Middle Cross-sections Research Articles

Evaluation of Canal Transportation and Centering Ability of RaCe and Af f-one Systems by Cone-beam Computed Tomography: An in Vitro Study.

Rotary systems have made significant advances to improve their root canal preparation efficacy. These instruments can properly preserve the root canal anatomy and morphology. The present in vitro study aimed to compare canal transportation and centering ability of RaCe and Af f-one systems using cone-beam computed tomography. Thirty-six mandibular molars were included. The samples were randomly assigned to two groups (n=18): group 1, RaCe, and group 2, Af f-one. Canal preparation was conducted using the respective files according to the manufacturers' instructions. The cone-beam computed tomographic scanning of the samples was performed before and after preparation. The data were analyzed by using two-way ANOVA. In both the RaCe and Af f-one rotary systems, canal centrality and transportation were similar at coronal, middle, and apical cross-sections. In addition, canal transportation and centrality were identical in the RaCe and Af f-one rotary files (P<0.05). The two studied rotary systems did not exhibit significant differences in root canal transportation and preservation of root canal centrality in the apical, middle, and coronal thirds.

Quantification of carpal tunnel morphology using centroid-to-boundary distance shape signatures.

Morphology analysis is valuable to understanding risk factors and the etiology of carpal tunnel (CT) syndrome. The objective of this study was to investigate morphology changes along the length of the CT using shape signatures (SS). Analysis was performed on ten cadaveric specimens in neutral wrist posture. Centroid-to-boundary distance SS were generated for proximal, middle, and distal CT cross-sections. Phase shift and Euclidean distance were quantified relative to a template SS for each specimen. Medial, lateral, palmar, and dorsal peaks were identified on each SS to generate metrics of tunnel width, tunnel depth, peak amplitude, peak angle. Width and depth measures were also performed using previously reported methods to serve as a basis of comparison. The phase shift revealed twisting of 21° between the ends of the tunnel. Distance from the template and width varied significantly over the length of the tunnel, while depth did not. Measures of width and depth using the SS method were consistent with previously reported methods. The SS method afforded the advantage of peak analysis with overall trends of peak amplitude indicating flattening of the tunnel at the proximal and distal ends relative to a rounder shape in the middle.

PECULIARITIES OF INTERACTION OF Cu-W COMPOSITE MATERIALS WITH THERMAL ARC DISCHARGE PLASMA

This work is a part of acomplex investigation of the interaction of Cu-W composite materials with thermal electric arc discharge plasma. The plasma of 3.5 A DC arc discharge between novel Cu-W composite materials, fabricated by shock pressing technology at the temperature of 750°C, was studied at this stage. Spectra of such plasma emission were registered and treated to determine the radial distributions of plasma temperature in three different cross-sections of the plasma channel, namely in near-cathode, near-anode and middle cross-sections.

Quantitative Analysis of Cone-Beam Computed Tomography Artifacts Induced by Nonmetallic Root Canal Filling Materials Using Different Fields of View: In Vitro Study.

Cone-beam computed tomography (CBCT) imaging artifacts can hinder accurate diagnosis of several conditions. The aim of this study was to quantify CBCT artifacts created by nonmetallic root canal filling materials using two fields of view (FOV). Root canals of twenty extracted maxillary central incisors (n = 20) were instrumented and randomly divided into four equal groups: canals in Group 1 were filled with gutta-percha, canals in Group 2 with mineral trioxide aggregate (MTA) and gutta-percha, canals in Group 3 with gutta-percha and glass-fiber posts, and canals in Group 4 with MTA and glass-fiber posts. Each tooth was mounted on a silicon block and scanned three times using a CBCT machine, first with a prefilling scan (control) and then with postfilling scans, using two different FOV (40∗50 mm and 80∗50 mm). Imaging software was used to measure grayscale pixel values of canal cross sections. Data were analyzed using t-test and paired t-test statistical tests, with statistical significance set at p ≤ 0.05. Dentin at the apical and middle third of the teeth showed a significant decrease in minimum grayscale values in association with gutta-percha (p = 0.027, p = 0.034). However, a wide 80∗50 FOV showed a significant increase in maximum grayscale values of coronal (p = 0.048) and apical dentin (p = 0.049). Glass-fiber posts in middle third cross sections also corresponded to an increase in maximum grayscale values (p = 0.018). Gutta-percha produced dark band artifacts in the root's middle and apical thirds, whereas white streak artifacts were produced by gutta-percha in the coronal third and glass-fiber posts in the coronal and middle thirds when imaged with a wider FOV. A smaller FOV is therefore recommended for CBCT imaging, as it produces fewer artifacts.

Cortical Thickness Adaptive Response to Mechanical Loading Depends on Periosteal Position and Varies Linearly With Loading Magnitude.

The aim of the current study was to quantify the local effect of mechanical loading on cortical bone formation response at the periosteal surface using previously obtained μCT data from a mouse tibia mechanical loading study. A novel image analysis algorithm was developed to quantify local cortical thickness changes (ΔCt.Th) along the periosteal surface due to different peak loads (0N ≤ F ≤ 12N) applied to right-neurectomised mature female C57BL/6 mice. Furthermore, beam analysis was performed to analyse the local strain distribution including regions of tensile, compressive, and low strain magnitudes. Student’s paired t-test showed that ΔCt.Th in the proximal (25%), proximal/middle (37%), and middle (50%) cross-sections (along the z-axis of tibia) is strongly associated with the peak applied loads. These changes are significant in a majority of periosteal positions, in particular those experiencing high compressive or tensile strains. No association between F and ΔCt.Th was found in regions around the neutral axis. For the most distal cross-section (75%), the association of loading magnitude and ΔCt.Th was not as pronounced as the more proximal cross-sections. Also, bone formation responses along the periosteum did not occur in regions of highest compressive and tensile strains predicted by beam theory. This could be due to complex experimental loading conditions which were not explicitly accounted for in the mechanical analysis. Our results show that the bone formation response depends on the load magnitude and the periosteal position. Bone resorption due to the neurectomy of the loaded tibia occurs throughout the entire cross-sectional region for all investigated cortical sections 25, 37, 50, and 75%. For peak applied loads higher than 4 N, compressive and tensile regions show bone formation; however, regions around the neutral axis show constant resorption. The 50% cross-section showed the most regular ΔCt.Th response with increased loading when compared to 25 and 37% cross-sections. Relative thickness gains of approximately 70, 60, and 55% were observed for F = 12 N in the 25, 37, and 50% cross-sections. ΔCt.Th at selected points of the periosteum follow a linear response with increased peak load; no lazy zone was observed at these positions.

Prevalence of C-shaped second mandibular molar canals in the population of central Serbia: A cone-beam computed tomography study

Background/Aim. C-shaped canals are a complex morphological variation of the tooth root canal system that, if present, could greatly affect the outcome of endodontic therapy. The prevalence of these canal configurations varies between the populations of different ethnic and geographical origins. Therefore, the goal of this study was to analyze the prevalence and morphology of mandibular second molar C-shaped canals in the population of Central Serbia. Methods. The study included a total of 1 99 mandibular second molars receiving a cone-beam computed tomography (CBCT) examination and determining the presence of C-shaped canal systems, their configuration, minimal wall thickness and its relative position on axial cross-sections at the coronal, middle, and apical level. Results. The prevalence of C-shaped mandibular second molars was 5.53%. C1 canal configuration was the most frequent at the coronal cross-section, while C2 configuration was the most frequent at middle and apical cross-sections. Minimal wall thickness decreased going apically, with the mean value of 1.01 mm at the coronal, 0.87 mm at the middle, and 0 .67 mm at the apical cross-sections. Minimal wall thickness was mostly directed lingually at all cross-sectional levels. Conclusion. C-shaped canals should be expected in mandibular second molars of the population of Central Serbia. CBCT was shown to be the most valuable technique to determine C-shaped canals and facilitate understanding of the C-shaped canal morphology; its implementation could improve the success of endodontic therapy, especially if the complex root canal configuration is present.

Load variation of the wheel-mounted brake disc bolts of a high-speed train

The reliability of brake disc bolts is crucial to the operational safety of high-speed electrical multi-units (EMUs). It is of great significance to investigate the bolt loads to ensure the bolt service life. A theoretical analysis is completed according to the jointed structure and the service condition of the bolts. By establishing a finite element model of the wheel-rail contact, the bolt loads of the wheel-mounted brake disc under high-speed rotation are simulated. A field experiment is implemented to obtain the dynamic loads of wheel-mounted brake disc bolts of a Chinese high-speed train based on a load test technique. The tested bolt loads include the tensile force, radial bending moment and circumferential bending moment. The simulation results are compared with the field test data. It validates the finite element model. The results indicate that the bolt loads are closely related to the operation speed of the high-speed EMU. The theoretical calculation method and the finite element method both prove that the amplitude and the direction of the radial bending moment along the bolt are inconsistent. The extrema of the radial bending moments appear in the left, middle and right cross-sections. The radial bending moment at the left cross-section is larger than that at the right cross-section because of the asymmetry of the wheel structure.

Influence of Different Types of Root Canal Irrigation Regimen on Resin-based Sealer Penetration and Pushout Bond Strength.

IntroductionThe main objective of root canal treatment is to eliminate the micro-organism from the root canal system and three-dimensional obturation. The proper cleaning and shaping can be accomplished only by using appropriate instruments and effective irrigants during the root canal treatment.AimTo evaluate the influence of three different final irrigation regimen on depth of penetration of root canal sealers and push-out bond strength of obturation material.Materials and methodsThirty-six extracted single-rooted mandibular premolar human teeth with straight canals were decoronated and instrumented according to groups. Group I: Root canals were irrigated with 3% sodium hypochlorite (NaOCl), then irradiated with 980 nm diode laser (n = 12), Group II: Root canals were irrigated with 3% NaOCl, followed by 17% ethylenediaminetetraacetic acid (EDTA) (n = 12), Group III: Root canals were irrigated with 3% NaOCl, followed by 10% citric acid (n = 12). In each sample, single cone obturation was done with gutta-percha using AH plus sealer incorporated with rhodamine B dye. After seven days coronal, middle and apical thin cross sections were made for evaluation of dentinal tubule sealer penetration depth and pushout bond strength using confocal laser scanning microscope (CLSM) and universal testing machine, respectively. Statistical analysis among the three groups was done by using Kruskal-Wallis and post hoc test.ResultsMean tubular penetration depth between diode laser (136.57 ± 48 µm), EDTA (130.56 ± 53 µm) and citric acid (113.37 ± 34 µm; P < 0.05) showed statistically highly significant results. Pushout bond strength did not differ significantly between diode laser (1.21 ± 0.48 Mpa), EDTA (1.05 ± 0.45 Mpa) and citric acid (0.93 ± 0.44 Mpa; P > 0.05).ConclusionMean tubular penetration depth of AH plus sealer was better in diode laser than in EDTA and citric acid. Average push-out bond strength of obturation material did not differ significantly between diode laser, EDTA and citric acid.

Effect of Relining with Different Composite Resins on the Push-out Bond Strength of Anatomical Fiber Posts to Root Canal Dentin.

Relining fiber posts using composite resins helps the posts adapt to the anatomical space of the root canals. The aim of this study was to evaluate the effect of composite resin type on the push-out bond strength of anatomical fiber posts to intra canal dentin. Forty-eight bovine upper incisors were prepared for post space after root canal therapy and randomly divided in to six groups. Five different types of composite resin (GrandioSO, GrandioSO Heavy Flow, X-tra Fil, X-tra base and everX Posterior) were used for relining the prepared fiber posts. In the control group, the prepared post was cemented into the post space without relining. Cervical, middle and apical cross-sections were achieved from each root and push-out test was conducted at a crosshead speed of 0.5 mm/min. One sample from each group was scanned using a micro-CT scanner which provided views from the apical, middle and coronal thirds. Data were analyzed using Kolmogorov-Smirnov test, repeated measures ANOVA and post hoc tests using SPSS 17 (P<0.05). Statistical analysis showed significant differences in terms of mean push-out bond strengths between different composite resin types and cross-sections (P<0.001). The mean push-out bond strength of the samples relined with Grandio SO composite resin (15.48±2.32) and X-tra Fil Bulk-fill composite resin (14.09±1.98) were significantly higher than that of other groups (P<0.05). The unrelined group had a mean push-out bond strength (5.94±1.45) which was significantly lower than that in other groups (P<0.05). In addition, there was a relationship between cross-sections and composite resin types (P<0.05). This in vitro study showed that the composite resins used for relining can affect the push-out bond strength to intra canal dentin based on their physical and mechanical properties.

Apical bud break and early vegetative shoot growth improving the mango malformation development: a new point of view

Mango malformation induced by Fusarium spp. is one of the most destructive diseases worldwide. The production losses vary from 50 to 80%. Mango growth is intermittent being characterized by resting periods (RP) intercalary between each vegetative flow. Each new flush promotes changes in the intensity of epidemics, but the interaction of the RPs on the pathogen virulence and pathogenesis are unknown. To provide some information about this interaction, the effect of Fusarium spp. infection on incubation periods (PI), maximum severity (Ymax) and days to maximum severity (DYmax) was compared in nursery plants of cvs ‘Mallika’ and ‘Haden’ inoculated in the resting and active early growth (juvenile) stages, using the veneer grafting technique to end the rest phase in 2016. When both cultivars were inoculated in the resting stage, at 14 and 0 incubation days before grafting (dbg), ‘Haden’ was more susceptible than ‘Mallika’ showing quicker PIs and greater DYmax and Ymax in 42, 55 and 82% respectively. Likewise, ‘Haden’ shoots inoculated during resting stages or active early growth, at 22 days after grafting (dag), had a shortest PI and DYmax values, by up to 32 and 45% respect to mature inoculated shoots that remained attached to the plant. Ymax was not affected by the phenology of the inoculated shoots and PI were higher only in shoots inoculated at 75–85 dag (P < 0.05%). Middle and apical cross sections of mature and juvenile ‘Haden’ and ‘Mallika’ shoots observed under scanning electron microscope showed contrasted anatomical differences in tissue differentiation.

Salinization pattern and its spatial distribution in the irrigated agriculture of Northern Ethiopia: An integrated approach of quantitative and spatial analysis

Salinity adversely affects the environment, agro-ecosystems and agricultural productivity of arid and semi-arid regions worldwide. This salinization occurs due to natural, human or both actions on the dynamic earth system. This study was conducted to quantify the magnitude and map the spatial distributions of salinity of the irrigated agriculture in northern Ethiopia. A total of 717 soil and 13 water samples from nine irrigation schemes were used for analysis. The soil samples were collected on a grid basis from 0 to 15 cm and 15–30 cm soil depths in the plant's root zone whilst surface water samples were collected from the irrigation water source, middle and lower cross-sections of the irrigation schemes. These soil and water samples were analyzed quantitatively for 14 salinity parameters and results compared with worldwide standard values. In addition, the spatial analysis was made for three basic salinity parameters of hydrogen ion concentrations (pH), Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR). Even if, there are non-significant variations between soil depths and among the irrigation cross-sections, a salinity is observed at 33% of the schemes. Higher pH average values are spatially concentrated downstream whilst SAR and EC showed inconsistent variations among irrigation schemes. The quantitative and spatial salinity analysis revealed that Gum Selassa, Gereb Kunchi and Tegahne irrigation schemes have potential salinity levels. As a result, salinity management strategies and community-based salinity management approaches that involve farmers’ participation is vital to create a sense of ownership. Irrigation users and decision makers should consider possible measures of minimizing salinity build-up thereby increasing agricultural productivity in a sustainable way.

Numerical study of turbulent natural convection in a cube having finite thickness heat-conducting walls

Three-dimensional transient natural convection in a cubic enclosure having finite thickness solid walls subject to opposing and horizontal temperature gradient has been investigated by a finite volume method. The turbulent flow considered into the volume is described mathematically by the 3D Reynolds averaged Navier–Stokes equations using the standard k–e model with wall functions, including the energy equation. The velocity and temperature distributions were calculated at fixed Prandtl number, Pr = 0.7 and different values of the Rayleigh number, thermal conductivity ratio and dimensionless time. Three-dimensional velocity and temperature fields, temperature profiles at middle cross-sections and average Nusselt numbers have been presented. It has been found that an insertion of the third coordinate for the conjugate problem leads to a decrease in the average Nusselt number by 5.8 % in conditions of a stationary heat transfer mode.

Finite Element ANSYS Analysis of the Behavior for 6061-T6 Aluminum Alloy Tubes under Cyclic Bending with External Pressure

In this paper, by using adequate stress-strain relationship, mesh elements, boundary conditions and loading conditions, the finite element ANSYS analysis on the behavior of circular tubes subjected to symmetrical cyclic bending with or without external pressure is discussed. The behavior includes the moment-curvature and ovalization-curvature relationships. In addition, the calculated ovalizations at two different sections, middle and right cross-sections, are also included. Experimental data for 6061-T6 aluminum alloy tubes subjected to cyclic bending with or without external pressure were compared with the ANSYS analysis. It has been shown that the analysis of the elastoplatic moment-curvature relationship and the symmetrical, ratcheting and increasing ovalization-curvature relationship is in good agreement with the experimental data.

The Early Pleistocene water buffalo associated with Gigantopithecus from Chongzuo in southern China

Water buffalo materials were unearthed from the cave deposits paleomagnetically dated at 1 Ma during the excavation of Gigantopithecus in Queque Cave in Chongzuo, Guangxi, southern China. The morphological comparison and phylogenetic analyses show that the materials represent a new subspecies, Bubalus brevicornis chowi subsp. nov. It is a water buffalo with relatively short and stout horn core, the proximal and middle core cross sections are nearly equilateral triangular; a short neck or pedicle is present between the frontal and core. The materials represent the earliest record of fossil water buffalo. A consequent review of all fossil water buffaloes from China suggests integrating the previously reported ten species into a proposed six species.

Aroma Profile and Volatiles Odor Activity Along Gold Cultivar Pineapple Flesh

Physicochemical attributes, aroma profile, and odor contribution of pineapple flesh were studied for the top, middle, and bottom cross-sections cut along the central axis of Gold cultivar pineapple. Relationships between volatile and nonvolatile compounds were also studied. Aroma profile constituents were determined by headspace solid-phase microextraction at 30 °C, followed by gas chromatography/mass spectrometry analysis. A total of 20 volatile compounds were identified and quantified. Among them, esters were the major components which accounted for 90% of total extracted aroma. Methyl butanoate, methyl 2-methyl butanoate, and methyl hexanoate were the 3 most abundant components representing 74% of total volatiles in pineapple samples. Most odor active contributors were methyl and ethyl 2-methyl butanoate and 2,5-dimethyl 4-methoxy 3(2H)-furanone (mesifuran). Aroma profile components did not vary along the fruit, but volatile compounds content significantly varied (P < 0.05) along the fruit, from 7560 to 10910 μg/kg, from the top to the bottom cross-sections of the fruit, respectively. In addition, most odor-active volatiles concentration increased from the top to the bottom 3rd of the fruit, concurrently with soluble solids content (SSC) and titratable acidity (TA) differences attributed to fruitlets distinct degree of ripening. Large changes in SSC/TA ratio and volatiles content throughout the fruit found through this study are likely to provoke important differences among individual fresh-cut pineapple trays, compromising consumer perception and acceptance of the product. Such finding highlighted the need to include volatiles content and SSC/TA ratio and their variability along the fruit as selection criteria for pineapples to be processed and quality assessment of the fresh-cut fruit.

Dilated basilar arteries in patients with congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) patients show hypoventilation during sleep and severe autonomic impairments, including aberrant cardiovascular regulation. Abnormal sympathetic patterns, together with increased and variable CO 2 levels, lead to the potential for sustained cerebral vasculature changes. We performed high-resolution T1-weighted imaging in 13 CCHS and 31 control subjects using a 3.0-T magnetic resonance imaging scanner, and evaluated resting basilar and bilateral middle cerebral artery cross-sections. Two T1-weighted image series were acquired; images were averaged and reoriented to common space, and regions containing basilar and both middle cerebral arteries were oversampled. Cross-sections of the basilar and middle cerebral arteries were manually outlined to calculate cross-sectional areas, and differences between and within groups were evaluated. Basilar arteries in CCHS were significantly dilated over control subjects, but both middle cerebral artery cross-sections were similar between groups. No significant differences appeared between left and right middle cerebral arteries within either group. Basilar artery dilation may result from differential sensitivity to high CO 2 over other vascular beds, damage to serotonergic or other chemosensitive cells accompanying the artery, or enhanced microvascular resistance, and that dilation may impair tissue perfusion, leading to further neural injury in CCHS.

Ex vivo study on root canal instrumentation of two rotary nickel–titanium systems in comparison to stainless steel hand instruments

To investigate instrumentation time, working safety and the shaping ability of two rotary nickel-titanium (NiTi) systems (Alpha System and ProTaper Universal) in comparison to stainless steel hand instruments. A total of 45 mesial root canals of extracted human mandibular molars were selected. On the basis of the degree of curvature the matched teeth were allocated randomly into three groups of 15 teeth each. In group 1 root canals were prepared to size 30 using a standardized manual preparation technique; in group 2 and 3 rotary NiTi instruments were used following the manufacturers' instructions. Instrumentation time and procedural errors were recorded. With the aid of pre- and postoperative radiographs, apical straightening of the canal curvature was determined. Photographs of the coronal, middle and apical cross-sections of the pre- and postoperative canals were taken, and superimposed using a standard software. Based on these composite images the portion of uninstrumented canal walls was evaluated. Active instrumentation time of the Alpha System was significantly reduced compared with ProTaper Universal and hand instrumentation (P < 0.05; anova). No instrument fractures occurred in any of the groups. The Alpha System revealed significantly less apical straightening compared with the other instruments (P < 0.05; Mann-Whitney U test). In the apical cross-sections Alpha System resulted in significantly less uninstrumented canal walls compared with stainless steel files (P < 0.05; chi-squared test). Despite the demonstrated differences between the systems, an apical straightening effect could not be prevented; areas of uninstrumented root canal wall were left in all regions using the various systems.

Changes in the bovine teat canal during the nonlactating period and early lactation, as measured by teat canal impressions

Summary Changes in dimensions of impressions of the lumen of the teat canals of 13 cows were examined at 17 intervals during the nonlactating period and early lactation. Impressions were made of teats of 2 diagonally opposed quarters of each cow, using dental impression material. Impression length was measured and cross sections of the impressions at the proximal (distal to Furstenburg rosette), distal (proximal to the teat orifice), and middle (midway between the 2), portions of the teat canal were prepared. Cross sections were photographed and enlarged, and circumference and area were determined by use of planimetry. Effects of making repeated impressions during the nonlactating period and early lactation on new infection rates and somatic cell counts were also assessed. Mean length of teat canal impressions decreased between days 0 and 3 of involution and during the prepartum periods. Depending on the level from which they were taken, cross-sectional areas of impressions tended to increase or increased significantly during the period of involution and again in the prepartum period. Significant changes in cross-sectional area were not observed during early lactation. Changes in circumference of proximal, middle, and distal cross sections followed trends similar to area measurements, but were more variable and differences were less statistically significant. On the basis of our findings, we suggest that heightened susceptibility to new infection during mammary involution and the prepartum period may be attributable, in part, to changes in the patency of the teat canal. Making impressions repeatedly throughout the nonlactating period and early lactation did not affect the number of new intramammary infections.

High-power TE11 and TM11 circular polarizers in oversized waveguides at 70 GHz

Elliptical deformation of oversized, smooth-wall circular waveguides can produce choosable elliptical or circular polarization from a linearly polarized TE11 or TM11 mode used as intermediate linearly polarized modes in TEO1 to HE11 mode conversion sequences in electron cyclotron resonance heating (ECRH) of magnetically confined thermonuclear fusion plasmas with high-power gyrotrons. Mode coupling in elliptically distorted overmoded circular waveguides has been studied theoretically and experimentally in order to optimize TE11 (and TM11) polarizers (I.D.=27.79 mm) for the 1 MW/70 GHz long-pulse (3s) ECRH system on the Garching Stellarator W VII-AS. Coupling coefficients for ellipticity coupling of non-degenerate modes are given (coupled-mode differential equations formalism). The polarization converters essentially consist of smooth-wall circular waveguides which are gradually squeezed. A sine-squared function of the length coordinate is used to get an almost elliptical crosssection in the middle and circular cross sections at both ends. Arbitrary elliptical polarization states can be generated introducing an extremely low level (<<1%) of undesired spurious modes. Well defined differential phase characteristics have been achieved.

An in vitro histological comparison of the step-back, sonic, and ultrasonic instrumentation techniques in small, curved root canals

The effectiveness of different methods of root canal instrumentation in small, curved canals was assessed by histological examination. Compared were the step-back hand instrumentation technique, sonic instrumentation with the Endostar 5, and ultrasonic instrumentation with the Cavi-Endo and PZ-KTec prototype systems. Eighty root canals in freshly extracted humanteeth were randomly placed into these four instrumentation groups of 20 teeth each. Five uninstrumented canals served as controls. Following canal preparation and histological processing, coronal, middle, and apical cross-sections were examined for areas of remaining debris and predentin, the percentage of planed canal walls, and percentage of increase in canal area. The results showed significant differences among the four canal preparation methods in all evaluation categories.