可塑纤维桩弯曲强度的测定

目的:比较可塑纤维桩与成品纤维桩、金属铸造桩的弯曲强度,初步了解可塑纤维桩的弯曲强度。方法:将长为16mm、直径为1.5mm的EverStick可塑纤维桩、Tenax Fiber White纤维桩、镍铬金属铸造桩各5根采用三点弯曲实验测试各组桩的弯曲强度。结果:EverStick可塑纤维桩、Tenax Fiber White纤维桩、镍铬金属铸造桩的弯曲强度之间差异有统计学意义(P<0.05),铸造桩强度最大,可塑纤维桩强度最低。结论:可塑纤维桩自身弯曲强度较低,其修复根管治疗牙后修复体的整体抗折强度及折裂模式能否满足临床需要,有待进一步研究。     

数字体层图像后处理方法对检测肺结节准确性的影响

目的 探讨数字体层图像两种后处理方法(位移叠加法与滤波反投影法)对肺结节检测准确性的影响。方法 采集经CT证实的50例肺部结节患者的数字体层图像,采用滤波反投影法和位移叠加法进行后处理。由3名不同年资的放射诊断医师阅片并记录评分结果。102个CT证实的结节按直径分为3组:＜5 mm、5~10 mm、>10 mm组;按密度分为实性密度组及毛玻璃密度组。对两种处理方法检出的肺结节进行统计分析。结果 位移叠加法检出肺结节52个,滤波反投影法检出86个,差异有统计学意义(P＜0.001)。对于直径＜5 mm和5~10 mm组,滤波反投影法检出的肺结节数均多于位移叠加法(P=0.001、0.005)。结节直径>10 mm时两种方法的检出数量差异无统计学意义(P=0.317)。在不同密度组中,滤波反投影法检出的结节亦较多,与位移叠加法差异有统计学意义(P均<0.05)。结论 滤波反投影法对检出直径≤10 mm的肺结节、实性结节和毛玻璃结节均优于位移叠加法。     

不同疏水性能冠脉支架表面对溶血性能及蛋白吸附影响

目的探讨不同疏水强度冠脉316L不锈钢支架表面对溶血性能及对白蛋白吸附作用影响。方法应用化学方法将丙基三乙氧基硅烷、辛基三乙氧基硅烷、γ-(2,3环氧丙氧)丙基三甲氧基硅烷修饰到冠脉支架材料316L不锈钢表面获得疏水支架表面,通过接触角测试评价疏水强度,进行其溶血性能及血清蛋白吸附测试。结果实验结果显示,不同疏水强度不锈钢溶血率≤5%,说明符合溶血试验要求。随着接触角改变,支架表面对白蛋白的吸附量存在有差异。结论通过修饰不同链长的硅烷可改变支架表面的疏水性能,具有良好的血液相容性,随着疏水增强其白蛋白吸附的能力增强。     

金属加强丝与义齿基托修理后弯曲强度:不同数目影响的差异(英文)

背景:聚甲基丙烯酸甲酯长期以来作为义齿基托材料在牙科领域得到了广泛应用,然而义齿折裂是修复学至今尚未解决的难题.因此,如何增强义齿修理后的弯曲强度显得尤为重要.目的:研究加入不同数目的金属加强丝对义齿基托修理后弯曲强度的影响.方法:用聚甲基丙烯酸甲酯热凝树脂制作25个50 mm×30 mm×2.5 mm 的长方体试件,将试件在万能试验机上压断,测得其弯曲强度.各组试件断面经预备后分别加入1～4根不锈钢丝,未加入钢丝组为对照组,并用自凝树脂修理裂缝,测定修理后试件的弯曲强度,计算强度恢复率.结果与结论:各组试件修理后的弯曲强度均明显低于修理前(P<0.01).除加入1根钢丝组外,其余各组强度恢复率均高于对照组(P<0.05).加入2,3,4根钢丝各组间强度恢复率比较,差异无显著性意义(P>0.05).结果证实加入2～4叫根金属加强丝可增强义齿基托修理后的弯曲强度.     

纳米羟基磷灰石/聚乳酸复合材料的性能测试

目的:测定纳米羟基磷灰石/聚乳酸复合材料的性能。方法:实验于2005-02/2006-08在兰州交通大学材料工程研究所实验室完成。基体材料采用荷兰普拉克生化公司生产的聚乳酸(Mr 400000)。增强材料采用纳米羟基磷灰石(自制)。聚乳酸在使用前进行纯化。纳米羟基磷灰石采用水热法合成。采用共混复合工艺制备不同纳米羟基磷灰石质量分数(0,0.05,0.10,0.15,0.20)的纳米羟基磷灰石/聚乳酸复合材料,并对其力学性能(弯曲强度、弯曲模量、剪切强度)和降解性能(降解速率)进行测试。结果:①力学性能:复合材料的弯曲强度随着纳米羟基磷灰石体积分数的增加而增大,在羟基磷灰石微粒的质量分数为0.15(体积分数为0.064)时弯曲强度出现峰值(153.6MPa),降解12周后复合材料弯曲强度仍有123.7MPa。复合材料的弯曲模量随着纳米羟基磷灰石体积分数的增加而增大,有一定的弯曲模量(5.7GPa),降解12周后复合材料弯曲模量为5.3GPa。复合材料的剪切强度随着纳米羟基磷灰石体积分数的增大呈下降趋势。②降解性能:随着降解时间的延长,复合材料的降解速率变化不大。结论:纳米羟基磷灰石/聚乳酸复合材料能满足松质骨的骨折内固定的力学性能要求。     

玻璃微珠改性双酚A甲基丙烯酸缩水甘油酯复合的树脂充填材料

背景：口腔复合树脂修复材料存在聚合收缩率大和机械强度低等缺点,不能很好地满足临床使用的要求。目的：观察双酚A甲基丙烯酸缩水甘油酯和二甲基丙烯酸三甘醇酯的比例及改性实心玻璃微珠添加量对口腔复合树脂弯曲强度与聚合体积收缩率的影响。方法：以硅烷偶联剂KH-550对实心玻璃微珠进行硅化处理。向双酚A甲基丙烯酸缩水甘油酯与二甲基丙烯酸三甘醇酯配比分别为7／3、6／4、5／5的口腔复合树脂中再分别添加质量分数10％,30％,50％,70％,90％的实心玻璃微珠,机械搅拌均匀后,快速填入模具中固化,设置不添加实心玻璃微珠的树脂作为对照参考,分析口腔复合树脂的机械性能和收缩率。结果与结论：随着实心玻璃微珠添加量的增加,口腔复合树脂的弯曲强度呈先增加后减小的趋势,体积收缩率呈降低趋势：当双酚A甲基丙烯酸缩水甘油酯与二甲基丙烯酸三甘醇酯的比例为5／5、实心玻璃微珠的添加量为70％时,口腔复合树脂的弯曲强度最高,为（88．29±0．66）MPa（P〈0．05）;当双酚A甲基丙烯酸缩水甘油酯与二甲基丙烯酸三甘醇酯的配比为7／3、玻璃微珠添加量为70％时,聚合体积收缩率最小,为0．898％。     

异体皮质骨板不同固定方式的生物力学比较（英文）

背景:同种异体骨内固定材料已用于临床,但因为强度小仅用于应力较小的部位,如何提高其固定的强度以扩大应用范围是目前研究的关键。目的:探讨同种异体皮质骨板采用不同固定方式的强度差异及机制。设计、时间及地点:体外生物力学实验,于2005-10/2006-03在南华大学生物力学实验室完成。材料:防腐尸体上取下股骨27根;同种异体骨板制备成110mm×10mm×3mm的骨板45块;骨螺钉90个。方法:27根股骨制作骨折模型,分为双骨板嵌合组、双骨板骨螺钉组、单骨板骨螺钉组,9个/组。双骨板嵌合组:用2块大小为110mm×10mm×3mm同种异体皮质骨板嵌合固定。双骨板骨螺钉组:用2块110mm×10mm×3mm同种异体皮质骨板和5枚骨螺钉固定。单骨板骨螺钉组:用1块110mm×10mm×3mm骨板和5枚骨螺钉固定。主要观察指标:分别对以上3组进行生物力学实验,测试其压缩、弯曲及扭转刚度和极限载荷。结果:不同固定方式显示不同的力学特征。双骨板嵌合组的抗压刚度与双骨板骨螺钉组相似,高于单骨板骨螺钉组,但抗弯和抗扭刚度显著高于后两组,差异有统计学意义(P<0.05)。双骨板嵌合组压缩、弯曲、扭转极限载荷大于双骨板骨螺钉组(P<0.05),显著大于单骨板骨螺钉组(P<0.01)。结论:同种异体皮质骨板固定的强度与固定方式有关。双板嵌合固定比骨板骨螺钉固定具强度和刚度更大,可满足临床需要。     

穹顶形开窗减压对腰椎稳定性影响的生物力学评估

目的:通过生物力学测定了解穹顶形开窗减压术治疗腰椎管狭窄症对腰椎稳定性的影响。方法:手术处理于2005-04-05/05-02在中日合作连云港市骨科研究中心进行,生物力学实验于2005-07-01/07-07在上海生物力学工程研究所进行。选用30具正常新鲜成年雄性家猪腰椎L1～L6标本,剔除肌肉,保留韧带和关节囊,逐步处理分为3组:A组进行全椎板切除,B组行模拟穹顶形开窗减压术,C组不处理。以生物力学方法测试3组载荷-应变变化、应力-强度变化、载荷-位移变化、轴向刚度、扭转强度和刚度、极限力学性能等6项指标。结果:①载荷-应变测量结果:在生理载荷作用下,平均应变A,B组比C组分别高37%,18%(应变小说明脊柱稳定性好),A组比B组高22%。腰椎在后伸位和中立位应变较小,应变较大的是前屈位和侧屈位。中立位与前屈、后伸、侧屈位相比,分别相差19%,30%,19%。②应力-强度测量结果:A,B,C组平均应力强度为2.93,2.28,1.86MPa。椎体在中立位应力较小,为2.27MPa;后伸时应力强度最小,为1.58MPa;前屈应力强度为2.78MPa;侧屈2.80MPa。③载荷-位移变化的测量结果:A组比B组位移高34%,与C组比,穹顶形开窗减压仅增加21%的位移,而全椎板切除增加了48%,显示脊柱产生不稳定状态。腰椎在后伸位移最小,为2.02mm,侧屈位移为2.17mm,前屈位移较大,为2.26mm,中立位为1.73mm。④轴向刚度实验结果:A,B,C组平均为187,288,368N/mm,A,B组与C组相比较,分别相差22%和49%,A,B组相差35%。腰椎在后伸位轴向刚度264N/mm,比前屈234N/mm大12%。⑤扭转强度和刚度测量结果:C组与B组扭转强度相差12%,与A组相差39%,;A、B两组相比,B组强于A组30%。在同一扭转强度下,A,B组与C组相比较,分别相差4%和16%,B组优于A组。若在同一扭角下,A,B组与C组相比较,分别相差8%和21%。⑥极限力学性能试验结果:极限载荷和极限位移C组最强,其次是B组,A最差,两者与C相比分别相差15%和38%;屈服载荷B组优于A组,屈服位移也是如此。结论:进行穹顶形开窗减压的腰椎6项指标均接近未处理的正常腰椎,优于全椎板切除的腰椎。说明穹顶形开窗减压术对腰椎后部结构破坏少,对其稳定性影响小。     

Budd-Chiari综合征下腔静脉超声检查方法及病变分型再探讨

目的 探讨超声检查布-加综合征(Budd-Chiari syndrome,BCS)下腔静脉病变的方法并进行分型诊断.方法 常规经腹和应用心脏探头经胸右心房下腔静脉入口切面详细观察300例BCS患者下腔静脉的二维及血流声像图特征,并对其中277例存在病变者进行分型.所有病例均经数字血管减影(DSA)证实.其中52例行CT血管成像(CTA)检查.结果 下腔静脉病变分为隔膜性病变、节段性病变以及外压性病变三大类.①隔膜性病变(病变厚度≤15 mm):分为隔膜狭窄和隔膜闭塞.隔膜狭窄型根据隔膜厚度又进一步分为薄隔膜狭窄型(厚度≤5 mm)和厚隔膜狭窄型(5 mm＜厚度≤15 mm);隔膜闭塞型则分为薄隔膜闭塞型(厚度≤5 mm)和厚隔膜闭塞型(5 mm＜厚度≤15 mm).②节段性病变(病变长度＞15 mm):分为节段狭窄和节段闭塞.节段狭窄型又分为长节段狭窄型(＞30 mm)和短节段狭窄型(15mm＜狭窄长度≤30 mm);节段闭塞型进一步分为长节段闭塞型(闭塞长度＞20 mm)和短节段闭塞型(15mm＜闭塞长度≤20 mm).③外压性病变:主要为肿大肝尾状叶压迫所致的下腔静脉狭窄.各型均具相应超声表现.结论 经腹和应用心脏探头经胸右心房下腔静脉入口切面超声检查能对BCS患者下腔静脉病变准确分型,有助于指导临床治疗.     

X线阻射石英纤维桩的制备和性能测试

目的:制备X线阻射的石荚纤维桩并对其性能进行评价.方法:采用拉挤工艺,分别制备3种不同纤维含量的X线阻射的石英纤维桩材料,测试其弯曲强度和弯曲模量,并拍摄X线片评价其阻射性,电镜观察纤维桩断面.结果:成功制备了3种不同纤维含量的X线阻射的石英纤维桩材料,其纤维质量含量分别为52.7%,61.8%和72.1%,获得临床可接受的X线阻射性,弯曲强度最高达1 055.86 MPa,相应的弯曲模量为27 577 MPa,可满足临床要求.结论:成功制备了X线阻射的石英纤维桩材料.     

磷酸钙骨水泥对颈椎前路螺钉置入体强化作用的生物力学分析

背景:有研究表明磷酸钙骨水泥通过改善骨与螺钉界面的质量,从而强化螺钉的即刻和早期固定强度.目的:实验拟验证磷酸钙骨水泥对颈椎前路单皮质骨螺钉的强化作用.设计:对比观察.单位:中南大学湘雅医学院附属湘雅一医院骨科.材料:实验于2003-09/2004-01在中南大学材料科学与工程学院电子拉伸力学性能室完成.由张家港市欣达医疗器械有限公司生产的颈椎前路单皮质骨自攻螺钉,材质为纯钛.注射型磷酸钙骨水泥由上海瑞邦生物材料有限公司生产.轴向拔出套筒由中南大学机械制造基地制造.方法:①选取4具新鲜青年男性尸体C3～C6椎体标本共16个椎体,单个椎体骨密度测量,证实无骨质疏松.4具新鲜老年男性尸体C3～C6椎体标本共16个椎体,单个椎体骨密度测量,证实骨质疏松.标本由中南大学湘雅医学院解剖教研室提供,死者生前自愿捐献遗体,家属均知情同意.每组随机选择12个椎体进行3个试验,轴向拔出试验选取6个椎体,周期抗屈试验和抗屈后抗剪切试验选取6个椎体.在椎体前方中线两侧8 mm处向中线倾斜5°攻丝锥导孔,钻出钉道备用,不穿透椎体后方骨皮质.②轴向拔出实验:随机选取椎体一侧置入螺钉作为对照组,在材料实验机上行轴向拔出实验,拔出速率为5 mm/min.螺钉拔出后用磷酸钙骨水泥 0.10～0.15 mL修复钉道再次置入螺钉作为修复组,另一侧直接以磷酸钙骨水泥填充后置入螺钉作为强化组,37 ℃下放置24 h后再行轴向拔出试验.③周期抗屈试验和抗屈后抗剪切试验:随机选取椎体一侧置入螺钉作为对照组,另一侧直接以磷酸钙骨水泥填充后置入螺钉作为强化组行周期抗屈试验和抗屈后抗剪切试验.主要观察指标:①螺钉的最大轴向拔出力.②周期抗屈实验后螺钉的位移.③周期抗屈后螺钉的最大抗剪切力.结果:①轴向拔出试验:骨质正常椎体,对照组拔出力为(313± 64)N,修复组为(376±88)N,强化组为(446±121)N;骨质疏松椎体,对照组拔出力为(106±47)N,修复组为(154±67)N,强化组为(191±80)N.修复组、强化组的轴向拔出力均明显高于对照组(P < 0.05).②周期抗屈实验:强化组在相同载荷下产生的位移明显小于对照组(P < 0.05).③最大抗剪切力:骨质正常椎体:对照组为(301± 79)N,强化组为(395±105)N.骨质疏松椎体:对照组为(87±39)N,强化组为(149±63)N,强化组的最大抗剪切力明显强于对照组(P < 0.05).结论:磷酸钙骨水泥能提高螺钉的轴向拔出力及抗剪切能力,在骨质疏松时强化效果更加明显.     

Spatial discrimination thresholds for pain and touch in human hairy skin

The traditional concept that pain is poorly localized has been challenged by recent studies, where subjects were able to point to the stimulated spot on the skin with an accuracy of 10-20 mm. Pointing movements themselves, however, have errors of about 15 mm. To determine the limits of sensory performance of the nociceptive system independent of motor performance, point localization of heat pain (540 mJ punctate laser stimuli, 5 mm diameter), mechanical pain (256 mN punctate probe, 200 microm diameter), and touch (16 mN von Frey probe, 1.1 mm diameter) were tested in a two-alternative forced-choice paradigm in 12 healthy subjects. Stimuli were applied in randomized order to two parallel lines on the back of the hand (4-32 mm distance). The cumulative distribution functions for correct localization were of similar sigmoid shape for all test stimuli, indicating logarithmic normal distributions. The 75% correct localization threshold for painful heat was 8.6 mm (3.1 +/- 0.1 log2 units) and did not differ significantly from that of non-painful touch (9.0 mm, 3.2+/-0.2 log2 units). Localization of mechanically-induced pain (5.1 mm, 2.4 +/- 0.2 log2 units) was significantly more accurate than both heat pain and touch, possibly due to a synergism of two different sensory channels, the tactile channel and the nociceptive channel, which were activated simultaneously. For all three stimuli, discrimination was significantly better in radial-ulnar compared to proximal-distal direction, which might be related to oval receptive field shapes. Sequential spatial discrimination for touch was significantly better than simultaneous spatial discrimination tested with a grating orientation task (18.9 mm), but both were one order of magnitude worse than at the finger tip (1.3 mm, 0.4 +/- 0.1 log2 units). In conclusion, pain evoked by radiant heat pulses and touch evoked by von Frey probes were localized with similar precision on the back of the hand. These findings indicate that outside the tactile fovea at finger tips or lips the spatial discrimination capacities of the nociceptive and tactile systems are about equal.     

悬臂梁实验评价玻璃纤维增强树脂桩材料的挠曲特性

背景:玻璃纤维增强树脂桩替代传统的金属桩已越来越多被应用于牙体缺损的修复治疗,但其形状特殊、尺寸较小,使用传统的弯曲实验很难准确评价其机械性能。目的:利用悬臂梁实验对3种市售玻璃纤维增强树脂桩(GFP,FBK和EVS)的挠曲特性进行评价。方法:根据玻璃纤维增强树脂桩的直径范围(0.9～1.0mm,1.2～1.25mm,1.4～1.5mm和1.6mm)将其分为4组。将每根玻璃纤维增强树脂桩一端包埋于树脂水门汀后作为测试样本,借助夹具固定于物性测试仪上,以6mm/min加载速率完成悬臂梁测试。结果与结论:典型的载荷-挠度曲线可见3种玻璃纤维增强树脂桩在超过比例限发生折断之前均伴有数次显著的载荷下降。实验将首次载荷下降前的峰值(称为pop-in载荷)作为玻璃纤维增强树脂桩的一个重要机械性能参数进行了测量。在pop-in载荷后的玻璃纤维增强树脂桩表面扫描电镜照片中可见呈剥离状态的玻璃纤维及沿纤维走行方向产生的裂隙。虽然最大载荷值随玻璃纤维增强树脂桩直径的增加而增大,但挠曲强度值却呈现减小趋势。GFP和FBK桩的弹性模量值随桩直径的增大而明显减小,直径1.0mmFBK桩的挠曲强度和弹性模量值最高。结果表明悬臂梁实验可以在模拟临床条件下用于评价玻璃纤维增强树脂桩的挠曲性能;pop-in载荷值是评价玻璃纤维增强树脂桩临床预后的有用指标。     

悬臂梁实验评价玻璃纤维增强树脂桩材料的挠曲特性

背景：玻璃纤维增强树脂桩替代传统的金属桩已越来越多被应用于牙体缺损的修复治疗,但其形状特殊、尺寸较小,使用传统的弯曲实验很难准确评价其机械性能。目的：利用悬臂梁实验对3种市售玻璃纤维增强树脂桩（GFP,FBK和EVS）的挠曲特性进行评价。方法：根据玻璃纤维增强树脂桩的直径范围（0.9～1.0mm,1.2～1.25mm,1.4～1.5mm和1.6mm）将其分为4组。将每根玻璃纤维增强树脂桩一端包埋于树脂水门汀后作为测试样本,借助夹具固定于物性测试仪上,以6mm/min加载速率完成悬臂梁测试。结果与结论：典型的载荷-挠度曲线可见3种玻璃纤维增强树脂桩在超过比例限发生折断之前均伴有数次显著的载荷下降。实验将首次载荷下降前的峰值（称为pop-in载荷）作为玻璃纤维增强树脂桩的一个重要机械性能参数进行了测量。在pop-in载荷后的玻璃纤维增强树脂桩表面扫描电镜照片中可见呈剥离状态的玻璃纤维及沿纤维走行方向产生的裂隙。虽然最大载荷值随玻璃纤维增强树脂桩直径的增加而增大,但挠曲强度值却呈现减小趋势。GFP和FBK桩的弹性模量值随桩直径的增大而明显减小,直径1.0mmFBK桩的挠曲强度和弹性模量值最高。结果表明悬臂梁实验可以在模拟临床条件下用于评价玻璃纤维增强树脂桩的挠曲性能;pop-in载荷值是评价玻璃纤维增强树脂桩临床预后的有用指标。     

静电纺丝聚乳酸-羟基乙酸纳米纤维膜与磷酸钙骨水泥复合物力学性能的研究

目的模仿天然骨同心圆的结构,制备静电纺丝聚乳酸-羟基乙酸共聚物[Poly（1actide—co—glycolideacid）,PL-GA]纳米纤维膜／磷酸钙骨水泥（calciumphosphatecement,CPC）复合物,通过力学实验初步探讨静电纺丝PLGA纳米纤维膜改善CPC韧性强度的效果。方法实验分为两组：实验组为CPC／PLGA复合物、对照组为单纯的CPC,将CPC复合物或单纯的CPC制备6mm×6mm×20mm的长方体试件,进行三点弯曲试验测试材料的韧性强度、弯曲强度和弹性模量。结果与CPC组相比较,CPC／PLGA组的韧性强度提高了71．4倍,差异具有统计学意义（P=0．00）;弯曲强度提高28．8％,弹性模量降低37．8％,差异无统计学意义（P〉0．05）。结论静电纺丝PLGA纳米纤维膜可以改善CPC的韧性,静电纺丝PLGA纳米纤维膜／CPC复合物具有较好的力学特性。     

Rapid application fracture fixators - an evaluation of mechanical performance

OBJECTIVE: This study evaluates the mechanical performance of the Pinless and Centrafix fixators for rapid application to tibial fractures in a disaster or battlefield scenario. DESIGN: Comparative study based on measurements made in the laboratory. BACKGROUND: The Pinless and Centrafix fixators may be considered for rapid application to stabilise fractures in emergency conditions without the aid of electrical equipment such as power drills for bone screw insertion or image intensifiers to facilitate bone alignment. METHODS: Stiffnesses, maximum service loads and fatigue strengths of the fixators were measured in the orientations of loading that correspond to walking and stretcher-bearing. These properties were compared with measurements on three conventional fixators, the AO, Shearer and Triax. RESULTS: The Centrafix stiffnesses were 31 N/mm (axial), 1 N/ degrees (torsional shear), 0.4 N/ degrees (coronal plane bending), 4 N/ degrees (sagittal plane bending) and 11 N/mm (transverse shear) and strengths were 95 N (axial) and 1.9 Nm (bending). Corresponding Pinless stiffnesses were 43 N/mm, 0.7 N/ degrees, 0.3 N/ degrees, 8 N/ degrees and 50 N/mm, and strength was 55 N (axial). CONCLUSIONS: The stiffness and strength of both rapid application fixators in simulated walking was judged to be low, and additionally the stiffness and strength of the Centrafix in simulated stretcher-bearing was judged to be low. RELEVANCE: The Pinless is not recommended for weight-bearing subjects with unstable fractures. The Centrafix is not recommended for stretcher-bearing or weight-bearing with unstable fractures.     

Intraoral measurement of tactile and filament-prick pain threshold using shortened Semmes-Weinstein monofilaments

OBJECTIVES: Semmes-Weinstein monofilaments are too long for use in parts of the oral cavity. The present study used shortened Semmes-Weinstein monofilaments to evaluate reliability and spatial differences in the intraoral tactile detection threshold (TDT) and the filament-prick pain detection threshold (FPT) in healthy volunteers. METHODS: For practical purposes, classic Semmes-Weinstein monofilaments with 20 different diameters were cut to half their length (ie, 19 mm) and the bending forces were measured. Eighteen men and 18 women (age range, 20 to 33 y) were recruited to evaluate the reliability and reproducibility of measurements using half-cut monofilaments. The TDT and the FPT were measured on the labial maxillary gingiva, on the palatal maxillary gingiva, and at the anterior tip of the tongue, using a double random staircase method. RESULTS: According to the forces needed to bend the half-cut filaments, they were renumbered from 2.55 to 6.86. There were significant differences of bending force between the half-cut and original monofilaments (P<0.001), Using half-cut filaments, the following differences could be detected; the labial maxillary gingiva had a significantly higher TDT threshold compared with the other test sites (P<0.001). By contrast, the palatal posterior maxillary gingiva had a significantly higher FPT threshold compared with the other test sites (P<0.001). DISCUSSIONS: The present study illustrated that in healthy participants, half-cut Semmes-Weinstein monofilaments reliably and easily assess TDT and FPT intraorally. A combined examination of sensory and pain thresholds using these filaments contributes to the clinical examination for orofacial pain.     

脱脂对异体皮质骨生物力学的影响

背景:脱脂的目的在于通过清除脂肪和脂蛋白,减少特殊细胞表面抗原,以降低免疫排斥反应,改善异体骨的生物相容性,提高异体骨移植的成骨能力,但目前有关脱脂对骨生物力学性能的影响尚无统一观点.目的:探讨脱脂对异体皮质骨生物力学性能的影响.设计、时间及地点:随机分组自身对照观察实验,于2006/2008在广东医学院附属福田人民医院完成.材料:新鲜宰杀的成年健康牛股骨8对.从每一对牛股骨相应位置中挑取约50 mm长,10 mm宽的骨块,将骨块打磨成7 mm×7 mm×40 mm长方体牛皮质骨试件24对.方法:将24对试件随机抽签法分成2组(n=12),每对中随机抽取一个试件为实验组,另一个试件为对照组.实验组试件在1:1的三氯甲烷:甲醇混合液500 mL中脱脂24 h:对照组标本按同样流程在去离子水中浸泡24 h.两组分别选取6个试件进行抗压缩试验及三点弯试验.主要观察指标:力学试验中每一试件所能承受的载荷、挠度.结果:压缩试验显示,与对照组比较,实验组的试件所能承受的最大压力明显减小,且脱脂后每个试件间所受最大应力的差别明显缩小,试件的脆性增加,最大应变减小,弹性模量增大(P均<0.05);三点弯试验显示,与对照组比较,实验组的试件所能承受的最大载荷明显减小,所受最大应力的差别明显缩小,最大挠度减小,弹性模量增大(P均<0.05).结论:脱脂后皮质骨的力学强度下降,脆性增加.     

Preliminary interpretive criteria for disk diffusion susceptibility testing of SCH 27899, a compound in the everninomicin class of antimicrobial agents

As antimicrobial resistance among Gram-positive species becomes more common, alternative agents need to be developed for the therapy of serious infections. SCH 27899 is a compound from the everninomicin class of antimicrobial agents that possesses a potent Gram-positive spectrum. We evaluated three disk concentrations (0.25,1, and 5 μg) of three SCH 27899 formulations including SCH 27899 base (SCHB), N-methylglucamine SCH 27899 (NMG-SCH), and NMG-SCH complexed with hydroxypropyl β-cyclodextrin. Disk zone diameters were correlated with minimum inhibitory concentration for 209 aerobic, nonfastidious Gram-positive strains and selected Gram-negative bacilli to develop disk diffusion interpretive criteria. No significant differences in activity were noted among the three SCH 27899 preparations. Of the three disk concentrations, the correlation coefficient was greatest (r = 0.88) for the 5-μg SCHB disk test. For a tentative break point of ≤2 μg SCHB/ml, preliminary disk interpretive criteria were: susceptible at ≥12 mm, intermediate at 10–11 mm, and resistant at ≤9 mm (absolute categorical agreement, 99.5%). Zones were small secondary to drug solubility and diffusion limitations. Using these criteria for the SCHB 5-μg disks, nearly all of the tested Gram-positive organisms were susceptible including methicillin-resistant staphylococci and vancomycin-resistant enterococci.     

Differences between the cutaneous two-point discrimination thresholds of chiropractic students at different stages in a 5-year course

OBJECTIVE: To investigate differences between the tactile acuity of the fingers measured at different stages in a chiropractic training course. METHODS: Two-point discrimination (2-PD) thresholds for the skin of the dominant and nondominant index fingers and the dominant forearm were measured in 74 subjects taken from the 5 years of a chiropractic degree course. Measurements were made with modified electronic engineering callipers mounted on a lever arm, which allowed the points to be lowered onto the skin with a constant pressure. ANALYSIS: Differences in the 2-PD measurements recorded among the year-groups were analyzed with 1-way analysis of variance and between the dominant and nondominant index fingers with the paired Student t test. RESULTS: Students in years 4 and 5 of the course had significantly smaller mean 2-PD threshold values (P <.05) for both dominant (year 5: 1.39 +/- 0.06 mm) and nondominant (1.50 +/- 0.08 mm) index fingers compared with students in year 1 (dominant mean, 1.66 +/- 0.09 mm; nondominant mean, 1.80 +/- 0.10 mm). There was no significant difference between the 2-PD thresholds measured on the forearm of any of the groups. When the data from all 5 years were grouped, the 2-PD thresholds for the dominant index finger (mean 1.52 +/- 0.035 mm) was found to be significantly smaller (paired Student t test, P <.0001) than for the nondominant finger (mean 1.65 +/- 0.038 mm, n = 74). CONCLUSION: The results demonstrate that the tactile acuity of students in the later years of the course at the Anglo-European College of Chiropractic is greater than that of students in the first year. This may be a result of the intensive training in palpatory techniques that the students receive during their course. However, this requires confirmation by further investigation.