A Paradigm Shift for Torsional Stiffness of Nickel-Titanium Rotary Instruments: A Finite Element Analysis

IntroductionThe aim of this study was to investigate the influence of mass and the polar moment of inertia on the torsional behavior of nickel-titanium rotary instruments to understand which parameter of cross-sectional design had a key role in terms of torsional resistance.MethodsFour different instrument models were designed and meshed using computer-aided engineering software (SolidWorks; Dassault Systems, Waltham, MA). Instrument models shared the same characteristics, except for cross-sectional design; triangle, rectangle, square, and hollow square geometry was selected. Finite element analysis was performed simulating a static torsional test using the FEEPlus internal solver (Solid Works). Von Mises stress and torsional load at fracture were calculated by the software. Linear regression analysis was performed to investigate the relationship of the polar moment of inertia, cross-sectional area, inner core radius, and mass per volume on the torsional resistance of nickel-titanium rotary instruments.ResultsThe polar moment of inertia positively affected the maximum torsional load with the highest level of correlation (R² = 0.917). It could be stated that the higher the polar moment of inertia is, the more maximum torsional load at fracture is present. Mass and cross-sectional area had a lower level of correlation compared with the polar moment of inertia (R² = 0.5533). According to this, 2 instruments with the same mass/mm and/or cross-sectional area could have different torsional resistance.ConclusionsThe polar moment of inertia can be considered as the most important cross-sectional factor in determining the torsional resistance of rotary instruments over metal mass and cross-sectional area.     

常规消毒对ProTaper镍钛根管锉抗拉强度的影响

目的 探讨超声清洗时间和消毒灭菌频率对镍钛根管锉的抗拉性能的影响,以了解超声清洗和高温高压消毒灭菌法在镍钛根管锉灭菌中应用的安全性和可行性.方法 采用全新的ProTaper S2锉和F2锉各25支,分为5组:标准组(未处理)、对照组(未超声-高压灭菌)、A组(超声震荡50 min+高压灭菌5次)、B组(超声震荡100 min+高压灭菌10次)、C组(超声震荡150 min+高压灭菌15次),分别用万能测试仪对其进行抗拉伸强度的性能试验.结果 S2及F2的标准组之间的抗拉伸强度差异无统计学意义(P>0.05),提示样本间不存在差异性;经不同时间超声清洗及不同次数高温高压处理的S2镍钛锉抗拉伸强度测试结果显示:对照组、A组、B组、C组分别为(76.58±4.87)MPa、(71.00±5.39)MPa、(72.33±3.43)MPa、(66.81±4.08)MPa;F2镍钛锉抗拉伸强度结果分别为:(111.75±6.83)MPa、(110.46±3.88)MPa、(107.29±3.89)MPa、(94.53±6.61)MPa;A、B组与对照组的ProTaper S2锉和F2锉的抗拉强度差异均无统计学意义(P>0.05),即镍钛锉经超声震荡50 min+高压灭菌5次及超声震荡100 min+高压灭菌10次消毒后,其抗拉伸强度无明显影响;C组与对照组间差异存在统计学意义(P<0.05),即镍钛锉经超声震荡150 min+高压灭菌15次消毒后,对其抗拉伸强度有影响.结论 常规超声-高压灭菌消毒超过一定频率可能增加ProTaper系统镍钛根管锉折断可能性.     

A randomized controlled trial comparing surgical excisional biopsies using CO2 laser,Er:YAG laser and scalpel

This randomized controlled trial (RCT) (ClinicalTrials.gov ID: NCT03001791) compared excisional biopsies of fibrous hyperplasia performed using a CO₂ laser (140 Hz, 400 μs, 33 mJ), Er:YAG laser (35 Hz, 297 μs, 200 mJ, air–water cooling), or scalpel (15c blade). Clinical parameters recorded were duration of the intervention, intraoperative bleeding, need for electrocauterization and/or suturing, postoperative side effects, complications, pain, and intake of analgesics. Histopathological linear measurements of the thermal damage zone were performed on the laser biopsies. Results showed that the duration of the intervention was significantly shorter for both lasers compared to the scalpel (P < 0.001). Intraoperative bleeding occurred less frequently with the CO₂ laser (P < 0.001). Additional electrocautery was used in 92% of Er:YAG laser interventions (P < 0.001). Postsurgical complications, pain, and the intake of analgesics did not differ between the groups. The measured thermal damage zones differed significantly between the CO₂ laser (median of 72.6 μm) and Er:YAG laser (30.9 μm) (P < 0.001). This RCT showed that CO₂ laser, Er:YAG laser, and scalpel are all adequate for excisional biopsies of small lesions in the oral mucosa. While patient postoperative morbidity is similar, the ideal instrument can be selected according to the surgical advantages preferred for the individual situation.     

三种机用镍钛锉预备弯曲根管的中心定位能力比较研究

目的　评价M3-Pro 2018、M3-L铂金版及ProTaper universal三种机用镍钛锉预备弯曲根管的中心定位能力。方法　收集2018年10月至2019年3月在常州市第一人民医院口腔科拔除的上颌第一磨牙,筛选出30个近中颊根管弯曲度为20 ~ 40°的近中颊根,随机分成3组,分别为M3-Pro组、M3-L组和ProTaper组,每组10个样本,分别使用M3-Pro 2018机用镍钛锉、M3-L铂金版单支锉系统及ProTaper universal机用镍钛锉预备根管。各样本在处理前后均使用CBCT扫描并利用软件mimics17.0测算距根尖5 mm范围内每毫米处的根管偏移量及轴中心率。结果　距根尖1 mm区域,M3-Pro组、M3-L组和ProTaper组的根管偏移量均值分别为0.06、0.16和0.22 mm,轴中心率均值分别为0.86、0.71和0.49,3组间差异均有统计学意义（F值分别为3.404和3.499,均P < 0.05）。距根尖3 mm区域,M3-Pro组、M3-L组和ProTaper组的根管偏移量均值分别为0.13、0.19和0.26 mm,轴中心率均值分别为0.63、0.51和0.32,3组间差异均有统计学意义（F值分别为7.567和3.996,均P < 0.05）。进一步两两比较发现,距根尖1 mm和3 mm处M3-Pro组与ProTaper组的根管偏移量及轴中心率的差异有统计学意义（P < 0.05）;距根尖3 mm处M3-L组与ProTaper组的根管偏移量差异有统计学意义（P < 0.05）,而两组的轴中心率差异无统计学意义（P > 0.05）。其余观测面上的根管偏移量和轴中心率在3组之间的差异均无统计学意义（均P > 0.05）。结论 M3-Pro 2018机用镍钛锉在弯曲根管的根尖区预备中能更好地顺应根管形状,减小根管偏移量,中心定位能力优于其他两种镍钛锉。     

便携式病原微生物分子诊断技术应用现状和展望

病原微生物导致的感染严重威胁人类公共卫生。便携式病原微生物分子诊断技术能够快速准确地检出病原体,在提高基层医疗机构和现场检疫方面发挥重要作用。本文概览了便携式病原微生物分子诊断的技术和产品要求,重点介绍了国内外已上市或正在上市的便携式病原微生物分子诊断仪器特性和应用领域,存在的缺陷及应用展望。随着技术的发展和持续优化,便携式病原微生物分子诊断仪器在保证高性能的同时,提高质量控制并控制成本,将有利于更广泛的应用。     

不同清洗口腔器械方法的效率与质量比较

目的 比较手工、手工联合超声清洗口腔器械的效率与质量。方法 将安徽医科大学附属口腔医院2019年1~6月口腔器械按随机数字表法分为A组（手工清洗）与B组（手工联合超声清洗）,每组200件。比较两组器械清洗耗时及合格率。结果 A组器械一次清洗耗时（1.02±0.29）h,B组（1.33±0.19）h,两组差异有统计学意义（t=-12.500,P<0.001）;A组器械二次清洗耗时（0.68±0.32）h,B组（0.32±0.20）h,两组差异有统计学意义（t=4.318,P<0.001）;A组器械完全合格清洗耗时（1.12±0.44）h,B组（1.34±0.21）h,两组差异有统计学意义（t=-6.367,P<0.001）。A组器械一次清洗合格率为85.50%,B组为94.50%,两组差异有统计学意义（χ²=9.000,P=0.003）。A组器械二次清洗合格率为89.66%,B组为100.00%,两组差异无统计学意义（P>0.05）。结论 手工联合超声清洗口腔器械,效率、清洗质量更高。     

Real‐Time Observation of Thrombus Growth Process in an Impeller of a Hydrodynamically Levitated Centrifugal Blood Pump by Near‐Infrared Hyperspectral Imaging

Understanding the thrombus formation in cardiovascular devices such as rotary blood pumps is the most important issue in developing more hemocompatible devices. The objective of this study was to develop a hyperspectral imaging (HSI) method to visualize the thrombus growth process within a rotary blood pump and investigate the optical properties of the thrombus. An in vitro thrombogenic test was conducted using fresh porcine blood and a specially designed hydrodynamically levitated centrifugal blood pump with a transparent bottom. The pump rotating at 3000 rpm circulated the blood at 1.0 L/min. The bottom surface of the pump was illuminated with white light pulsed at the same frequency as the pump rotation, and the backward‐scattered light was imaged using the HSI system. Using stroboscopic HSI and an image construction algorithm, dynamic spectral imaging at wavelengths ranging from 608 to 752 nm within the rotating pump was achieved. After completing the experiment, we collected the red thrombus formed in the pump impeller and quantified the thrombus hemoglobin concentration (Hb_thrombus). The spectrum changed around the center of the impeller, and the area of change expanded toward the impeller flow path. The shape corresponded approximately to the shape of the thrombus. The spectrum change indicated that the light scattering derived from red blood cells decreased. The Hb_thrombus was 4.7 ± 1.3 g/dL versus a total hemoglobin of 13 ± 0.87 g/dL. The study revealed that Hb_thrombus was reduced by the surrounding blood flow.     

Will diminishing cochlear delay affect speech perception in noise?

Objective: Normal auditory systems appear well habituated to time/phase delays inherent to sound encoding along the hearing organ, sending frequency information non-simultaneously to the central auditory system. Eliminating, or simply perturbing, the cochlear delay might be expected to decrease speech recognition ability, especially under demanding listening conditions. Resources of a larger-scale investigation permitted a preliminary examination of this issue, particularly on a relevant timescale of empirically demonstrated cochlear delays. Design: In a randomized controlled trial study, word recognition was tested for mono-syllabic tokens treated digitally to exacerbate, if not diminish/nullify, such delays. Speech-weighted noise was used to interfere with listening to time-frequency reversed (nominally no delay) versus non-reversed (natural timing) transforms under three treatments of speech tokens: (1) original-digitally recorded; digitally processed to emphasize (2) transient versus (3) quasi-steady-state components. Study sample: Ten normal-hearing young-adult females. Results: The findings failed to demonstrate statistically significant differences between delay conditions for any of the three speech-token treatments. Conclusions: An algorithm putatively diminishing frequency-dependent cochlear delays failed to systematically deteriorate performance in all subjects for the fixed time-frequency transform, stimulus parameters, and test materials employed. Yet, trends were evident such that some effect of perturbing cochlear delays could not be ruled out completely.