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PubMedDate not supplied

Hyperpolarizing dorsal root potentials recorded from single fibres of the dorsal root in the cat.

In non-anaesthetized spinal cats hyperpolarizing dorsal root potentials (DRPs) were recorded from single fibres of the dorsal root. They were evoked by volleys in saphenous and quadriceps nerves activating group II muscle afferents and cutaneous A afferents. Hyperpolarizing DRPs were most frequently encountered in fibres originating from muscle receptors. Their frequency was lower in fibres from deep receptors, from low threshold mechanoreceptors and from mechanical nociceptors. The amplitude of hyperpolarizing DRP was related to the modality of fibres from which DRP was recorded. During conditioning the time course of depression of testing hyperpolarizing DRP recorded from muscle receptor fibres did not exceed 100 msec. Hyperpolarization produced by repetitive stimulation was maintained in muscle afferent fibres but subsided to zero in fibres from low threshold mechanoreceptors.

Action Potentials↗
PubMed1975

Ultrastructure of dorsal root projections in the toad spinal cord. An experimental neuroanatomical study following transection of dorsal root.

The distribution and the modalities of termination of the dorsal root afferents in the toad spinal cord have been investigated. The morphological changes of degenerating fibres and boutons at different survival times after root transection have been followed. Degenerating boutons were clearly identified due to the occurrence of both the dark and the filamentous types of degeneration similar to that described in cats. Most of the central endings of the primary afferents terminated in the dorsal horn of the spinal cord; however, degenerating boutons were also observed in the ventral horn region of the gray matter. The density of the degenerating elements located in the ventral gray was always lower than that observed in the dorsal horn. Dark and filamentous boutons which were present in the motoneuronal region, did not appear to be in synaptic contact with the soma of the motoneurons.

Animals↗
PubMed1995

[The neurite-outgrowth promoting effect from Clarke's nucleus of cat spinal cord with spared dorsal root preparation under electro-acupuncture stimulation on dorsal root ganglion of chicken embryo].

A modification of the double-coverslip hanging-drop culture technique originated from Maximow was introduced in the present report. The neurite - outgrowth promoting effect from Clarke's nucleus of cat spinal cord with partially lumbosacral dorsal rhizotomy as well as acupuncture stimulation of the points located within the peripheral innervating field of the spared dorsal root was examined with the modified culture technique. Findings demonstrated that an increased neurite-outgrowth promoting effect appeared in Clarke's nucleus of cat spinal cord with partial deafferentation, and that electro-acupuncture stimulation could enhance the neurite-outgrowth promoting effect further. It suggested that the increment of the neurite-outgrowth promoting effect might be related to the collateral sprouting of spared dorsal root and to the sprouting-promotion effect of acupuncture stimulation.

Animals↗
PubMed1978

Submergence of roots for alveolar bone preservation. I. Endodontically treated roots.

Mandibular premolars in four dogs were endodontically treated and then totally submerged. Histologic and radiographic findings showed that this procedure should be considered as an alternative to extraction of key teeth in an effort to preserve alveolar bone. 1. Periodic follow-up on this procedure should be done to rule out cystic formation. 2. Beveling the coronal portion to the buccal is advocated to compensate for the thin buccal plate. 3. The procedure should be done in two steps to allow the root canal sealer to set, or an amalgam should be placed over the pulp canal. 4. New cementum and connective tissue will form over the coronal surface separating the dentin from new bone.

Alveolar Process↗
PubMed1995

A comparison of three different root canal sealers when used to obturate a moisture-contaminated root canal system.

Sealing ability of three classes of endodontic sealers, in moisture-contaminated canals, was evaluated. A total of 120 single-rooted extracted teeth were divided into three groups. The groups were obturated with either Procosol, Sealapex, or Ketac-Endo using saline as a moisture contaminant in all cases. Half (20 teeth) of each group was placed in a saline storage medium for 9 months. The remainder of the samples were placed in India ink, under a vacuum, cleared, and the amount of dye penetration measured under magnification. The stored samples were similarly treated after the 9-month storage period. In a moisture-contaminated canal, Procosol exhibited the least amount of apical leakage, followed by Sealapex, then Ketac-Endo. There was no significant difference in the amount of dye penetration after 9 months of storage over that found initially, which indicates that the deleterious effects of moisture contamination occur during the initial placement and setting reaction.

Analysis of Variance↗
PubMed1994

Assessment of coronal leakage in teeth root filled with gutta-percha and a glass of ionomer root canal sealer.

The effect on coronal leakage of the use of either a single gutta-percha cone or cold lateral condensation of gutta-percha, with a glass ionomer sealer cement was studied. In addition, the effect of the removal of the smear layer was also determined. Eighty-eight single-rooted teeth were prepared chemomechanically using hand files, with the balanced force technique. Lubrication was provided by either Hibiscrub (maintaining the smear layer) or an EDTA-containing paste (to remove the smear layer). Copious irrigation was carried out with 2.2% sodium hypochlorite. The teeth were allocated randomly to four groups of 20 teeth each, the remaining eight teeth served as controls. Two groups of teeth, one with and one without smear layer, were obturated with either a single gutta-percha cone or cold laterally condensed gutta-percha, with Ketac Endo as the sealer. The teeth were stored for 6 weeks, thermocycled, and the extent of coronal leakage determined for each group after immersion in India ink for 90 h. The teeth were demineralized, dehydrated and immersed in methyl salicylate, which rendered them transparent. Linear measurement of maximum dye penetration was recorded. The mean depth (+SD) of leakage for the groups in which the smear layer was left intact was 1.68 mm (+0.38) for the single cone (A1) and 2.29 mm (+1.58) for lateral condensation (B1). When the smear layer was removed the mean depth of leakage for the single cone group (A2) was 2.04 mm (+0.73) and 2.37 mm (+1.70) for the laterally condensed group (B2). There was no significant difference in coronal leakage between the groups (P > 0.05).

Dental Leakage↗
PubMed1996

Variation in the microleakage produced by four different techniques in root fillings in a simulated root canal model.

An in-vitro investigation was performed to assess the extent of apical microleakage in simulated canals in clear resin blocks. Four different methods of producing dye penetration were employed: passive dye penetration alone, centrifugation alone, vacuum plus passive dye penetration, and increased pressure plus passive dye penetration. Forty simulated root canals were prepared and obturated. The specimens were randomly allocated into four groups and each group was subjected to a different leakage technique using methylene blue dye as the detector. The maximum apical dye penetration observed through each of the four faces of the blocks was recorded. There were large variations in the leakage recorded in each individual specimen and between the specimens within each group. There were statistically significant differences between passive dye penetration and each of the other three techniques. There was no significant differences between the centrifugation, vacuum and pressure techniques.

Analysis of Variance↗
PubMed2005

The removal of gutta-percha and root canal sealers from root canals.

The removal of gutta-percha from root-filled teeth is required for re-treatment of failed endodontic treatment and to prepare a space for placement of a post. Complete removal of filling material and sealer is a requirement for success. A review was undertaken of the current literature on methods of gutta-percha and sealer removal. Clinical recommendations based on current evidence are included. A combination of methods may be required to remove filling materials effectively.

Gutta-Percha↗
PubMed2005

[Root canal preparation: shaping and cleaning of the root canal].

Primary shaping is of paramount importance for a succesfull root canal treatment. In this article the basis principles of apical terminus location, shape, size and diameter are discussed. The use of NiTi instruments and crown-down preparation techniques are explained.

Dental Instruments↗
PubMed2005

Comparative evaluation of the preparation efficacies of HERO Shaper and Nitiflex root canal instruments in curved root canals.

OBJECTIVES: To comparatively evaluate the shaping efficacies of HERO Shaper rotary instruments and Nitiflex hand files. STUDY DESIGN: The mesial roots of 40 mandibular molars were used. In 20 teeth, the mesiobuccal canals were instrumented with HERO Shaper and the mesiolingual canals with Nitiflex. In the remaining 20 teeth, the mesiobuccal canals were instrumented with Nitiflex and the mesiolingual canals with HERO Shaper. Pre- and postoperative sections were obtained from the coronal, middle, and apical portions and analyzed. Statistical analysis was performed using the Student t test. RESULTS: More dentin was removed from the middle portion with HERO Shaper (P < .05). No statistically significant difference was observed in terms of transportation (P>.05). No instrument fracture or deformation was noted. CONCLUSIONS: Both HERO Shaper and Nitiflex can be recommended for clinical practice. Further studies can focus on the comparison of HERO Shaper with other rotary instruments as there is an increasing trend for the utilization of these systems.

Dental Alloys↗
PubMed1996

Effect of power settings on temperature change at the root surface when using a Holmium YAG laser in enlarging the root canal.

The aim of this study was to determine the maximum amount of power, in watts, that a Holmium YAG laser could deliver via a 245-micron fiberoptic to the canal surface and still not raise the temperature (delta T) of the cementum by > 5 degrees C. Sixty single-rooted teeth were divided into three groups according to power selection (0.50, 0.75, and 1.00 W). The three main outcome variables were: change in apical temperature, change in coronal temperature, and maximum size of an endodontic file that could fit into the canal after lasing. The group means for apical delta T were: 1.00 W = 2.2 degrees C, 0.75 W = 2.68 degrees C, and 0.50 W = 1.58 degrees C. The group means for coronal delta T were: 1.00 W = 1.15 degrees C, 0.75 W = 0.99 degree C, and 0.50 W = 0.56 degree C. The group means for file size were: 1.00 W = 41.25, 0.75 W = 38.75, and 0.50 W = 40.75. The canal size was increased from a size 25 file up to approximately a size 40 file with all power groups. There were no significant differences between the groups for change in apical temperature (p = 0.32), coronal temperature (p = 0.17), or maximum file size (p = 0.86) when adjustments were made for tooth dimensions. In all groups studied, the delta T was < 5 degrees C. This represents a safe and predictable laser procedure.

Analysis of Variance↗
PubMed1998

Root development: new meanings for root canals?

During Arabidopsis root development, a radial pattern of tissues is extended by the meristem. These tissues form continuous layers and recent data suggest that tissue continuity is instrumental for constraining the direction of signaling in a process termed channeling. In the ground tissue, fate-determining signals originate from contiguous cells of the same layer, possibly due to specific symplastic connections. Mutant analysis supports the hypothesis that vascular tissue continuity may facilitate and depend on the directional transport of a vascular fate-determining signal, possibly the phytohormone auxin.

Arabidopsis↗
PubMed1991

The influence of different root canal instruments on root canal preparation: an in vitro study.

Nine endodontic instruments from different manufacturers (Reamers, K-files, Hedstrom files, K-Flex files, Flexofiles, S-files, Burns Unifiles, Flexicut files and Flex-R files) were used to prepare 180 simulated root canals in resin blocks. The instrument's ability to reproduce a theoretical pre-established ideal canal shape was assessed by comparing the original canal path with the resulting enlarged canal shape by a double exposure photographic method. The individual ability of each instrument to transport debris was also observed during instrumentation under a stereomicroscope. Regardless of the instrument type, none was able to reproduce ideal results; however, clinically acceptable results could be obtained with all of them. The coronal and apical debris transportation characteristics proved to be similar with all instruments.

Root Canal Therapy↗
PubMed2001

Apomictic, polyphagous root-knot nematodes: exceptionally successful and damaging biotrophic root pathogens.

Most apomictic root-knot nematodes (RKN; Meloidogyne spp.) have host ranges that encompass the majority of flowering plants, and M. incognita is possibly the world's most damaging crop pathogen. The ancestors, age, and origins of the polyphagous RKN are obscure, but there is increasing evidence that M. incognita, M. javanica, and M. arenaria are closely related, heterogeneous species with a recent, hybrid (reticulate) origin. If so, they must owe much of their current worldwide distributions to spread by agriculture. Host resistance appears to be generally durable in the field, but laboratory studies suggest that apomixis does not prevent evolution in response to selection by a parasitic bacterium (Pasteuria penetrans) and host resistance. Maintaining general fitness may be the evolutionary priority for most populations of polyphagous RKN, and a wide host range, important in the field but not in the laboratory, may be conserved by apomixis. Several factors may help confer a wide host range, including suppression of host resistance, perhaps as a consequence of the strength of the induced susceptible response. Resistance genes effective against RKN appear not to have resulted from coevolution. Rates of juvenile invasion and/or development are low in many wild and some crop plants, with the result that they are both poor hosts and sustain less damage. Overall, it is suggested that greater coordination, particularly of fundamental research, is required.

Animals↗
PubMed2002

Role of a positive regulator of root hair development, CAPRICE, in Arabidopsis root epidermal cell differentiation.

In Arabidopsis, root hairs are formed only from a set of epidermal cells named trichoblasts or hair-forming cells. Previous studies showed CAPRICE (CPC) promotes differentiation of hair-forming cells by controlling a negative regulator, GLABRA2 (GL2), which is preferentially expressed in hairless cells. Here, we show that CPC is also predominantly expressed in the hairless cells, but not in the neighboring hair-forming cells, and that CPC protein moves to the hair-forming cells and represses the GL2 expression. We also show that the N terminus of bHLH protein interacts with CPC and is responsible for the GL2 expression. We propose a model in which CPC plays a key role in the fate-determination of hair-forming cells.

Arabidopsis↗
PubMed1988

[Periodontal surgical approach to the vertical fracture of the root. The application of composite resin to the fractured root surface].

For a patient who had a deep periodontal pocket without an attached gingiva on labial central area of left upper canine, a free gingival graft from the palate was done. After that, a flap was reflected and the cause of the lesion was determined. It became clear that there was a vertical fracture of the root and a composite resin (Clearfil-SC) was used to fill the fractured area. It has been 2 1/2 years since the therapy and the prognosis is good.

Gingiva↗