Shaping ability of progressive versus constant taper instruments in curved root canals of extracted teeth

AIM: To compare the shaping ability of progressive versus constant taper shaft instruments in curved root canals of extracted human teeth. METHODOLOGY: A total of 40 root canals of mandibular molars with curvatures ranging between 20 degrees and 40 degrees were divided into two groups of 20 canals each and embedded in a muffle system. The root canals sectioned horizontally at three levels before preparation and then remounted into the mould. All root canals were prepared with ProTaper (progressive taper) or Hero Shaper (constant taper) instruments. Pre- and post-instrumentation radiographs and cross-sectional images were obtained. The parameters evaluated were: working safety (instrument failure, apical blockage and loss of working length) and shaping ability (straightening, cross-sectional area, transportation and centring ability). The data were analysed statistically using Student's t-test. RESULTS: No instrument fractured during preparation. One Hero Shaper instrument permanently deformed. Both instrument systems maintained working length well. The canals prepared with Hero Shaper instruments were straightened to a lesser degree (P < 0.05). ProTaper instruments removed more dentine in the coronal and the middle sections of the canals. Canals prepared with Hero Shaper instruments had less transportation (P < 0.01) and better centring ability (P < 0.05) in the apical section. CONCLUSIONS: Both instrument systems were safe to use and maintained working length well. The canals prepared with Hero Shaper had less transportation and were better centred in the apical region, possibly because their smaller taper reduced instrument stiffness.     

Antimicrobial effect of triclosan and triclosan with Gantrez on five common endodontic pathogens

Microbial control of the root canal system is one of the key objectives of root canal therapy. Triclosan is a widely accepted broad spectrum antimicrobial agent proven to be effective against many gram-positive and gram-negative bacteria. Triclosan acts by blocking bacterial fatty acid biosynthesis. The addition of Gantrez copolymer has been shown to enhance the antimicrobial activity of triclosan. The purpose of this study was to determine the minimum inhibitory and bactericidal concentrations of triclosan and triclosan with Gantrez against Prevotella intermedia, Fusobacterium nucleatum, Actinomyces naeslundii, Porphyromonas gingivalis, and Enterococcus faecalis. The minimum inhibitory concentration (MIC) of both test solutions was determined for each of the 5 microorganisms by using microtiter serial dilutions. Samples were streaked on 5% sheep blood agar plates and placed in an anaerobic incubator to determine the minimum bactericidal concentration (MBC). The MBC of triclosan ranged from 12-94 microg/mL. The MBC of triclosan with Gantrez ranged from <0.3-10.4 microg/mL. The addition of Gantrez enhanced the bactericidal activity of triclosan. Both triclosan and triclosan with Gantrez demonstrated bactericidal activity against the 5 specific endodontic pathogens.     

Leakage along warm gutta-percha fillings in the apical canals of curved roots

The aim of this study was to investigate the leakage along the apical portion of warm gutta-percha obturated curved canals. Human mandibular premolars with single, curved (21 degrees-40 degrees) canals were prepared using the Lightspeed technique. Two groups of prepared canals, matched according to curvature and prevalence of apical transportation, were obturated by two techniques. Coronal gutta-percha was removed immediately after root obturation was completed to simulate the procedure for post space preparation. Leakage along the apical 3 mm of root filling was measured with a fluid transport device. Vertical condensation of warm gutta-percha and Pulp Canal Sealer provided less leakage than Thermafil plastic obturators and AH26 sealer (P = 0.002).     

钌红电镜组织化学技术应用

目的 采用钌红电镜组织化学技术对涎腺多形性腺瘤，肌上皮瘤，腺样囊性癌和基底细胞瘤进行研究以示踪肿瘤中蛋白多糖的形成和分布。方法 新鲜标本分切后固定于2.5%戊二醛中24小时，其中含0.2%的钌红；0.1M二甲肿酸钠缓冲液冲洗过夜；1%OsO4后固定1小时；丙酮逐级脱水，Epon812包埋，在半薄切片上定位，超薄切片用Opton109型电镜观察，结果 在多形性腺瘤和肌上皮瘤中，粘液样区域内充满了蛋白多糖，这种蛋白多糖是由NMCs分泌产生的，腺样囊性癌的NMCs也分泌产生蛋白多糖，该瘤中筛状结构形成是由于NMCs分泌蛋白多糖所致，这种分泌功能的出现是肌上皮细胞向肿瘤性细胞转变的一个标志。结论 钌红电镜组织化学技术方法可检涎腺肿瘤中蛋白多糖形成和分布，是一种简便，易行的方法。     

口腔修复临床医生与患者目视比色的差异对比

目的：研究金属烤瓷冠修复的临床医生与患者目视比色之间的差异。方法：应用PR650型分光光谱测色仪，在离体黑背景下，对本院修复科门诊前牙镍铬金属烤瓷冠修复的69例患者中，医生与患者所选Vita比色板色样的色度值进行了测量，测量结果用CIEl976L*a*B*系统表示。结果：医生选色比患者平均明度偏亮、平均红绿色品偏红。医生选用Vita比色板A系列色样的占65．2％，尤其A2、A3较多，而患者选色各系列系列较为平均。结论：医生与患者在选色上存在明显差异。     

表皮生长因子受体在颊粘膜鳞状细胞癌中的表达及其临床病理学意义

表皮生长因于受体（EGFR）是一单跨膜糖蛋白，与细胞的增殖、转化有关。本文采用免疫组化ABC法检测8例正常颊粘膜上皮及40例颊粘膜鳞癌中EGFR的表达状况，结果显示：EGFR在颊癌组织中呈异质性表达，其阳性率明显高于正常颊粘膜组织（P＜0．05）；EGFR表达状况与颈淋巴结转移及预后间存在相关关系（P＜0．05）。EGFR（＋）表达者多数伴有颈淋巴结转移，预后差。以上结果说明，EGFR在颊癌组织中的表达水平，可作为评估颊癌细胞增殖状态，颈淋巴结转移情况及患者预后的一项参考指标。     

大块状生物活性玻璃陶瓷表面复合骨髓-骨松质的成骨作用研究

将自体骨髓-骨松质(ABMC)复合于块状生物活性玻璃陶瓷(BGC)表面，植入12条杂种狗无骨膜的下颌骨缺损区，分别于术后4周、12周、20周和40周处死，采用光镜、荧光显微镜及扫描电镜观察局部新骨生成与改建状况。发现术后4同时植入BGC上面有多量的新生骨形成，随时间的推移，此层骨组织增厚，并从不规则的骨芽向小梁骨转化，沉积在BGC表面或微孔内。而对照组始终末见骨形成。经结果表明BGC可以作为ABMC的生物载体，促进ABMC的异位成骨效应。BGC表面复合ABMC种植改善了BGC的力学强度．扩大了临床应用范围。     

Compositional analysis of human acquired enamel pellicle by mass spectrometry

Relatively little is known about the formation of the acquired enamel pellicle other than that it involves the selective adsorption of specific proteins from oral fluids. Previous studies on the identification of pellicle components have relied largely on immunological or enzymatic detection and have been hampered by the fact that only minute quantities of pellicle can be removed from tooth surfaces. The present work describes an improved method of harvesting pellicle that combines mechanical and chemical removal; this approach was used to investigate systematically the desorption of in vitro pellicle components with different solutions. Eleven major in vitro pellicle proteins were identified by using a combination of electrophoretic separation and matrix-assisted laser desorption/ionization-reflectron time-of-flight mass spectrometry. A similar analysis of in vivo-formed pellicle revealed the presence of intact statherin, lysozyme, albumin and amylase. Further analysis of in vivo pellicle by liquid chromatography-electrospray ionization mass spectrometry suggested the presence of numerous low molecular-weight fragments of precursor proteins. The protein composition of in vitro whole-salivary pellicle adsorbed to hydroxyapatite and that of in vivo enamel pellicle differed for proline, the result of a reduction in the content of acidic proline-rich proteins in the in vivo samples. Unique features of the oral environment such as enzymatic activities or mineral surface properties may account for these differences between in vivo and in vitro pellicle formation.