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Ceyhanli, K. Tolga, Murat Turkun, Necdet Erdilek, Cem Peskersoy et Timur Kose. « Evaluation of the apical adaptation performance of various root canal instruments ». European Journal of Dentistry 07, S 01 (septembre 2013) : S041—S044. http://dx.doi.org/10.4103/1305-7456.119070.
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ABSTRACT Objective: The aim of this study was to evaluate the apical root canal adaptation performance of various root canal instruments. Materials and Methods: A total of 40 freshly extracted single-rooted mandibular incisors were used in this study. Coroner parts of all teeth were removed from cemento-enamel junction and root canal of each tooth was explored with a size 8 K-file until the tip of the file was just visible at the apex. Working lengths (WLs) were determined as 1 mm short of these measurements. ProTaper, K-file, profile and hedstroem files were inserted into the root canals of 10 teeth to the WL following the flaring of the coronal and middle thirds. Instruments were fixed in the root canals with acrylic resin. The apical 1 mm of each root tip was ground on wet sandpaper to expose the canal and the instrument at the WL and the apical region of each tooth was examined under stereomicroscope. The stereoscopic images of the teeth were digitized and analyzed with software in order to determine the differences between the areas of root canals and file tips. Result data were analyzed using the one-way analysis of variance test (p = 0.05). Results: There were no significant differences between apical file/root canal areas of the evaluated instruments (p > 0.05). Conclusions: None of the evaluated instruments performed a perfect adaptation with the apical root canal surface at the WL in mandibular incisors. Therefore, total removal of the debris from the apical canal surface may not be achieved when these filing instruments are used.
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Lewis, Richard F., Wangsong Gong, Mitchell Ramsey, Lloyd Minor, Richard Boyle et Daniel M. Merfeld. « Vestibular adaptation studied with a prosthetic semicircular canal ». Journal of Vestibular Research 12, no 2-3 (27 juin 2003) : 87–94. http://dx.doi.org/10.3233/ves-2003-122-304.
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We have developed and tested a prosthetic semicircular canal that senses angular head velocity and uses this information to modulate the rate of current pulses applied to the vestibular nerve via a stimulating electrode. In one squirrel monkey, the lateral canals were plugged bilaterally and the prosthesis was secured to the animal's head with the angular velocity sensor parallel to the axis of the lateral canals. In the first experiment, the stimulating electrode was placed near the ampullary nerve of one lateral canal. Over a period of two weeks, the gain of the horizontal VOR during yaw axis rotation gradually increased, although the response magnitude remained relatively small. In the second experiment, the stimulating electrode was placed near the ampullary nerve of the posterior canal, but the orientation of the velocity sensor remained parallel to the axis of the lateral canals. Over a one-week period, the axis of the VOR response gradually shifted towards alignment with the (yaw) axis of head rotation. Chronic patterned stimulation of the eighth nerve can therefore provide adequate information to the brain to generate a measurable VOR response, and this can occur even if the prosthetic yaw rotation cue is provided via a branch of the VIIIth nerve that doesn't normally carry yaw rotational cues. The results provided by this pilot study suggest that it may be feasible to study central adaptation by chronically modifying the afferent vestibular cue with a prosthetic semicircular canal.
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Chen, Huan, Xinyuan Zhao, Yu Qiu, Dengyou Xu, Li Cui et Buling Wu. « The Tubular Penetration Depth and Adaption of Four Sealers : A Scanning Electron Microscopic Study ». BioMed Research International 2017 (2017) : 1–8. http://dx.doi.org/10.1155/2017/2946524.
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Background. The tubular penetration and adaptation of the sealer are important factors for successful root canal filling. The aim of this study was to evaluate the tubular penetration depth of four different sealers in the coronal, middle, and apical third of root canals as well as the adaptation of these sealers to root canal walls. Materials and Methods. 50 single-rooted teeth were prepared in this study. Forty-eight of them were filled with different sealers (Cortisomol, iRoot SP, AH-Plus, and RealSeal SE) and respective core filling materials. Then the specimens were sectioned and scanning electron microscopy was employed to assess the tubular penetration and adaptation of the sealers. Results. Our results demonstrated that the maximum penetration was exhibited by RealSeal SE, followed by AH-Plus, iRoot SP, and Cortisomol. As regards the adaptation property to root canal walls, AH-Plus has best adaptation capacity followed by iRoot SP, RealSeal SE, and Cortisomol. Conclusion. The tubular penetration and adaptation vary with the different sealers investigated. RealSeal SE showed the most optimal tubular penetration, whereas AH-Plus presented the best adaptation to the root canal walls.
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Remy, Vimal, Vineesh Krishnan, Tisson V. Job, Madhavankutty S. Ravisankar, CV Renjith Raj et Seena John. « Assessment of Marginal Adaptation and Sealing Ability of Root Canal Sealers : An in vitro Study ». Journal of Contemporary Dental Practice 18, no 12 (2017) : 1130–34. http://dx.doi.org/10.5005/jp-journals-10024-2188.
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ABSTRACT Aim This study aims to compare the marginal adaptation and sealing ability [mineral trioxide aggregate (MTA)-Fillapex, AH Plus, Endofill sealers] of root canal sealers. Materials and methods In the present study, the inclusion criteria include 45 single-rooted extracted mandibular premolar teeth, with single canal and complete root formation. The sectioning of the samples was done at the cementoenamel junction using a low-speed diamond disc. Step-back technique was used to prepare root canals manually. The MTA-Fillapex, AH Plus, and Endofill sealers were the three experimental sealer groups to which 45 teeth were distributed. Under scanning electron microscope (SEM), marginal gap at sealer and root dentin interface were examined at coronal and apical halves of root canal. Results Among the three maximum marginal adaptations were seen with AH Plus sealer (4.10 ± 0.10) which is followed by Endofill sealer (1.44 ± 0.18) and MTA-Fillapex sealer (0.80 ± 0.22). Between the coronal and apical marginal adaptation, significant statistical difference (p = 0.001) was seen in AH Plus sealer. When a Mann–Whitney U-test was done on MTA-Fillapex sealer vs AH Plus sealer and AH Plus sealer vs Endofill sealer, there was a statistically significant difference (p < 0.05) found between the above two groups at coronal and apical third. Conclusion The present study proves that AH Plus sealer has a better marginal adaptation when compared with other sealers used. Clinical significance For sealing space of crown wall and main cone in root canal treatment, sealers play an important role. The other advantages of sealers are that they are used to fill voids and irregularities in root channel, secondary, lateral channels, and space between applied gutta-percha cones and also act as tripper during filling. How to cite this article Remy V, Krishnan V, Job TV, Ravisankar MS, Raj CVR, John S. Assessment of Marginal Adaptation and Sealing Ability of Root Canal Sealers: An in vitro Study. J Contemp Dent Pract 2017;18(12):1130-1134.
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ISMUHAJAROH, Bakti Nur, Didik INDRADEWA, Budiastuti KURNIASIH et Sri Nuryani Hidayah UTAMI. « Interrelationships of Air Canal Adaptation in the Leaves of Water Lilies and Water Depth of Lebak Swampland in Kalimantan Selatan ». Journal of Environmental Management and Tourism 13, no 1 (4 mars 2022) : 197. http://dx.doi.org/10.14505/jemt.v13.1(57).18.
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Nymphaea pubescens grows in Lebak swampland in its different levels of water depth. This aquatic plant has an absorption system that moves gases through the laminae and has a convective flow system through air canals in midrib and petiole. This study aims to determine the adaptive structure of air canal in the water lilies (Nymphaea pubescens) laminae and how its structure varies along with water-depth fluctuations. The research was conducted by observing plants in 4 (four) different zones of water depth: (1) water depth between 28-95 cm (zone I), (2) 28-99 cm (zone II), (3) 54-112 cm (zone III), and (4) 55-124 cm (zone IV).
Every lamina area, lamina thickness, and cross-sectional area (XS) of petiole, a number and area of air canals in midrib and petiole were collected for analysis. The results showed that the cross-sectional area of the laminae N. pubescens increased along with water depth, but the correlation with laminae thickness decreased. The midrib air canals are symmetrically divided and there was one main canal pair, an additional three pairs of canals, and a pair of smaller canals.
The cross-sectional area of the midrib and air canal increased along with water depth. The calculation of the area of four pairs of air canals is 75%. Air canals make up 34% of midrib cross-sectional area. The midrib air canals produced one pair of air canals, an additional two pairs of canals and a pair of smaller canals. The calculation of the area of three pairs of airways is 93%. Air canals make up 31% of the cross-sectional area of the petiole. The length of the petiole, the volume of the petiole, and the volume of the air canal increased along with water depth, but the cross-sectional area of the petiole and the air canal were not related by water depth.
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Velozo, Christianne, Hugo Dantas, Basílio Rodrigues Vieira, Frederico Barbosa de Sousa, Victor Felipe Farias do Prado, Ismael Sebastião da Silva Sousa, Maria Beatriz Arruda Albuquerque et Diana Santana de Albuquerque. « Adaptation of the single-cone in prepared long oval-shaped canals : a micro-computed tomography study ». Research, Society and Development 10, no 15 (29 novembre 2021) : e444101523301. http://dx.doi.org/10.33448/rsd-v10i15.23301.
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The present study aimed to evaluate adaptation of the single gutta-percha cone on root canal walls prepared with the two systems, the XP-endo Shaper (XPS; FKG Dentaire, La Chaux-de-Fonds, Switzerland) and ProTaper Next systems (PTN; Dentsply Sirona, Ballaigues, Switzerland) by using micro-computed tomography (micro-CT) technology. Twenty long oval-shaped canals in mandibular incisors were scanned by micro-CT (Skyscan 1172; Bruker microCT, Kontich, Belgium). Two groups were divided into (n = 10) according to the canal preparation protocol: XPS group with an extra 45 s of instrumentation and PTN group. A gutta percha cone, with respect to the protocol used for each group (size 40, .04 taper, XPS and size 40, .06 taper, PTN) was adapted to the canal at the working length of all the samples, and all root canals were filled, using the single-cone technique. The mean values for volume of voids and percentage relative to the mentioned space were correspondingly higher in XPS group than they were PTN group, mean values for volume of voids (3.61 mm3 - 1.92 mm3) and for percentage of voids (39.25% - 23.28%), respectively, significant differences were recorded (p < 0.05) between the two groups (XPS and PTN, Student’s-t test for homogenous variances and Mann–Whitney test). The canals prepared with XPS, in the procedure performed with an extra 45 s of instrumentation, showed a higher volume of voids than those prepared with the PTN system, in obturation of the root canal with the single cone technique.
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Yakushin, Sergei B., Theodore Raphan, Jean A. Büttner-Ennever, Jun-Ichi Suzuki et Bernard Cohen. « Spatial Properties of Central Vestibular Neurons of Monkeys After Bilateral Lateral Canal Nerve Section ». Journal of Neurophysiology 94, no 6 (décembre 2005) : 3860–71. http://dx.doi.org/10.1152/jn.01102.2004.
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Thirty-seven neurons were recorded in the superior vestibular nucleus (SVN) of two cynomolgus monkeys 1–2 yr after bilateral lateral canal nerve section to test whether the central neurons had spatially adapted for the loss of lateral canal input. The absence of lateral canal function was verified with eye movement recordings. The relation of unit activity to the vertical canals was determined by oscillating the animals about a horizontal axis with the head in various orientations relative to the axis of rotation. Animals were also oscillated about a vertical axis while upright or tilted in pitch. In the second test, the vertical canals are maximally activated when the animals are tilted back about −50° from the spatial upright and the lateral canals when the animals are tilted forward about 30°. We reasoned that if central compensation occurred, the head orientation at which the response of the vertical canal-related neurons was maximal should be shifted toward the plane of the lateral canals. No lateral canal-related units were found after nerve section, and vertical canal-related units were found only in SVN not in the rostral medial vestibular nucleus. SVN canal-related units were maximally activated when the head was tilted back at −47 ± 17 and −50 ± 12° (means ± SD) in the two animals, close to the predicted orientation of the vertical canals. This indicated that spatial adaptation of vertical canal-related vestibular neurons had not occurred. There were substantial neck and/or otolith-related inputs activating the vertical canal-related neurons in the nerve-sectioned animals, which could have contributed to oculomotor compensation after nerve section.
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Apostolska, Sonja, Elizabeta Gjorgievska, Vasilka Rendzova, Marina Eftimoska, Rade Zivkovic et Ivica Stancic. « Adaptability of different canal sealers to the root canal dentin - scanning electron microscopy analysis ». Medical review 70, no 5-6 (2017) : 141–45. http://dx.doi.org/10.2298/mpns1706141a.
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Introduction. The aim of this in vitro study was to test and analyze the sealing ability of three endodontic materials used for permanent obturation, in between the dentin walls and the gutta-percha points, using a scanning electron microscope. Material and Methods. Forty-five recently extracted single-root teeth, treated by a step-back technique, were divided into three groups (15 teeth in each); the canals were filled with three different permanent obturation materi?als: N2 - zinc oxide root canal cement, Gutta Flow (Coltene), and Endomethasone N (Septodont). Their sealing ability and adhesive properties were analyzed using field emission gun scanning electron microscope, at the time when they were applied between the dentin walls of the canal and the gutta-percha. Results. The results of the scanning electron microscope analysis have shown that all the three sealers have good adhesion properties when used over the root canal walls in the apical third. Good adaptation of the filling used for the root canal walls in the middle and the cervical third was found only in teeth obturated using Gutta Flow, while samples obturated by N2 - zinc oxide root canal cement and Endomethasone showed the weak?est adhesion, and greatest number of cracks between the sealer and the canal wall. Conclusion. When using a single-cone obturation technique, compared to other obturation materials, Gutta Flow shows considerably better adaptation to the root canal wall and the gutta-percha points in the apical, middle, and the cervical third of the root.
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Angelaki, D. E., et B. J. Hess. « Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. II Spatiotemporal properties of the adapted slow-phase eye velocity ». Journal of Neurophysiology 76, no 5 (1 novembre 1996) : 2954–71. http://dx.doi.org/10.1152/jn.1996.76.5.2954.
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1. The ability of the vestibuloocular reflex (VOR) to undergo adaptive modification after selective changes in the peripheral vestibular system was investigated in rhesus monkeys by recording three-dimensional eye movements before and after inactivation of selective semicircular canals. In the preceding paper we showed that the horizontal VOR gain evoked by passive yaw oscillations after lateral semicircular canal inactivation recovers gradually over time in a frequency-specific manner. Here we present the spatial tuning of the adapted slow-phase eye velocity and describe its spatiotemporal properties as a function of time after canal inactivation. 2. The spatial organization of the VOR was investigated during oscillations at different head positions in the pitch, roll, and yaw planes, as well as in the right anterior/left posterior and left anterior/right posterior canal planes. Acutely after bilateral inactivation of the lateral semicircular canals, a small horizontal response could still be elicited that peaked during rotations in pitched head positions that would maximally stimulate vertical semicircular canals. In addition, the phase of horizontal slow-phase velocity abruptly reversed through 180 degrees at positions close to upright, similarly to torsional slow-phase velocity. These spatial response properties suggest that the small, residual horizontal response components that are present acutely after plugging of both lateral canals originate from vertical semicircular canal signals. 3. As the horizontal response amplitude increased over time, consistent changes were also observed in the spatiotemporal tuning of horizontal slow-phase velocity. 1) The spatiotemporal response properties of horizontal slow-phase velocity acquired noncosine tuning characteristics, primarily in the pitch plane, in the right anterior/left posterior and left anterior/right posterior canal planes. Accordingly, horizontal response amplitude was nonzero during rotation in any head position in these planes and response phase varied significantly as a function of head orientation. 2) The peak horizontal response amplitude shifted spatially over time, such that 5–10 mo after plugging it was maximal during rotations at head positions close to upright. 4. In parallel to these unique spatiotemporal response properties characterizing the adapted horizontal VOR, torsional slow-phase velocity also exhibited small spatiotemporal changes after lateral canal inactivation that tended to precede in time the changes associated with the horizontal response components. In contrast, vertical slow-phase velocity in the plugged animals was unaltered and continued to be characterized by cosine-tuned spatial properties in three dimensions. 5. Recovery of the horizontal response gain during yaw oscillations in upright position, as well as the unique, noncosine spatiotemporal characteristics of the adapted horizontal VOR, were also observed in an animal with all but one vertical semicircular canals inactivated. There was, however, no sign of VOR gain recovery up to 2 mo after all semicircular canals were inactivated. These results suggest that the observed recovery of horizontal VOR is at least partly due to signals originating from the remaining intact vertical canal(s). Even in the presence of a single intact vertical canal, the improvement in horizontal gaze stability is at least partly restored through spatiotemporal changes in the processing of vestibuloocular signals that improve the gain and spatial tuning of horizontal VOR at the expense of temporal response properties.
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Lewis, Richard F., Csilla Haburcakova, Wangsong Gong, Chadi Makary et Daniel M. Merfeld. « Vestibuloocular Reflex Adaptation Investigated With Chronic Motion-Modulated Electrical Stimulation of Semicircular Canal Afferents ». Journal of Neurophysiology 103, no 2 (février 2010) : 1066–79. http://dx.doi.org/10.1152/jn.00241.2009.
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To investigate vestibuloocular reflex (VOR) adaptation produced by changes in peripheral vestibular afference, we developed and tested a vestibular “prosthesis” that senses yaw-axis angular head velocity and uses this information to modulate the rate of electrical pulses applied to the lateral canal ampullary nerve. The ability of the brain to adapt the different components of the VOR (gain, phase, axis, and symmetry) during chronic prosthetic electrical stimulation was studied in two squirrel monkeys. After characterizing the normal yaw-axis VOR, electrodes were implanted in both lateral canals and the canals were plugged. The VOR in the canal-plugged/instrumented state was measured and then unilateral stimulation was applied by the prosthesis. The VOR was repeatedly measured over several months while the prosthetic stimulation was cycled between off, low-sensitivity, and high-sensitivity stimulation states. The VOR response initially demonstrated a low gain, abnormal rotational axis, and substantial asymmetry. During chronic stimulation the gain increased, the rotational axis improved, and the VOR became more symmetric. Gain changes were augmented by cycling the stimulation between the off and both low- and high-sensitivity states every few weeks. The VOR time constant remained low throughout the period of chronic stimulation. These results demonstrate that the brain can adaptively modify the gain, axis, and symmetry of the VOR when provided with chronic motion-modulated electrical stimulation by a canal prosthesis.
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Juhlin, Jon J., Richard E. Walton et Joseph S. Dovgan. « Adaptation of thermafil components to canal walls ». Journal of Endodontics 19, no 3 (mars 1993) : 130–35. http://dx.doi.org/10.1016/s0099-2399(06)80507-8.
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Cañadas, Piedad S., Ester Berástegui, Patrícia Gaton-Hernández, Léa A. B. Silva, Giselle A. Leite et Roberto S. Silva. « Physicochemical Properties and Interfacial Adaptation of Root Canal Sealers ». Brazilian Dental Journal 25, no 5 (octobre 2014) : 435–41. http://dx.doi.org/10.1590/0103-6440201300037.
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This study compared the physicochemical properties and interfacial adaptation to canal walls of Endo-CPM-Sealer, Sealapex and Activ GP with the well-established AH Plus sealer. The following analyses were performed: radiopacity, pH variation and solubility using samples of each material and scanning electron microscopy of root-filled bovine incisors to evaluate the interfacial adaptation. Data were analyzed by the parametric and no-parametric tests (α=0.05). All materials were in accordance with the ANSI/ADA requirements for radiopacity. Endo-CPM-Sealer presented the lowest radiopacity values and AH Plus was the most radiopaque sealer (p=0.0001). Except for ActiV GP, which was acidic, all other sealers had basic chemical nature and released hydroxyl ions. Regarding solubility, all materials met the ANSI/ADA recommendations, with no statistically significant difference between the sealers (p=0.0834). AH Plus presented the best adaptation to canal walls in the middle (p=0.0023) and apical (p=0.0012) thirds, while the sealers Activ GP and Endo-CPM-Sealer had poor adaptation to the canal walls. All sealers, except for ActiV GP, were alkaline and all of them fulfilled the ANSI/ADA requirements for radiopacity and solubility. Regarding the interfacial adaptation, AH Plus was superior to the others considering the adaptation to the bovine root canal walls.
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Pawar, Ajinkya M., Anuj Bhardwaj, Kulvinder S. Banga, Gurdeep Singh, Anda Kfir, Alexander Maniangat Luke, Vialyne Dinata et Dian Agustin Wahjuningrun. « Deficiencies in Root Canal Fillings Subsequent to Adaptive Instrumentation of Oval Canals ». Biology 10, no 11 (21 octobre 2021) : 1074. http://dx.doi.org/10.3390/biology10111074.
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The purpose of this study was to explore the influence of instrumentation and the potential for debris deposition using XP-endo shaper plus (XP-SP) and full-sequence SAF (F-SAF) on the adaption of thermoplastic root canal fillings in oval canals. Following the manufacturer’s instructions, ninety human permanent mandibular incisors with a single oval canal 6 mm from the apex (verified using pre-operative CBCT scanning) were instrumented with XP-SP and F-SAF. Obtura III Max apparatus was used for root canal obturation without the use of a root canal sealer. The roots were then sectioned 6 mm from the apex and examined with a digital stereomicroscope at x25 magnification to assess the root canal fillings. The F-SAF was associated with a significantly higher (p < 0.01) percentage of entire adaptation of the root fillings (76%) compared to the XP-SP (57%). Furthermore, the XP-SP group was also associated with higher (p < 0.01) defective obturation with debris at 17% and with voids at 26%. However, the F-SAF had lower percentages of defective obturations (7% with debris and 17% with voids). The quality of obturation of oval canals instrumented using full-sequence SAF was better.
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Fan, Kai-Fang. « The Adaptation Features and Text Reconstruction in Translating Grand Canal Poems into English ». Studies in Linguistics and Literature 6, no 3 (23 août 2022) : p92. http://dx.doi.org/10.22158/sll.v6n3p92.
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The English and Chinese versions of the Grand Canal poems have different adaptation features, which have an influence on the text reconstruction of the English versions of the Grand Canal poems. This study analyzes the pragmatic adaptation features of the English versions of the Grand Canal poems in terms linguistic choices and non-linguistic choices with the representative works of the English and Chinese versions of the Grand Canal poems as the corpus. The study finds that at the level of linguistic choices, the English versions of the Grand Canal poems is, to a large extent, adaptive to the current communicative purpose of the Grand Canal culture expressed in the original Chinese versions, but at the level of non-linguistic choices, it is, to a little extent, adaptive to the above communicative purpose. Therefore, the practice of translating Grand Canal poems into English needs to be improved in terms of linguistic choices at the level of vocabulary, syntax and rhetoric, as well as non-linguistic choices at the level of state of mind, moods and cultural image, so as to reconstruct English versions of Grand Canal poems that are adaptive adequately and fully to the pragmatic features of poems expressed in the Chinese versions and the needs of target readers of English versions.
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Demer, Joseph L., et Benjamin T. Crane. « Vision and vestibular adaptation ». Otolaryngology–Head and Neck Surgery 119, no 1 (juillet 1998) : 78–88. http://dx.doi.org/10.1016/s0194-5998(98)70176-7.
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This article summarizes six recent degree-of-freedom studies of visual-vestibular interaction during natural activities and relates the findings to canalotolith interactions evaluated during eccentric axis rotations. Magnetic search coils were used to measure angular eye and head movements of young and elderly subjects. A flux gate magnetometer was used to measure three-dimensional head translation. Three activities were studied: standing quietly, walking in place, and running in place. Each activity was evaluated with three viewing conditions: a visible target viewed normally, a remembered target in darkness, and a visible target viewed with x2 binocular telescopic spectacles. Canal-otolith interaction was assessed with passive, whole-body, transient, and steady-state rotations in pitch and yaw at multiple frequencies about axes that were either oculocentric or eccentric to the eyes. For each rotational axis, subjects regarded visible and remembered targets located at various distances. Horizontal and vertical angular vestibulo-ocular reflexes were demonstrable in all subjects during standing, walking, and running. When only angular gains were considered, gains in both darkness and during normal vision were less than 1.0 and were generally lower in elderly than in young subjects. Magnified vision with x2 telescopic spectacles produced only small gain increases as compared with normal vision. During walking and running all subjects exhibited significant mediolateral and dorsoventral head translations that were antiphase locked to yaw and pitch head movements, respectively. These head translations and rotations have mutually compensating effects on gaze in a target plane for typical viewing distances and allow angular vestibulo-ocular reflex gains of less than 1.0 to be optimal for gaze stabilization during natural activities. During passive, whole-body eccentric pitch and yaw head rotations, vestibulo-ocular reflex gain was modulated as appropriate to stabilize gaze on targets at the distances used. This modulation was evident within the first 80 msec of onset of head movement, too early to be caused by immediate visual tracking. Modeling suggests a linear interaction between canal signals and otolith signals scaled by the inverse of target distance. Vestibulo-ocular reflex performance appears to be adapted to stabilize gaze during translational and rotational perturbations that occur during natural activities, as is appropriate for relevant target distances. Although immediate visual tracking contributes little to gaze stabilization during natural activities, visual requirements determine the performance of vestibulo-ocular reflexes arising from both canals and otoliths. (Otolaryngol Head Neck Surg 1998;119:78-88.)
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Abognah, Asma. « Smear Layer in Endodontics : A review of its role and management ». Khalij-Libya Journal of Dental and Medical Research 4, no 2 (15 octobre 2020) : 38–50. http://dx.doi.org/10.47705/kjdmr.204206.
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Whatever the technique used for root canal instrumentation; a layer of debris termed “smear layer” is formed. This is a layer composed of an organic and inorganic substance and it harbors bacteria and their by-products. Removing the smear layer enhances the cleaning and disinfecting of root canal walls and grant maximum adaptation of root canal filling materials. Nonetheless, the existence of smear layer can seal the dentinal tubules and decrease the probability of dentinal tubule’s invasion by bacteria and their toxins, this issue is still controversial. Smear layer removal approaches including chemical, ultrasonics, and laser have been widely studied. However, none of them is entirely efficient along the length of all canals or is universally recognized. If the decision was to remove smear layer, irrigating root canals with EDTA followed by NaOCl will fulfill the objective. It is still debatable whether the removal of smear layer will decrease the apical leakage or not. Additional research is required to determine the consequence of removing or preserving the smear layer.
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Rabbitt, R. D., R. Boyle, G. R. Holstein et S. M. Highstein. « Hair-Cell Versus Afferent Adaptation in the Semicircular Canals ». Journal of Neurophysiology 93, no 1 (janvier 2005) : 424–36. http://dx.doi.org/10.1152/jn.00426.2004.
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The time course and extent of adaptation in semicircular canal hair cells was compared to adaptation in primary afferent neurons for physiological stimuli in vivo to study the origins of the neural code transmitted to the brain. The oyster toadfish, Opsanus tau, was used as the experimental model. Afferent firing-rate adaptation followed a double-exponential time course in response to step cupula displacements. The dominant adaptation time constant varied considerably among afferent fibers and spanned six orders of magnitude for the population (∼1 ms to >1,000 s). For sinusoidal stimuli (0.1–20 Hz), the rapidly adapting afferents exhibited a 90° phase lead and frequency-dependent gain, whereas slowly adapting afferents exhibited a flat gain and no phase lead. Hair-cell voltage and current modulations were similar to the slowly adapting afferents and exhibited a relatively flat gain with very little phase lead over the physiological bandwidth and dynamic range tested. Semicircular canal microphonics also showed responses consistent with the slowly adapting subset of afferents and with hair cells. The relatively broad diversity of afferent adaptation time constants and frequency-dependent discharge modulations relative to hair-cell voltage implicate a subsequent site of adaptation that plays a major role in further shaping the temporal characteristics of semicircular canal afferent neural signals.
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Suciu, Ioana, Bogdan Dimitriu, Mihai Ciocardel, Mihaela Chirila, Oana Amza, Sinziana Scarlatescu, Cristina Preoteasa, Mihaela Grigorie et Monica Voiculeanu. « Evaluation of the sealer/gutta-percha ratio on sets of root section surfaces of some extracted teeth sealed using the cold lateral condensation technique ». Journal of Medicine and Life 14, no 3 (juin 2021) : 337–46. http://dx.doi.org/10.25122/jml-2021-0102.
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Canal filling must be well adapted to the walls of the root canal to prevent bacterial infiltration. Endodontic seals play an essential role in ensuring tightness, without which the canal filling would suffer infiltrations. This study aimed to evaluate the areas occupied by the two components of the canal filling, as well as the sealer/gutta-percha ratio in the root canals of the maxillary central incisors after their filling using the cold lateral condensation technique with gutta-percha. Thirty extracted upper central incisors were rotatably prepared with ProTaper Universal up to F3 and sealed using the cold lateral condensation technique with gutta-percha. After setting the sealer, the roots of the teeth were sectioned perpendicularly to 1 (L1), 3 (L3), 6 (L6), and 8 (L8) mm from the apex. The surface of the sections was analyzed with a Leica EZ4D stereomicroscope and photographed at two magnification orders: 10x and 25x. The areas corresponding to the gutta-percha, sealer, gaps, and root canal were expressed in pixels using the ImageJ software, version 1.50i. The difference in the representation of sealer areas, gutta-percha and voids was statistically significantly different for all four sections analyzed. The best adaptation of the canal obturation was observed in L1 and L3. The gutta-percha area was statistically significantly higher than that of the sealer for the L1, L3, and L6 levels, while the sealer/gutta-percha ratio recorded the lowest value at the L3 level (0, 30) and the highest at its L8 (0.70) level, without registering statistically significant differences regarding the area at the four analyzed levels. The voids were mostly absent or recorded a minimal percentage area (<1%). Cold lateral condensation of gutta-percha has led to a good adaptation of gutta-percha to the root canal wall, with a small amount of sealer, especially to the sections made at 3 mm from the apex. Given the limitations of this study, we noted that the voids were few – observed in the 6 and 8 mm sections – and were negligible in many cases.
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Wang, Jiayu, Menghan Wang, Haohan Dou, Mingming Su, Hangyu Dong et Zhenhua Liu. « Research on Climate Change and Water Heritage Tourism Based on the Adaptation Theory—A Case Study of the Grand Canal (Beijing Section) ». Sustainability 15, no 9 (6 mai 2023) : 7630. http://dx.doi.org/10.3390/su15097630.
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Water is at the forefront of climate change and is seen as a major channel through which the effects of climate change are felt. The function of water heritage is closely related to the water bodies on which it depends. Under climate change, the conservation and tourism uses of water heritage resources are facing impacts and challenges. Taking the Beijing Section of the Grand Canal of China as a case, this research applied the adaptation theory to explore the impacts of climate change on heritage tourism of the section of the Grand Canal in Beijing. It was identified that changes in the temperature and the precipitation formed climate-related stimuli to tourism along the Canal from 2012 to 2021 in Beijing. Second, from the supply side of tourism, policies were formulated at a national or municipal level to respond to the changing climate and its impacts on the Canal and its tourism uses. Natural-based solutions (NbS) have been applied to rehabilitate the ecosystem of the Canal, contributing to the enhanced tourism landscape, and providing opportunities for ecological education. Third, from the demand side, high tourism participation along the Canal was examined during the high-temperature years. Meanwhile, the increasing tourist needs for water spaces and activities were observed with evident seasonal patterns. Accordingly, suggestions for climate adaptation of the Grand Canal from a tourism perspective were proposed. For heritage conservation, actions of ecological restoration and monitoring should be further implemented. To assist in the climate adaptation and sustainable development of Grand Canal tourism, suggestions are proposed to enhance the overall tourism planning, increase water accessibility, and heritage interpretation for tourists.
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Betti, Lia, et Andrea Manica. « Human variation in the shape of the birth canal is significant and geographically structured ». Proceedings of the Royal Society B : Biological Sciences 285, no 1889 (24 octobre 2018) : 20181807. http://dx.doi.org/10.1098/rspb.2018.1807.
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The human birth canal shows a tight fit with the size of the neonate, which can lead to obstetric complications. This is not the case in other apes, and has been explained as the outcome of conflicting evolutionary pressures for bipedal locomotion and parturition of a highly encephalized fetus. Despite the suggested evolutionary constraints on the female pelvis, we show that women are, in fact, extremely variable in the shape of the bony birth canal, with human populations having differently shaped pelvic canals. Neutral evolution through genetic drift and differential migration are largely responsible for the observed pattern of morphological diversity, which correlates well with neutral genetic diversity. Climatic adaptation might have played a role, albeit a minor one, with populations from colder regions showing a more transversally oval shape of the canal inlet. The significant extent of canal shape variation among women from different regions of the world has important implications for modern obstetric practice in multi-ethnic societies, as modern medical understanding has been largely developed on studies of European women.
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Xiang, Yongqing, Sergei B. Yakushin, Bernard Cohen et Theodore Raphan. « Modeling Gravity-Dependent Plasticity of the Angular Vestibuloocular Reflex With a Physiologically Based Neural Network ». Journal of Neurophysiology 96, no 6 (décembre 2006) : 3349–61. http://dx.doi.org/10.1152/jn.00430.2006.
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A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular vestibuloocular reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal–otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal–otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal–otolith-convergent neurons are adapted for a given head orientation.
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Cheung, Carol C., Heiko Hecht, Thomas Jarchow et Laurence R. Young. « Threshold-based vestibular adaptation to cross-coupled canal stimulation ». Journal of Vestibular Research 17, no 4 (1 avril 2008) : 171–81. http://dx.doi.org/10.3233/ves-2007-17403.
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Prior experiments have demonstrated that people are able to adapt to cross-coupled accelerations associated with head movements while spinning at high rotation rates (e.g., 23 rpm or 138°/s). However, while adapting, subjects commonly experience serious side effects, such as motion sickness, non-compensatory eye movements, and strong and potentially disorienting illusory body tilt or tumbling sensations. In the present study, we investigated the feasibility of adaptation using a threshold-based method, which ensured that the illusory tilt sensations remained imperceptible or just barely noticeable. This was achieved by incrementally increasing the angular velocity of the horizontal centrifuge while supine subjects made repeated consistent yaw head turns. Incremental adaptation phases started at centrifugation speeds of 3 rpm. Centrifuge speed was slowly increased in steps of 1.5 rpm until a light illusory tilt was experienced. At the end of the incremental procedure, subjects were able to make head turns while rotating 14 rpm without experiencing illusory tilt. Moreover, motion sickness symptoms could be avoided and a limited carry over of the adaptive state to stronger stimulation at 23 rpm was found. The results are compared to prior studies which adapted subjects to super-threshold stimuli.
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PERDIGAO, J., M. LOPES et G. GOMES. « Interfacial Adaptation of Adhesive Materials to Root Canal Dentin ». Journal of Endodontics 33, no 3 (mars 2007) : 259–63. http://dx.doi.org/10.1016/j.joen.2006.10.002.
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Sadeghi, Soroush G., Jay M. Goldberg, Lloyd B. Minor et Kathleen E. Cullen. « Effects of Canal Plugging on the Vestibuloocular Reflex and Vestibular Nerve Discharge During Passive and Active Head Rotations ». Journal of Neurophysiology 102, no 5 (novembre 2009) : 2693–703. http://dx.doi.org/10.1152/jn.00710.2009.
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Mechanical occlusion (plugging) of the slender ducts of semicircular canals has been used in the clinic as well as in basic vestibular research. Here, we investigated the effect of canal plugging in two macaque monkeys on the horizontal vestibuloocular reflex (VOR) and the responses of vestibular-nerve afferents during passive head rotations. Afferent responses to active head movements were also studied. The horizontal VOR gain decreased after plugging to <0.1 for frequencies <2 Hz but rose to about 0.6 as frequency was increased to 15 Hz. Afferents innervating plugged horizontal canals had response sensitivities that increased with the frequency of passive rotations from <0.01 (spikes/s)/(°/s) at 0.5 Hz to values of about 0.2 and 0.5 (spikes/s)/(°/s) at 8 Hz for regular and irregular afferents, respectively (<50% of responses in controls). An increase in phase lead was also noted following plugging in afferent discharge, but not in the VOR. Because the phase discrepancy between the VOR and afferent discharge is much larger than that seen in control animals, this suggests that central adaptation shapes VOR dynamics following plugging. The effect of canal plugging on afferent responses can be modeled as an increase in stiffness and a reduction in the dominant time constant and gain in the transfer function describing canal dynamics. Responses were also evident during active head rotations, consistent with the frequency content of these movements. We conclude that canal plugging in macaques is effective only at frequencies <2 Hz. At higher frequencies, afferents show significant responses, with a nearly 90° phase lead, such that they encode near-rotational acceleration. Our results demonstrate that afferents innervating plugged canals respond robustly during voluntary movements, a finding that has implications for understanding the effects of canal plugging in clinical practice.
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Alkahtani, Ahmed, Sara Al-Subait et Sukumaran Anil. « AnIn VitroComparative Study of the Adaptation and Sealing Ability of Two Carrier-Based Root Canal Obturators ». Scientific World Journal 2013 (2013) : 1–7. http://dx.doi.org/10.1155/2013/532023.
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The study was done to assess the sealing ability and adaptation of RealSeal 1, and to compare it with Thermafil. 65 single-rooted extracted teeth were selected and root canal treatment was performed. Root canals were obturated with RealSeal 1 or Thermafil. A double chamber bacterial leakage model usingE. faecaliswas developed to assess the sealing ability. Samples were monitored daily for 60 days. After the bacterial leakage test, samples were embedded in resin and sectioned horizontally at 2 and 4 mm from the apical foramen. Specimens were examined under scanning electron microscope and digitally photographed. AutoCAD software was used to measure the gap between the canal surface and obturation material. Results were statistically analyzed using nonparametric Kaplan-Meier survival analysis for the bacterial leakage andt-test to compare the means of gap in RealSeal 1 and Thermafil at 2 and 4 mm. There was no significant difference between the RealSeal 1 and Thermafil with respect to leakage over time. At 2 mm and 4 mm, RealSeal 1 had significantly more gaps than Thermafil. From the observations it can be concluded that RealSeal 1 and Thermafil have comparable performance in terms of adaptation and sealing ability.
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Angelaki, Dora E., et J. David Dickman. « Gravity or translation : Central processing of vestibular signals to detect motion or tilt ». Journal of Vestibular Research 13, no 4-6 (28 décembre 2003) : 245–53. http://dx.doi.org/10.3233/ves-2003-134-609.
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The processing and detection of tilts relative to gravity from actual motion (translational accelerations) is one of the most fundamental issues for understanding vestibular sensorimotor control in altered gravity environments. In order to better understand the nature of multisensory signals in detecting motion and tilt, we summarize here our recent studies regarding the central processing of vestibular signals during multi-axis rotational and translational stimuli. Approximately one fourth of the cells in the vestibular nuclei exclusively encoded rotational movements (Canal-Only neurons) and were unresponsive to translation. The Canal-Only central neurons encoded head rotation in canal afferent coordinates, exhibited no orthogonal canal convergence and were characterized by significantly higher sensitivities to rotation as compared to canal afferents. Another fourth of the neurons modulated their firing rates during translation (Otolith-Only cells). During rotations, these neurons typically only responded when the axis of rotation was earth-horizontal and the head was changing orientation relative to gravity. The remaining cells (approximately half of total population) were sensitive to both rotations and translations (Otolith+Canal neurons). Maximum sensitivity vectors to rotation were distributed throughout the 3D space, suggesting strong convergence from multiple semicircular canals. Only a small subpopulation (approximately one third) of these Otolith+Canal neurons seems to encode a true estimate of the translational component of the imposed passive head and body movement. These results provide the first step in further understanding multisensory convergence in normal gravity, as this task is fundamental to our appreciation of neurovestibular adaptation to altered gravity.
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Pahlawan, Priscilla Daniego, Rahmi Alma Farah et Myrna Nurlatifah Zakaria. « White MTA as a Material to Seal Iatrogenic Perforation for Furcation Teeth : A Case Report ». Key Engineering Materials 829 (décembre 2019) : 232–40. http://dx.doi.org/10.4028/www.scientific.net/kem.829.232.
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Iatrogenic perforation is a common complication in endodontic treatment or restoration procedure. Recent developments in dentistry have improved tooth perforation prognosis. MTA (Mineral Trioxide Aggregate) is one of the chosen materials to seal tooth perforation. This case report discuss the management of an iatrogenic furcal perforation using White Angelus MTA to seal the furcal perforation on tooth 26 and its final restoration. Furcal perforation accured while removing the calcification in the mesio buccal canal using Protapper Next rotary file after sealing the perforation site, further root canal preparation was carried on, and root canals were medicated by Calcium Hydroxide. After 2 weeks root canal were obturated with Gutta Percha. After one week observation post obturation patient had no complain, and radiographic evaluation show good sealing by MTA. In Conclusion Angelus MTA have good sealing ability marginal adaptation, and the absence of calcium sulfate had reduced the setting time of the material. It is a suitable material to seal iatrogenic furcal perforation due to its biocompatibility, antimicrobial, good sealing ability, and low solubility.
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Lin, Galvin Sim Siang, Wen Wu Tan, Daryl Zhun Kit Chan, Kah Hoay Chua, Teoh Chai Yee et Mohd Aizuddin Mohd Lazaldin. « Quality of endodontic record-keeping and root canal obturation performed by final year undergraduate dental students : An audit during the COVID-19 pandemic ». PLOS ONE 17, no 10 (3 octobre 2022) : e0275634. http://dx.doi.org/10.1371/journal.pone.0275634.
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Background To assess the quality of endodontic record-keeping and root canal obturation performed by undergraduate final year dental students during the COVID-19 pandemic. Materials and methods Dental records and dental radiographs of patients who received endodontic treatments between March 2020 and March 2022 by undergraduate students during the COVID-19 pandemic were included. The audit data were collected based on the European Society of Endodontology guidelines retrospectively via assessing the patient’s clinical records and intraoral periapical radiograph. Root canal obturation quality was evaluated based on the following parameters: adaptation, length, taper, and mishap. A root filling is defined as satisfactory only when all four parameters were graded as acceptable. Subsequently, the data were recorded and analysed using Chi-Square test with the level of significance set at p = 0.05. Results A total of 111 patient records with 111 root canal-treated teeth were evaluated. The highest percentage of documented evidence was noted in the patient’s general records, while the endodontic treatment records showed the lowest percentage of documented evidence. 78 (70.3%) of root canal-treated teeth were deemed satisfactory with acceptable adaptation, length, taper, and absence of mishap. Moreover, no statistical significance in terms of root canal filling quality was noted between anterior and posterior teeth, and between maxillary and mandibular arch. Conclusions Although patient records and root canal fillings quality were deemed satisfactory in most cases, strict documentation requirements and continuing dental education in audit training are necessary for quality assurance.
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KUDO, TAKA. « A problem of hearing aid adaptation by a canal simulator. » AUDIOLOGY JAPAN 33, no 5 (1990) : 669–70. http://dx.doi.org/10.4295/audiology.33.669.
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BAUMGARDNER, KIRK R., JAY TAYLOR et RICHARD WALTON. « CANAL ADAPTATION AND CORONAL LEAKAGE : LATERAL CONDENSATION COMPARED TO THERMAFIL ». Journal of the American Dental Association 126, no 3 (mars 1995) : 351–56. http://dx.doi.org/10.14219/jada.archive.1995.0180.
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AL-HADDAD, Afaf, Noor Hayaty ABU KASIM et Zeti Adura CHE AB AZIZ. « Interfacial adaptation and thickness of bioceramic-based root canal sealers ». Dental Materials Journal 34, no 4 (2015) : 516–21. http://dx.doi.org/10.4012/dmj.2015-049.
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Correia, M. J., A. A. Perachio, J. D. Dickman, I. B. Kozlovskaya, M. G. Sirota, S. B. Yakushin et I. N. Beloozerova. « Changes in monkey horizontal semicircular canal afferent responses after spaceflight ». Journal of Applied Physiology 73, no 2 (1 août 1992) : S112—S120. http://dx.doi.org/10.1152/jappl.1992.73.2.s112.
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Extracellular responses from single horizontal semicircular canal afferents in two rhesus monkeys were studied after recovery from a 14-day biosatellite (COSMOS 2044) orbital spaceflight. On the 1st postflight day, the mean gain for 9 different horizontal canal afferents, tested using one or several different passive yaw rotation waveforms, was nearly twice that for 20 horizontal canal afferents similarly tested during preflight and postflight control studies. Adaptation of the afferent response to passive yaw rotation on the 1st postflight day was also greater. These results suggest that at least one component of the vestibular end organ (the semicircular canals) is transiently modified after exposure to 14 days of microgravity. It is unclear whether the changes are secondary to other effects of microgravity, such as calcium loss, or an adaptive response. If the response is adaptive, then this report is the first evidence that the response of the vestibular end organ may be modified (presumably by the central nervous system via efferent connections) after prolonged unusual vestibular stimulation. If this is the case, the sites of plasticity of vestibular responses may not be exclusively within central nervous system vestibular structures, as previously believed.
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Gama, MER, GS Balbinot, GC Ferreira, EG Mota, VCB Leitune et FM Collares. « CAD/CAM Milled Glass Fiber Posts : Adaptation and Mechanical Behavior in Flared Root Canals ». Operative Dentistry 46, no 4 (1 juillet 2021) : 438–47. http://dx.doi.org/10.2341/20-198-l.
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SUMMARY This study aimed to evaluate the cementation and mechanical behavior of flared root canals restored with CAD/CAM milled glass fiber post-and-core systems. Sixty-six endodontically treated human canines with a flared root canal were divided into three different groups according to the type of post: GPF received prefabricated posts; GREL received relined glass fiber posts, and GMILLED received CAD/CAM milled glass fiber posts. Cementation was performed with self-adhesive resin cement. The samples were submitted to x-ray microcomputed tomography analysis for the analysis of voids and gaps. The roots were sectioned and submitted to the push-out bond strength test. The load-to-fracture was evaluated in post-and-core systems. GMILLED presented lower void and lower gap volumes when compared to GPF and GREL. On the load-to-fracture test, GREL presented statistically significant higher values than GMILLED. GPF values had no statistically significant difference from the two other groups. On the push-out bond strength test, GPF presented statistically significant lower values when compared to GREL and GMILLED. The most common failure pattern was between dentin and cement in all groups. CAD/CAM milled glass fiber post-and-core systems presented an enhanced adaptation of glass fiber posts to flared root canal systems. Their results were comparable to relined posts in bond strength, while load-to-fracture-results for GMILLED were lower than those for GPF.
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Hwang, Hyun-sook, Kyung-mo Cho et Jin-woo Kim. « A comparison of thermoplasticized injectable gutta-percha techniques in ribbon-shaped canals : adaptation to canal walls ». Journal of Korean Academy of Conservative Dentistry 27, no 4 (2002) : 411. http://dx.doi.org/10.5395/jkacd.2002.27.4.411.
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Angelaki, Dora E., et Bernhard J. M. Hess. « Visually Induced Adaptation in Three-Dimensional Organization of Primate Vestibuloocular Reflex ». Journal of Neurophysiology 79, no 2 (1 février 1998) : 791–807. http://dx.doi.org/10.1152/jn.1998.79.2.791.
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Angelaki, Dora E. and Bernhard J. M. Hess. Visually induced adaptation in three-dimensional organization of primate vestibulo-ocular reflex. J. Neurophysiol. 79: 791–807, 1998. The adaptive plasticity of the spatial organization of the vestibuloocular reflex (VOR) has been investigated in intact and canal-plugged primates using 2-h exposure to conflicting visual (optokinetic, OKN) and vestibular rotational stimuli about mutually orthogonal axes (generating torsional VOR + vertical OKN, torsional VOR + horizontal OKN, vertical VOR + horizontal OKN, and horizontal VOR + vertical OKN). Adaptation protocols with 0.5-Hz (±18°) head movements about either an earth-vertical or an earth-horizontal axis induced orthogonal response components as high as 40–70% of those required for ideal adaptation. Orthogonal response gains were highest at the adapting frequency with phase leads present at lower and phase lags present at higher frequencies. Furthermore, the time course of adaptation, as well as orthogonal response dynamics were similar and relatively independent of the particular visual/vestibular stimulus combination. Low-frequency (0.05 Hz, vestibular stimulus: ±60°; optokinetic stimulus: ±180°) adaptation protocols with head movements about an earth-vertical axis induced smaller orthogonal response components that did not exceed 20–40% of the head velocity stimulus (i.e., ∼10% of that required for ideal adaptation). At the same frequency, adaptation with head movements about an earth-horizontal axis generated large orthogonal responses that reached values as high as 100–120% of head velocity after 2 h of adaptation (i.e., ∼40% of ideal adaptation gains). The particular spatial and temporal response characteristics after low-frequency, earth-horizontal axis adaptation in both intact and canal-plugged animals strongly suggests that the orienting (and perhaps translational) but not inertial (velocity storage) components of the primate otolith-ocular system exhibit spatial adaptability. Due to the particular nested arrangement of the visual and vestibular stimuli, the optic flow pattern exhibited a significant component about the third spatial axis (i.e., orthogonal to the axes of rotation of the head and visual surround) at twice the oscillation frequency. Accordingly, the adapted VOR was characterized consistently by a third response component (orthogonal to both the axes of head and optokinetic drum rotation) at twice the oscillation frequency after earth-horizontal but not after earth-vertical axis 0.05-Hz adaptation. This suggests that the otolith-ocular (but not the semicircular canal-ocular) system can adaptively change its spatial organization at frequencies different from those of the head movement.
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AL-Oulabi, Ayman, Yew Hin Beh, Zaihan Ariffin et Yanti Johari. « Individually Formed Glass Fibre Reinforced Composite Posts for Compromised Teeth with Oval and Flared Endodontic Canals ». Dental Update 48, no 1 (1 janvier 2021) : 62–67. http://dx.doi.org/10.12968/denu.2021.48.1.62.
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Potential excessive removal of tooth structure during retreatment, and canal preparation for a post will weaken the tooth substantially. An alternative to prefabricated or cast metal and fibre posts, is a soft and flexible fibre-reinforced composite post that can be used to aid a good adaptation and preserve the tooth structure. These two case reports highlight the use of fibre-reinforced composite posts in teeth with severe loss of tooth structure with wide flared and oval canals. CPD/Clinical Relevance: Case selection and proper treatment planning are important before considering and selecting any type of post placement.
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Angelaki, D. E., B. J. Hess, Y. Arai et J. Suzuki. « Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. I. Frequency-specific recovery of horizontal VOR after inactivation of the lateral semicircular canals ». Journal of Neurophysiology 76, no 5 (1 novembre 1996) : 2941–53. http://dx.doi.org/10.1152/jn.1996.76.5.2941.
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1. The adaptive plasticity of the vestibuloocular reflex (VOR) following a selective lesion of the peripheral vestibular organs was investigated in rhesus monkeys whose lateral semicircular canals were inactivated by plugging of the canal lumen in both ears. Gain and phase of horizontal, vertical, and torsional slow-phase eye velocity were determined from three-dimensional eye movement recordings obtained acutely after the plugging operation, as well as in regular intervals up to 10 mo later. 2. Acutely after plugging, horizontal VOR was minimal during yaw rotation with gains of < 0.1 at all frequencies. Horizontal VOR gain gradually increased over time, reaching gains of 0.4–0.5 for yaw oscillations at 1.1 Hz approximately 5 mo after lateral canal inactivation. This response recovery was strongly frequency dependent: horizontal VOR gains were largest at the highest frequency tested and progressively decreased for lower frequencies. Below approximately 0.1 Hz, no consistent horizontal VOR could be elicited even 10 mo after plugging. 3. The frequency-dependent changes in gain paralleled changes in horizontal VOR phase. Below approximately 0.1–0.05 Hz large phase leads were present, similarly as in semicircular canal primary afferents. Smaller phase leads were also present at higher frequencies, particularly at 1.1 Hz (the highest frequency tested). 4. Consistent with the afferent-like dynamics of the adapted horizontal VOR, per- and postrotatory horizontal responses to constant-velocity yaw rotations were short lasting. Time constants of the slow-phase eye velocity envelope of the horizontal postrotatory nystagmus were approximately 2 s. Nonetheless, a consistent horizontal optokinetic afternystagmus was evoked in plugged animals. 5. A torsional component that was absent in intact animals was consistently present during yaw rotation acutely after lateral canal inactivation and remained approximately constant thereafter. The frequency response characteristics of this torsional component resembled those of the adapted horizontal slow-phase responses: gain decreased and large phase leads were introduced at frequencies below approximately 0.05–0.1 Hz. Torsional responses elicited by roll oscillations in supine position, on the other hand, were indistinguishable in their dynamics from intact animals. No consistent vertical nystagmus was elicited during yaw rotation. 6. Our results show that there is a slow, frequency-specific recovery of horizontal VOR after selective inactivation of the lateral semicircular canals. Both the spatial organization and the dynamic properties of the adapted VOR responses are distinctly different from responses in intact animals, suggesting complex changes in the underlying vestibuloocular circuitry.
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Enggardipta, Raras Ajeng, Raphael Tri Endra Untara, Pribadi Santosa, Aqilla Tiara Kartikaningtyas, Andina Widyastuti et Diatri Nari Ratih. « Apical sealing ability of chitosan nanoparticles in epoxy-resin-based endodontic sealer ». Majalah Kedokteran Gigi Indonesia 5, no 2 (31 janvier 2020) : 69. http://dx.doi.org/10.22146/majkedgiind.40995.
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A good sealing ability of apical part of root canal system is needed to prevent microleakage thus resulting long-lasting successful treatment. Chitosan nanoparticles as nanofillers could be added to epoxy resin sealer to increase adaptation to dentinal wall. The purpose of this study was to evaluate the apical sealing ability of chitosan nanoparticles addition to epoxy-resin-based sealer. Thirty mandibular premolars were used in this study. The root canals were prepared using rotary files up to #30/0.09. The canal was irrigated with 2.5% NaOCl and 17% EDTA, then was rinsed with sterile water. All teeth were randomly divided into 3 groups (n=10). Group I was obturated with gutta-percha, Group II was obturated with gutta-percha and epoxy resin sealer, group III was obturated with gutta-percha and epoxy resin sealer that was added with chitosan nanoparticles. All specimens were stored in an incubator for 7 days at 37 °C. After that, specimens were tested with centrifuging dye penetration method with methylene blue 2% solution. The specimens were longitudinally sectioned, observed under stereomicroscope (8x magnification) and measured in millimeters (mm). The data were analyzed using one-way Anova. The results of one-way Anova showed that dye penetration in apical part of the root canal in all groups was statistically significant difference. The addition of chitosan nanoparticles to epoxy resin sealer increases the apical sealing ability of root canal obturation material.
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Moura-Netto, Cacio, Anna Carolina Volpi Mello-Moura, Renato Miotto Palo, Igor Prokopowitsch, Cornelis H. Pameijer et Marcia Martins Marques. « Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers ». Journal of Biomedical Optics 20, no 3 (18 mars 2015) : 038002. http://dx.doi.org/10.1117/1.jbo.20.3.038002.
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Mantokoudis, Georgios, Ali S. Saber Tehrani, Aaron L. Wong, Yuri Agrawal, Angela Wenzel et John P. Carey. « Adaptation and Compensation of Vestibular Responses Following Superior Canal Dehiscence Surgery ». Otology & ; Neurotology 37, no 9 (octobre 2016) : 1399–405. http://dx.doi.org/10.1097/mao.0000000000001196.
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Cusimano, P., E. M. Cumbo, S. Provenzano, C. Goracci, G. Gallina et M. Ferrari. « Assessment of gutta-percha adaptation with different root canal obturation techniques ». Dental Materials 26 (janvier 2010) : e68-e69. http://dx.doi.org/10.1016/j.dental.2010.08.155.
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Weller, R. Norman, W. Frank Kimbrough et Ronald W. Anderson. « A comparison of thermoplastic obturation techniques : Adaptation to the canal walls ». Journal of Endodontics 23, no 11 (novembre 1997) : 703–6. http://dx.doi.org/10.1016/s0099-2399(97)80406-2.
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Kuehn, Amanda L., Andrew H. Lee, Russell P. Main et Erin L. R. Simons. « The effects of growth rate and biomechanical loading on bone laminarity within the emu skeleton ». PeerJ 7 (25 septembre 2019) : e7616. http://dx.doi.org/10.7717/peerj.7616.
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The orientation of vascular canals in primary bone may reflect differences in growth rate and/or adaptation to biomechanical loads. Previous studies link specific canal orientations to bone growth rates, but results between different taxa are contradictory. Circumferential vascular canals (forming laminar bone) have been hypothesized to reflect either (or both) rapid growth rate or locomotion-induced torsional loading. Previous work on the hindlimb biomechanics in the emu shows that the femur and tibiotarsus experience large shear strains, likely resulting from torsional loads that increase through ontogeny. Here, we test how growth rate and biomechanical loading affect bone laminarity in wing and hindlimb elements from growing emu (2–60 wks). If laminar bone is an adaptation to torsion-induced shear strains, it should increase from juveniles to adults. Alternatively, if bone laminarity reflects rapid growth, as has been shown previously in emu, it should be abundant in fast-growing juveniles and decrease with age. Transverse mid-shaft histological sections from the limb bones (femur, tibiotarsus, humerus, ulna, and radius) were prepared and imaged. Growth rates were measured using fluorescent bone labels. Vascular canal orientation was quantified using laminarity index (proportion of circumferential canals). Principal components analysis was performed to convert highly correlated variables (i.e., mass, age, growth rate, and shear strain) into principal components. Random-intercept beta regression modeling determined which principal components best explained laminarity. The fastest growth rates were found in young individuals for all five skeletal elements. Maximum growth rate did not coincide with peak laminarity. Instead, in the femur and tibiotarsus, elevated laminarity is strongly correlated with adult features such as large size, old age, and modest growth rate. This result is contrary to predictions made based on a previous study of emu but is consistent with results observed in some other avian species (penguin, chicken). Shear strain in the caudal octant of the femur and tibiotarsus is positively correlated with laminarity but has a weaker effect on laminarity relative to mass, age, and growth rate. Laminarity in the wing elements is variable and does not correlate with ontogenetic factors (including mass, age, and growth rate). Its presence may relate to relaxed developmental canalization or a retained ancestral feature. In conclusion, ontogeny (including growth rate) is the dominant influence on vascular canal orientation at least in the hindlimb of the emu.
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Yakushin, S., M. Dai, J. Suzuki, T. Raphan et B. Cohen. « Semicircular canal contributions to the three-dimensional vestibuloocular reflex : a model-based approach ». Journal of Neurophysiology 74, no 6 (1 décembre 1995) : 2722–38. http://dx.doi.org/10.1152/jn.1995.74.6.2722.
Texte intégralRésumé :
1. We studied the contribution of the individual semicircular canals to the generation of horizontal and torsional eye movements in cynomolgus monkeys. Eye movements were elicited by sinusoidal rotation about a vertical (gravitational) axis at 0.2 Hz with the animals tilted in various attitudes of static forward or backward pitch. The gains of the horizontal and torsional components of the vestibuloocular reflex (VOR) were measured for each tilt position. The gains as a function of tilt position were fit with sinusoidal functions, and spatial gains and phases were determined. After control responses were recorded, the semicircular canals were plugged, animals were allowed to adapt, and the test procedure was repeated. Animals were prepared with only the anterior and posterior canals intact [vertical canal (VC) animals], with only the lateral canals intact [lateral canal (LC) animal], and with only one anterior and the contralateral posterior canals intact [right anterior and left posterior canal (RALP) animals; left anterior and right posterior canal (LARP) animals]. 2. In normal animals, the gain of the horizontal (yaw axis) velocity of the compensatory eye movements decreased as they were pitched forward or backward, and a torsional velocity appeared, reversing phase at the peak of the horizontal gain. After the anterior and posterior canals were plugged (LC animal), the horizontal component was reduced when the animal was tilted backward; the gain was zero with about -60 degrees of backward tilt. The spatial phase of the torsional component had the same characteristics. This is consistent with the fact that both responses were produced by the lateral canals, which from our results are tilted between 28 and 39 degrees above the horizontal stereotaxic plane. 3. After both lateral canals were plugged (VC animals), horizontal velocity was reduced in the upright position but increased as the animals were pitched backward relative to the axis of rotation. Torsional velocities, which were zero in the upright position in the normal animal, were now 180 degrees out of phase with the horizontal velocity. The peak values of the horizontal and torsional components were significantly shifted from the normal data and were closely aligned with each other, reaching peak values at approximately -56 degrees pitched back (-53 degrees horizontal, -58 degrees torsional). The same was true for the LARP and RALP animals; the peak values were at -59 degrees pitched back (-55 degrees horizontal, -62 degrees torsional). Likewise, in the LC animal the peak yaw and roll gains occurred at about the same angle of forward tilt, 35 degrees (30 degrees horizontal, 39 degrees torsional). Thus, in each case, the canal plugging had transformed the VOR from a compensatory to a direction-fixed response with regard to the head. Therefore there was no adaptation of the response planes of the individual canals after plugging. 4. The data were compared with eye velocity predictions of a model based on the geometric organization of the canals and their relation to a head coordinate frame. The model used the normal to the canal planes to form a nonorthogonal coordinate basis for representing eye velocity. An analysis of variance was used to define the goodness of fit of model predictions to the data. Model predictions and experimental data agreed closely for both normal animals and for the animals with canal lesions. Moreover, if horizontal and roll components from the LC and VC animals were combined, the summation overlay the response of the normal monkeys and the predictions of the model. In addition, a combination of the RALP and LARP animals predicted the response of the lateral-canal-plugged (VC) animals. 5. When operated animals were tested in light, the gains, peak values, and spatial phases of horizontal and roll eye velocity returned to the preoperative values, regardless of the type of surgery performed. This indicates that vision compensated for the lack o
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S. Awad, Anas, et Iman M. Al-Zaka. « Comparative Analysis of Marginal Adaptation of Different Root Canal Sealers Using Scanning Electron Microscope ». Mustansiria Dental Journal 19, no 2 (30 décembre 2023) : 251–59. http://dx.doi.org/10.32828/mdj.v19i2.982.
Texte intégralRésumé :
Aims:The present study aimed to evaluate and examine the degree of marginal adaptation of several root canal sealers using a scanning electron microscope (AH Plus, MTA-Fillapex, Total-Fill, and GuttaFlow Bioseal) to root dentine.
Methods and Material:Forty extracted mandibular premolars with completely formed apices and a single root were selected. The root canals were instrumented after the decoronation of teeth. The samples (n = 10) were divided randomly into four groups. Group (1) was sealed with a resin-based sealer (AH Plus), Group (2) with an MTA-based sealer (MTA-Fillapex), Group (3) with a bioceramic sealer (TotalFill BC), and Group (4) with a silicone-based sealer (GuttaFlow Bioseal). After horizontally slicing samples with a diamond disk, marginal adaptability was evaluated using SEM.
One-way ANOVA test and the multiple Post hoc test of Tukey was reliant on the statistical analysis of the data.
Results: TotalFill BC has shown significantly higher marginal adaptation than MTA-Fillapex and GuttaFlow Bioseal (P < 0.05). There is no significant difference between apical and coronal sections in the four tested groups under SEM (P < 0.05).
Conclusions: Total fill BC outperformed the other tested sealers in terms of marginal adaptability.
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Rodriguez, L. P., J. M. Maestre, E. F. Camacho et M. C. Sánchez. « Decentralized ellipsoidal state estimation for linear model predictive control of an irrigation canal ». Journal of Hydroinformatics 22, no 3 (13 avril 2020) : 593–605. http://dx.doi.org/10.2166/hydro.2020.150.
Texte intégralRésumé :
Abstract A centralized linear MPC is used to stabilize an irrigation system whose operation is represented by an integrator-delay model. Since not all the state variables can be measured, a decentralized ellipsoidal estimation strategy is proposed. This approach keeps the quality of a centralized estimation and reduces significantly the computation time for the systems considered. An adaptation of Test Canal 1, developed by the ASCE Task Committee on Canal Automation Algorithms, is used as a case study to show the performance of the proposed methodology.
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Formby, C., et D. A. Robinson. « Measurement of vestibular ocular reflex (VOR) time constants with a caloric step stimulus* ». Journal of Vestibular Research 10, no 1 (1 février 2000) : 25–39. http://dx.doi.org/10.3233/ves-2000-10104.
Texte intégralRésumé :
A protocol is described for measuring responses to a broadband (1–2 Hz) caloric step stimulus from which the vestibular ocular reflex (VOR) and adaptation time constants can be estimated. This novel stimulation is the caloric equivalent to a rotatory step of head acceleration. In this protocol, the ear is irrigated continuously for 5 min with water at a constant temperature. During the initial 2-min period of irrigation the subject is seated and leaning forward in a nonstimulable position (horizontal canals in a horizontal plane). This irrigation phase establishes a steady-state thermal gradient across the horizontal canal, effectively eliminating thermal dynamic properties of the caloric transmission as a confounding factor. At the end of this phase, the subject is rapidly reclined to a stimulable position (horizontal canals in vertical plane) that elicits the VOR nystagmus response to an on-step of force on the cupula. Consistent with adaptation processes, the VOR response first increases and then declines gradually over the 2-min period that the step of force is maintained. Four minutes after the onset of irrigation, the subject is rapidly returned to the nonstimulable position (off-step), which is then maintained for a final 1 min. The response after the off-step, which releases the force on the cupula, reveals reversed after-nystagmus due to adaptation. Five subjects provided caloric step responses for 26 caloric temperature conditions spanning the range from 28.4 to 43.0 ∘ C. The resulting responses were fitted with an adaptation model similar to models applied to rotatory acceleration step responses. Estimates of the model parameters for robust caloric stimulation, including time constants for the VOR (18.3 sec) and for vestibular adaptation (153.2 sec), are considered in relation to corresponding values reported in the literature for rotatory and caloric vestibular stimulation. The results suggest that caloric step stimulation can be used successfully to probe VOR dynamics.
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Stroparo, Geraldo Fernando, Jeferson Luis De Oliveira Stroparo, Paula de Moura, Tatiana Miranda Deliberador, Allan Abuabara, Natanael Henrique Ribeiro Mattos, Camila Paiva Perin, Marilisa Carneiro Leão Gabardo, Arissa Michelle Yamada Corrêa et Flares Baratto-Filho. « Technical adaptations of manual and rotary instruments for preparing a giant canine tooth ». Research, Society and Development 10, no 8 (14 juillet 2021) : e39710817416. http://dx.doi.org/10.33448/rsd-v10i8.17416.
Texte intégralRésumé :
Teeth with extraordinary length are a rare condition that complicates endodontic procedures due to the difficult in being reached the working length and making the adequate preparation of the root canal, once there are no endodontic instruments longer than 31 mm commercially available. This study presents a description of technical adaptations for endodontic preparation of a maxillary canine with 39.59 mm of length. The procedures adopted were based on the consultation of the literature regarding the treatment of long teeth, and included endodontic instrument adaptation and changing the reference point of the instrument. This study shows that extremely long teeth can be successfully instrumented endodontically using the described clinical techniques.
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A, Tamara Nitya, Nanik Zubaidah et Moch Mudjiono. « The Effectiveness of 2.5% NaOCl Irrigation and 17% EDTA against the Sealing Ability of Resin Paste ». Conservative Dentistry Journal 9, no 2 (25 juin 2020) : 105. http://dx.doi.org/10.20473/cdj.v9i2.2019.105-108.
Texte intégralRésumé :
Background: Root canal irrigation seeks the elimination of bacteria and its products from the root canal. If debris is left in the root canal, it can prohibit adaptation between obturationmaterial and root canal wall. Therefore, it can decrease the sealing ability of obturation material. Purpose: To assess the effectiveness of 2.5% NaOCl and 17% EDTA on the apical sealing ability of resin obturation paste. Method: The roots of 18 human mandibular premolar teeth were selected and the root canal was prepared using a conventional technique. Samples were irrigated with 2.5% NaOCl, and17% EDTA, and sterile aquadest (Aqua Deastilata) as a control group. Samples were filled with gutta-percha and top seal. Samples were soaked in 2% methylene blue for 48 hours to measure the depth of microleakage. Result: The mean apical leakage after irrigation with 2.5% NaOCl; 17% EDTA; and sterile aquadest in the sequence were 0.92 mm; 3.6 mm; and 8.08 mm. Conclusion: 2.5% NaOClhas less depth of microleakage than 17% EDTA. However, the depth of microleakage cannot demonstrate the exact sealing ability of the resin paste due to some factors.
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Jain, A., S. Chandra, S. Chandra et R. Srivastava. « Effect of various root canal irrigante on the adaptation of root canal sealer in permanent teeth – A SEM study ». Endodontology 11, no 1 (1999) : 21. http://dx.doi.org/10.4103/0970-7212.347451.
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