Investigating the mechanical and optical properties of novel Urethandimethacrylate (UDMA) and Urethanmethacrylate (UMA) based rapid prototyping materials

ObjectiveThis study is focused on testing experimental rapid prototyping materials for occlusal splints made from Urethandimethacrylate (UDMA) and Urethanmethacrylate (UMA).MethodsMaterials were mixed from UDMA and UMA in ratios of 1.0:0.0, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0.0:1.0. Specimens were printed using digital light processing (DLP). After post-processing, the specimens underwent testing on flexural strength, modulus of elasticity, hardness, wear behavior, surface roughness, gloss and color stability. All tests were performed after 24 h (baseline) and 10 days of water storage (aging). Splints underwent cyclic pull-off and insertion testing, which was alongside simulated using finite element analysis.ResultsThe mechanical properties were significantly influenced by changes in the UDMA:UMA ratio. Statistical analysis revealed that increased amounts of UMA correlated with a decrease in flexural strength (92.0 to 30.7 MPa), modulus of elasticity (2.4 to 0.6 GPa), hardness (155.1 to 102.0 N/mm²) and wear resistance (−1394.9 to −1742.1 μm). Materials with higher amounts of UMA were also more likely to be influenced by water storage. Specimens with 75% and 100% UMA content were partly not analyzable due to soft consistency.Optical properties showed only minor influence from UMA content and aging. Differences in surface roughness (3.9 to 2.4 μm) and color stability were insignificant. Gloss was partly influenced by the UDMA:UMA ratio and water storage.Mean survival rates for cyclic pull-off and insertion testing ranged from 2537 to 23,857 cycles. A correlation between the amount of UMA and survival rates was observed.SignificanceThe addition of up to 25% UMA showed promising results, complying with clinical standards and delivering acceptable results in the cyclic pull-off and insertion test. Further investigation on increments between 0 and 25% UMA could help to find an optimum.     

Impression of Subgingival Dental Preparation Can Be Taken with Ultrasound

Because of its ability to capture hard structures behind soft tissue, ultrasound-based micro-scanning may be a promising alternative for taking digital impressions of teeth, especially in the case of subgingival margin preparations. The aim of this study was to assess the accuracy of ultrasound impressions taken of subgingivally prepared teeth compared with digital optical impressions. Ten extracted human teeth (7 pre-molars, 3 molars) were prepared for crowns with chamfer finish line and then digitized using two different intra-oral scanners (Cara Trios, 3 Shape, Heraeus Kulzer, Hanau, Germany; and Lava COS; 3M ESPE, Seefeld, Germany) and one extra-oral scanner (Cares CS2, Straumann, Basel, Switzerland). Afterward, the preparation margin was covered with porcine gingiva (thickness ranged between 0.3 and 0.9 mm), and every sample was scanned with a high-frequency ultrasound scanner under experimental subgingival conditions. Optical scanning processes were performed without gingiva. The data sets were superimposed on each other for pairwise comparisons, and deviations between different scans were determined using a 3-D evaluation software (CloudCompare). Kruskal–Wallis and post hoc tests (Dunn–Bonferroni) were applied to detect significant differences at p ≤ 0.05. The ultrasound scanner was able to detect subgingival preparation margins. Mean deviations for all comparisons ranged from 12.34 to 46.38 µm. There were no statistically significant differences between superimpositions of intra-oral and extra-oral scans (Trios–Lava, Lava–CS2, Trios–CS2), whereas in comparisons between intra-/extra-oral scans and ultrasound scans, mean deviations were statistically significantly higher. There were no significant differences with respect to type of tooth (pre-molar and molar). However, gingiva thickness was significantly correlated with the quality of the ultrasound scan; thin layers had better image quality than thicker layers. Ultrasound was able to scan tooth preparation margins covered with gingiva, although with less accuracy than achieved by conventional optical scanners (non-covered margins). Gingiva thickness may play an important role in ultrasound scan accuracy.     

Quantitative analysis of 3-isopropylamino-1,2-propanediol as a degradation product of metoprolol in pharmaceutical dosage forms by HILIC-CAD

Aryloxypropanolamine is an essential structural scaffold for a variety of β-adrenergic receptor antagonists such as metoprolol. Molecules with such a structural motif tend to degrade into α, β–hydroxypropanolamine impurities via a radical–initiated oxidation pathway. These impurities are typically polar and nonchromophoric, and are thus often overlooked using traditional reversed phase chromatography and UV detection. In this work, stress testing of metoprolol confirmed the generation of 3-isopropylamino-1,2-propanediol as a degradation product, which is a specified impurity of metoprolol in the European Pharmacopoeia (impurity N). To ensure the safety and quality of metoprolol drug products, hydrophilic interaction chromatography (HILIC) methods using Halo Penta HILIC column (150 mm × 4.6 mm, 5 μm) coupled with charged aerosol detection (CAD) were developed and optimized for the separation and quantitation of metoprolol impurity N in metoprolol drug products including metoprolol tartrate injection, metoprolol tartrate tablets, and metoprolol succinate extended-release tablets. These HILIC-CAD methods were validated per USP validation guidelines with respect to specificity, linearity, accuracy, and precision, and have been successfully applied to determine impurity N in metoprolol drug products.     

经食管心房起搏彩色多普勒负荷超声在冠心病诊断中的价值

目的通过食管心房起搏负荷试验,使用彩色多普勒超声心动图对左室室壁运动状态及左室舒缩功能改变进行评价,以提高冠心病诊断的敏感性和特异性.方法49例冠心病患者和34例正常对照组使用心脏程序刺激仪经食管起搏导管调整心率达次极量,同时使用彩色多普勒超声心动仪进行左室室壁运动记分(WMS)并记录二尖瓣口及主动脉瓣环部血流频谱.结果经食管心房起搏负荷后彩色多普勒检查,左室每搏量(SV),主动脉瓣环部流速积分(VTIAO),等容舒张时间(IVRT),二尖瓣口流速积分(VTIMV),快速充盈分数(RFI)及室壁运动记分对冠心病诊断敏感性和特异性均有提高,WMS结合上述两项阳性指标其冠心病诊断的敏感性可达95%,特异性为97%.结论经食管心房起搏彩色多普勒负荷超声心动图(TPDE)在冠心病诊断中有较高的应用价值,因其简便、实用和安全,宜在临床广泛推广使用.     

Dual defibrillation in patients with refractory ventricular fibrillation

In the setting of cardiac arrest, refractory ventricular fibrillation (VF) is difficult to manage, and mortality rates are high. Double sequential defibrillation (DSD) has been described in the literature as a successful means to terminate this malignant rhythm, after failure of traditional Advanced Cardiac Life Support (ACLS) measures. The authors herein present a case of refractory VF in a patient with cardiac arrest, on whom DSD was successful in reversion to sinus rhythm, and provide a thorough review of similar cases in the literature.