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PubMed1997

Root cold tolerance of black spruce seedlings: viability tests in relation to survival and regrowth.

Root systems of 6-month-old, cold-hardened, container-grown black spruce seedlings (Picea mariana (Mill.) B.S.P.) were exposed to 0, -5, -10, -15, -20, or -22.5 degrees C. Freezing-induced damage to fine roots, coarse roots and the whole root system was assessed by various viability tests including leakage of electrolytes, leakage of phenolic compounds, water loss, root and shoot water potentials, and live root dry mass. To assess the long-term effects of freezing-induced root damage, seedling survival and regrowth were measured. Leakage of both electrolytes and phenolic compounds differed among fine roots, coarse roots, and whole root systems. In coarse roots and the whole root system, but not in fine roots, leakage of electrolytes, leakage of phenolic compounds, water loss, and root and shoot water potentials were correlated with percentage of live root dry mass which, in turn, was highly correlated with seedling survival and regrowth. Compared with live root dry mass, electrolyte and phenolic leakage, water loss, and root and shoot water potentials were less well correlated with seedling survival and regrowth. Among the viability tests, electrolyte leakage of the whole root system correlated most closely with seedling survival and regrowth. Under freezing conditions that destroyed less than 50% of each seedling's root system, about 70% of the seedlings survived and subsequent growth was little affected, whereas under freezing conditions that destroyed 70% of each seedling's root system, only about 30% of the seedlings survived and subsequent growth was reduced compared with that of undamaged plants.

Journal Article↗

PubMed1996

The behaviour of normal and agravitropic transgenic roots of rapeseed (Brassica napus L.) under microgravity conditions.

In the TRANSFORM experiment for IML-2 on the Space Shuttle Columbia, normal (wild type = WT) and genetically transformed agravitropic rapeseed roots were tested under microgravity conditions. The aim of the experiment was to determine if the wild-type roots behaved differently (growth, morphology, gravitropical sensitivity) from the transgenic roots. The appearance of the organelles and distribution of statoliths (i.e. amyloplasts with starch grains) in the gravitropic reactive cells (statocytes) under weightlessness was compared for the two types of roots. Attempts have also been made to regenerate new plants from the root material tested in space. Both the WT and the transgenic root types showed the expected increase in length during 36 h of photorecording. Contrary to the results of the ground controls, no significant difference in elongation rates was found between the WT and transgenic roots grown in orbit. However, there are indications that the total growth both in the WT and the transgenic roots was higher in the ground control than for roots in orbit. After a 60 min 1 x g stimulation of the roots on board the Shuttle, no detectable curvatures were obtained in either the transgenic or the WT roots. However, it cannot be excluded that a minute curvature development occurs in the root tips but was not detected due to technical reasons. The ultrastructure was well preserved in both the WT and the transgenic roots, despite the fact that the tissue was kept in the prefixative for over 3 weeks. No marked differences in ultrastructure were observed between the transformed root statocyte cells and the equivalent cells in the wild type. There were no obvious differences in root morphology during the orbital period. Light micrographs and morphometrical analysis indicate that the amyloplasts of both the wild type and transformed root statocytes are randomly distributed over the cells kept under micro-g conditions for 37 h after a 14 h stimulation on the 1 x g centrifuge. The main scientific conclusion from the TRANSFORM experiment is that the difference in growth found in the ground control between the WT and the transgenic root types seems to be eliminated under weightlessness. Explanations for this behaviour cannot be found in the root ultrastructure or in root morphology.

Brassica↗

PubMed2005

Root curvature: differences among dental morphotypes and modifications after mechanical instrumentation.

BACKGROUND: This study was designed to describe a method for measuring root curvature of extracted teeth, compare root curvature of four different dental morphotypes before mechanical instrumentation, and measure root curvature after mechanical instrumentation. METHODS: Fifty-five maxillary (14 central incisors, 13 lateral incisors, 14 cuspids, 14 premolars) extracted teeth were analyzed. Measurements were recorded on the horizontal plane at the most apical point of the cemento-enamel junction (CEJ). A 4 mm wide root portion on the buccal aspect was selected and recorded on this plane. A digital scanner traced the circle coinciding with the profile of this root portion and calculated its radius, arc, chord, and arrow (i.e., the perpendicular bisector of the chord). Since root curvature is the inverse of the radius (1/r), the radius was related to root curvature; the arc to the mesio-distal dimension of the root portion; and the reduction of the arrow to root flattening after mechanical instrumentation. The measurements were recorded four times: before treatment (baseline), after polishing, after a first root planing, and after a second root planing. The radii of each dental morphotype (upper central incisors, upper lateral incisors, upper canines, upper premolars) recorded in the first measurement were calculated and used for the statistical analyses: one-way analysis of variance (ANOVA) test and the Tukey multiple comparison method were used to study the curvature. The measurements of the radius, the arc, and the arrow at the four times were used for the statistical analyses: the two-way ANOVA test and the Tukey multiple comparison method were applied in the study of the root modifications after mechanical instrumentation. The accuracy and reliability of the method were also evaluated. RESULTS: The mean radii of the four dental morphotypes were: central incisors: 3.613 +/- 0.258 mm; lateral incisors: 2.558 +/- 0.256 mm; canines: 2.822 +/- 0.238 mm; and premolars: 2.321 +/- 0.179 mm. The statistical analyses revealed differences among central incisors, canines, lateral incisors, and premolars. There was no statistically significant difference between lateral incisors and premolars. Regarding the root modifications after mechanical treatment, the radius did not show statistically significant differences in any of the comparisons. The arc and the arrow did not show significant differences between baseline and polishing, while they did show significant differences after the second root planing. CONCLUSIONS: This study indicates that: 1) the method of measuring is accurate and reliable; 2) there are statistically significant differences among the root curvatures of different dental morphotypes; and 3) polishing did not modify the root. A vigorous root planing did not modify root curvature, but it did reduce the mesio-distal dimension and flatten the root surface slightly.

Analysis of Variance↗

PubMed2006

Detection of quantitative trait loci for seminal root traits in maize (Zea mays L.) seedlings grown under differential phosphorus levels.

Suboptimal phosphorus availability is a primary constraint for terrestrial plant growth. Seminal roots play an important role in acquisition of nutrients by plant seedlings. The length and number of seminal roots may be particularly important in acquisition of immobile nutrients such as phosphorus by increasing soil exploration. The objective of this study was to identify quantitative trait loci (QTL) controlling seminal root growth in response to phosphorus stress in maize, and to characterize epistatic interactions among QTL. Seminal root length and number were evaluated in 162 recombinant inbred lines derived from a cross between B73 and Mo17 in seedlings grown in a controlled environment. B73 and Mo17 significantly differed for seminal root length under low phosphorus, but not under adequate phosphorus conditions. Seminal root length of the population grown under low phosphorus ranged from 0 to 79.2 cm with a mean of 32.3 cm; while seminal root length of plants grown under high phosphorus ranged from 0.67 to 59.0 cm with a mean of 23.4 cm. Under low phosphorus, one main-effect QTL was associated with seminal root length and three QTL with seminal root number; under high phosphorus, two QTL with seminal root length and three QTL for seminal root number. These accounted for 11, 25.4, 22.8, and 24.1% of the phenotypic variations for seminal root length and number at low phosphorus, and seminal root length and number at high phosphorus, respectively. Di-genic epistatic loci were detected for seminal root length at low phosphorus (two pairs) seminal root number at low phosphorus (eight pairs), seminal root length at high phosphorus (four pairs), and seminal root number at high phosphorus (two pairs), which accounted for 23.2, 50.6, 32.2, and 20.3% of the total variations, respectively. Seminal root traits observed here were positively yet weakly correlated with shoot biomass in the field under low phosphorus, although no coincident QTL were detected. These results suggest that epistatic interactions are important in controlling genotypic variation associated with seedling seminal root traits.

Chromosome Mapping↗

PubMed2005

Clustered root distribution in mature stands of Fagus sylvatica and Picea abies.

Distribution of small roots (diameter between 2 mm and 5 mm) was studied in 19 pits with a total of 72 m(2) trench profile walls in pure stands of Fagus sylvatica and Picea abies. Root positions within the walls were marked and transformed into x-coordinates and y-coordinates. In a GIS-based evaluation, zones of potential influence around each root were calculated. The total potential influence produced isoline maps of relative root influence zones, thus indicating small root clustering. The questions studied were (1) whether there were marked clusters of small roots in the soil and (2) whether trees surrounding the pit (defined as tree density) correlate with the root abundance and distribution on the trench profile walls. Small roots of both species showed maximum abundance in the top 20 cm of the soil, where pronounced root clusters occurred next to areas with only low root accumulation. The area of root clusters did not differ significantly between the two stands. Weighted clumping, WC, calculated as a product of root class, and its area was used as an index of root clustering, which again did not differ between beech and spruce stands. However, evaluations on a single root level showed that beech achieved the same degree of clustering with lower number of roots. Regardless of soil properties related to root clusters, a significantly higher clustering acquired per root for beech than for spruce suggests beech to be more efficient in belowground acquisition of space. Because none of the parameters describing root clustering were correlated with tree density around the investigated soil profiles, clusters of small roots are inherently present within the tree stands.

Austria↗

PubMed1997

Evaluation of the post-operative lumbar spine with MR imaging. The role of contrast enhancement and thickening in nerve roots.

PURPOSE: Two new signs of lumbar nerve-root affection have been reported in recent years on the basis of MR examinations, namely: thickening in nerve roots; and contrast enhancement in nerve roots. The aim of this study was to assess contrast enhancement in nerve roots in a standardised way, and to evaluate the clinical significance of contrast enhancement and of nerve-root thickening in the symptomatic post-operative lumbar spine. MATERIAL AND METHODS: A total of 121 patients (who had previously been operated on for lumbar disc herniation) underwent 152 MR examinations, mainly on a 1.5 T system. Focal nerve-root enhancement was identified by visual assessment. Intradural enhancement was also quantified by pixel measurements that compared the affected nerve roots before and after contrast administration. Non-affected nerve roots were used as reference. RESULTS: Enhanced nerve roots in the dural sac increased at least 40-50% in signal intensity after contrast administration compared to pre-contrast images and also compared to non-affected nerve roots. Intradural nerve-root enhancement was seen in 10% of the patients and focal enhancement in the root sleeve was seen in a further 26%. Nerve-root thickening was seen in 30%. Good correlation with clinical symptoms was found in 59% of the patients with intradural enhancement, in 84% with focal enhancement, and in 86% with nerve-root thickening. The combination of thickening and enhancement in the nerve root correlated with symptoms in 86% of the patients. CONCLUSION: Nerve-root enhancement (whether focal or intradural) and thickening in the nerve root are significant MR findings in the post-operative lumbar spine. In combination with disc herniation or nerve-root displacement, these two signs may strengthen the indication for repeat surgery. However, root enhancement within 6 months of previous surgery may be a normal post-operative finding.

Adult↗

PubMed2001

Maturation, topophysis and other factors in relation to rooting in Larix.

We examined effects of mist quantity, topophysis (origin of cutting in the crown of 6-year-old trees), maturation state of the donor stock, and time of sticking on rooting and root system quality of cuttings representing five full-sib hybrid larch families obtained with Larix decidua Mill., L. laricina (du Roi) K. Koch, and L. kaempferi (Lamb.) Sarg. (Sieb. and Zucc.) Gord., as parents. Mist frequency, supplemental watering and family all had highly significant effects on percentage of cuttings rooting and root system quality. The high-frequency misting regime yielded both higher rooting percentages and higher quality root systems than the low-frequency regime without supplemental watering. Supplemental watering of the rooting medium in the low-frequency misting regime increased both percent rooting and root system quality to values comparable with those obtained by cuttings in the high-frequency misting regime. Rooting of cuttings from the top, middle and bottom whorls of 5-year-old plantation grown trees tended to decline with increasing height for three of the five families. Overall, height of cutting origin did not significantly affect rooting, but when analyzed separately, two families exhibited a significant decline in rooting toward the top of the trees. Age of donor ortet (ranging from 1 to 7 years) significantly affected both percent rooting and root system quality. Rooting percentages declined linearly with age, and root system quality declined more sharply than percent rooting. The relatively poor root system quality of cuttings from ortets older than 1 year was closely associated with plagiotropic growth. Softwood cuttings (stuck in mid-July) rooted better than hardwood cuttings (stuck in early September) across all families.

Forestry↗

PubMed1990

Root canal anatomy of mandibular second molars. Part I.

The root canal anatomy of 149 mandibular second molars was studied using a technique in which the pulp was removed, the canal space filled with black ink and the roots demineralized and made transparent. Of the 149 teeth, 22 per cent had single roots, 76 per cent had two roots and 2 per cent had three roots. In the single-rooted teeth, three canals were most common, while in the mesial root of the two-rooted teeth, two canals that joined near the apex and one canal in the distal root were most frequent. Round canals were most common in two-rooted teeth and C-shaped canals in single-rooted teeth. Transverse anastomoses were found in 33 per cent of roots, most commonly in the middle third of the root. Lateral canals were found in 72 per cent of roots, most commonly in the apical third of the root. The apical foramen was positioned at the apex in only 33 per cent of roots, and apical deltas were found in 35 per cent. The patient's age and race affected canal shape, with more round canals present in patients over 35 years of age, and more C-shaped canals in Asians. The sex of the patient and the side of the mouth affected the presence of apical deltas, with more being found in males and on the left side. Single-rooted teeth had more complex root canal systems than two-rooted teeth, with more lateral canals, transverse anastomoses, apical deltas and C-shaped canals.

Adolescent↗

PubMed1996

Root-end cavity preparation using the MicroMega Sonic Retro-prep Tip. SEM analysis.

The objective of this laboratory study was to compare root-end cavities prepared with sonic Retro-prep tips in a MM1500 Sonic Air handpiece with those created by burs in a conventional handpiece. A total of 80 single-rooted extracted human teeth with mature apices and straight canals were included in the study. Four groups of 20 extracted teeth were prepared as follows: I, a 3-4 mm root-end resection perpendicular to the long axis of the root, with a size 40 sonic Retro-prep tip creating an apical cavity 3 mm into root canal system; II, a 45 degrees bevel of the root-face removing a 3-4 mm root segment and root-end preparation as per group I; III, root-end resection as per group I, with an apical cavity prepared using a size 010 inverted cone bur 3 mm down the long axis of the root; IV, resection as per group II, followed by an apical cavity preparation with a size 010 inverted cone bur 3 mm into the root canal system. The apical root portion and root-end cavities were replicated and prepared for SEM analysis at x 20 and x 80 magnification. The degree of chipping associated with the margin of the root-end cavities, as evaluated with a standard grading system, and the incidence of root-face cracks were noted. Marginal chipping of root-end cavities prepared using sonic instrumentation was significantly worse than that produced by burs (P < 0.001). Perpendicular root-end resections showed significantly better scores than bevelled root-end resections (P < 0.005). The incidence of root-face cracking was low with no significant difference between the experimental groups.

Dental Instruments↗

PubMed2000

Tornado1 and tornado2 are required for the specification of radial and circumferential pattern in the Arabidopsis root.

The cell layers of the Arabidopsis primary root are arranged in a simple radial pattern. The outermost layer is the lateral root cap and lies outside the epidermis that surrounds the ground tissue. The files of epidermal and lateral root cap cells converge on a ring of initials (lateral root cap/epidermis initial) from which the epidermal and lateral root cap tissues of the seedling are derived, once root growth is initiated after germination. Each initial gives rise to a clone of epidermal cells and a clone of lateral root cap cells. These initial divisions in the epidermal/lateral root cap initial are defective in tornado1 (trn1) and trn2 plants indicating a requirement for TRN1 and TRN2 for initial cell function. Furthermore, lateral root cap cells develop in the epidermal position in trn1 and trn2 roots indicating that TRN1 and TRN2 are required for the maintenance of the radial pattern of cell specification in the root. The death of these ectopic lateral root cap cells in the elongation zone (where lateral root cap cells normally die) results in the development of gaps in the epidermis. These observations indicate that TRN1 and TRN2 are required to maintain the distinction between the lateral root cap and epidermis and suggest that lateral root cap fate is the default state. It also suggests that TRN1 and TRN2 repress lateral root cap fate in cells in the epidermal location. Furthermore, the position-dependent pattern of root hair and non-root hair cell differentiation in the epidermis is defective in trn1 and trn2 mutants. Together these results indicate that TRN1 and TRN2 are required for the maintenance of both the radial pattern of tissue differentiation in the root and for the subsequent circumferential pattern within the epidermis.

Arabidopsis↗

PubMed2001

Effect of topical alendronate on root resorption of dried replanted dog teeth.

Alendronate (ALN) is a third generation bisphosphonate with demonstrated osteoclast inhibitory activity that may slow down the resorptive process after severe traumatic injuries. Eighty-two premolar roots of five mongrel dogs were endodontically treated and restored, extracted and treated as follows: 70 roots were bench dried for either 40 or 60 min. Thirty-eight of these roots were then soaked for 5 min in a 1 mM solution of ALN in Hanks' Balanced Salt Solution (HBSS) and replanted. Thirty-two roots were soaked for 5 min in HBSS and replanted. In the remaining 12 roots which were not exposed to the bench drying procedure, a 0.5 mM deep lingual mid-root cemental defect was made. Six of these roots were soaked in a 1 mM solution of ALN in HBSS for 5 min and replanted. The other six roots were soaked for 5 min in HBSS and replanted. Historical negative and positive controls were used from similarly treated teeth in our previous studies. After 4 months the dogs were killed and the roots prepared for histological evaluation. Five-microm-thick cross-sections of the root and surrounding tissue taken every 70 microm were evaluated for healing according to the criteria of Andreasen. In the 12 roots with cemental defects, healing with cementum of the damaged root surface was evaluated. In addition, residual root mass was also measured to determine the extent of root structure loss for each soaking method. Cemental healing took place in all 12 artificially damaged roots, indicating that these soaking media did not inhibit cementogenesis. The alendronate-soaked roots had statistically significantly more healing than the roots soaked in HBSS without alendronate. This improvement in healing was seen in all dogs except one and in all teeth except the first premolar. Soaking in alendronate also resulted in significantly less loss in root mass due to resorption compared to those teeth soaked in HBSS without alendronate.

Administration, Topical↗

PubMed1992

Nitrate-regulated growth and cytokinin responses in seminal roots of barley.

The influence of nitrate availability on growth of seminal roots, and root cytokinin levels, was studied in barley (Hordeum vulgare L. cv Golf). Nitrate was continuously supplied to initially N-starved seedlings at relative addition rates (RA) of 0.03 to 0.21 per day (standard cultures) or at RA 0.09 per day in split root cultures with the nitrate additions distributed in ratios of 100:0 or 80:20 to the two subroots. Data were collected both during a phase of acclimation (first 10 days of N additions) and in the acclimated stage (>10 days after onset of N additions). Limitation of whole-plant growth was observed at RA <0.15 per day. The lateral root frequency increased with RA in plants of equal chronological age. However, the lateral root frequency was related to root size rather than to RA; roots of uneven age but having comparable total root lengths also had comparable lateral root frequencies. Growth of individual subroots in split root systems during acclimation was proportional to the fraction of the total N addition that was fed to the root. All subroots had comparable relative growth rates in acclimated plants, and their lateral root frequency correlated with total root length in the same manner as in standard cultures. Onset of N additions in a 80:20 split root culture resulted in doublings of zeatin riboside (ZR) levels in shoots and in the "80" root, whereas the response of the "20" root was small. No effect of perturbed nitrate availability on xylem translocation of ZR was observed. The ZR levels remained higher in the "80" root during acclimation but returned to the level of the "20" root after acclimation. Root cytokinin levels and xylem translocation in acclimated standard cultures were unaffected by RA in the lower range but increased at high RA. Arguments for involvement of cytokinins in the nitrate-regulated growth response are discussed.

Journal Article↗

PubMed2003

Touch and gravitropic set-point angle interact to modulate gravitropic growth in roots.

Plant roots must sense and respond to a variety of environmental stimuli as they grow through the soil. Touch and gravity represent two of the mechanical signals that roots must integrate to elicit the appropriate root growth patterns and root system architecture. Obstacles such as rocks will impede the general downwardly directed gravitropic growth of the root system and so these soil features must be sensed and this information processed for an appropriate alteration in gravitropic growth to allow the root to avoid the obstruction. We show that primary and lateral roots of Arabidopsis do appear to sense and respond to mechanical barriers placed in their path of growth in a qualitatively similar fashion. Both types of roots exhibited a differential growth response upon contacting the obstacle that directed the main axis of elongation parallel to the barrier. This growth habit was maintained until the obstacle was circumvented, at which point normal gravitropic growth was resumed. Thus, the gravitational set-point angle of the primary and lateral roots prior to encountering the barrier were 95 degrees and 136 degrees respectively and after growing off the end of the obstacle identical set-point angles were reinstated. However, whilst tracking across the barrier, quantitative differences in response were observed between these two classes of roots. The root tip of the primary root maintained an angle of 136 degrees to the horizontal as it traversed the barrier whereas the lateral roots adopted an angle of 154 degrees. Thus, this root tip angle appeared dependent on the gravitropic set-point angle of the root type with the difference in tracking angle quantitatively reflecting differences in initial set-point angle. Concave and convex barriers were also used to analyze the response of the root to tracking along a continuously varying surface. The roots maintained the a fairly fixed angle to gravity on the curved surface implying a constant resetting of this tip angle/tracking response as the curve of the surface changed. We propose that the interaction of touch and gravity sensing/response systems combine to strictly control the tropic growth of the root. Such signal integration is likely a critical part of growth control in the stimulus-rich environment of the soil.

Arabidopsis↗

PubMed2005

Technical quality of root canal treatment and detection of iatrogenic errors in an undergraduate dental clinic.

AIM: To evaluate the technical quality of root canal treatment (RCT) and detect iatrogenic errors in an undergraduate dental clinic. METHODOLOGY: Three-hundred and eighty-eight root-filled teeth from the records of the Department of Endodontology at the Aristotle University of Thessaloniki, Greece were evaluated. Evaluation of root-filled teeth was based on two variables: length and presence of voids within the root filling. The technical standard of root fillings was categorized as: < or = 2 mm from the apex with no voids (acceptable); >2 mm from the apex with no voids; overfilling with no voids; < or = 2 mm from the apex with voids; >2 mm from the apex with voids and overfilling with voids. Iatrogenic errors that were detected included ledges, root perforations, furcation perforations, strip perforations and presence of fractured instruments. Chi-squared analysis was used to determine statistically significant differences between frequencies of root fillings between each tooth type. Significant differences were also determined between frequencies of ledges and root perforations according to tooth type and separately in molars according to tooth number, canal location and root canal curvature. Results Three-hundred and forty-three out of 620 root canals (55.3%) had a root filling that was classified as 'acceptable'. The frequency of root canals with an 'acceptable' filling was significantly greater in the anterior teeth (72.1%) than in pre-molars (55.2%) (P < 005) or in molars (46.7%) (P < 0.001). One-hundred and fifty-four (24.8%) root canals had ledges and 17 (2.7%) had a root perforation. The frequency of ledged root canals was significantly greater (P < 0.001) in molars than in anterior teeth. In molars, 105 out of 270 root canals (38.9%) had been ledged. Mesiobuccal, mesiolingual and distobuccal root canals were the most frequently ledged. Canal curvature was found to be the most important factor associated with ledges and root perforations. Conclusions Technical quality was found to be acceptable more often in anterior teeth. Ledges were identified more often in curved canals in molar teeth.

Dental Instruments↗

PubMed2004

Root length in transplanted premolars.

The objectives of the present prospective longitudinal study were to establish the survival and success rates for premolars with partly developed roots transplanted according to a set protocol, and to analyze the effect of varying pre-surgery root development on final root length. Standardized periapical radiographs of 132 consecutively transplanted premolars were obtained at predetermined intervals over a 4-year follow-up period. Survival and success rates were calculated on the basis of presence of teeth and recording of defined radiological variables, respectively. Final root length was compared to normative metric data for root morphology. From the total sample, 54 patients with 68 transplanted premolars suitable for analysis of root growth relative to initial root length were identified, and divided into subsamples according to root length pre-transplantation. Survival rates were 100% after 1, 2, and 3 years, and 98.6% 4 years post-transplantation. The success rates were 92.9%, 92.8%, 89%, and 90.5% in subsamples collected 1, 2, 3, and 4 years after transplantation, respectively. The transplants obtained on average 78% of normative root length, and by dichotomizing the transplanted teeth in subsamples with 'short' and 'long' roots pre-surgery, similar final root lengths were observed even if 'short' roots had the greatest increase. Very early transplantation (roots < 7 mm), however, tended to result in short final root length. It is concluded that the success and survival rates were comparable to results obtained in similar studies. Initial root length was a significant predictor of root length increase. Transplanting teeth with short roots is to risk short final root length.

Bicuspid↗

PubMed2005

Determining the apical terminus of root-end resected teeth using three modern apex locators: a comparative ex vivo study.

AIM: To assess ex vivo the accuracy of various electronic apex locators in locating the apical terminus of root-end resected teeth. METHODOLOGY: Ninety extracted human posterior teeth (182 root canals) were prepared to a minimum size of 40 and filled with gutta-percha and sealer. After resection of the apical 3 mm of the root, the root canal filling was removed using HERO rotary instruments. The size of the root canal at the apical terminus after removal of the filling ranged from size 50 to 90. The root canal length to the apical terminus was determined using 3 apex locators (Root ZX, Raypex4 and Apex Pointer). A new mounting model that utilized a micrometer was used to perform the measurements and to visually determine the actual position of the apical terminus. The frequency of locating the apical terminus and the corresponding 95% confidence interval (CI) were calculated. Additionally, the coefficient of repeatability of each apex locator and the limits of inter-operator agreement were determined. RESULTS: All apex locators showed an acceptable repeatability (0.02-0.03 mm coefficient of repeatability) and narrow limits of inter-operator agreement (+0.07 and -0.07 mm). The accuracy of determining the apical terminus within 1 mm in the root canal was as follows: Root ZX 90% (164/182 root-canals) [95%CI: 86-94%], Raypex4 74% (135/182 root-canals) [95%CI: 68-80%], and Apex Pointer 71% (129/182 root canals) [95%CI: 65-77%]. No over-instrumentation resulted when the Root ZX device was used. In contrast, using the Raypex4 or the Apex Pointer device resulted in over-instrumentation in 8 of 182 root canals (4%). CONCLUSIONS: Under the conditions of this study all three apex locators were able to detect the apical terminus of root-end resected teeth with an acceptable range. The Root ZX device was the most accurate without over-instrumentation of the root canals.

Dental Pulp Cavity↗

PubMed2002

Mapping QTLs for root morphology of a rice population adapted to rainfed lowland conditions.

In the rainfed lowlands, rice ( Oryza sativa L.) develops roots under anaerobic soil conditions with ponded water, prior to exposure to water stress and aerobic soil conditions that arise later in the season. Constitutive root system development in anaerobic soil conditions has been reported to have a positive effect on subsequent expression of adaptive root traits and water extraction during progressive water stress in aerobic soil conditions. We examined quantitative trait loci (QTLs) for constitutive root morphology traits using a mapping population derived from a cross between two rice lines which were well-adapted to rainfed lowland conditions. The effects of phenotyping environment and genetic background on QTLs identification were examined by comparing the experimental data with published results from four other populations. One hundred and eighty-four recombinant inbred lines (RILs) from a lowland indica cross (IR58821/IR52561) were grown under anaerobic conditions in two experiments. Seven traits, categorized into three groups (shoot biomass, deep root morphology, root thickness) were measured during the tillering stage. Though parental lines showed consistent differences in shoot biomass and root morphology traits across the two seasons, genotype-by-environment interaction (GxE) and QTL-by-environment interaction were significant among the progeny. Two, twelve, and eight QTLs for shoot biomass, deep root morphology, and root thickness, respectively, were identified, with LOD scores ranging from 2.0 to 12.8. Phenotypic variation explained by a single QTL ranged from 6% to 30%. Only two QTLs for deep root morphology, in RG256-RG151 in chromosome 2 and in PC75M3-PC11M4 in chromosome 4, were identified in both experiments. Comparison of positions of QTLs across five mapping populations (the current population plus populations from four other studies) revealed that these two QTLs for deep root morphology were only identified in populations that were phenotyped under anaerobic conditions. Fourteen and nine chromosome regions overlapped across different populations as putative QTLs for deep root morphology and root thickness, respectively. PC41M2-PC173M5 in chromosome 2 was identified as an interval that had QTLs for deep root morphology in four mapping populations. The PC75M3-PC11M4 interval in chromosome 4 was identified as a QTL for root thickness in three mapping populations with phenotypic variation explained by a single QTL consistently as large as 20-30%. Three QTLs for deep root morphology were found only in japonica/indica populations but not in IR58821/IR52561. The results identifying chromosome regions that had putative QTLs for deep root morphology and root thickness over different mapping populations indicate potential for marker-assisted selection for these traits.

Journal Article↗

PubMed2002

Age-related loss of rooting capability in Arabidopsis thaliana and its reversal by peptides containing the Arg-Gly-Asp (RGD) motif.

We describe here an experimental system to study the age-related decline of adventitious root formation in Arabidopsis thaliana L. (Heynh), ecotype Landsberg erecta (Ler). The system is based on the different rooting capacity of hypocotyls from de-rooted juvenile (12-day-old) and adult (26-day-old) plants. Hypocotyls from de-rooted juvenile plants rooted readily within a week of culture, and the rooting process was not dependent on exogenous auxin. In contrast, hypocotyls from de-rooted adult plants rooted poorly and only after longer periods of time. Exogenously applied auxin had no effect on rooting of hypocotyls from de-rooted adult plants. Rooting capacity, although correlated with the transition to flowering, did not depend on this transition. Root induction declined in a similar manner when the transition to flowering was delayed, either genetically with the fve mutant or physiologically with short days. The results showed that rooting of hypocotyls from de-rooted adult plants depended on the effect of peptides containing the RGD motif. Both the percentage of rooting and the number of roots were largely increased when the hypocotyls were treated transiently with the RGD peptide. The effect of the RGD peptide was a necessary, but not sufficient, condition for rooting of hypocotyls from de-rooted adult plants.

Journal Article↗