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 487 records · Page 27Linked to original sources
PubMed1984

A light and electron microscopic study of osteodentin formation in the rat incisor after adriamycin administration.

The effect of adriamycin (10 mg/kg body weight) on the rat incisor was investigated in 8-day-old animals at 9 days and 14 days after subcutaneous injection. The drug produced changes that were still present 14 days after administration. During this time osteodentin formation, which appeared to be the principal effect of the drug on the incisors, occurred to such an extent that in some regions of the teeth the pulp chamber was almost completely occluded. The formation of osteodentin began at the periphery of the pulp and gradually advanced towards the central region. Moreover, in some sections of the incisor the dentin layer was greatly reduced to a thin superficial layer, while osteodentin surrounded most of the pulp chamber. Cells that appeared to be differentiated pulp-mesenchymal cells were found within as well as on the surface of the irregular osteodentin matrix. Since this drug has been used in the treatment of childhood osteosarcomas, the possibility of dental abnormalities developing in these children cannot be overlooked.

Animals↗
PubMed1984

A radioautographic study of the incorporation of iron 55 by the ameloblasts in the zone of maturation of rat incisors.

This study was designed to study the time course of the incorporation of 55Fe into the ameloblasts of maturation in rat incisors. Male Sherman rats (100 +/- 5 gm) were injected intravenously with 0.9 mCi of 55Fe and sacrificed in pairs by perfusion at various time intervals from 5 min to 7 days after injection. The incisors were demineralized in 4.13% disodium EDTA, postfixed in 1% osmium tetroxide in veronal acetate buffer, and embedded in Epon. Incisors from control rats injected with only physiological saline were treated in the same way. Sections from blocks of tissue in the zone of maturation were prepared for light microscope radioautographic observations. The greatest incorporation of iron occurred at 9 mm within the zone; at this site the ameloblasts contained few pigment granules. About 5 mm deeper into the zone the activity fell off to zero, as observed at 2.5 hr after injection of 55Fe. Between 1 day and 7 days after injection the 55Fe labeling was found over the cells containing many pigment granules, while the initial labeling over the cells within 9 mm of the zone had diminished. These data have shown that at any given time, from 30 min to 4 hr, the iron enters the maturation ameloblasts over a wide extent of the zone, reaching a maximum at about 9 mm from the onset of maturation. However, at longer times (1 day to 7 days) the labeling curve shifts and shows the greatest activity beyond 9 mm within the zone.

Ameloblasts↗
PubMed1987

Agenesis of succedaneous teeth: an expression of the homozygous state of the gene for the pegged or missing maxillary lateral incisor trait.

Agenesis of the permanent teeth that replace the primary teeth, the succedaneous teeth, was found in children from two kindreds wherein both parents had pegged maxillary lateral incisor teeth. The trait small-pegged-missing maxillary lateral incisor teeth is inherited in an autosomal dominant manner, as demonstrated in the literature and in these families. Agenesis of succedaneous teeth is most likely an autosomal recessive trait due to the homozygous state of the gene for small-pegged-missing maxillary incisor teeth.

Adolescent↗
PubMed1987

Single central maxillary incisor and holoprosencephaly.

A holoprosencephalic child was born to a mother with a single central maxillary incisor. The infant had a median cleft lip, a flat nose with a single nostril, hypotelorism, and normal chromosomes. The head was brachycephalic and small, and computed tomography (CT) of the brain showed semilobar holoprosencephaly. The mother had mild hypotelorism but no anosmia, and her brain CT was normal. She was of normal intelligence and stature. Other relatives did not have single central maxillary incisors, hypotelorism, or oral clefts. Whether the mother's anomaly was a new mutation or had been inherited is unknown. We show the significance of a single central maxillary incisor as an indicator or potential holoprosencephaly in the next generation, even if other relatives are apparently normal.

Abnormalities, Multiple↗
PubMed1977

Congenital defects of the upper lateral incisors (ULI): condition and measurements of the other teeth, measurements of the superior arch, head and face.

We surveyed a French male population for the incidence of missing or reduced upper lateral incisors (ULI). In 5,738 subjects, we observed an incidence of 1.59% with one or two reduced ULI (the other normal) and 1.90% with one or two missing ULI (the other normal or reduced), altogether, 3.49% affected subjects. Furthermore, 250 random controls were observed. Agenesis of other teeth is more frequent in propositi. Missing thir molars were 12.4% in controls, 24.0% in propositi with reduced ULI and 39.6% in propositi with two missing ULI. Furthermore, agenesis of incisors, canines and premolars ranges from 0.4% in controls to 1.3% in propositi having reduced ULI and 5.0% in propositi with two missing ULI. So, propositi with reduced ULI are intermediate between the controls and the propositi with missing ULI with respect to the freeuency of agenesis of other teeth. On the other hand, a different ranking is observed with respect to the teeth measurements: reduction of tooth size is more marked in propositi with reduced ULI than in propositi with missing ULI. The reduction mainly affects canines, incisors and to a lesser degree, premolars. Arch length and interpremolar diameters are smaller in propositi with missing ULI, compared with controls.

Adolescent↗
PubMed1981

The development of enamel structure in rat incisors as compared to the teeth of monkey and man.

The rat incisor is an excellent model system in which to study amelgenesis. However, the information obtained has not been extrapolated to the human because of alleged structural differences between the teeth. The obvious differences include continuous eruption in rat incisors and an enamel rod pattern in rats which seemingly differs from the keyhole pattern of human enamel. A comprehensive analysis was made of those features of enamel structure considered fundamental to the understanding of its formation. This was done by applying the knowledge of amelogenesis obtained in rat incisors to the teeth of monkey and man. The following points of basic similarity were established between these species: (1) Interrod enamel is secreted first. It forms the side walls of cavities which are initially occupied by Tomes' processes. (2) The formation of interrod cavities is followed by deposition of enamel rods within these spaces. (3) The rods conform to the shape of the cavities and are secreted from one surface of Tomes' process. (4) At the initial site of rod deposition its enamel is continuous with the interrod enamel wall. (5) Growth of the rod compresses the process to one side of the cavity resulting in an arcade-shaped "space" between the rod and the remaining interrod walls. This study demonstrates that it is no longer necessary to postulate a keyhole structure for primate enamel, and it has established that a fundamental similarity exists in the basic structure and in the mode of formation of enamel in all three species.

Amelogenesis↗
PubMed1985

The effect of adriamycin on rat incisor one day after administration.

The effect of adriamycin on rat incisor was investigated 1 day after administration. Rats were injected intravenously with adriamycin at a dose of 5 mg/kg body weight and sacrificed by perfusion with a 2.5% phosphate buffered glutaraldehyde solution. The principal effect of the drug on the incisor was the production of cell degeneration. This was extensive in the apical region, being present along the entire periphery of the dental papilla. In sections examined more incisally, cell degeneration gradually disappeared from the labial portion of the incisor but was present in the lingual portion. This degeneration of cells was not present at the site where mature odontoblasts had differentiated on the lingual surface of the pulp chamber. It appears that the affected cells were early preodontoblasts and the precursors of preodontoblasts. However, as these cells became more differentiated they apparently became more resistant to the drug's effect.

Animals↗
PubMed1985

Odontoblast turnover in the impeded and unimpeded rat incisor derived from computerized histomorphometry.

A computerized histomorphometric method was devised to estimate the kinetics of odontoblast turnover and dentinogenesis in rat incisors. The method was applied to two groups of rats: one group with lower incisors in impeded eruption and another group with the left lower incisor in the unimpeded state. The teeth were divided into six equal segments, from which consecutive ground sections were obtained. The distance of each ground section from the posterior border of the alveolar bone was calculated. Each section was magnified, traced, and the tracings fed into a computer by a sonic digitizer. The perimeters and areas of dentine and pulp in each ground section were calculated by the computer. The mean odontoblast density along the predentine was evaluated from histological sections taken both from the same tooth segments and from teeth sectioned midsagittally. These served for the estimation of the predentine area occupied by the average odontoblast. In the impeded group, this area was 11% larger than in the unimpeded one. Outer dimensions of teeth, namely the circumference of the dentine, the labiolingual width, and the mesiolateral width remained constant and equal for both groups. Daily rates of dentine apposition were computed and were found to vary according to the age of the odontoblasts. Odontoblasts of impeded teeth started to secrete matrix at a rate of 17 microns/day, which increased slightly to 19 microns/day and later declined to 7 microns/day on the 38th day. Dentine production of unimpeded odontoblasts, on the other hand, started at a rate of 16 microns/day and gradually increased to 34 microns/day on the 17th day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The effect of streptozotocin on the secretory activity of ameloblasts in rat incisor as revealed by radioautography after 3H-proline administration.

The effect of a diabetogenic dose of streptozotocin on the secretory activity of ameloblasts was investigated in the rat incisor by radioautography. One group of male Sprague-Dawley rats was injected intravenously with streptozotocin in citrate buffer (pH 4.5). One hour later, this group was again injected intravenously with 3H-proline (2 mCi/kg). A control group of animals was injected with 3H-proline only. All the animals were sacrificed in groups of three at 5 min, 1 h, 2 h, 4 h and 8 h after 3H-proline injection by perfusion with 3% phosphate-buffered formaldehyde followed by an additional perfusion with 2.5% phosphate-buffered glutaraldehyde. The incisors were extracted with the jaws, demineralized, and prepared for radioautographic observations and analysis. The principal effects of streptozotocin were as follows: There was an inhibition of 3H-proline incorporation into the secretory ameloblasts at 5 min after injection. This was followed by a larger uptake and a slower passage of the label out of the cells into the enamel matrix than that seen in the control sample. Finally, there was a slower secretion of labeled proteins out of Tomes' processes between 1 and 4 h after injection. Therefore, streptozotocin had a temporary inhibitory effect on the incorporation and secretion of 3H-proline by the secretory ameloblasts of the rat incisor. This effect was present for about 4 h and was completely reversed 9 h after streptozotocin injection.

Ameloblasts↗
PubMed1989

Banding patterns in rat incisor enamel stained by histochemical complexing methods for calcium.

A characteristic banding pattern can be visualized at the surface of the rat incisor in the maturation zone of amelogenesis by staining with glyoxal bis(2-hydroxyanil) (GBHA). Other banding patterns can be obtained with certain histological and fluorochrome stains and by radioautography following 45Ca injection. In this study, several histochemical reagents known to complex with different states of calcium were used to stain the surface of enamel. Rat incisors were quickly dissected and immediately immersed in solutions containing the following calcium-binding reagents: arsenazo III, calmagite, murexide, N,N-naphthaloylhydroxylamine, and calcein. Routinely, one contralateral lower incisor from each pair was counterstained with GBHA in order to relate each of the staining patterns to the banded distribution of maturation ameloblasts that is reflected by the characteristic GBHA staining pattern in the enamel. Each of the reagents used in this study demonstrated a staining pattern consisting of a series of broad bands running transversely and obliquely across the enamel. In all cases, the dyes stained predominantly that enamel associated with ruffle-ended ameloblasts, i.e. enamel left unstained by GBHA. Some of the reagents also stained enamel in the secretion zone. The appearance and distribution of the staining patterns reflect the banded distribution of maturation ameloblasts and appear to be controlled on a time scale related to the rapid modulation of these cells.

Animals↗
PubMed1993

Effects of chronic fluoride exposure on morphometric parameters defining the stages of amelogenesis and ameloblast modulation in rat incisors.

The response of ameloblasts to long-term (6 weeks) exposure to 100 ppm fluoride was examined in continuously erupting mandibular incisors of female Sprague-Dawley rats as compared to control rats receiving a similar diet (Teklad L-356) but no sodium fluoride in their drinking water. After treatment, animals from both groups were perfused intravascularly with glutaraldehyde, and the incisors were removed and processed for light microscope morphometric analyses directly from 1 microns thick Epon sections. Other animals were injected intravenously with calcein (green fluorescence) followed 4 hours later by xylenol orange (red fluorescence) in order to reveal smooth-ended ameloblast modulation bands and thereby allow quantification of parameters related to the creation and movement of modulation waves within the maturation zone of these teeth. The results indicated that rat incisors expressed four major changes in normal amelogenesis which could be attributed to the chronic fluoride treatment. First, ameloblasts produced a thinner than normal enamel layer by the time they completed the secretory stage and entered the maturation stage of amelogenesis. Second, enamel organ cells within the maturation zone, especially those from the papillary layer, were shorter in height than normal. Third, ameloblasts related to maturing enamel in areas where it was partially soluble and/or fully soluble in EDTA modulated at a rate that was much slower than normal. In some locations ameloblasts remained ruffle-ended for as much as 30% longer than normal per cycle. This upset the usual pattern such that fewer total modulation cycles were completed per unit time by these ameloblasts. Fourth, enamel proteins were lost from the maturing enamel layer at a rate that was about 40% slower than normal. The data suggested that ameloblasts detected the delay in the extracellular breakdown and/or loss of enamel proteins and they responded by remaining ruffle-ended for longer intervals than usual (positive feedback).

Ameloblasts↗
PubMed1994

Collagen fibrils in the odontoblast layer of the rat incisor by scanning electron microscopy using the maceration method.

BACKGROUND: There is not universal agreement on the existence of the extracellular pathway from the pulp along the odontoblast layer to the predentin. METHOD: To confirm this pathway, the architecture of collagen fibrils in the rat incisor dentin and pulp, especially in the odontoblast layer of the lateral (periodontal ligament) sides of the tooth, was demonstrated in the present investigation using scanning electron microscopy of the maceration method for collagen networks. RESULTS: Numerous collagen bundles were observed in the odontoblast layer in the mature odontoblast region which, except for the young odontoblast region, comprises the major portion of the incisor. The collagen bundles went from the pulp, through the odontoblast layer, and were woven into the collagen network of the predentin. The meshwork structure was composed of fine secondary fibrils among these collagen bundles. The surface of the predentin contained many oval-shaped holes which were surrounded by collagen fibrils. Fracturing the dentin longitudinally relative to the dentinal tubules revealed that the arrangement of the collagen fibrils at the surface of the tubules was either circular or oblique. In the young odontoblast region, i.e., the thin portion from the apical end of the incisor where the mineralization of the dentin does not occur and where the height of the odontoblasts was less than 30 microns, many thick bundles composed of thick collagen fibrils ran straight from the pulp to the predentin through the odontoblast layer and fanned out in the collagen network of the predentin. These thick bundles might correspond to the so-called "von Korff fibers." The distribution of collagen fibrils in the pulp was random except on the surface of the blood vessels where the fibrils comprised two sheets of collagen: the inner sheet which coursed longitudinally to the long axis of the vessel, and the outer sheet which ran transversely. CONCLUSION: It was considered that the fluid in the pulp could flow to the predentin along the collagen fibrils through the tight junction between the odontoblasts.

Animals↗
PubMed2004

Alveolar bone Sharpey fibers of the rat incisor in normal and altered functional conditions examined by scanning electron microscopy.

The morphology and the area density of Sharpey fibers in the socket of the rat incisor under normo-, hyper-, and hypofunctional conditions were evaluated using scanning electron microscopy. Sharpey fibers appeared either as dome-shaped projections, when highly mineralized, or as depressions when less mineralized. Near the alveolar crest, most of the fibers were fully mineralized and arranged in compact longitudinal rows. Toward the basal end of the socket, the rows became interrupted, forming islets of gradually smaller size and number. The density of the Sharpey fibers was higher (P < 0.01) in the mesial and distal faces than in the lingual face in most of the socket length. In normofunctional conditions, in all faces the density decreased 70 to 90 times from the crestal toward the basal region of the socket (P < 0.01). The degree of mineralization of the Sharpey fibers also decreased steadily in the same direction, indicating that, for support, the periodontal ligament matures from basal to incisal and is fully developed only in the crestal region. In hyper- and hypofunctional conditions, the same distribution was observed. The area density of the Sharpey fibers in the hyperfunctional condition showed a slight increase at the basal levels of the socket mesial and distal faces (P < 0.01 or P < 0.05). In hypofunctional incisors, the density decreased significantly (P < 0.01) at the mesial and distal faces in all regions of the socket, and at the lingual face, the decrease (P < 0.05) was restricted to the incisal regions. This may be one of the factors for the weakening of the periodontal ligament in hypofunctional incisors.

Alveolar Process↗
PubMed2000

Causes and prevalence of traumatic injuries to the permanent incisors of school children aged 12 years in Jaragua do Sul, Brazil.

AIM: To assess the causes and the prevalence of traumatic injuries to the permanent incisors of 12-year-old schoolchildren in Jaragua do Sul, Brazil. DESIGN: Cross-sectional survey. SETTING: Public and private primary schools. PARTICIPANTS: 476 children of both sexes, selected by multistage sampling technique. METHODS: Clinical examination of upper and lower permanent incisors. MAIN OUTCOME MEASURES: Incisal overjet, lip coverage, traumatised anterior teeth, cause of trauma. Parents' levels of education and employment status and family income. RESULTS: Boys experienced double the percentage of injuries compared to girls. Children with incisal overjet greater than 5 mm (P = 0.077) and inadequate lip coverage (P = 0.667) were not more likely to have experienced dental injuries. The main causes of injuries to the permanent incisors were falls (26 per cent), traffic accidents (20.5 per cent), sports (19.2 per cent), violence (16.4 per cent) and collisions with people or inanimate objects (6.8 per cent). Socio-economic measures had no significant effect on prevalence of trauma. CONCLUSIONS: Policy makers must take the causes of trauma into account when developing a strategy for the prevention of dental injuries. The role of violence in causing traumatic dental injuries has been underestimated.

Accidental Falls↗
PubMed2001

Human mandibular incisors from the late Middle Pleistocene locality of Hoedjiespunt 1, South Africa.

The Hoedjiespunt 1 locality is an archaeological and palaeontological site located on the Hoedjiespunt Peninsula at Saldanha Bay, South Africa. In 1996 two human teeth, a left central mandibular incisor and a left lateral mandibular incisor, were discovered during excavations in the late Middle Pleistocene palaeontological layers. These teeth are described and are found to belong to a single subadult individual. Despite their developmental stage, these incisors already display early signs of wear. Their crown diameters are larger than modern and archaeological African comparative material and are most closely comparable with crown diameters of an early Middle Pleistocene and late Middle Pleistocene dental sample from Africa, Europe and Asia. In the light of this metrical evidence, data on two previously excavated maxillary molars, most probably belonging to the same individual, were re-examined. It was found that the Hoedjiespunt 1 hominid possessed dental metrical features (large anterior teeth and small molars) comparable with other African and European hominids referred to the Middle Pleistocene.

Biological Evolution↗
PubMed1988

Innervation of periodontal ligament and dental pulp in the rat incisor: an immunohistochemical investigation of neurofilament protein and glia-specific S-100 protein.

Nervous elements in the periodontal ligament and dental pulp of rat incisors were investigated by means of immunohistochemistry for neurofilament protein (NFP) and glia-specific S-100 protein. The periodontal ligament in the incisors was densely innervated by NFP-immunoreactive nerve fibers; the distribution of the nerve fibers and their terminations differed markedly from those in molars. NFP-positive, thick nerve bundles entered the lingual periodontal ligament through slits located in the mid-region of the alveolar socket, and immediately formed numerous Ruffini-like corpuscles. In the labial periodontal ligament, all of the NFP-immunoreactive nerve fibers terminated in free endings. The restricted location of the stretch receptor, Ruffini-like corpuscle, in the lingual periodontal ligament appears to be an essential element, because this region is regularly extended during mastication. The nervous elements were restricted to the alveolar half of the periodontal ligament in every region; they avoided the dental half of the periodontal ligament, which presumably moves continuously with the tooth. Pulpal nerve fibers in incisors also showed a characteristic distribution different from those in molars; individual nerve fibers with beaded structures ran in the center of the pulp toward the incisal edge, and did not form the subodontoblastic nerve plexus of Raschkow. Immunostaining for S-100 protein revealed a distribution pattern of nervous elements similar to that for NFP, suggesting that the nerves supplying the periodontal ligament and dental pulp were mostly covered by a Schwann sheath.

Animals↗
PubMed1996

Forces applied by the incisors and roles of periodontal afferents during food-holding and -biting tasks.

The force exerted by the central incisors while holding and splitting a food morsel was analyzed to characterize human biting behavior. The force was continuously sampled by a transducer-equipped plate upon which a small piece of dry biscuit or half a peanut rested. Subjects were instructed to position the plate between the incisor teeth and to split the morsel either immediately ("split task") or after holding it for a brief period ("hold-and-split task"). While holding either food substance between the incisors, subjects automatically exerted light contact forces of less than 1 N (0.36-0.76N range among subjects). Considering that the subjects had no instructions about what force levels to employ, the hold force was remarkably stable during individual trials and highly similar among trials. Even during the split task, subjects opted to "hold" the morsel momentarily on ca. 50% of the trials with a similar, low contact force. For both tasks, subjects split the morsel by exerting a distinct, rapidly executed ramp increase in force. The split occurred at 7.8-10.3 N (range among subjects) bite force for the biscuit and 16.0-19.0 N for the peanut. The magnitude of the forces used during the hold phase were within the range over which most periodontal afferents are optimally sensitive to changes in force, i.e., forces below about 1 N. This observation suggested that the subjects automatically adjusted the force to maximize the availability of information from periodontal afferents and avoided higher forces at which the sensitivity of most afferents was not optimal. We further confirmed that the periodontal receptors serve a role in controlling the hold force by anesthetizing the periodontal tissues: subjects employed considerably higher and more variable hold forces, but there was no effect on the split phase. In addition, the morsel frequently escaped from the incisal edges of the teeth while the subject attempted to maintain it in position. It was concluded that subjects rely on signals from periodontal afferents to regulate the jaw muscles, particularly when they first contact, manipulate, and hold food substances between the teeth.

Adolescent↗
PubMed1993

Scanning electron microscopy of final enamel formation in rat mandibular incisors following single injections of 1-hydroxyethylidene-1,1-bisphosphonate.

A single, high dose of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) results in three different types of lesions along the enamel surface of the rat incisor, one of which is seen as a "bright band" crossing the final enamel surface in the scanning electron microscope (SEM). The present study presents the structural surface features of final enamel formation and its subsequent maturation in normal and HEBP-exposed rats. The position of the bright band is examined in relation to where the Tomes processes pits disappear (DTPP), where the boundary between "light" and "dark" enamel (LDB) as seen by SEM is located, and in particular, where the so-called opaque boundary (OB) is positioned. Groups of rats were given a subcutaneous dose of 0, 5, or 10 mg P/kg body wt of HEBP and killed at intervals of either 12 hours or 2 or 9 days. The mandibular incisors were processed for SEM after enzymatic digestion of enamel organ remains. Enamel surface nodules, 100-300 nm in diameter and composed of smaller units, were evident at the start of final enamel formation which was defined as the area from DTPP to LDB. With increasing maturation, the nodules merged to form a smooth surface. In HEBP-treated animals, growth and merging of these surface nodules became arrested at the time of injection resulting in an irreversible "porous" stage corresponding to that part of the surface enamel. This area--the bright band--developed corresponding to the start of the area of final enamel formation and was subsequently carried incisally during the eruption of the incisor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗