下颌第二恒磨牙C形根管的离体实验研究

目的：寻找一种预备C形根管的有效器械,提高下颌第二恒磨牙的治愈率。方法：选用80颗具有C形根管的下颌第二恒磨牙,选择四种器械进行根管预备,第一组用不锈钢K锉,第二组用不锈钢K锉和手用镍钛器械,第三组用机用镍钛器械,第四组用超声根管治疗仪,预备中均用3％双氧水和生理盐水交替反复冲洗根管,预备后用Vitapex糊剂和牙胶尖冷侧压方法充填根管,观察根充后X线片和根尖微渗漏情况,评价充填效果。结果：四种器械根充后微渗漏有明显差异（P〈0．05）。结论：不锈钢K锉和手用镍钛器械联合应用及超声根管治疗仪为预备C形根管的有效器械。     

三江平原湿地多级沟渠系统底泥可溶性有机碳的分布特征

沿着土壤和土地利用类似的三江平原多级沟渠系统采集不同沟渠单元底泥,这些不同沟渠系统单元由湿地和农田边界排水沟渠到相当大的主干渠变化着,测定底泥中可溶有机碳（DOC）含量,研究多级沟渠系统底泥中DOC的分布特征。结果发现,随沟渠等级增加,DOC在底泥中所占的比重逐渐增加（40～60cm层增加近5倍）,DOC富集层逐渐有规律的向底泥底层转移（40～60cm）。研究表明,排水沟渠既是湿地或农田DOC的最初汇聚地,又是河道DOC的输出源;沟渠重复性的排水将湿地或农田DOC通过零星径流带入沟渠系统中,连续的沟渠径流携带着大量DOC与不同等级沟渠系统相互作用使得沟渠系统底泥中DOC呈现出一定的水平、垂直分布特征;排水沟渠排水历时、DOC流量、滞留时间、径流发生频率等都会影响多级沟渠系统底泥中DOC的分布特征;另外,沟渠系统内生长的植被也通过径流阻塞和有机质过程影响底泥中DOC的分布特征。     

脉冲Nd∶YAG激光在根管预备中的临床应用——与超声根管预备、传统手动根管预备比较

为了观察脉冲Ｎｄ∶ＹＡＧ激光在根管预备（以下简称根备）中的作用,我们用Ｎｄ∶ＹＡＧ激光辅助,对３０颗患牙进行根备,根备后即时根充。并与超声根备后即时根充、传统根备后即时根充比较,结果表明：激光组的术后疼痛反应少于超声组与传统组,远期疗效与超声组相仿,而优于传统组。     

不同根管冲洗方法在瘘管型根尖周炎治疗中的疗效分析

目的:比较普通冲洗和超声冲洗方法对瘘管型慢性根尖周炎一次性根管治疗疗效的影响,以期为超声冲洗方法在慢性根尖周炎临床治疗中的应用提供指导。方法:将2010年6月-2012年6月来我科就诊的166名瘘管型慢性根尖周炎患者随机分为2组,超声冲洗组和普通冲洗组,根据分组分别在一次性根管治疗术中的根管清理过程采用超声根管冲洗方法和普通注射器冲洗方法,术后1周和半年时复诊记录患者一次性根管治疗效果,通过以患者术后1周内的主观"疼痛程度"作为短期评价指标和术后半年治疗效果作为长期评价指标进行比较,采用X2检验进行统计分析。结果:与普通注射器冲洗方法相比,超声冲洗方法可以明显减低一次性根管治疗后短期不适症状的发生率(P0.05),特别是重度反应的发生(P0.05);而术后出现的轻度和中度疼痛反应无明显差异。同时,超声冲洗方法可以明显增加一次性根管治疗术的长期成功率(P0.05)。结论:一次性根管治疗术中使用超声冲洗方法替代常规注射器冲洗方法,能够明显减轻患者短期术后以"疼痛"为主要表现的不适症状,提高一次性根管治疗术在瘘管型根尖周治疗中的长期成功率,是一种较为理想的根管治疗冲洗方法。     

Ultrastructural shape and three-dimensional organization of the intracuticular canal systems in the mineralized cuticle of the green crab Carcinus maenas

Two main self-contained canal systems are present in the crab mineralized cuticle. The first, or fibre canal system, is constituted by simple, unbranched vertical canals containing axially running fibres in close association with myoepidermal junctions. The second, or pore canal system, is composed of procuticular pore canals and epicuticular channels that prolong the procuticular canals. In opposition to widespread opinion, pore canals make up a three-dimensional branched system extending from the apical plasma membrane of the epidermis up to the epicuticle. Branching occurs by projections of lateral horizontal from the vertical canals at the lower level of the pigmented layer and by innumerable ramifications of epicuticular canals. In agreement with Neville's model for insects, vertical procuticular pore canals of crustacean mineralized cuticle, and also fibre canals, exhibit a twisted ribbon structure reflecting the helicoidal arrangement of the horizontal chitin-protein microfibrils.     

Localization of digestion activities in polyps ofNausithoe planulophora andThecoscyphus zibrowii (Coronatae, Scyphozoa, Cnidaria)

Coronate polyps are unique among cnidarians in having a complete peridermal tube, a ring canal, and four radial canals or pores at their oral region. Moreover, most of these species possess tooth whorls that narrow the gastric cavity considerably. Using fluorescence-labeled prey, it was demonstrated that the ring canal is not involved in digestion or redistribution of nutrients but possibly serves as a hydrostatic flex point for the fast retraction of the tentacle crown into the exoskeleton. The tooth whorls considerably affect the localization of digestion activities by blocking the passage of large prey fragments. Hence, endocytosis in a coronate species with tooth whorls occurred around the uppermost tooth whorl whereas, in a species lacking tooth whorls endocytosis occurred at the basal end. To meet the high nutrient demands of the basal region, nutrients must be redistributed in the species with tooth whorls. The extra energy required for this redistribution could be an important disadvantage of tooth whorls.     

Detection of Treponema denticola in root canal systems in primary and secondary endodontic infections. A correlation with clinical symptoms

AIM: The aim of the study was to investigate the presence of Treponema denticola in primary and secondary root-infected canal systems with periapical pathology and correlations with clinical signs and symptoms. METHODOLOGY: Endodontic samples were obtained from canals of 102 teeth: 79 had primary endodontic disease and 23 secondary endodontic disease. For each tooth, clinical data including symptoms and X-ray appearance were examined. The presence of T. denticola biological samples from the root canal space was detected by a PCR assay. RESULTS: T. denticola was detected in 24 out of the 79 teeth with primary infection and in 8 out of the 23 teeth with secondary infection. Teeth with specific clinical symptoms were frequently associated with T. denticola presence inside the root canal system. CONCLUSIONS: The presence of T. denticola in root canal system in association with specific clinical signs and symptoms of endodontic disease strongly suggests that this spirochete might play a critical role in the pathogenesis of the acute infection and rapid bone tissue alterations in both primary and secondary endodontic infections.     

The Sensory Canal Systems of the Living Coelacanth, Latimeria Chalumnae: A New Instalment

Entire sensory canal systems of the coelacanth, Latimeria chalumnae, are described: not only the course of principal canals with their primary and secondary collaterals, but also the course and branches of the pit-line and reticular canals. The number of pores on the left side of the head were found to be 296 in an early (yolksac) embryo, 321 in a late term fetus, 485 in a juvenile, and 2974 in adults. This means that in latimeria most of the lateral-line canal system develop after parturition. Pit lines of the living coelacanth are not rows of superficial neuromasts but canals covered by a thin epidermis like in other sensory canals of the lateral line. These pit-line canals, however, have a very specific structure and branching pattern: the medial dorsal pit-line canal is connected by fine branches on top of the head. The infra-dentary pit-line canal connects via these branches with canals deep inside the bones. Several fine and richly branched canaliculi of unknown function radiate from each quadratojugal pit-line canal. The gular plate pit-line canal has superficially branching arms as well as connections to numerous deeper canals inside the bone. These canals consist of fine branches that in turn lead to and open on the ventral surface of the gular plates as small pores. The system is reminiscent of the reticular (pore) canal system known only from some fossil agnathans and fishes. Thus latimeria combines the reticular system of ancient vertebrates with the lateral-line system of modern fishes. The significance of this gular (possibly electro-sensory) system for feeding by the coelacanth will be discussed.     

Support Immersion Endoscopy in Post-Extraction Alveolar Bone Chambers: A New Window for Microscopic Bone Imaging In Vivo

Using an endoscopic approach, small intraoral bone chambers, which are routinely obtained during tooth extraction and implantation, provide visual in vivo access to internal bone structures. The aim of the present paper is to present a new method to quantify bone microstructure and vascularisation in vivo. Ten extraction sockets and 6 implant sites in 14 patients (6 men / 8 women) were examined by support immersion endoscopy (SIE). After tooth extraction or implant site preparation, microscopic bone analysis (MBA) was performed using short distance SIE video sequences of representative bone areas for off-line analysis with ImageJ. Quantitative assessment of the microstructure and vascularisation of the bone in dental extraction and implant sites in vivo was performed using ImageJ. MBA revealed bone morphology details such as unmineralised and mineralised areas, vascular canals and the presence of bleeding through vascular canals. Morphometric examination revealed that there was more unmineralised bone and less vascular canal area in the implant sites than in the extraction sockets.     

Viperous fangs: development and evolution of the venom canal

Fangs are specialised long teeth that contain either a superficial groove (Gila monster, Beaded lizard, some colubrid snakes), along which the venom runs, or an enclosed canal (viperid, elapid and atractaspid), down which the venom flows inside the tooth. The fangs of viperid snakes are the most effective venom-delivery structures among vertebrates and have been the focus of scientific interests for more than 200 years. Despite this interest the questions of how the canal at the centre of the fang forms remains unresolved. Two different hypotheses have been suggested. The mainstream hypothesis claims that the venom-conducting canal develops by the invagination of the epithelial wall of the developing tooth germ. The sides of this invagination make contact and finally fuse to form the enclosed canal. The second hypothesis, known as the "brick chimney", claims the venom-conducting canal develops directly by successive dentine deposition as the tooth develops. The fang is thus built up from the tip to the base, without any folding of the tooth surface. In an attempt to cast further light on this subject the early development of the fangs was followed in a pit viper, Trimeresurus albolabris, using the expression of Sonic hedgehog (Shh). We demonstrate that the canal is indeed formed by an early folding event, resulting from an invagination of epithelial cells into the dental mesenchyme. The epithelial cells proliferate to enlarge the canal and then the cells die by apoptosis, forming an empty tube through which the poison runs. The entrance and discharge orifices at either end of the canal develop by a similar invagination but the initial width of the invagination is very different from that in the middle of the tooth, and is associated with higher proliferation. The two sides of the invaginating epithelium never come into contact, leaving the orifice open. The mechanism by which the orifices form can be likened to that observed in reptiles with an open groove along their fangs, such as the boomslang. It is thus tempting to speculate that the process of orifice formation in viperids represents the ancestral pleisomorphic state, and that enclosed canals developed by a change in the shape and size of the initial invagination.     

A direct comparison between extracted tooth and filter-membrane biofilm models of endodontic irrigation using Enterococcus faecalis

Endodontic restorations often fail due to inadequate disinfection of the root canal even though the antimicrobial irrigants used have been shown to be capable of killing the bacterium frequently implicated in this complication, Enterococcus faecalis (Ef). Extracted human teeth were root-prepared and filled with a liquid culture of Ef. Following incubation, the root canals were irrigated with 1% sodium hypochlorite (NaOCl), electrochemically activated water or saline control. Irrigation was modelled using an electronic pipette to deliver the solutions at a reproducible flow velocity. A series of parallel experiments employed a membrane biofilm model that was directly immersed into irrigant. Experimental conditions where contiguous between the extracted tooth model and biofilm model wherever possible. After 60 s of exposure, 1% NaOCl effectively sterilised the biofilm model, whereas log 3.36 viable Ef where recoverable from the analogous extracted tooth model, the other irrigants proved ineffective. Biofilms of Ef were susceptible to concentrations of irrigant that proved ineffective in the tooth model. NaOCl was the most effective biocide in either case. This suggests that the biofilm modality of bacterial growth may not be the most important factor for the recalcitrance of root canal infections during endodontic irrigation; it is more likely due to the inability of the irrigant to access the infection.     

The Evolution of Bat Vestibular Systems in the Face of Potential Antagonistic Selection Pressures for Flight and Echolocation

The vestibular system maintains the body’s sense of balance and, therefore, was probably subject to strong selection during evolutionary transitions in locomotion. Among mammals, bats possess unique traits that place unusual demands on their vestibular systems. First, bats are capable of powered flight, which in birds is associated with enlarged semicircular canals. Second, many bats have enlarged cochleae associated with echolocation, and both cochleae and semicircular canals share a space within the petrosal bone. To determine how bat vestibular systems have evolved in the face of these pressures, we used micro-CT scans to compare canal morphology across species with contrasting flight and echolocation capabilities. We found no increase in canal radius in bats associated with the acquisition of powered flight, but canal radius did correlate with body mass in bat species from the suborder Yangochiroptera, and also in non-echolocating Old World fruit bats from the suborder Yinpterochiroptera. No such trend was seen in members of the Yinpterochiroptera that use laryngeal echolocation, although canal radius was associated with wing-tip roundedness in this group. We also found that the vestibular system scaled with cochlea size, although the relationship differed in species that use constant frequency echolocation. Across all bats, the shape of the anterior and lateral canals was associated with large cochlea size and small body size respectively, suggesting differential spatial constraints on each canal depending on its orientation within the skull. Thus in many echolocating bats, it seems that the combination of small body size and enlarged cochlea together act as a principal force on the vestibular system. The two main groups of echolocating bats displayed different canal morphologies, in terms of size and shape in relation to body mass and cochlear size, thus suggesting independent evolutionary pathways and offering tentative support for multiple acquisitions of echolocation.     

Perspectives for the comprehensive examination of semicircular canal and otolith function.

A review is presented on the three-dimensional aspects of the vestibulo-oculomotor system and the current functional tests for unilateral examination of the individual receptors in the vestibular labyrinth. In the presentation, attention is directed towards the recently developed vestibular tests, which promise a more comprehensive examination of labyrinth function. More explicitly, unilateral tests for the utricle, saccule and the individual semicircular canals are discussed. Caloric irrigation and rotatory testing are widely used as tests for the integrity of the (horizontal) semicircular canals. Little useful diagnosis is made however on the vertical canals, not to mention the otolith organs. A promising approach to the examination of individual semicircular canal function has been described. This involves the perception of self-rotation in each of the planes of the semicircular canals. The patient/subject is rotated by an arbitrary amount on a standard Barany chair and then required to return the chair to its original position, by joystick control of the chair velocity. In order to test the vertical canals, the head of the subject/patient is positioned so that the plane of each canal lies in the plane of rotation. A promising unilateral test of saccular function involves the use of vestibular evoked myogenic potentials. Here it has been demonstrated that the saccules can be activated using brief, high-intensity acoustic clicks. The myogenic potential is measured using surface electrodes over the sternocleidomastoid muscles. Initial data from patients has indicated that the test is specific for unilateral saccule disorders. The unilateral test of utricle function is based on the eccentric displacement profile. Thus, eccentric displacement of the head to 3.5 cm during constant velocity rotation about the earth-vertical axis generates an adequate unilateral stimulation of the otolith organ, without involving the semicircular canals. This paradigm has also proved efficient in localizing peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing. In contrast to the otolith-ocular response, the subjective visual vertical also reflects the processing of otolithic information in the higher brain centres (thalamus, vestibular cortex). Exploitation of the two complementary approaches therefore provides useful information for both experimental and clinical scientists. Of direct interest is the finding that testing with the subject rotating on-centre is sufficient to localize peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing. In addition to caloric testing, which has remained the classical unilateral test of vestibular function, the newly developed tests should improve the differential diagnosis of vestibular disorders.     

F-actin rings are associated with the ring canals of the Drosophila egg chamber

Staining of Drosophila egg chambers with rhodaminyl-lysine-phallotoxin (RLP), a specific stain for F-actin, has demonstrated the presence of dense F-actin rings associated with the inner surfaces of the ring canals. They were first observed in the distal part of the germarium where rings of four different size classes were found, differing in diameter by up to twofold. The ring sizes are considered to correspond to the ring canals formed at each of four successive incomplete cleavages. During the growth of the egg chamber the actin rings were found to increase in diameter from less than 1 micron to approx. 10 micron. Concomitantly a secondary outer ring of more diffuse material is built up in association with the cell membranes. A well developed array of microfilament bundles was also associated with the nurse cell plasmalemma. In stages where the transfer of the bulk of the nurse cell cytoplasm into the oocyte was occurring the rings came closer together in a central area. In late stage chambers the F-actin rings and the microfilament bundles appeared to be incorporated into large irregular masses of actin, which subsequently disappeared as the mature oocyte formed. The F-actin rings are suggested to act as mechanical strengthening elements for the canal plasmalemma, whilst cytoplasmic transport occurs through the ring canals.     

Development of the cartilage canals and the secondary center of ossification in the distal chondroepiphysis of the prenatal human femur.

The cartilaginous epiphysis of the distal femur is vascularized by a network of cartilage canals during prenatal development. The vascular invasion of the epiphysis begins at approximately eight to ten weeks of gestation with the initiation of cartilage canal formation. A complex vascular system develops within the canals and is well defined by fourteen weeks of gestation. The vascular system is fully developed several months prior to the development of the secondary center of ossification. The formation of the secondary center of ossification within the distal femoral epiphysis is preceded by changes that occur simultaneously within both the chondrocytes in the central portion of the epiphysis and the vascular and perivascular elements contained within the cartilage canals in the central portion of the epiphysis. These concurrent changes in the cellular morphology of the central chondrocytes and in the cellular structure of the central cartilage canals appear to be linked with the initiation of the process of osteogenesis.     

The functional significance of lateral line canal morphology on the trunk of the marine teleost Xiphister atropurpureus (Stichaeidae)

We investigated the filter properties of the highly branched trunk lateral lines of the stichaeid Xiphister atropurpureus and compared them to the filter properties of simple lateral line canals. For this purpose artificial canals were constructed, some of which were fitted with artificial neuromasts. In still water, the response of a simple canal versus two types of Xiphister-like canals to a vibrating sphere stimulus were similar, as was the decrease in the responses as a function of sphere distance. Also comparable was the mechanical coupling between neighboring parts of the main canal. However, compared to the simple canal, the Xiphister-like canals showed a lower spatial resolution. Equipping artificial lateral line canals with artificial neuromasts revealed that Xiphister-like canals, i.e., lateral lines canals with tubuli that contained widely spaced pores, improve the signal-to-noise ratio in a highly turbulent environment. Even though a reduced spatial resolution is the price for this improvement, Xiphister may compensate for this compromise by having four instead of the usual single trunk lateral line canal. We suggest that lateral line canals with tubuli that contain widely spaced pores and multiple lateral line canals on each body side are an adaptation to a highly turbulent aquatic environment.     

Trophic ecology and reproductive aspects of Trichomycterus areolatus (Pisces, Trichomycteridae) in irrigation canal environments

Twelve of the sixteen species of fishes present in the Itata river basin enter the irrigation canals at least once a year, constituting a habitat that is frequently utilized by the native fish assemblages. However, only Trichomcterus areolatus, a native siluriform, is found in great number throughout the entire year, being the dominant species of such artificial environments. Among the factors that could explain the relative success of T. areolatus are its benthonic habits, adaptation to rithral habitat, an offer of trophic resources that is in line with its feeding habits, and a lower abundance of predators in the canals. In this study, the trophic ecology of this species in 174 individuals inhabiting the Itata river (Octava Región, Chile) and 231 from irrigation canals that arise from this river are analyzed and compared. In addition, the length-weight relationship and seasonal frequencies of reproductive status are analyzed, with the purpose of inferring on the status of these populations and their possible condition of resident in these canals. In canals, its diet includes a greater number of different taxa as well as total number of preys consumed in comparison with the river populations, including items of greater biomass, such as lumbriculides. The selectivity analysis showed that T. areolatus prefer prey items like Chironomidae, Baetidae, Elmidae, Plecoptera and Hyallela. Although both the river as well as canal populations show an isometric type growth, they reach greater body lengths and weights in the latter. According to the reproductive states analysis in different periods of the year, populations inhabiting canal environments reproduce synchronically with those of the river, although these latter tend to show a slight delay in the reproductive activity.     

机用ProTaper 进行恒磨牙根管预备的临床评价

目的:评价机用ProTaper镍钛根管器械进行恒磨牙根管预备的临床疗效。方法:2007年7月至2010年12月期间就诊的需进行根管治疗的109患者,共计128颗磨牙,包括牙髓炎54颗牙,慢性根尖周炎74颗牙。按随机配对原则分入实验组和对照组,每组64颗牙。实验组用机用ProTaper镍钛根管锉预备根管,对照组用不锈钢K型锉预备根管。两组均采用侧向加压法充填根管,记录每颗患牙的单个根管预备所用时间、根管充填效果、术后不良反应及随访到的远期疗效。结果:机用ProTaper镍钛器械预备单根管所耗时间明显少于对照组,根管预备后疼痛发生率明显低于对照组,根管适充率实验组明显优于对照组,根管治疗术后1年疗效比较也优于对照组。结论:使用机用ProTaper器械进行恒磨牙根管预备快速有效,根充效果好,并发症发生率低,远期疗效确切,值得临床推广。     

The significance of lenticels for successful<Emphasis Type="Italic"> Pityogenes chalcographus</Emphasis> (Coleoptera: Scolytidae) invasion of Norway spruce trees [<Emphasis Type="Italic">Picea abies</Emphasis> (Pinaceae)]

In this study we tested whether Pityogenes chalcographus L. beetles preferably infest their host tree, Picea abies (L.) Karst., through lenticels or not. In a second step the resin canal system, which is important for defence against bark beetles, was investigated under lenticels and under lenticel-free periderm. Beetle colonisation tests on breeding logs resulted in 93.2% successful invasions through lenticels, 4.2% through lenticel-free periderm, 1.2% through wounds, and 1.4% near branches (n=1,606). Three main reasons why beetles invade preferable sites are discussed, taking the function of lenticels to supply gas exchange of the interior tissues into consideration. First, attractive volatiles are more easily detectable over the lenticels, and this could be a stimulus for the bark beetles to invade their hosts through these structures. Secondly, the very loosely arranged tissues of the lenticel and bigger intercellular spaces in the cortex and secondary phloem under the lenticel permit the beetles easier movement towards the vascular cambium. Thirdly, the total resin canal area of both primary and secondary canals and the number of secondary resin canals were reduced under lenticels. A higher resin canal density beneath lenticels would constitute a barrier to gas movement.     

Comparative Anatomy of Resin Canals of the Needles of Picea Grown in China

The comparative anatomy of the leaves of 21 species and 5 varieties of the genus Picea has been investigated with special reference to their resin canals. Resin canals are found in the needles of all Picea species under study. They are always arranged in longitudinal series, mostly being interrupted by transverse partitions of mesophyll except in a few species where they exhibit two disinterrupted canals. The number of the canal segments in a needle is quite variable in different species, and even in different needles of the same species. Their arrangement, according to the frequency of the occurrence of two-canals, one-canal and no canal in the middle transection of the needles and from the observation of the clearing specimens, can be classified into four groups (fig. 1). It would seem preferable that the characteristic difference of the resin canals, which might be of texonomic importance, lie in their discrepancy in the relative distribution of the resin canals rather than in the number or the relative length of the canals in each needle. This study also suggests that those with two canals lying along the lateral angles of the needles might be considered as the primitive types, from which other forms have been derived. Long canals may be broken into short cystic segments or subsequently degenerated into residue canals located only on one side of the needles.