Effects of enamel and dentine thickness on laser doppler blood-flow signals recorded from the underlying pulp cavity in human teeth in vitro

Objective

To determine the effect of enamel and dentine thickness on laser Doppler blood-flow (LDF) signals recorded from dental pulp.

Design

Observations were made on 18 human premolars that had been extracted from young patients during orthodontic treatment. The apical 2/3 of the root was cut off and the remaining pulp removed. Blood flow signals were recorded from the buccal surface of the crown with a laser Doppler flow metre while dilute blood was pumped at 10 ml/min. through a cannula inserted into the pulp cavity. Recordings were made from the enamel surface and at 0.5 mm steps through the enamel and dentine.

Results

The blood flow signal increased significantly as the cavity depth increased and at 2.0 mm, the median flux signal was more than ten times greater than that obtained on the enamel surface. The backscattered light intensity did not change with cavity depth.

Conclusion

When recording pulpal blood flow from a human tooth with a laser Doppler flow metre, a substantially better signal-to-noise ratio should be obtained by placing the probe on dentine in the floor of a cavity than on the enamel surface.     

The Science behind Topical Negative Pressure Therapy

Topical negative pressure therapy (TNP) is an established part of modern wound healing. With an increasing choice in TNP providers, understanding the differing modes of action, the biochemical and biophysical effects on the wound at a microscopic and macroscopic level, plus the role of the interface dressings, will aid the clinician in planning a clear goal of therapy. This article reviews the scientific evidence for TNP to date and explores each mechanism of action and the implications for wound healing and patient outcomes.     

Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves

Introduction

In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench.

Objective

To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream.

Methods

To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. ) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements.

Results

It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found.

Conclusions

Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.     

Impact of Pulsatile Perfusion on Clinical Outcomes of Neonates and Infants With Complex Pathologies Undergoing Cardiopulmonary Bypass Procedures

The aim of this clinical trial was to evaluate the pulsatile perfusion mode in pediatric patients who had complex cardiac pathologies according to Jenkins stratifications (category 4) undergoing cardiopulmonary bypass procedures (CPB). Patients with transposition of great arteries (TGA) and ventricular septal defect (VSD) were included in this clinical study. Eighty‐nine consecutive pediatric patients undergoing open heart surgery for repair of TGA‐VSD were prospectively entered into the study and were randomly assigned to either the pulsatile perfusion group (Group P, n = 58) or the nonpulsatile perfusion group (Group NP, n = 31). There were no differences between groups in terms of demographical and intraoperative parameters. The pulsatile group needed significantly less inotropic support (P < 0.05) and had lower lactate levels (P < 0.001), higher urine output (P < 0.01), and higher albumin levels (P < 0.05). In addition, the pulsatile group had less ICU (P < 0.01) and hospital stays (P < 0.001). We conclude that the use of pulsatile flow is a better option and should be considered for repair of the complex congenital heart defects.     

冠状动脉慢血流现象患者内皮功能的研究

目的 探讨冠状动脉慢血流(CSF)现象患者的内皮功能.方法 我院2006年1月-2007年3月因可疑冠心病行冠状动脉造影检查显示冠状动脉无明显病变的患者60例,采用TMI记帧法记录各支冠状动脉的TMI帧数,冠状动脉平均的TMI帧数＞27为CSF,将患者分为CSF组(28例)和对照组(32例).所有患者分别于冠状动脉造影术24h后取血,行血清一氧化氮(NO)、血浆内皮素-1(ET-1)测定.结果 CSF组患者血NO 水平显著低于对照组,ET-1水平高于对照组,两组比较差异均有统计学意义(P＜0.05).结论 CSF患者可能存在内皮功能障碍,内皮功能障碍发生的病理生理机制可能参与CSF现象发生的病理生理过程中.     

冠状动脉慢血流患者一氧化氮和内皮素1浓度的变化

目的探讨冠状动脉慢血流(coronary slow flow,CSF)患者的血管内皮功能。方法选择因胸痛行冠状动脉造影的患者40例,根据造影结果分为CSF组20例和对照组20例。2组分别于静息和多巴酚丁胺负荷试验结束时立即抽取血标本,检测血浆内皮素1、血清NO浓度,并进行比较。结果 CSF组静息时血浆内皮素1浓度较对照组升高,但差异无统计学意义(P>0.05),而药物负荷试验后血浆内皮素1浓度较对照组明显升高,差异有统计学意义[(37.60±6.93)ng/L vs(14.16±5.73)ng/L,P<0.01]。CSF组静息时和药物负荷试验后血清NO浓度均明显低于对照组,差异有统计学意义[(42.36±9.72)μmol/L vs(50.39±9.77)μmol/L,(24.88±9.28)μmol/L vs(61.06±8.20)μmol/L,P<0.01)]。结论 CSF患者无论静息或者药物负荷状态下均存在内皮素1及NO平衡失调,负荷状态下这种平衡失调现象更加明显。     

TEAS复合药物全麻行控制性降压后胃血流的变化

目的:探讨经皮穴位电刺激(transcutaneous electrical acupoint stimulation,TEAS)复合药物全麻行控制性降压至不同血压水平的胃血流变化,从而明确针药复合麻醉的胃保护机制.方法:54只,♂,比格犬随机分为9组:单纯全麻组、60%对照组、60%实验组、50%对照组、50%实验组、40%对照组、40%实验组、30%对照组、30%实验组,每组6只,后8组动物均以异氟醚联合硝普钠行控制性降压,将动脉血压降至60%、50%、40%、30%基础平均动脉血压水平并维持60min,单纯全麻组不行控制性降压.实验组采用TEAS干预处理,采用激光多普勒组织血流仪监测不同水平相应时间点胃表面血流的变化.结果:在行控制性降压至目标低血压水平(T0)时,所有对照组胃血流均显著低于各自基础水平(P<0.05),而60%实验组、50%实验组胃血流未明显降低,在维持10min(T1)时,除50%实验组外,其他各控压组胃血流均显著低于各自基础水平和同期单纯全麻组水平(P<0.05),50%实验组与同水平对照组相比有显著统计学差异(P<0.05),在血压回升阶段,50%、30%、40%实验组胃血流先后恢复至基础水平和同期单纯全麻组水平,而同水平对照组未明显恢复.结论:轻度控压时(尤其是50%水平),TEAS的胃保护效应明显.重度控压时(尤其是30%水平),TEAS基本无保护效应,但在血压回升结束时,TEAS可促进胃血流的较快恢复.