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At least 595 records · Page 33Linked to original sources
PubMed1996

Resumed tooth development following avulsion of a permanent central incisor.

A case is presented in which an upper right central incisor was avulsed because of trauma at age six. At the time of trauma it was suspected that the pulp had remained in the socket although the tooth had been lost. No attempt was made to treat the socket, remove the pulp, or replant the tooth. Follow-up radiography showed that, despite initial apparent complete loss of the calcified portion of the tooth, root development proceeded to completion.

Child↗
PubMed1997

The treatment of nonvital immature teeth with calcium hydroxide-sterile water paste: two case reports.

Death of the dental pulp before completion of root development results in a tooth with an open apex. During endodontic treatment, the open apex makes obturation difficult, because there is no apical stop against which the filling can be packed and condensed. For many years, open apices have been treated by root canal fillings or by periapical surgery with or without a reverse seal. Currently, the conservative approach is preferred over surgical management, to avoid the physical and psychological trauma of surgery to a young patient. Two patients were treated by calcium hydroxide-sterile water paste to promote the apexification of the nonvital teeth with an incompletely formed apex. Normal endodontic preparation of the canal had been carried out in the immature tooth. Radiologic examination after 6 to 9 months showed that the apex of the maxillary incisors was completed by newly formed tissue.

Calcium Compounds↗
PubMedDate not supplied

Modern endodontic therapy for an incompletely developed tooth.

An important goal of modern dentistry is to preserve a functional, esthetic, and pain-free dentition. If irreversible pulp pathology occurs in an immature permanent tooth from traumatic or carious exposure, normal apical maturation may be interrupted. Conventional endodontic obturation techniques, if necessary, will be difficult and may not be adequate in such a tooth. The endodontic techniques of apexogenesis and apexification have been successful in achieving adequate root development and apical construction. These conventional techniques and materials are reviewed along with a promising material called mineral trioxide aggregate.

Aluminum Compounds↗
PubMed2002

Syndecan-1 expression during postnatal tooth and oral mucosa development in rats aged from two days to six weeks.

Syndecans are a family of heparan sulphate proteoglycans that regulate cell-matrix interactions that influence cell growth, proliferation and morphology. The aim of this study was to observe changes in the expression of Syndecan-1 in the developing epithelium of the rat oral mucosa and in the epithelial cell rests of Malassez in the developing periodontium of normal rat molars, from late crown development through to early eruption. Immuno-histochemistry (Syndecan-1 N-18) and histochemistry (Alcec Bluel were used to observe changes in the expression of Syndecon-1 in rats aged two to 42 days. Results indicated that during normal tooth development in the rat, labelling or staining of variable intensity for Syndecan-1 was demonstrated in the stratified oral epithelium above the stratum basale in the rat tongue and palate, and in ameloblasts of the developing molar in rats aged two to 14 days. Histochemical staining of the predentine and dentine layers was consistent in all specimens. Labelling or staining for Syndecan-1 was negative in the rat periodontal ligament, which may suggest that either Syndecan-1 was not expressed during normal molar root development or that continued work is required for identification of a suitable label in rats.

Ameloblasts↗
PubMed1986

In vitro regeneration of plantlets from embryonic and seedling explants of Engelmann spruce (Picea engelmannii Parry).

A protocol has been developed for the in vitro production of plantlets of Engelmann spruce. Embryos and various parts of Engelmann spruce seedlings formed multiple shoots when cultured on defined media containing a cytokinin. The site and time of occurrence of the shoot buds, as well as their number, differed in the various explants. The frequency of shoot-forming explants was influenced by the salt formulation used, the type and concentrations of cytokinins and their mode of application. Development of buds was achieved by transferring the explants to basal medium containing no growth regulators. Elongation of shoots was stimulated by reducing the concentration of salts and sugar, addition of activated charcoal and transferral to increased photoperiod and lower temperature regimes. Maximum rooting was induced by giving a pulse of high concentration of indolebutyric acid to the shoots. The roots developed within 8-10 weeks and the regenerated plantlets were transferred to soil under non-sterile conditions.

Journal Article↗
PubMed2005

Evaluation of chronological age based on third molar development in the Spanish population.

A cross-sectional study was carried out to assess chronological age estimation based on the stages of third lower molar development, following the eight stages (A-H) method of Demirjian et al. The final sample consisted of 1,054 orthopantomograms from Spanish individuals of known chronological age (range 14-21 years) and gender (462 males and 592 females). Results showed a stronger correlation for males (r(2)=0.54) than for females (r(2)=0.45). Root formation occurred earlier in males than females, in stages 5, 6 and 7. The mean difference between chronological and estimated age was -0.10 years (+/-1.23 SD) for left third molar, and -0.07 years (+/-1.22 SD) for right third molar, with slight variations regarding sex. Comparative tables are provided regarding medicolegal questions concerning age 18 prediction in the Spanish population, showing that legal age is reached in stage 7 (G) by women and in stage 8 (H) by men. No differences have been observed between sides (p<0.0001). Differences were observed between Spaniards and other previously studied populations. Third molar maturity takes place earlier in the Spanish than French-Canadian, Scandinavian, American, German, Japanese and South African populations and is more similar to US Hispanics in root development.

Adolescent↗
PubMed2003

The poplar root transcriptome: analysis of 7000 expressed sequence tags.

To date, most poplar expressed sequence tags (ESTs) are from above-ground tissues such as wood, leaf and buds. Here, we present a large-scale production of ESTs from roots of the hybrid cottonwood, Populus trichocarpaxdeltoides. cDNA libraries were generated from the root system of 2-month-old rooted cuttings, and roots of 2.5-month-old cuttings water-stressed for 19 days. Partial sequences obtained from 7013 clones were assembled into 1347 clusters and 3527 singletons. This set of ESTs represents 4874 unique transcripts expressed in roots. Putative functions could be assigned to 3021 (62%) of the transcripts. A significant portion of the ESTs encode proteins of common metabolic pathways; energy and metabolism represented 5% and 8% of total transcripts, respectively. Of specific interest to root functions are the 6% of ESTs involved in signalling pathways and hormone metabolism, and 4% encoding transporters and channels. The current poplar root ESTs and the aspen root ESTs present in public databases represent 6700 unique transcripts. The Unigene set was selected from the ESTs and used to generate nylon microarrays. Changes in aquaporins and transporter transcripts were then studied during adventitious root development.

Aquaporins↗
PubMed1993

Epidemiology of root caries.

Many epidemiological studies have been conducted on a variety of populations. Unfortunately, comparison of the prevalence data, and to a lesser degree of the incidence data, between the various studies is of little use due to the lack of standardised diagnostic criteria, reporting methods and population diversity. In the few incidence studies which have been conducted around 30-40% of people developed root caries, although many adults in the population appear to have been affected by root caries. Many risk factors associated with the occurrence of root caries have been identified and these include oral, medical, mental, behavioural and psychosocial conditions.

Adolescent↗
PubMed2002

The vascular prepattern enhancer trap marks early vascular development in arabidopsis.

Vascular development is a fundamental component of leaf morphogenesis, and the mechanisms that control vascular patterning are poorly understood. We report here the identification of an enhancer trap line, Vascular Prepattern (VPP), that acts as a marker for early vascular development. GUS reporter gene expression in VPP was detected in provascular cells from the earliest stages of primary midvein formation in leaf primordia and subsequently coincided with the early specification of higher order veins. GUS expression in VPP also marks the quiescent center cells of the root apical meristem at all stages of root development. VPP provides a marker for early vascular development and will be a useful tool for studying vascular patterning.

Arabidopsis↗
PubMed1989

Pulpal healing after luxation injuries and root fracture in the permanent dentition.

Pulpal healing patterns were studied in a clinical material of 637 luxated and 95 root-fractured permanent incisors followed routinely for up to 11 years. It was found that pulpal healing patterns could generally be divided into 3 groups according to the degree of injury sustained by the pulp: little, moderate or severe. Thus after luxation injuries, pulp survival could be without radiographic change (PS), with pulp canal obliteration (PCO) or nonhealing (pulp necrosis (PN]. After root fracture, similar healing patterns could be observed: healing by hard tissue union of fragments (HT), by connective tissue union of fragments (CT) or by nonunion due to interposition of granulation tissue between fragments (GT) resulting from PN of the coronal fragment. In both trauma situations, healing or nonhealing could be determined by type of luxation injury, stage of root development and type of fixation used (forceful application of orthodontic bands vs. passively applied acid-etch fixation). Pulpal healing complications (PN or GT) were based on clinical findings (coronal discoloration, loss of pulpal sensibility) and radiographic findings (resorption processes of the lamina dura at the root apex or at the level of the root fracture). However, in both injury groups the same changes could also be seen to be intermediate steps in the pulpal healing process. Based on findings from these studies, hypotheses for the mechanics of pulpal healing are proposed as well as guidelines for acute and later treatment of dental luxations, root fractures and the diagnosis of healing complications.

Dental Pulp↗
PubMed2005

Soil moisture redistribution as a mechanism of facilitation in savanna tree-shrub clusters.

Plant-soil water relations were examined in the context of a selective removal study conducted in tree-shrub communities occupying different but contiguous soil types (small discrete clusters on shallow, duplex soils versus larger, extensive groves on deep, sandy soils) in a subtropical savanna parkland. We (1) tested for the occurrence of soil moisture redistribution by hydraulic lift (HL), (2) determined the influence of edaphic factors on HL, and (3) evaluated the significance of HL for overstory tree-understory shrub interactions. Diel cycling and nocturnal increases in soil water potential (Psisoil), characteristic signatures of HL, occurred intermittently throughout an annual growth cycle in both communities over a range of moisture levels (Psisoil=-0.5 to -6.0 MPa) but only when soils were distinctly stratified with depth (dry surface/wet deep soil layers). The magnitude of mean (+/-SE) diel fluctuations in Psisoil (0.19+/-0.01 MPa) did not differ on the two community types, though HL occurred more frequently in groves (deep soils) than clusters (shallow soils). Selective removal of either Prosopis glandulosa overstory or mixed-species shrub understory reduced the frequency of HL, indicating that Prosopis and at least one other woody species was conducting HL. For Zanthoxylum fagara, a shallow-rooted understory shrub, Prosopis removal from clusters decreased leaf water potential (Psileaf) and net CO2 exchange (A) during periods of HL. In contrast, overstory removal had neutral to positive effects on more deeply-rooted shrub species (Berberis trifoliolata and Condalia hookeri). Removal of the shrub understory in groves increased A in the overstory Prosopis. Results indicate the following: (a) HL is common but temporally dynamic in these savanna tree-shrub communities; (b) edaphic factors influencing the degree of overstory/understory development, rooting patterns and soil moisture distribution influence HL; (c) net interactions between overstory and understory elements in these woody patches can be positive, negative and neutral over an annual cycle, and (d) Prosopis-mediated HL is an important mechanism of faciliation for some, but not all, understory shrubs.

Carbon Dioxide↗
PubMed1996

An Ethylene-Mediated Increase in Sensitivity to Auxin Induces Adventitious Root Formation in Flooded Rumex palustris Sm.

The hormonal regulation of adventitious root formation induced by flooding of the root system was investigated in the wetland species Rumex palustris Sm. Adventitious root development at the base of the shoot is an important adaptation to flooded conditions and takes place soon after the onset of flooding. Decreases in either endogenous auxin or ethylene concentrations induced by application of inhibitors of either auxin transport or ethylene biosynthesis reduced the number of adventitious roots formed by flooded plants, suggesting an involvement of these hormones in the rooting process. The rooting response during flooding was preceded by increased endogenous ethylene concentrations in the root system. The endogenous auxin concentration did not change during flooding-induced rooting, but a continuous basipetal transport of auxin from the shoot to the rooting zone appeared to be essential in maintaining stable auxin concentrations. These results suggest that the higher ethylene concentration in soil-flooded plants increases the sensitivity of the root-forming tissues to endogenous indoleacetic acid, thus initiating the formation of adventitious roots.

Journal Article↗
PubMed2001

Root hair initiation is coupled to a highly localized increase of xyloglucan endotransglycosylase action in Arabidopsis roots.

Root hairs are formed by two separate processes: initiation and subsequent tip growth. Root hair initiation is always accompanied by a highly localized increase in xyloglucan endotransglycosylase (XET) action at the site of future bulge formation, where the trichoblast locally loosens its cell wall. This suggests an important role of XET in the first stages of root hair initiation. The tip of growing root hairs is not marked by localized high XET action. Experiments in which root hair initiation was modulated and observations on root hair mutants support this view. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid shifts both root hair initiation and the local increase in XET action toward the root tip. On the other hand, roots treated with the ethylene inhibitor aminoethoxyvinyl-glycine, as well as roots of mutants affected in root hair initiation (rhl1, rhd6-1, and axr2-1) revealed no localized increases of XET action at all and consequently did not initiate root hairs. Disruption of actin and microtubules did not prevent the localized increase in XET action. Also, the temporal and spatial pattern of action as the specific pH dependence suggest that different isoforms of XET act in different processes of root development.

Actins↗
PubMed1989

Hertwig's epithelial root sheath differentiation and initial cementum and bone formation during long-term organ culture of mouse mandibular first molars using serumless, chemically-defined medium.

Studies were designed to test the hypothesis that Hertwig's epithelial root sheath (HERS) synthesizes and secretes enamel-related proteins that participate in the process of acellular cementum formation. Our experimental strategy was to examine sequential root development of the mouse mandibular first molar in vivo and in long-term organ culture in vitro using serumless, chemically-defined medium. Using anti-amelogenin, anti-enamelin and anti-peptide antibodies, enamel-related antigens were localized within intermediate cementum during HERS differentiation and root formation in vivo. Cap stage molars maintained for periods of up to 31 days in organ culture expressed morphogenesis and cytodifferentiation as identified by tooth crown and initial root, cementum and bone formation. Metabolically-labeled HERS products were analyzed by immunodetection using enamel-related antibodies and one- and two-dimensional SDS gel electrophoresis. A 72 kDa and 26 kDa polypeptide were identified in forming mouse cementum. Both of these root putative cementum proteins yield similar (identical) amino acid compositions; however, both proteins differed from the compositions of either mouse crown enamelin or amelogenin proteins. This approach provides a new and novel in vitro model towards understanding HERS differentiation and functions related to root and bone formation. The data support the hypothesis that HERS cells synthesize polypeptides related to but also different from canonical crown enamel proteins.

Animals↗
PubMed2004

Behavior of partially formed roots of teeth submitted to orthodontic movement.

The occurrence of root resorption in orthodontically treated permanent incisors with partially formed roots was investigated using periapical radiographs taken before and after the orthodontic leveling in the mixed dentition. The mean age at the beginning of treatment was 9 years and the mean treatment time was 7.1 months. The findings showed that the orthodontic movement during root formation causes no root resorption. The longitudinal follow-up showed that incompletely formed roots developed normally.

Child↗
PubMed2002

An 18-month longitudinal study on a new silicon-based sealer, RSA RoekoSeal: a leakage study in vitro.

OBJECTIVE: Because leakage along root fillings may increase or decrease during the long period after filling, the accumulated leakage data measured repeatedly after filling are clinically more relevant than the data measured just once shortly after filling. The aim of this study was to determine the long-term sealing ability of a recently developed root canal sealer RSA RoekoSeal (Roeko Dental Products, Langenau, Germany). STUDY DESIGN: Eighty extracted human mandibular premolars were equally divided into 4 groups (n = 20) and root canal instrumented. Canals in group 1 were obturated with laterally compacted gutta-percha points and RSA, in groups 2 to 4 with vertically compacted warm gutta-percha using RSA in group 2, Pulp Canal Sealer (Kerr, Romulus, Mich) in group 3, and no sealer in group 4. With the use of a fluid transport model, leakage along entire root fillings was measured before post space preparation. After post space preparation, leakage along the remaining apical root fillings was measured repeatedly at 1 week, 1, 2, 6, 12, and 18 months respectively and recorded in microliters per day. RESULTS: Before post space preparation, groups 1 and 2 leaked significantly less than groups 3 and 4 (P = .001), whereas no significant difference existed between the groups 1 and 2 (P = .317) or between the groups 3 and 4 (P = .074). For each group, a summation of the leakage at all time intervals after the post space preparation showed that the 2 RSA groups leaked significantly less than the other 2 groups (P =.000). However, no significant difference existed between the 2 RSA groups (P = .993) and between the groups 3 and 4 (P = .149). CONCLUSION: RSA used in combination with either cold laterally compacted or warm vertically compacted gutta-percha provided a consistent seal during a period of 18 months.

Bicuspid↗
PubMed2003

Dual genetic pathways controlling nodule number in Medicago truncatula.

We report the isolation and characterization of a new Medicago truncatula hyper-nodulation mutant, designated sunn (super numeric nodules). Similar to the previously described ethylene-insensitive mutant sickle, sunn exhibits a 10-fold increase in the number of nodules within the primary nodulation zone. Despite this general similarity, these two mutants are readily distinguished based on anatomical, genetic, physiological, and molecular criteria. In contrast to sickle, where insensitivity to ethylene is thought to be causal to the hyper-nodulation phenotype (R.V. Penmetsa, D.R. Cook [1997] Science 275: 527-530), nodulation in sunn is normally sensitive to ethylene. Nevertheless, sunn exhibits seedling root growth that is insensitive to ethylene, although other aspects of the ethylene triple response are normal; these observations suggest that hormonal responses might condition the sunn phenotype in a manner distinct from sickle. The two mutants also differ in the anatomy of the nodulation zone: Successful infection and nodule development in sunn occur predominantly opposite xylem poles, similar to wild type. In sickle, however, both infection and nodulation occur randomly throughout the circumference of the developing root. Genetic analysis indicates that sunn and sickle correspond to separate and unlinked loci, whereas the sunn/skl double mutant exhibits a novel and additive super-nodulation phenotype. Taken together, these results suggest a working hypothesis wherein sunn and sickle define distinct genetic pathways, with skl regulating the number and distribution of successful infection events, and sunn regulating nodule organogenesis.

Ethylenes↗
PubMed2005

Morphometric analysis of root shape.

Alterations in the root shape in plant mutants indicate defects in hormonal signalling, transport and cytoskeleton function. To quantify the root shape, we introduced novel parameters designated vertical growth index (VGI) and horizontal growth index (HGI). VGI was defined as a ratio between the root tip ordinate and the root length. HGI was the ratio between the root tip abscissa and the root length. To assess the applicability of VGI and HGI for quantification of root shape, we analysed root development in agravitropic Arabidopsis mutants. Statistical analysis indicated that VGI is a sensitive morphometric parameter enabling detection of weak gravitropic defects. VGI dynamics were qualitatively similar in auxin-transport mutants aux1, pin2 and trh1, but different in the auxin-signalling mutant axr2. Analysis of VGI and HGI of roots grown on tilted plates showed that the trh1 mutation affected downstream cellular responses rather than perception of the gravitropic stimulus. All these tests indicate that the VGI and HGI analysis is a versatile and sensitive method for the study of root morphology.

Arabidopsis↗