia three-unit bridges prepared using 5Y-PSZ-based zirconia blanks. METHODS: Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Their fracture resistance was analyzed by dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir SteelTM) was compared with the sintered control restoration (untreated cementation surface). Finite Element Analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load. RESULTS: The fracture resistance of the test restorations was significantly higher than that of the control restorations for all the manufacturers considered in this study (P < 0.05). Furthermore, the restoration made of BruxZirⓇ Esthetic treated with BruxZir SteelTM had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blocks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir SteelTM treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of BruxZir Steel-treated sample compared to the control. SIGNIFICANCE: The fracture resistance of 5Y-PSZ-based BruxZir SteelTM-treated three-unit bridges was significantly higher (min. 30%, max. 198%) than control.

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OBJECTIVES: To evaluate the fracture toughness and brittleness of a newly developed CAD/CAM resin composite block and compare it with five other resin composite blocks and one polymer-infiltrated ceramic block. METHODS: Fracture toughness was determined through single-edge notched beam (SENB) method according to ASTM D5045-14. Parallelepiped specimens (thickness × width × length = 1.8 × 3.6 × âˆ¼18 mm) with a V notch (length = âˆ¼1.8 mm) (n = 10) were made from block materials using a low-speed water-cooled diamond precision saw and razor blade. Brittleness index (BI) was calculated from Vickers hardness and fracture toughness. Data were analyzed using one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05). RESULTS: The experimental block showed significantly higher fracture toughness than all commercial block materials (p < 0.001) and has a brittleness index similar to most commercial blocks (p > 0.05) which have significantly lower brittleness index than Vita Enamic (p < 0.001). A moderate or strong correlation was observed between fracture toughness and flexural strength (Pearson's correlation coefficient R = 0.66) or diametral tensile strength (R = 0.86) or filler loading (R = 0.66), and between brittleness and Vickers hardness (R = 0.87). SIGNIFICANCE: The new composite block exhibited significantly higher fracture toughness and lower brittleness among the commercial CAD/CAM composite block materials tested, indicating a lower tendency to fracture and marginal chipping, and better machinability. The new composite block with higher fracture toughness and lower brittleness is suitable to use in the fabrication of CAD/CAM indirect restorations with potential long-term clinical success.

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Objective: To evaluate a newly developed self-adhesive resin cement on physical, mechanical, and adhesive properties and compare it with other commercial self-adhesive resin cements. Materials and Methods: Experimental self-adhesive resin cement (SARC) was formulated by our proprietary adhesive resin and filler technology. Maxcem Elite, RelyX Unicem 2, SpeedCem Plus, SmartCEM 2, and Calibra Universal 2 were selected for comparison. Working and setting times, film thickness, water sorption and solubility, flexural strength, and modulus were measured in accordance with ISO-4049. Consistency was tested according to modified ISO 4823. Shear bond strengths were conducted according to ISO 29022. The data were analyzed by one-way ANOVA and post hoc Tukey's tests (p ≤ 0.05). Results: All cements showed about 2-4 min working time and about 3-6 min setting time except that RelyX Unicem 2 has a longer working time (9'58") and setting time (10'18"). All cements meet ISO standards for film thickness (≤50 µm), water sorption (≤40 µg/mm3) except Maxcem Elite (46.19 µg/mm3), and water solubility (≤7.5 µg/mm3) except SmartCEM 2 (11.35 µg/mm3) and Calibra Universal (9.87 µg/mm3). Experimental SARC showed significantly higher flexural strength and modulus than other cements (p < 0.001). For self-curing, Experimental SARC has statistically higher bond strength than other cements (p < 0.001) except statistically the same as RelyX Unicem 2 (p > 0.05). For light-curing, Experimental SARC showed significantly higher bond strength than other cements (p < 0.001) except statistically the same as Maxcem Elite and RelyX Unicem 2 (p > 0.05). For dual-curing, the bond strength of Experimental SARC is significantly higher than that of other cements (p < 0.001). Conclusion: The newly developed self-adhesive resin cement exhibited favorable bonding capability and physical and mechanical properties compared to other commercial self-adhesive resin cements and is a good option for cementation of indirect restorations with potential long-term clinical success.

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Lung transplantation is increasingly being performed for end-stage lung disease in patients with bronchiectasis and pulmonary hypertension. Outcomes of bilateral lung transplantation (BLT) are better in patients with pulmonary hypertension, whereas single lung transplant remains a controversy in bronchiectasis with fear of infections from the residual diseased lung. However, in patients with adhesions and extreme structural changes due to severe disease, BLT may be considered technically challenging. We describe a case of successful management of a patient with bronchiectasis-induced lung disease causing extreme mediastinal shift with a BLT. The patient was successfully bridged to transplant with central veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for acute decompensated pulmonary hypertension while awaiting transplantation.

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OBJECTIVE: To evaluate the shrinkage, accuracy, and mechanical properties of a newly developed photo-polymerizable resin material for 3D printing dental applications and compare it with three commercially available resins. METHODS: An experimental novel proprietary resin material for 3D printing was formulated. This new resin, Die and Model Tan (SprintRay), Formlabs Grey (FormLabs), and LCD Grey (Roxel 3D) were evaluated and tested for volumetric shrinkage, accuracy, and flexural and tensile properties. Volumetric shrinkage was measured using the AcuVol video imaging method. The accuracy of the 3D printed objects through the DLP (digital light processing) printing system was determined by the 3D deviation between the scanned model and the original computer-aided-design (CAD) digital model. Parallelepiped specimens (2 × 2 × 25 mm, n = 5) were printed for flexural strength, flexural modulus, and modulus of resilience and measured in accordance with ISO-4049. Dumbbell-shaped specimens (Type V, n = 5) were printed to investigate the tensile strength and tested according to ASTM-D638. Data were analyzed using one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05). RESULTS: The experimental resin exhibited significantly lower volumetric shrinkage and significantly higher accuracy than the other commercially available resins (p < 0.001). The experimental resin showed flexural strength, flexural modulus, and tensile strength similar to Die and Model Tan resin (SprintRay) (p > 0.05), and these parameters were significantly higher than those of Formlabs Grey resin (Formlabs) and lower than those of LCD Grey resin (Roxel3D)(p <0.001). CONCLUSION: The newly formulated 3D printing resin demonstrated lower volumetric shrinkage, high accuracy, and adequate mechanical properties compared to the commercially available resin materials. CLINICAL SIGNIFICANCE: The new 3D printed objects exhibited higher accuracy, good stability over time, and adequate mechanical properties; hence, it is a good candidate for modeling applications for restoration, orthodontics and implants.

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OBJECTIVE: To determine the mechanical properties of a newly-developed CAD/CAM resin composite block and compare with other resin composite blocks and a polymer-infiltrated ceramic block. METHODS: Experimental composite block was formulated by our proprietary resin and filler technologies and cured via Hot Isostatic Pressing (HIP). Bar-shaped specimens (1 × 4×12 - 13 mm, n = 10) for flexural strength, flexural modulus and modulus of resilience were sectioned from block materials and measured in accordance to modified ISO-6872. Cylinder specimens for compressive strength (2 × 4 mm, n = 8) and for diametral tensile strength (6 × 3 mm, n = 8) were milled from the block materials and tested according to ASTM-D695 and ANSI/ADA-Specification #27, respectively. Block specimens (5 mm, n = 3) for Vickers hardness were polished and measured for five indentations on each specimen. The data was analyzed by one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05). RESULTS: Experimental composite block showed higher or significantly higher flexural strength, flexural modulus, modulus of resilience, compressive strength, diametral tensile strength and Vickers hardness than the other commercially available block materials except Vita Enamic for flexural modulus and hardness and Cerasmart for modulus of resilience. Some positive correlations were observed among the different mechanical properties. SIGNIFICANCE: New composite block exhibited higher mechanical properties as compared to commercially available composite block materials. Superior mechanical properties for resin composite block materials were obtained by composite and curing processing technologies. Resin composite blocks with higher mechanical properties are good options for the fabrication of CAD/CAM indirect restorations.

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