Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “INCISOR”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed1988

Demonstration by staining and radioautography of cyclical distributions of protein at the enamel surface in rat incisors.

Staining patterns in the enamel during the maturation stage of amelogenesis reflect the banded distribution of ruffle-ended and smooth-ended ameloblasts. This study investigated the possibility that proteins at the enamel surface may be distributed cyclically according to cyclical changes in ameloblast morphology. Dissected lower rat incisors were wiped free of their enamel organs and immediately immersed in fixative containing one of the following heavy metal and histological stains: uranyl acetate, lead citrate, Coomassie blue, alcian blue and ruthenium red. Other animals were injected with [35S]methionine to label newly-formed enamel proteins. Their incisors were dissected, the enamel organs were wiped from the enamel surface, and the teeth were processed as whole mounts for radioautography. Teeth stained by heavy metals were also viewed by back-scattered electron imaging. The in-situ staining revealed that proteins were distributed in bands and stripes across maturing enamel. Radioautography revealed that the proteins in the stripes were newly-synthesized and secreted into the enamel by certain maturation ameloblasts. We conclude that the enamel organ expresses cyclical activity in part through secretion of proteins.

Ameloblasts↗
PubMed1989

Cyclical incorporation of 33P into rat incisor enamel in vivo as visualized by whole-mount radioautography.

Phosphorus uptake during amelogenesis was investigated in the continuously erupting rat incisor. Five minutes after intravenous injection of 33P-labelled ortho phosphoric acid, whole-mount radioautography of entire incisors revealed heavy labelling in the form of bands and narrow parallel stripes at the surface of the enamel in the maturation zone. There was relatively little labelling over enamel in the secretion zone and over pigmented enamel. Thus 33P is incorporated cyclically into maturing enamel and is visualized as (1) a banded pattern that reflects the modulation of ruffle-ended and smooth-ended maturation ameloblasts and (2) a striped pattern that reflects the distribution of newly-formed protein secreted by maturation ameloblasts. Presumably these P incorporation patterns are closely related to other cyclical events known to occur during enamel maturation.

Ameloblasts↗
PubMed1989

Adenine nucleotide changes in submandibular salivary glands of rats following isoproterenol or incisor tooth amputation.

Male rats (180-220 g) were injected daily with isoproterenol (2 mg/kg of body weight) for up to 6 days, or their incisor teeth were amputated on every other day for up to six amputations. The animals were subdivided into groups killed 12 or 24 h after the first or last intervention. In the development of sialadenosis caused by isoproterenol, the levels of ATP were greater (13-30%), while those of AMP were lower (13-19%) in the experimental groups. No variation was noted in ADP content. In tooth-amputated animals, only the five and six amputation subgroups showed higher values for ATP (approx. 17%), and ADP (12 and 15%, respectively). The inorganic phosphate level was lower in both experimental groups (between 11-28% for isoproterenol and 13-22% for amputation). Thus isoproterenol caused different metabolic responses in submandibular salivary glands from those induced by incisor amputation.

Adenine Nucleotides↗
PubMed1989

Studies on the influx of [3H]-histidine and 45Ca through a surgical opening to rat incisor ameloblasts and adjacent enamel.

Considerable controversy exists about the role of ameloblasts in transport of calcium to mineralizing enamel. The rate and pattern of incorporation of calcium and an enamel precursor (histidine) were studied autoradiographically by introducing the isotopes through a surgically created defect in the lower border of the rat mandible. Influx of the isotopes to both secretory and maturation ameloblasts and adjacent enamel was examined in large survey sections of the entire incisor at intervals of 3 min to 2 h. Substantial concentrations of silver grains were observed over both secretory and maturation ameloblasts within 5 min of placement of either isotope. 45Ca was also present in secretory and maturation enamel within this short time. The overall patterns of influx and uptake of both precursors were similar to those found when such isotopes have been administered parenterally. The amount of influx of 45Ca across secretory, smooth-ended, and ruffle-ended maturation ameloblasts was compared qualitatively and found to be similar. The reproducibility of this surgical technique was demonstrated as well as its usefulness in combination with survey sections for multi-method investigations of rat incisor enamel formation and mineralization.

Ameloblasts↗
PubMed1990

Zinc deficiency-induced changes in the lipid composition and ultrastructure of rat incisor teeth.

The lipids and ultrastructure of the forming, maturing and erupted parts of incisors were compared in rats fed a zinc-deficient diet for 28 days, pair-fed rats and control rats. The lipid levels in the forming portions of zinc-deficient incisors were 30-50% below control levels and were associated with longer Tomes' processes in the secretory ameloblasts, porosities in the forming enamel and fewer malachite green-aldehyde-phospholipid aggregates in the predentine. No marked structural changes were seen in the erupted portions of the teeth, although variations in lipid composition were detected both in the maturing and erupted parts. No differences were found between teeth from the 3 groups of animals for Na, Mg, Cl, Ca and P signals with the electron microprobe.

Animals↗
PubMed1990

Effects of single doses of 1-hydroxyethylidene-1,1-bisphosphonate on the mineralizing front of rat incisor enamel: a microradiographic and scanning electron microscopic study.

The effects of a single dose of HEBP were examined by injecting rats subcutaneously with various doses (0.5, 1, 2.5, 5 and 10 mg P/kg body wt) and killing them either 2 or 9 days after injection. The maxillary incisors were processed for microradiography and the mandibular incisors for scanning electron microscopy after enzymatic digestion of the enamel organ remains. All doses resulted in a hypomineralized incremental band corresponding to the position of the mineralizing front at the time of injection. At 5 and 10 mg P/kg body wt, a hypomineralized lesion was found throughout the whole thickness of the enamel in an area which corresponded to the stage of late enamel secretion at the time of injection. The surface layer covering this lesion was elevated or disrupted. By scanning electron microscopy, there were three different types of lesions along the enamel surface: a "demarcation groove" corresponding to the initial enamel formation at the time of injection; an "area containing mineral globules" and a "bright band" corresponding to the stages of late secretory and final enamel formation, respectively, at the time of injection. A single injection of HEBP thus interferes with different stages of enamel formation. The findings may be explained as of the physico-chemical effects of HEBP on the mineral phase alone, but a direct effect of the drug on ameloblast function cannot be excluded.

Amelogenesis↗
PubMed1991

An electron microscopic study of dental plaque of the rat incisor.

Because rat incisors continuously erupt they provide an opportunity for the study of dental plaque at all stages of its development. The youngest plaque would be visible at the gingival margin of the tooth as it erupts, and the older plaque higher on the tooth. The ultrastructural features of these plaques were studied by transmission electron microscopy. Cocci and short rods colonized the cementum surface, forming a monolayer. The plaque had a maximum thickness of about 40 microns, with the inner third rich in fibrillar matrix and the organisms forming microcolonies perpendicular to the tooth surface. Cells were haphazardly distributed in a loose matrix on the surface of the plaque. In the area of plaque disorganization the cementum was covered by isolated groups of bacteria and the matrix had holes in it. The rat mandibular incisor may provide a unique model for study of how plaque on cementum is initially formed, matures and finally is degraded.

Animals↗
PubMed1993

The distribution of cellular retinoic acid-binding protein I during odontogenesis in the rat incisor.

Retinoids are important molecules in various aspects of embryological development. Here the distribution of cellular retinoic acid-binding protein I (CRABPI) was studied in the continuously growing incisor of adult rats using an affinity-purified rabbit polyclonal antibody. CRABPI was present throughout the presecretory and secretory ameloblast layer. The protein disappeared from that layer during its maturation phase. The adjacent dental mesenchyme of the developing pulp stained positively for CRABPI, especially in the layer immediately beneath the fully differentiated odontoblasts. Little CRABPI was present in the odontoblast layer itself. The distribution of CRABPI, both in the undifferentiated basal region of the incisor tooth and associated with the cells during hard-tissue formation, suggests a role for this molecule during differentiation and hard-tissue genesis.

Ameloblasts↗
PubMed1993

Role of substance P in neurogenic inflammation in the rat incisor pulp and the lower lip.

Vascular permeability was significantly increased in the incisor pulp and skin of the lower lip in the rat after antidromic electrical stimulation of the inferior alveolar nerve, and this response was significantly inhibited by a substance-P antagonist. The content of substance P in the pulp and lip was also increased after stimulation. The permeability response was reduced by aspirin and bradykinin antagonists (both B1- and B2-receptor types) in the pulp and lip, indicating that prostaglandins and bradykinin may be involved. Mepyramine and methysergide inhibited the vascular response in the lip but not the pulp; the roles of histamine and serotonin differ in the two tissues. Injection of substance P into the incisor pulp and the lip skin caused dye leakage. This response was inhibited by pretreatment with compound 48/80 in the lip but not the pulp. Lip histamine content was decreased significantly after antidromic stimulation of the inferior alveolar nerve and pretreatment with compound 48/80, but was not changed in the pulp. The results suggest that substance P in the lip, after being released from the peripheral sensory-nerve endings, may act on the vascular system via histamine release from mast cells; but in the pulp may cause vascular response directly because of the scarcity of mast cells.

Animals↗
PubMed1994

The effect of vinblastine on the incorporation of [3H]-glycine into proteins of the periodontal ligament of impeded and unimpeded mouse incisors.

The effect of vinblastine on the protein metabolism of the periodontal ligament of impeded and unimpeded mouse incisors was studied by [3H]-glycine labelling and radioautography. The silver-grain concentration was determined in areas adjacent to the tooth, areas adjacent to bone and, as an internal control, in the dentine matrix. From 1 to 12 h there was no difference between treated and control animals; thus the drug did not alter protein biosynthesis. Later, the silver-grain concentration was significantly higher in areas adjacent to both bone and tooth in vinblastine-treated animals, suggesting a longer half-life of the labelled proteins. No significant differences between normal or unimpeded erupting incisors of both groups were detected. Dentine matrix showed a possibly higher re-utilization of the labelled amino acid in vinblastine-treated animals. The amount of labelled protein removed by collagenase was similar in both groups, while the concentration of grains due to collagenase-resistant proteins was significantly higher in treated animals, particularly at 96 h after the injection of labelled glycine. The relation between the increased amount of non-collagenous proteins in the periodontal ligament and the decrease in the rate of eruption caused by vinblastine was not established. However, among these proteins, fibronectin and proteoglycans are thought to be important factors in tooth eruption.

Alveolar Process↗
PubMed1995

Haemodynamic and immunohistochemical studies of rat incisor pulp after denervation and subsequent re-innervation.

The effects of injury to the inferior alveolar nerve on the distribution of neuropeptides and neurogenic blood-flow reactions were studied in rat mandibular dental pulp. In normal incisor pulps, calcitonin gene-related peptide (CGRP)-like immunoreactivity was common, while substance P- and neurokinin (NKA)-positive nerve fibres were much less abundant. There were no signs of vasoactive intestinal peptide-like, neuropeptide Y-like or 5-hydroxytryptamine-like immunoreactivity. In normal pulps, electrical stimulation (100 microA, 5 ms, 15 Hz for 30 s) of the tooth crown resulted in transient vasoconstriction followed by vasodilation, which was enhanced after alpha-adrenoceptor blockade. At 3 days-4 weeks after unilateral nerve section there were no signs of CGRP-, substance P- and NKA-immunoreactivity, and there was no vasodilation in response to tooth stimulation. The vasoconstrictor response was also absent during this period but at 4 weeks postoperatively a weak response was obtained and after 7 weeks the vasoconstrictor response had regained normal amplitude. At 7 weeks postoperatively, a large number of CGRP-positive fibres had reappeared and at 11 weeks the pattern of CGRP-immunoreactivity was normal. However, substance P- and NKA-immunoreactivity were not found at 7 or 11 weeks after surgery. Vasodilator responses appeared at 7 weeks, and showed normal amplitude at 11 weeks after the creation of the nerve lesion. The results show that during nerve regeneration, sympathetic vasoconstriction was regained earlier than neurogenic vasodilation in rat incisor teeth. The reappearance of neurogenic vasodilation after nerve injury was temporarily associated with the presence of CGRP-immunoreactivity in regenerating trigeminal afferent nerves.

Adrenergic alpha-Antagonists↗
PubMed1982

Inferior alveolar nerve regeneration and incisor pulpal reinnervation following intramandibular neurotomy in the cat.

Regeneration of the inferior alveolar nerve and mandibular incisor pulpal reinnervation was qualitatively and quantitatively examined by electron microscopy 2 days--11 months after intramandibular neurotomy in young adult cats. Fifteen millimeters central to the proximal stump moderate atrophic alterations of myelinated axons were observed 1--2 months after surgery. By 4--11 months a principally normal picture had been restored. The proportion of unmyelinated axons was increased 2--4 months after operation but had normalized by 11 months. In the distal stump the first regenerating axons were observed at 2 weeks. The regenerated myelinated axons failed to re-establish the previous fibre size range and normal axo-glial relations did not appear. A seemingly stable morphological pattern was reached 4--11 months postoperatively. In the late survival period the proportion of unmyelinated axons was subnormal. In the incisor pulps virtually all axons disappeared after surgery. By two weeks pulpal reinnervation had begun. From two months on, a structurally largely normal pulpal axon population was present except for some persisting unmyelinated axon degeneration. The findings are consistent with previous physiological data and suggest that structural normalization at proximal and preterminal levels follows upon re-establishment of peripheral contacts.

Animals↗
PubMed1976

Reddening of the upper central incisors associated with periapical granuloma in lepromatous leprosy.

Four years after starting treatment for lepromatous leprosy in England a male Pakistani aged 26 was found to have red discoloration of the upper central incisor teeth. A radiograph suggested periapical abscess on the right with haziness in a corresponding area on the left. Right apicectomy was performed with removal of a solid mass attached to the apex, sections revealing a lepromatous infiltrate with acid-fast fragments of Mycobacterium leprae in the cytoplasm of foamy macrophages. Clinical and archaeological evidence for the frequent involvement of these teeth in lepromatous leprosy is reviewed. The upper incisor area is relatively cool, a factor which may be of critical importance for the lodgement and multiplication of this bacillus, as it is in other body sites in lepromatous leprosy.

Adult↗
PubMed1991

Localization of epidermal growth factor receptors in cells of the enamel organ of the rat incisor.

Epidermal growth factor (EGF) is a peptide shown to effect precocious incisor tooth eruption in rat pups. Binding sites for EGF were visualized in the continuously erupting adult rat incisor by light and electron microscope radioautography after in vivo injection of 125I-EGF. These binding sites represented EGF receptors because of (i) competition between 125I-EGF binding at 2 min after injection and a coinjected excess of unlabeled EGF; (ii) the receptor-mediated endocytosis of 125I-EGF at 15 and 30 min after injection; and (iii) the demonstration of EGF receptor kinase activation in vivo. The stem and the mitotic cells in the epithelial odontogenic organ at the growing end of the tooth develop into two nondividing layers of the enamel organ: (i) ameloblasts which secrete enamel and are subsequently involved in the enamel maturation process, and (ii) papillary layer cells situated between the blood supply and the ameloblasts. Although few EGF receptors were present at the mitotic end, receptor density was highest at the mature end of the enamel organ. High levels of 125I-EGF binding were found on papillary layer cells and ruffle-ended, but not smooth-ended, ameloblasts. This implies a cyclical exteriorization and internalization of receptors during modulations between the two cell types. These data suggest that the EGF receptor mediates a major function of the enamel organ in the formation of enamel.

Animals↗
PubMedDate not supplied

Mechanical responses of the periodontal ligament in the transverse section of the rat mandibular incisor at various velocities of loading in vitro.

Stress-strain curves of the periodontal ligament (PDL) were obtained at various velocities of extrusive loading of 1, 10, 10(2), 10(3) and 10(4) mm/24 h in vitro. Significant increases of the maximum shear stress, tangent modulus and failure strain energy density were found with increases in the velocity of loading. The maximum shear strain increased from a velocity of 1 to 10 mm/24 h but decreased from 10 to 10(4) mm/24 h. It was shown histologically that the free surface of the PDL adhering to the cementum after mechanical testing was rough and irregular at higher velocities and rather smooth at lower velocities. These results showed that the mechanical properties and mode of failure of the rat incisor PDL were greatly dependent on the strain rate. It is possible that the PDL of the continuously erupting rat incisor has mechanical characteristics favourable for resisting weakly to slow and small eruptive forces but strongly to the fast and large occlusal forces as suggested previously [Chiba and Komatsu, The Biological Mechanisms of Tooth Eruption and Root Resorption (1988)].

Alveolar Process↗
PubMed1980

The face-form as a guide for the selection of maxillary central incisors.

The outline forms of both maxillary central incisor teeth were compared with the "actual" and "apparent" face-forms in 70 subjects, to determine whether a close similarity of face-forms and tooth forms exists, which would support the "law of harmony" method for the selection of replacement of teeth. The results of the investigation do not support the contention of Williams but rather invalidate this method of teeth selection because more than two-thirds of the individuals showed no similarity between face-form and incisor tooth form.

Dental Occlusion, Centric↗
PubMed1985

Cantilever fixed prosthesis replacing the maxillary lateral incisor: design consideration.

A variation in design of a cantilever fixed prosthesis is suggested using a wrap-around configuration of the mesial surface of the lateral incisor pontic. The preparation on the canine is modified with one or more shallow grooves to provide additional resistance to rotational forces. All occlusal contacts on the lateral incisor pontic are avoided.

Denture Design↗