Mm Of Root Research Articles

Apical Sealing Ability of MTA in Different Liquid to Powder Ratios and Packing Methods.

In apical surgery, after apicoectomy and retro-preparation of canal, a retrofil material is applied to seal the apical region of the root canal. Mineral trioxide aggregate (MTA) is the gold standard material for this purpose. Changing water/powder ratios of MTA affects its properties. The purpose of this in vitro study was to determine the effect of liquid/powder ratio of retrofil MTA on apical dye leakage, and also compare two packing techniques for MTA. In this in vitro study, 126 intact single-root extracted teeth were instrumented using step-back technique, and obturated with lateral condensation method. The apical 3 mm of roots was resected, and retrograde preparation was performed by an ultrasonic device. Specimens were randomly assigned to 6 groups of 20 each and 6 teeth served as positive and negative controls. All teeth were retrofilled with White ProRoot MTA. Three groups were retrofilled with 0.28, 0.33, and 0.40 water/powder ratios of MTA and packed with plugger; the other three groups were retrofilled with 0.28, 0.33, and 0.40 water/powder ratios and packed with wet-cotton. Linear dye leakage was used to check apical sealing ability, and data were statistically analyzed using Kruskal-Wallis test. In 0.40 liquid/powder ratio the best applicator for packing MTA was plugger. In 0.28 liquid/powder ratio, moist cotton pellet was the best applicator; in 0.33 liquid/powder ratio, there was no significant difference between the two techniques. Under the condition of this in vitro study, packing with moist cotton pellet in lower liquid/powder ratios of MTA, as well as packing with a plugger in higher liquid/powder ration decreased apical dye leakage.

Effect of bleaching agents on sealing properties of different intraorifice barriers and root filling materials

Objective: To evaluate the effect of intracoronal bleaching agents on the sealing properties of different intraorifice barriers and root filling materials. Study Design: The root canals of extracted human premolars (n=180) were prepared by using System GT rotary files and filled with either gutta-percha+AH Plus or Resilon+Epiphany sealer. In both groups, the coronal 3mm of root filling was removed and replaced with one of the following materials applied as intraorifice barriers (n=30/group): 1. ProProot-MTA; 2. Conventional Glass ionomer cement; and 3. Hybrid resin composite. In each subgroup, intracoronal bleaching was performed using either sodium perborate with distilled water or 35% hydrogen peroxide gel for 3 weeks. The leakage of specimens was measured using fluid-filtration and dye penetration tests. The data were analyzed statistically with One-way ANOVA, Repeated Measures t-test and Independent Samples t-test (p=0.05). Results: The fluid conductance values of the test groups were not influenced by the type of the bleaching agent, the intraorifice barrier, or the root filling material (all p>0.05). However, the extent of dye leakage was significantly affected by the type of intraorifice barrier material (p<0.05), which showed the following statistical ranking: glass ionomer cement > resin composite > ProRoot-MTA (p<0.05). Conclusions: The effect of 35% hydrogen peroxide gel or sodium perborate/distilled water on the sealing properties of tested intraorifice barriers and root filling materials varied conforming leakage assessment. These properties were not affected by using fluid filtration test, while the glass ionomer barrier showed the greatest amount of dye leakage in both gutta-percha and Resilon root-filled teeth. Key words:Tooth Bleaching, root canal filling materials, glass ionomer cement, mineral trioxide aggregate, micro leakage

Evaluation of the Doxycycline Release from AH26 Sealer-Doxycycline Combination: An ex vivo Study.

The purpose of this ex vivo study was to determine the releasing characteristics and doxycycline dentinal diffusion of AH26 sealer-doxycycline combination from apical 3mm of tooth root and apical foramen. One-hundred and two recently extracted single-rooted human teeth were decoronated and prepared with #3 and #4 Gates-Glidden drills and rotary Mtwo files. Smear layer was removed; all surfaces except for apical 3mm of each root were sealed with two coats of nail polish. To quantify the release and diffusion of the doxycycline at different time intervals (30 min, 48 and 72 h) after root canal obturation, the samples were randomly divided into three groups (n=30; 0.5 h, 48 h, 72 h). To evaluate the release of doxycycline from AH26 sealer-doxycycline combination at six concentrations of antibiotic including 0.5%, 1%, 2%, 5%, 10% and 20%; each experimental group was divided into six equal subgroups (n=5). Root canals were filled with gutta-percha and AH26-doxycycline combinations and then were placed in vials containing 1.25mL of phosphate buffer saline solution (PBS). After 30 min, 48 and 72 h, the amount of doxycycline released from specimens into PBS were determined by measuring the absorbance values using UV spectrophotometry at λ(max)=350 nm. Data were analyzed using two-way ANOVA. The findings of this study revealed that AH26 sealer-doxycycline combination released variable measures of antibiotic at each time interval and in the various concentrations. At 30 min, no statistically significant differences were obtained between the results of subgroups, but at 48 and 72 h these differences were significant (P<0.001). The results also showed that differences between 0.5 h, 48 h and 72 h were significant within subgroups (P<0.01). Under the conditions of this ex vivo study, doxycycline can be released from AH26 sealer-antibiotic combination through 3mm of apical root and apical foramen at 30 min, 48 and 72 h after mixing the sealer with doxycycline at concentrations of 0.5% up to 20%.

Three-dimensional Morphologic Analysis of Isthmuses in the Mesial Roots of Mandibular Molars

Introduction The purpose of this study was to investigate the three-dimensional (3-D) morphology of isthmuses in the mesial roots of mandibular molars. Methods One hundred twenty-six extracted mandibular molars including 70 first molars (MFMs) and 56 second molars (MSMs) from a Chinese population were scanned by micro–computed tomography, and the apical 5 mm of the root canals with or without isthmuses was reconstructed with 3D-Doctor software. Each reconstructed isthmus model was assigned to 1 of the following 4 categories: sheet connection, separate, mix, and cannular connection. The length of the isthmus (L i) and the distance from the bottom of the isthmus to apex (D ba) were measured and analyzed. Results The incidence of an isthmus in the apical 5 mm of the mesial roots was 85%. MFMs had more isthmuses with separate type and mixed type, whereas MSMs had more isthmuses with sheet connections. The L i and D ba in mandibular molars were 2.331 mm and 1.850 mm, respectively. Conclusions MFMs present different anatomical features of isthmuses in the apical part of the mesial roots than MSMs.

Isthmuses of the mesial root of mandibular first molar - An spiral computed tomographic study

Aim: To investigate invitro the incidence and position of root canal isthmuses in the apical 5 mm of the mesial root of mandibular first molars by means of high resolution spiral computed tomography (SCT) and to describe the morphology of the isthmuses. Methodology: Forty extracted mandibular first molars that had fully formed roots were selected. The mesial roots were sectioned from the distal roots and subjected to SCT. The number of sections showing isthmuses in each of the apical 5 mm of the root canals was recorded. In each one of the apical 5 mm of the 40 roots, a total of 400 sections observed. Data were analysed for the presence of isthmuses at all the sections in each of the apical 5 mm of each root and the morphology of isthmus was also evaluated. Results: Isthmuses were found to be present at all levels with prevalence figures between 18.25 and 50.25%. A significant difference in the distribution of isthmuses within section and it was found that sections in the third millimetre from the apex had more isthmuses Calcifications were found to be present in most isthmuses, occasionally lateral canals originated from the central part of the isthmuses. Conclusion: the incidence of root canal isthmus in the mesial root of the mandibular first molars was high. Particularly in the apical 3-5 mm from the apex. Cleaning the isthmus is a major challenge during root canal treatment. The results of clinical and surgical endodontic procedures performed in the mesial root of mandibular molars may be affected by this aspect of the root canal anatomy.

Preliminary observations on increasing root length during the eruptive phase of tooth development in modern humans and great apes

Ground sections of incisors, canines, and molars were selected that showed clear incremental markings in root dentine. The sample comprised 98 Homo sapiens, 53 Pan troglodytes, and a more limited combined sample of 51 Gorilla and Pongo sections. Daily rates of root dentine formation, together with the orientation of incremental markings in roots close to the cement-dentine junction (CDJ), were used to calculate root extension rates for the first 10 mm of root formed beyond the buccal enamel cervix. Modern human anterior tooth roots showed a more regular pattern of increase in root length than those in great apes. In Pan, root growth rose quickly to higher rates but then flattened off. The fastest extension rates in modern humans were in incisor roots (10–12 μm per day), followed by canines (8–9 μm per day). Extension rates in Pan rose to slightly greater values in canines (∼12–14 μm per day) than in incisors (∼10–11 μm per day). Molar tooth roots in both modern humans and great apes grew in a nonlinear manner. Peak rates in molars reduced from M1 to M3 (8, 7, and 6 μm per day, respectively). Like humans, root growth in Pan peaked earlier in M1s at rates of between 8 and 9 μm per day, and later in M3s at rates of 7 to 8 μm per day. The more limited data set for Gorilla and Pongo molars suggests that extension rates were generally higher than in Pan by approximately 1.0–1.5 μm per day. There were greater differences in peak extension rates, with Gorilla and Pongo extension rates being between 2.5 and 4.5 μm per day higher than those in Pan. These findings highlight for the first time that root growth rates differ between tooth types in both pattern and rate and between taxa. They provide the basis with which to explore further the potential comparative relationships between root growth, jaw growth, and the eruption process.

A comparison of ammonium, nitrate and proton net fluxes along seedling roots of Douglas‐fir and lodgepole pine grown and measured with different inorganic nitrogen sources

Significant spatial variability in NH4+, NO3- and H+ net fluxes was measured in roots of young seedlings of Douglas-fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta) with ion-selective microelectrodes. Seedlings were grown with NH4+, NO3-, NH4NO3 or no nitrogen (N), and were measured in solutions containing one or both N ions, or no N in a full factorial design. Net NO3- and NH4+ uptake and H+ efflux were greater in Douglas-fir than lodgepole pine and in roots not exposed to N in pretreatment. In general, the rates of net NH4+ uptake were the same in the presence or absence of NO3-, and vice versa. The highest NO3- influx occurred 0-30 mm from the root apex in Douglas-fir and 0-10 mm from the apex in lodgepole pine. Net NH4+ flux was zero or negative (efflux) at Douglas-fir root tips, and the highest NH4+ influx occurred 5-20 mm from the root tip. Lodgepole pine had some NH4+ influx at the root tips, and the maximum net uptake 5 mm from the root tip. Net H+ efflux was greatest in the first 10 mm of roots of both species. This study demonstrates that nutrient uptake by conifer roots can vary significantly across different regions of the root, and indicates that ion flux profiles along the roots may be influenced by rates of root growth and maturation.

A Comparison of the Antimicrobial Efficacy of NaOCl/Biopure MTAD versus NaOCl/EDTA against Enterococcus faecalis

The purpose of this investigation was to compare the antimicrobial efficacy of irrigating with 1.3% NaOCl/Biopure MTAD versus irrigation with 5.25% NaOCl/15% EDTA in the apical 5 mm of roots infected with Enterococcus faecalis. Bilaterally matched human teeth were sterilized and inoculated with E. faecalis. After chemomechanical root canal preparation, the root-ends were resected and pulverized in liquid nitrogen to expose E. faecalis in dentinal tubules or other recesses away from the main root canal system. The number of colony forming units (CFU) of E. faecalis per mg was determined from the pulverized root-ends. No significant differences were seen (t = 0.70, p = 0.495) between the number of colony forming units of E. faecalis for teeth irrigated with 5.25% NaOCl/15% EDTA (mean 131 ± 291 CFU/mg) versus those teeth irrigated with 1.3% NaOCl/Biopure MTAD (mean 187 ± 237 CFU/mg). This study demonstrated that there is no difference in antimicrobial efficacy for irrigation with 5.25% NaOCl/15% EDTA versus irrigation with 1.3% NaOCl/Biopure MTAD in the apical 5 mm of roots infected with E. faecalis.

The influence of root canal shape on the sealing ability of two root canal sealers

To evaluate the influence of root canal form on the sealing ability of two root canal sealers. Twenty radiographically confirmed straight and 20 curved root canals were prepared with a stepback hand filing technique. Root canal aberrations created during preparation were determined by the use of double exposure radiographic technique. The prepared canals were filled with lateral condensation of gutta-percha and one or other of two root canal sealers (Pulp Canal Sealer and Sealapex). Leakage along the apical 10 mm of roots was measured with a fluid transport model at 1, 3, 6, 9 and 12-month intervals. There were no statistically significant differences between straight and curved root canals (P > 0.05) for prevalence of root canal transportation. The prevalence of apical transportation was 80% in the straight and 85% in the curved root canals. A complete seal was more frequently observed in straight canals compared with curved canals. Utilizing the pi* index, analysis showed the filling with Sealapex allowed more leakage than Pulp Canal Sealer at 1 year. Under the conditions of the study, root canal form influenced short-term sealing ability. In the long-term the seal was affected by the sealer rather than root canal form.

The isthmuses of the mesial root of mandibular molars: a micro‐computed tomographic study

To investigate the prevalence of root canal isthmuses in the apical 5 mm of the mesial root of mandibular molars by means of micro-computed tomography (MCT) and to describe the morphology of the isthmuses. Twenty extracted mandibular first molars that had fully formed roots were selected. The mesial roots were sectioned from the distal roots and subjected to MCT. The number of sections showing isthmuses in each of the apical 5 mm of the root canals was recorded. In each one of the apical 5 mm of the 20 roots examined, 40 sections were observed, giving a total of 800 sections observed in each group. Data were analysed as a contingency table using the chi-square statistic to test the null hypothesis that location of the sections in each of the apical 5 mm and presence of the isthmus were independent. Isthmuses were found to be present at all levels with prevalence figures between 17.25 and 50.25%. The chi-square test indicated a significant difference in the distribution of isthmuses with section (P = 0.001). It was found that sections in the first millimetre from the apex had fewer isthmuses than expected and that sections in the third millimetre from the apex had more isthmuses than expected under the null hypothesis. Calcifications were found to be present in most isthmuses, occasionally lateral canals originated from the central part of the isthmuses. Isthmuses were present in the vast majority of roots observed. The third millimetre from the apex showed more isthmuses than expected. The results of clinical and surgical endodontic procedures performed in the mesial root of mandibular molars may be affected by this aspect of the root canal anatomy.

Effect of salt priming on germination and seedling growth at low temperatures in watermelon seeds during development

The effect of salt priming (KNO 3 , 20°C, 3%, 6 d) on germination at seven and 14 days after planting and on root and shoot lengths of watermelon (Citrullus lanatus (Thunb.) Matsum and Nakai) seed lots harvested at a range of intervals from anthesis and at two levels of temperature was investigated during the years 2000 and 2001. Untreated seeds of 15, 20, 25 and 30 DAA (days after anthesis) were unable to germinate and final germination was lower than 20% in subsequent harvests until 60 DAA at 14°C. While at the same temperature treated seeds had germinated as early as 20 DAA and reached to 66% and 51% in 40 (2000) and 35 DAA ( 2001), respectively. Germinated seeds were unable to grow shoots at 14°C in either year. At 18°C, treatment was not effective on germination percentages at day seven in all three lots in 2000 but improved root and shoot lengths. The advantage obtained from the treatment varied among the lots with a minimum benefit of an increase of 15 mm in root and 28 mm in shoot length, respectively. Priming increased germination percentages at day seven and final and root and shoot length of all seed lots in 2001. Germination percentages in treated seeds varied between 68% and 84% in seeds harvested 20 DAA and thereafter. The less mature the seeds the higher the benefit obtained from the treatment. Maximum root and shoot lengths were recorded in seeds of 35 DAA as 37 and 40 mm in the control and as 60 and 61 mm in treated, respectively. We concluded that salt priming can be useful for improving germination, seedling growth and uniformity of heterogeneously matured watermelon lots at low temperatures to produce well developed seedlings in early spring sowings.

Change in root apical protein and peroxidase activity in response to aluminum in tolerant and sensitive maize inbred lines

The effects of a short-term (80 min) exposure to 222 µM aluminum (Al) on the protein content and expression and on peroxidase activity and isoenzymes in the primary root of maize were evaluated. Two inbred lines differing in their level of tolerance to Al were used: Cateto 237 (tolerant) and L36 (sensitive). The apical 20 mm of the primary root was divided into 2-mm-long segments that were analyzed for total protein content and peroxidase activity. These results demonstrate that the total protein content along the root apex was not affected by Al in the tolerant inbred line, but decreased in the sensitive line. In the apical 2 mm of the root of the sensitive line, the expression of low molecular weight proteins (43 kDa or smaller) was decreased. Expression of low molecular proteins increased in the tolerant inbred line, even though total protein content did not increase. This suggests that some of these proteins could play a role in metal tolerance, perhaps as binding peptides. While the peroxidase activity of the tolerant inbred line did not change with exposure to Al, peroxidase activity in the apical 6 mm of the root of the sensitive line decreased. The tolerant inbred line constitutively expressed more anionic peroxidase isoforms. These results demonstrate that maintenance of protein expression may be an important component of the plant's resistance to Al stress, and that resistance to Al stress is associated with the higher expression of anionic peroxidase isoforms.

Iron Deficiency Induced Changes in Iron Reductase Activity in Papaya Roots

Four papaya (Carica papaya L.) cultivars were cultured aeroponically or in perlite to determine the magnitude, timing, and root locality of Fe reductase induced by Fe deficiency. Five soybean [Glycine max (L.) Merrill] lines with a known range of Fe-deficiency chlorosis scores were cultured in perlite for comparison. Speed of inducement of Fe reductase activity was determined in plants cultured without Fe for 0 to 17 days. Location of Fe reductase activity was determined by sectioning roots from the tip to 60 to 70 mm proximal to the root tip from plants cultured without Fe for 16 to 19 days. The Fe reductase system was induced in all papaya cultivars after 7 to 11 days without Fe, and activity increased through 17 days. Iron reductase activity in all papaya cultivars was comparable to the most tolerant soybean line. The zone of highest activity was the apical 10 mm of roots. These results indicate that papaya roots are highly efficient in induced Fe reductase activity. The highest activity in root tips underscores the importance of maintaining a healthy, continually growing root system with numerous growing points when culturing papaya in alkaline substrates.

Effect of (+)-pulegone and other oil components of Mentha×piperita on cucumber respiration

Peppermint ( Mentha×piperita L.) essential oil and main components were assessed for their ability to interfere with plant respiratory functions. Tests were conducted on both root segments and mitochondria isolated by etiolated seedlings of cucumber ( Cucumis sativus L.). Total essential oil inhibited 50% of root and mitochondrial respiration (IC 50) when used at 324 and 593 ppm, respectively. (+)-Pulegone was the most toxic compound, with a 0.08 and 0.12 mM IC 50 for root and mitochondrial respiration, respectively. (−)-Menthone, followed (+)-pulegone in its inhibitory action (IC 50 values of 1.11 and 2.30 mM for root and mitochondrial respiration respectively), whereas (−)-menthol was the less inhibitory compound (IC 50 values of 1.85 and 3.80 mM respectively). A positive correlation was found for (+)-pulegone, (−)-menthone and (−)-menthol between water solubility and respiratory inhibition. The uncoupling agent, carbonyl-cyanide- m-chlorophenyl-hydrazone (CCCP), lowered (−)-menthol and (−)-menthone inhibition and annulled (+)-pulegone inhibition of mitochondrial respiration, whereas salicyl-hydroxamic acid (SHAM) 2-hydroxybenzohydroxamic acid, the alternative oxidase (AO) inhibitor, increased (−)-menthone inhibition and annulled both (+)-pulegone and (−)-menthol inhibitory activity. The possible interaction of (+)-pulegone and (−)-menthol with AO and the mechanism of action of (+)-pulegone, (−)-menthone and (−)-menthol on mitochondrial respiration are discussed.

Leakage Along Apical Root Fillings in Curved Root Canals. Part I: Effects of Apical Transportation on Seal of Root Fillings

Occurrence of apical transportation (AT) may complicate the root filling procedure and result in a compromised seal. In part I of this study, human mandibular premolars with single, curved (21 to 39 degrees), or straight canals were prepared by Lightspeed or a step-back hand filing technique. An AT index was determined using a double exposure radiographic technique. The prepared canals were obturated using lateral condensation of gutta-percha. Leakage along the apical 3 mm of root filling was measured with a fluid transport model. After hand filing, AT and perforation occurred in 87% of the curved canals. The AT indices were > or = 0.4 mm. After Lightspeed preparation, AT occurred in only 19% of the curved canals. The hand filing/curved group leaked statistically significantly more than the hand filing/straight and Lightspeed/curved groups (p = 0.002). We conclude that occurrence of AT is a factor that negatively influences the apical seal when curved canals are obturated by lateral condensation of gutta-percha.

Leakage along warm gutta-percha fillings in the apical canals of curved roots.

The aim of this study was to investigate the leakage along the apical portion of warm gutta-percha obturated curved canals. Human mandibular premolars with single, curved (21 degrees-40 degrees) canals were prepared using the Lightspeed technique. Two groups of prepared canals, matched according to curvature and prevalence of apical transportation, were obturated by two techniques. Coronal gutta-percha was removed immediately after root obturation was completed to simulate the procedure for post space preparation. Leakage along the apical 3 mm of root filling was measured with a fluid transport device. Vertical condensation of warm gutta-percha and Pulp Canal Sealer provided less leakage than Thermafil plastic obturators and AH26 sealer (P = 0.002).

Localization and quantification of net fluxes of H+ along maize roots by combined use of pH-indicator dye videodensitometry and H+-selective microelectrodes

Two methods for measuring proton fluxes along intact maize roots grown with NH4+ or NO3− at pH 6.5 were compared. Videodensitometric measurement of changes in a pH-indicator dye by video camera was used to map pH around roots and determine the amounts of protons released by various root regions. This method was compared with potentiometric determination of the concentration of H+ in the unstirred layer at the root surface using ion-selective microelectrodes. With NH4+ the roots released large amounts of H+ in preferential regions where the rate of flux can reach 1.4 or even 2.5 nmol m−1 s−1. Videodensitometry indicated a first region of root acidification in the subapical zone, but this was more difficult to localize with microelectrodes. With NO3− both methods showed that the roots released small amounts of H+ and that the apical region took up H+ in the first 10 mm then sometimes released H+ over the following 10 mm of root. The H+ flux profiles obtained by both methods were in good agreement in terms of both order of magnitude of the fluxes and spatial differences along the root. These results suggest that videodensitometry, which is easier to use than potentiometry, can be used to screen different plant species or cultivars under various experimental conditions. The microelectrode technique is indispensable, however, for studying the underlying mechanisms of net H+ fluxes.

Relationship between tissue sugar content, phloem import and lateral root initiation in wheat

Split‐root experiments were conducted to test the hypothesis that adjustments in lateral root initiation, as might occur in response to localized soil conditions, are determined by the sugar content of the root and do not depend on changes in the import of phloem‐translocated phytohormones. Wheat (Triticum aesticum L. cv. Alexandria) seedlings were grown in hydroponics with their seminal roots divided between two compartments within the culture vessel. Two seminal roots of treated plants were supplied with standard nutrient solution supplemented with 50 mM glucose, whilst the remaining three roots received nutrient solution without glucose. Control plants had their roots divided in the same ratio, but both ‘halves’ received nutrient solution without glucose. Feeding glucose to one ‘half’ of the root system increased the frequency (number per unit length) of lateral root primordia in the fed axes. The increase was first observed 15 h after the start of treatment and was located within the apical 30 mm of root. At this time there was no significant treatment effect on the frequency of primordia in non‐fed axes. The enhanced initiation of lateral roots in glucose‐fed root tips was associated with an increase in their concentration of glucose and sucrose plus low molecular mass fructans. In contrast, there was a reduction in partitioning of 14C‐photosynthate to these root tips compared to the non‐fed roots of treated plants and controls. The results indicate that lateral root initiation can be stimulated by sugars in the absence of an increase in phloem translocation. It is proposed that proliferation of lateral roots in response to localized soil conditions, such as nutrient patches, may be signalled by an increase in sugar content of the tissue, rather than an altered flux of phytohormones or other material co‐transported with sucrose in the phloem.

Microleakage along apical root fillings and cemented posts

Statement of problem. Coronal leakage of endodontically treated teeth has been found to result in a high failure rate. Purpose. This study tested leakage along apical root fillings remaining after post space preparation and cemented posts in root canals. Material and methods. A total of 120 human roots were used in the study and divided into six groups, 20 roots for each group. By using a modified fluid transport model, leakage (in μL/hr) along ParaPost dowels that were cemented in the coronal 7 mm of root canals with Fuji Duet, Ketac Cem, Panavia EX, or zinc phosphate cements was compared with that along the coronal 7 mm of conventional root canal fillings. Leakage along the apical 4 mm of root filling remaining after post space preparation was compared with that along the 11 mm root filling before post space preparation. Results. More leakage was recorded along the apical 4 mm of root filling than along the 11 mm of original root filling ( p = 0.0325). ParaPost dowels cemented with any test cement did not produce more leakage than the 7 mm coronal root filling ( p = 0.2145). Conclusions. The apical 4 mm of root canal filling remaining after post space preparation leaks statistically significantly more than the original full-length root canal filling. The leakage created by removal of the coronal part of root canal filling during post space preparation may be compensated by the cemented posts. (J Prosthet Dent 1998;79:264-9)

Specific uptake of 6-deoxy-d-glucose and of 2-aminoisobutyric acid by sugar beet leaves and roots

Sugar beet was grown in pots and the transport of 6-deoxy-d-glucose (6-dg) and of 2-aminoisobutyric acid (AIB) into leaf and root tissue segments was examined. The uptake of 6-dg into both tissues displayed two kinetic components, one apparently of diffusional nature, the other saturable (half-saturation constant 0.22 mM in leaves, 0.10 mM in roots; limiting rate 0.37 and 0.10 nmol mg-1 (fresh mass) h-1 for leaves and roots, respectively). It was suppressed by d-glucose and inhibited by diethyl-stilbestrol (DES), suloctidil (SUL) and 2,4-dinitrophenol (DNP), but little by D2O and not at all by sodium vanadate. It showed a temperature optimum at 30 °C and a pH optimum at 6.0 - 6.5 in both tissues. The uptake of AIB was also two-componental but even the specific component had an immeasurably high half-saturation constant although it was inhibited by high concentrations of AIB as well as by DES, SUL, DNP and D2O. However, vanadate stimulated the uptake by as much as 40% in both leaves and roots. The temperature optimum in leaves lay at 30 °C while in the roots no maximum was present; its pH optimum was at 5.5 in leaves and again no maximum was observed in roots. Both transport systems were unaffected by 0.1M NaCl or 0.1 M KCl and by the presence of cytokinin in the incubation vessel. However, spraying with the cytokinin N6-(m-hydroxybenzyl) adenosine decreased both the half-saturation constant and the limiting velocity of 6-dg uptake slightly in the leaves and substantially in the roots. Spraying had an insignificant effect on the uptake of AIB.