Polylactic acid (PLA) root replica in ridge maintenance after loss of a vertically fractured incisor

Abstract A periodontally affected tooth was prepared for a special treatment: Calcium hydroxide was introduced into the apical half of the root canal whereas its cervical part was filled with glass ionomer cement. The tooth was shortened subgingivally. After 6 weeks of epithelization over the residual root a palatal full-thickness flap was mobilized. The root was carefully extracted and chairside copy-milled from the biodegradable polylactic acid (PLA) material. The PLA-replica was implanted immediately into the socket and the flap was sutured. Aim of the treatment was to prevent the ridge collapse of the extraction area. Ridge height could be preserved during the 21 months of observation. With time the radiographic density of the cancellous bone increased in the implanted area, indicating that a PLA-replica is replaced by host's bone tissue.     

龈下残根修复前正畸治疗五例

目的　对损坏至龈缘下 1 5～ 3 5mm的前牙牙根在修复前行正畸牵引 ,当损坏平齐龈缘时再桩冠修复的方法进行探讨。方法　 3例外伤、2例根面龋的患者 ,共 6个牙根接受完善根管治疗 ,修复前正畸暴露损坏 ,电刀修整牙龈 ,然后桩冠修复。结果　 5例患者在修复后均取得了较满意的效果。结论　若前牙牙根损坏位于龈下釉牙骨质交界处 ,在修复前进行正畸治疗 ,既可保留残根 ,又可制作出有较好功能和美观效果的修复体     

上颌第一恒磨牙根管治疗的临床疗效分析

目的 总结并分析上颌第一恒磨牙根管治疗的临床疗效。方法 对151颗上颌第一桓磨牙患牙进行根管治疗并观察疗效。结果 151例患牙完成根管充填136颗；治愈率为90.07%。共检出四根管32颗，检出率为21.19%。结论 熟悉髓室和根管的解剖形态，正确的根管预备，严密的根管充填，是提高上颌第一恒磨牙根管治疗疗效的必要条件。     

Learning root debridement with curettes and power-driven instruments in vitro: the role of operator motivation and self-assessment

The influence of systematic dummy-head training with Periopolishe (PP, group A) and Gracey instruments (GRA, group B) on the effectiveness of root debridement was evaluated by Rühling et al., 2002 (9). Their results indicate that independent of the instrument used, untrained operators were only able to debride root surfaces at low levels of effectiveness. It was possible to increase effectiveness to a high level through systematic training in both groups. The aim of the present study was to assess the role of operator motivation and self-assessment on scaling effectiveness. Before baseline, operators were asked to answer a questionnaire rating the expectation of the instrument performance. Four groups of inexperienced operators (n = 11 each) received 10 weeks dummy-head training. In groups A (GRA) and B (PP), training was combined with a motivational programme. Groups C (GRA) and D (PP) received the same training, but no additional motivational programme. In a dummy-head, 10 test teeth were debrided and operators were asked to estimate their effectiveness of debridement at each test day. Effectiveness was calculated as percentage of debrided root area on 10 test teeth at different time points with an image analysis programme (NIH Image) and ANOVA. Two groups were compared using the Mann-Whitney U-test (unpaired) and the Wilcoxon signed ranks test (paired). Motivated groups (A and B) reached about 25% higher debridement results (p < 0.001) and were able to estimate their effectiveness more precisely compared to groups C and D. In the low motivation groups (C and D), overestimation of more than 20% was evident (p < 0.001). The questionnaires revealed underestimation of the GRA instruments and overestimation of PP instruments. Operator motivation and self-assessment greatly influence learning of effective root debridement.     

神经根慢性嵌压损伤的动物模型建立

目的：建立一种由自身骨性增生造成神经根慢性嵌压损伤的动物模型，为相关实验提供造模方法一方法：30只健康家猫，手术显露右侧C7、C8和L5、L6冲经根及其椎问孔内口，用牙髓钻破坏椎间孔周围骨皮质后，将“V”形松质骨块沿骨壁嵌于神经根通道的骨性管道内及侧隐窝后方，左侧做正常对照。在造模术前和术后第2、4、8、12、24周行磁刺激运动诱发电位(MEP)检测，每次随机选6只，4～5只行影像学检查，以确定神经根通道的狭窄程度和神经根受压状态，6只均做病理组织学检查和椎间孔截面积测量。结果：术后早期实验侧肢体出现行为异常：而后有不同程度肌萎缩；后期部分肢体远端出现溃疡。影像学检查随着嵌压时间延长．实验侧椎间孔骨痂增多，狭窄加重。神经根受压变形，椎间孔骨性截面积8周后明显减小，与对照侧比较有显著性差异。术后2周，神经根组织学检查主要表现为神经束膜、内膜的水肿。髓鞘肿胀；4周后发生节段性脱髓鞘：8周时神经轴突增粗、断裂，远端瓦勒氏变性；12周后变性冲经结构崩解、吸收，形成空洞：24周时整个神经干纤维化。术后4周时实验侧MEP开始出现潜伏期延长；8周时伴有波形分化不清；12周波幅明显下降：24周MEP的引出困难，部分电位消失。结论：采用椎问孔内自体松质骨植入，造成神经根慢性嵌压性损伤模型成功率高，操作简单，适用于脊柱各个节段，其损伤部位和形式与临床更为接近。     

Low surface tension calcium hydroxide solution is an effective antiseptic

The antimicrobial effects of a saturated calcium hydroxide solution, and in combination with 10% and 20% detergent, were evaluated on Streptococcus faecalis. Strepto-coccus sanguis, Streptococcus mutans, Streptococcus salivarius, Neisseria sp., diphlheroid, Staphylococcus aureus, Lactobacillus sp., Staphylococcus epidermidis, Bacillus suhtilis and Candida albicans. The saturated calcium hydroxide solution was effective against only four of the 11 microorganisms studied over a 60-min exposure time. The calcium hydroxide solutions con-taining detergent killed all 11 test organisms over a 30-min exposure time. This difference was statistically significant (P<0.01). No statistically significant difference in antimicrobial action was found between the 10% and 20% detergent calcium hydroxide solutions (F>0.01). However, the low surface tension (46.5 × 10^?3 Nm^?1) and high pH (10.8) of the calcium hydroxide solution with 20% detergent establish it as the more effective solution.     

牙髓根管感染厌氧菌培养结果分析

从３４例牙髓根管感染中共分离出厌氧菌１１８株，经菌属分类依次为消化链球菌属，拟杆菌属，梭杆菌属，放线菌属，韦荣氏球菌属和珠网菌属，其中前３属为７７株，分离率为６５．３％，这一结果显示该３属细菌与极管感染有密切关系，是牙髓根管感染的优势菌。     

Dorsal root ganglia cocultured with macrophages: an in vitro model to study experimental demyelination

The present investigation introduces an in vitro model to study macrophage properties during demyelination. Rat dorsal root ganglia (DRG) were cultured for obtaining myelinated peripheral nerve fibers. These cultures were exposed to non-resident macrophages. In untreated control cultures, there was no indication of myelin removal by the added macrophages. DRG were exposed to enzymatically generated oxygen radicals using the xanthin/xanthin oxidase or the glucose/glucose oxidase system. Assessment of Schwann cell viability and ultrastructural morphology revealed different patterns of cell cytotoxicity and morphological changes in different experiments. High concentrations caused complete tissue necrosis of the DRG, while low concentrations did not affect either cell viability or ultrastructural morphology. Under intermediate experimental conditions, oxygen radicals caused non-lethal Schwann cell damage leading to Schwann cell retraction and myelin sheath rejection. Myelin lamellae were disrupted and decompacted. These changes were followed by a selective macrophage attack on myelin sheats, resulting in demyelination. Axons, Schwann cells and sensory ganglion cells survived this attack. The specificity of the oxygen radical effects was tested in experiments using the oxygen radical scavengers catalase and superoxide dismutase. Catalase prevented the described effects on cell morphology and subsequently blocked demyelination by non-resident macrophages.Supported by a grant from the Deutsche Forschungsgemeinschaft (DFG) (Br 1274/1-1)     

The use of coaxially aligned freeze-thawed skeletal muscle autografts in the repair of the cauda equina — in the sheep

Summary The aim was to develop a model for study of nerve regeneration in nerve roots above the level of the dorsal root ganglion and to investigate the use of freeze-thawed muscle autografts for repair of nerve roots at this level.Four adult sheep were used for the experiment. A laminectomy was performed at the lumbosacral junction and the S2 root identified. Both the dorsal and ventral S2 roots were divided unilaterally within the dura and a freeze-thawed muscle graft was inserted into the nerve gap.When assessed at 6 months an action potential was recordable from the ventral root in one sheep. Histological examination of the nerve roots showed evidence of regeneration across the graft in the ventral roots of all the sheep and the dorsal roots of some.This preliminary work indicates a capacity for regeneration of the cauda equina and that freeze-thawed muscle can support this. It provides a useful model for further study of nerve root repair.     

背根神经节内P物质、降钙素基因相关肽免疫阳性神经元与阴茎包皮系带感觉信息的传递

目的：探讨背根神经节（DRG）内P物质（SP）、降钙素基因相关肽（CGRP）免疫阳性神经元与阴茎包皮系带感觉信息传递之问的关系。方法：通过荧光金（FG）逆行标记对大鼠阴茎包皮系带内神经末梢的来源作追踪定位，并结合SP、CGRP免疫荧光标记法，研究大鼠DRG内FG标记阳性神经元中SP、CGRP免疫阳性神经元的形态和分布。结果：FG逆行标记结果发现，大鼠阴茎包皮系带内的神经末梢起源于第6腰髓对应的背根神经节（L6-DRG）和第1骶髓对应的背根神经节（S1-DRG）的神经元。对这些神经元分别作SP、CGRP免疫荧光标记后发现，标记细胞大小不等，分别呈深红色和深绿色，沿神经束成行排列或散在分布。FG／SP、FG／CGRP双标记阳性细胞均为中小型，其数量分别占FG逆行标记阳性细胞总数的1／3和1／2，FG／SP／CGRP三标记阳性细胞占FG逆行标记阳性细胞总数的1／5。结论：大鼠L6-DRG和S1-DRG内的SP、CGRP免疫阳性神经元可能参与阴茎包皮系带感觉信息的传递。