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At least 775 records · Page 43Linked to original sources
PubMed1998

Relationships between mandibular symphysis morphology and lower incisor inclination in skeletal class III malocclusion requiring orthognathic surgery.

The purpose of this study is to clarify symphysis morphological characteristics in skeletal class III malocclusion requiring orthognathic surgery and their relationships with symphysis morphology and inclination of the long axis of the lower incisor. The materials were pretreatment lateral cephalometric radiographs from 50 subjects diagnosed as requiring orthognathic surgery. Controls were 30 adults with normal occlusion and well-balanced faces. Detailed cephalometric measurements on the mandibular symphysis (angular, linear and proportional measurements) were recorded and analyzed statistically. In the surgical group, the long axis of the lower incisor demonstrated a significant lingual inclination in relation to the mandibular plane and symphysis. Moreover, because the symphysis demonstrated lingual inclination everywhere except in the basal bone region in relation to the mandibular plane, the curvature between the alveolar and the basal bone region was significantly smaller than that of normal occlusion group. The symphysis labial external surface in the alveolar and basal bone regions demonstrated lingual inclination in relation to the mandibular plane, however, there was no difference in curvature. Small mean values were obtained for Pt.B width, Pog width, and Sym height. Significant differences were observed only in Pt.B width. In both the surgical and normal occlusion groups, a significant correlation was observed between the inclination of the long axis of the lower incisors and symphysis inclination. In the basal bone region, however, there was no significant correlation.

Adult↗
PubMed1986

Effects of various agents on staining of the maturation pattern at the surface of rat incisor enamel.

In the maturation zone, two types of ameloblasts are arranged as bands across the rat incisor; these corresponded with a staining pattern at the surface which reflected the alternating pattern of ruffle-ended and smooth-ended ameloblasts. PAS stain showed bands and stripes similar to those following glyoxal bis(2-hydroxyanil) (GBHA) staining; these stains visualize the organic (PAS) and inorganic (GBHA) components of the maturation pattern. To further elucidate the nature of these bands, dissected rat incisors were treated with various agents prior to staining with GBHA or PAS. Guanidine for 2 h at room temperature showed no maturation pattern when stained with GBHA, as did teeth treated with EDTA and a bisophosphonate (HEBP). Hydrochloric acid and nitric acid removed the layer of outer enamel and incisors did not stain with GBHA, suggesting that the staining is a surface-related phenomenon. As staining was abolished by either the removal of mineral (EDTA) or protein (guanidine), the concurrent localization of non-crystal-bound calcium by GBHA staining, and of glycoprotein by PAS staining, indicates that calcium is associated with glycoprotein at the surface of the enamel.

Ameloblasts↗
PubMed2003

Enhancement of alkaline phosphatase synthesis in pulp cells co-cultured with epithelial cells derived from lower rabbit incisors.

Dental papilla mesenchymal cells differentiate into odontoblasts through epithelial-mesenchymal interactions. However, the mechanism by which enamel epithelial cells affect the differentiation of dental mesenchymal cells remains unknown. Alkaline phosphatase (ALPase) is a marker for odontoblast-like differentiation, because odontoblasts show much higher ALPase activity than dental undifferentiated mesenchymal cells. The continuously growing rabbit incisor is a good model for the epithelial-mesenchymal interaction during odontogenesis. In the present study, we isolated and maintained rabbit incisor-derived epithelial cells and rabbit incisor pulp-derived fibroblastic cells, and examined the effect of epithelial cells on ALPase activity in fibroblastic cells. Epithelial cells were stained with anti-cytokeratin 5 and 8 antibodies and showed the expression of tuftelin mRNA. In separate cultures of epithelial cells or fibroblastic cells, ALPase activity and mRNA levels were very low, but were upregulated in co-cultures of epithelial and fibroblastic cells. Histochemical analysis found high ALPase activity in fibroblastic cells close to epithelial cells. These findings suggest that epithelial cells play an important role in promoting ALPase expression in pulp fibroblastic cells. The co-culture system developed here will be useful for examining the role of the epithelial-mesenchymal interaction during odontoblast differentiation.

Alkaline Phosphatase↗
PubMed2000

Distribution of non-collagenous dentin matrix proteins and proteoglycans, and their relation to calcium accumulation in bisphosphonate-affected rat incisors.

It has been reported that multiple injections of 1-hydroxyethylidene- 1,1-bisphosphonate (HEBP) to rats prevent mineralization of incisor dentin, thereby revealing high concentrations of calcium in the non-mineralized matrix of circumpulpal dentin. To identify the molecules responsible for calcium accumulation in circumpulpal dentin matrix, rats were injected daily with HEBP (8 mg P/kg) for 7 d, and the incisors processed for various histochemical and immunohistochemical staining of non-collagenous matrices of dentin. Cuprolinic blue reactions for proteoglycans (PGs) were equally distributed in non-mineralized matrix of mantle and circumpulpal dentin layers. Dentin sialoprotein (DSP) and osteopontin (OPN) immunoreactions were found in non-mineralized circumpulpal dentin matrix, but not in mantle dentin. In normal incisors, however, predentin matrix showing significant DSP immunoreactivity was negative for Ca-GBHA reactions. HEBP-affected, non-mineralized OPN immunopositive bone matrix was also non-reactive for calcium. From these observations, neither PGs, OPN nor DSP appear to be responsible for calcium accumulation in HEBP-affected circumpulpal dentin. Stains-all reactive component, possibly dentin phosphoprotein (DPP), only showed the same distribution as that of Ca-GBHA in both HEBP-affected and normal dentin matrix, implicating a possible contribution of DPP to calcium accumulation in circumpulpal dentin and, hence, to appositional mineralization of dentin.

Animals↗
PubMed2002

Nociceptive behaviour induced by dental application of irritants to rat incisors: a new model for tooth inflammatory pain.

Animal models simulating acute human pulpitis are still lacking. The rat incisors present a particular situation where most of their innervation is considered to be unmyelinated and concentrated mainly in the tooth pulp. This study reports on a new model for dental pain induced by inflammatory agents applied to the tooth pulps of incisors. In different groups of rats, artificial crowns were fixed on the lower incisors, after cutting 1-2mm of their distal extremities. A volume of 7-10 microl of solutions of saline, capsaicin (1-10mg/ml) or formalin (2.5% or 5%) was injected in the crown cavity, and the nociceptive behaviour was quantitated following a devised scoring method of four scales. Intradental application of capsaicin produced nociceptive scores in the form of one plateau for 1-2h depending on the concentration used. Similar results were obtained with intradental application of formalin 2.5%. The one plateau of nociceptive scores obtained with formalin contrasts with the biphasic aspect of nociceptive behaviour described with the intradermal formalin test. This discrepancy could be attributed to a difference in the types of afferent fibres involved in each situation. Pretreatment with morphine (2 mg/kg) attenuated, in a naloxone-reversible manner, the nociceptive behaviour observed following intradental application of capsaicin. Pretreatment with meloxicam (a cyclo-oxygenase-2 inhibitor) exerted a less pronounced attenuation of the nociceptive scores when compared with morphine. These results provide evidence for the validity of the described model for the simulation of tooth pulp inflammatory pain in awake animals.

Analgesics, Opioid↗
PubMed1999

"Risk periods" associated with the development of dental fluorosis in maxillary permanent central incisors: a meta-analysis.

This systematic review of the dental literature (1966-98) concerns risk periods associated with dental fluorosis in the maxillary permanent central incisors. A literature search was organized through the MedLine and the ISI databases. In addition, one unpublished paper (in manuscript) was obtained, as well as one paper published before 1966. However, out of 143 catches, only 10 studies were included in this review. The main reason for exclusions was that the data presented did not meet the criteria given for the present meta-analysis. Among the included papers, 7 pertained to subjects whose exposure to fluoride started at different ages during the enamel formation (Group 1), and 3 were based on subjects who had been exposed from birth and then experienced an abrupt reduction in daily fluoride exposure at different ages during the amelogenesis period (Group 2). The meta-analysis for Group 1 found the odds ratio (OR) for dental fluorosis in children exposed to fluoride early in life (before 2 years of age) to be 7.24 (95% CI; 4.71-11.13) as compared to children exposed later in life (after 2 years of age). The meta-analysis for the studies in Group 2 found the overall OR to be 1.88 (95% CI; 1.35-2.61) for children who had a reduction in fluoride intake after 2 years of age, as compared to individuals who experienced reduction earlier (during the first 2 years). The studies from both groups were pooled and the duration of exposure to fluoride during the first 4 years of life was the independent variable. The meta-analysis now revealed an overall OR of 5.83 (95% CI; 2.83-11.94) for long periods of fluoride exposure (>2 out of the first 4 years) versus shorter periods of exposure (<2 out of the first 4 years of life) during the enamel formation in the maxillary central incisors. Based on the findings of the meta-analysis, no specific period of enamel formation is singled out as being the most critical for the development of dental fluorosis. The duration of fluoride exposure during the amelogenesis, rather than specific risk periods, would seem to explain the development of dental fluorosis in the maxillary permanent central incisor.

Amelogenesis↗
PubMed1986

A survey of excessively worn incisors and periodontal disease in sheep in Dunedin City, Silverpeaks, Bruce and Clutha Counties.

To determine the prevalence of excessively worn incisors (XSW) and periodontal disease (PD) in sheep in Dunedin City, Silverpeaks, Bruce and Clutha Counties, the incisors of 4049 mixed age ewes on 83 farms selected at random were examined between December 1983 and February 1984. Of these ewes, 14.9% had XSW (11.7% moderate, 3.2% severe), 13.7% had PD (10.5% moderate, 3.2% severe) and 71.4% had sound mouths. An additional 43 ewes had miscellaneous incisor faults, and these were excluded from the survey. Seventeen (>20.5%) and 25 (>30.1%) farms had 20% ewes with XSW and PD respectively. On two farms only did XSW and PD each occur at a prevalence of 15%. No association was found between the prevalence of XSW or PD and body condition score, breed or farm topography.

Journal Article↗
PubMed1997

Observations on the eruption of the permanent incisor teeth of farmed Javan rusa deer (Cervus timorensis russa) in New Caledonia.

The eruption of the permanent incisor teeth of 14 farmed Javan rusa deer (Cervus timorensis russa) of known birth date and their live weights were observed about every 2 weeks from 12 to 30 months of age. The permanent incisor pattern was 11, 14-17 months; 12, 18-23 months; 13, 20-26 months; and 14, 22-27 months. There was no significant relationship between body weight and timing of permanent incisor eruption.

Journal Article↗
PubMed1990

The inorganic components of cementum- and enamel-related dentin in the rat incisor.

Recently, we have shown that, in rodent incisors, the crown- and root-analogue dentin (enamel- and cementum-related dentin) show differences in mineralization rates (Beertsen and Niehof, 1986) and composition of the organic matrices (Steinfort et al., 1989). It was the aim of the present study to determine whether these differences were accompanied by differences in the inorganic components. Rat incisors were analyzed by means of hardness measurements, microradiography, and the determination of Ca, Mg, and PO4 content. The outer circumpulpal dentin layer of the enamel-related dentin (ERD) was considerably harder and denser than the comparable layer of the cementum-related dentin (CRD). Concomitantly, a higher Ca and PO4 content was found for the ERD than for the CRD, while the reverse occurred with respect to Mg. From the apical end of the incisor toward the incisal edge, the Ca/PO4 ratio tended to decrease for both ERD and CRD, while the Mg/PO4 ratio increased. All differences appeared to be statistically significant. It is concluded that differences in the non-collagenous organic matrix were accompanied by differences in the inorganic components. More specifically, a relatively high content of highly phosphorylated phosphoproteins (ERD) was associated with a higher Ca and a lower Mg content.

Animals↗
PubMed1996

[A quantitative study on mandibular incisor point border movement between the immediate complete denture wearers and the second complete denture wearers]

The mandibular incisor point border movement orbits of 20 patients wearing immediate complete dentures for 3 months and the same patients wearing the second complete dentures for 3 months were raced by SGG then measured and analysed.The results showed that the ranges of mandibular incisor point border movement of patients wearing immediate complete dentures for 3 months were significantly narrower than those of the same patients wearing the second complete dentures for 3 months (P<0.01).The ratio of the former to the latter was only 59.00%-69.96%.It could be concluded that the ranges of mandibular incisor point border movement of immediate complete denture wearers were limited.Thus the immediate complete dentures were transitional dentures and only used for treating purpose.The patients must have another pair of complete dentures after 3 months interim.

Journal Article↗
PubMed1990

[Comparisons of effects of vitamin D3 metabolites on mineralization: utilization of incisor dentin in parathyroidectomized rats].

The rat incisor is continuously growing throughout the animal's life recording the state of mineralization within its dentin at all times. Therefore, it was assumed that the incisor dentin was suitable material for studying the effects of various drugs on such mineralization. The present study set out to examine the effects of vitamin D3 metabolites on the remineralization of dentin and the serum calcium level in parathyroidectomized (PTX) rats. Male Wistar rats weighing about 200-250 g were parathyroidectomized. Each rat was given daily 12 g of a synthetic diet containing 0.1% Ca and 0.4% P (normal P) or 0.06% P (P deficient) without vitamin D. Exp. I: Three groups of rats given a normal P diet were orally administered vehicle, 25 (OH) D3 (50 IU/rat) or 1,25 (OH)2D3 (5 IU/rat) for 5 days from the 28th day after PTX, respectively. Exp. II: Two groups of rats given a normal P diet or a P deficient diet were further divided into 4 sub-groups and intramuscularly administered 0, 5,000, 10,000 or 20,000 IU of vitamin D3 on the 9th day after PTX, respectively. The active vitamin D3, 1,25 (OH)2D3 restored the mineralization of the dentin which had been suppressed following PTX, and elevated the serum calcium level to about 9 mg/dl. However, the 25 (OH) D3 neither restored the mineralization of the dentin nor elevated the serum calcium level in the PTX rats. At doses below 1,000 IU, vitamin D3 could not restore the mineralization of the dentin. However, at massive doses above 5,000 IU, the mineralization was restored in proportion to the dose. The serum calcium levels also increased in proportion to the dose. It is assumed that the increase of the serum calcium level was mainly due to the enhancement of calcium absorption from the intestine by vitamin D3. Both remineralization of the incisor dentin and increase of the serum calcium level were more marked in groups of rats given a P deficient diet than in those given a normal P diet. In all cases in the present experiments, the degree of mineralization of the dentin seemed to correspond with the degree of elevation of the serum calcium levels. These results suggest that the remineralization of the dentin in the PTX rats was attributable to the effect of the vitamin D3 metabolites on serum calcium regulation. Relative biological activities of 1,25 (OH)2D3, 25 (OH) D3 and vitamin D3 on the remineralization of dentin were estimated to be 1, less than 0.02 and less than 0.001, respectively.

Animals↗
PubMed1990

[Effects of 1,25-dihydroxyvitamin D3 on mineralization of incisor dentin in parathyroidectomized rats].

Male Wistar rats (8 weeks old) were parathyroidectomized (PTX) and given daily subcutaneous injections of different doses (0, 25, 50 or 100 ng/kg) of 1,25 (OH)2D3 for 13 days. Changes in plasma calcium and phosphorus levels were monitored at 3 day intervals. An appositional rate of dentin was estimated by a time marking method; that is, the distance of two lead lines deposited in a transverse section of the incisor dentin on the 9th and 12th days of the experimental period was measured. The plasma calcium levels that had been lowered by PTX were elevated dose-dependently following injections of the drug, but the plasma phosphorus levels that had been elevated by PTX were lowered. The body weight was not affected by the administration of the drug. However, the values for the dry weight and ash weight, and the calcium and phosphorus contents of the upper incisors increased dose-dependently. The mineralization of the dentin, that had been suppressed by PTX, also recovered dose-dependently. Apposition rates of the dentin in groups of rats given various doses of the drug (25, 50 and 100 ng/kg/day) averaged 46, 61 and 69 microns/3 days respectively. There was a significant correlation between the apposition rate of the dentin and the plasma calcium level. The correlation coefficients were estimated to be 0.956 (y = 17.2 + 4.6 chi, p less than 0.001) on the lingual aspect and 0.941 (y = 11.4 + 5.3 chi, p less than 0.001) on the labial aspect. However, the values for the mineralization of incisor dentin were inversely proportional to the plasma phosphorus levels. These results indicate that the stimulating effect of 1,25 (OH)2D3 on the mineralization of the dentin in PTX rats is primarily dependent upon the increase in plasma calcium levels by the hormone. The direct effect of 1,25 (OH)2D3 on the mineralization of dentin could not be demonstrated in this experiment.

Animals↗
PubMed1989

[Study of hard mineralized tissues effect of calcium-deficient diets with and without cholecalciferol supplementation on the incisor dentine of rats].

It has been known that both tooth and bone have an apatite structure similar to that of mineral hydroxyapatite. The apatite crystal in living tissues of tooth and bone generally is constructed from submicrocrystals and has many impurities. It seems that chemical and physical aspects of resistance of hard tissues depend on the diet. Consequently, the matrix of organic, free radicals in X-ray irradiated hard tissues were studied by means of electron spin resonance (ESR). The effects of calcium-deficient diets with and without cholecalciferol supplementation on the incisor dentine of rats were examined by the rate of decay of organic, free fadicals in X-ray irradiated incisor dentine of rats. The crystal size of incisor dentine became smaller in case of calcium contained diet.

Animals↗
PubMedDate not supplied

Bruxing patterns in children compared to intercuspal clenching and chewing as assessed with dental models, electromyography, and incisor jaw tracing: preliminary study.

The purpose of the present study was to compare bruxing patterns in children with chewing and maximum intercuspal clenching as defined in a clinical and laboratory environment. Six non-bruxing controls and six children who actively bruxed according to parent reports were evaluated. Both control and experimental subjects were assessed by an initial questionnaire, intraoral examination, extraoral examination, dental study models, incisor mandibular tracking, and bilateral surface electromyographic recordings (e.g., EMG). Bruxing was defined as grinding, clenching, or both in combination. The clinical examination consisted of an intraoral examination of the dentition, number of occlusal contacts, and wear facets. Dental study models were used to substantiate the intraoral findings for occlusal contact and wear facets. The mandibular incisors position was tracked during opening, closing, laterotrusion, protrusion, and chewing and compared to the bruxing movements in the experimental subjects. Bilateral surface EMG signals from the temporalis and masseter muscles were recorded in three maximum intercuspal clenches, ten chewing cycles on sugarless gum, and during simulated bruxing. The dental contacts were equal in number bilaterally in both control and bruxing subjects. Both groups demonstrated wear facets, but the bruxing subjects had more facets. The wear facets indicated lateral excursions but not clenching. Only the incisor jaw tracking and bilateral EMG differentiated the bruxing patterns. In those subjects (n = 4) who clenched during bruxing, the EMG pattern was not similar to that of intercuspal clenching and demonstrated its own unique muscle recruitment for the temporalis and masseter muscles. In the subjects who exhibited lateral excursions for bruxing (n = 2), the pattern of muscle recruitment of the two-closing muscles in terms of amplitude was similar for both the bruxing and chewing gum. Our findings support a concept that bruxing may depend upon factors that modify coactivation of muscle recruitment and do not depend upon occlusal contacts.

Analysis of Variance↗
PubMed2026

Effect of Various Types of Remineralizing Agents on the Remineralization of Mild and Moderate Defects Caused by Molar-Incisor Hypomineralization in Mexican Schoolchildren: A 12-month Follow-up Randomized Clinical Trial.

PURPOSE: Using Laser-Induced Fluorescence (LIF), this study aimed to evaluate the effect of three remineralizing agents on permanent molars and incisors with both mild and moderate Molar-Incisor Hypomineralization (MIH) in 8-to-12-year-old Mexican schoolchildren. MATERIALS AND METHODS: In this randomized clinical trial, 104 children were selected to participate and then divided randomly into four groups: Group I: control, Oral-B kids (toothpaste); Group II: Fluor Protector (varnish); Group III: Clinpro White Varnish; and Group IV: MI Paste (CCP-ACP). Both varnishes were applied once every four weeks for twelve months for each group. Remineralization was evaluated by LIF at intervals of 1, 3, 6, 9, and 12 months. Paired-sample t-tests and repeated-measures ANOVA were performed, while the Greenhouse-Geisser correction was used to evaluate sphericity. RESULTS: The three test agents used increased the level of remineralization observed at the site of mild and moderate MIH defects over the course of twelve months (p0.001). A similar decrease in average LIF values was observed across the three treatment groups. CONCLUSIONS: The use of both fluoride varnishes and the CPP-ACP toothpaste was observed to promote the remineralization of both mild and moderate MIH defects.

Humans↗
PubMed1998

Innervation of blood vessels in the rat incisor pulp: a scanning electron microscopic and immunoelectron microscopic study.

Although two types of nerve endings have been proposed to innervate blood vessels in the dental pulp, the precise innervation pattern is not well understood. This is mainly due to the lack of information regarding the positional relationships of nerve fibers with blood vessels at the electron microscopic level. The rat incisor pulp was investigated by scanning electron microscopy (SEM) after connective tissue digestion and by transmission electron microscopy after immunohistochemical localization with polyclonal anti-PGP 9.5 antibody. SEM specimens revealed that unmyelinated nerve fibers passed through the tunica adventitia of the blood vessel in the center of the pulp and that these fibers then entered the tunica media of the smaller arterioles. The nerve fibers divided into many collaterals, and these terminated on the surface of smooth muscle cells and endothelial cells. The fibers extended toward smaller vessels. The terminal fibers then reached the subodontoblastic capillary plexus and terminated on pericytes, while the odontoblastic capillary plexus had no direct innervation. In the pulpal venules, nerve fibers were located adjacent to the pericytes and endothelial cells, and they extended toward postcapillary venules. The same results were confirmed by immunoelectron microscopy. The present study demonstrated that in the rat incisor pulp the microvasculature as well as larger vessels were directly innervated by free nerve endings, suggesting that the local regulation of blood flow could take place not only at larger vessels but also at the level of the microvasculature in this tissue.

Animals↗
PubMed2001

SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature.

Solitary median maxillary central incisor (SMMCI) or single central incisor is a rare dental anomaly. It has been reported in holoprosencephaly (HPE) cases with severe facial anomalies or as a microform in autosomal dominant HPE (ADHPE). In our review of the literature, we note that SMMCI may also occur as an isolated finding or in association with other systemic abnormalities. These anomalies include short stature, pituitary insufficiency, microcephaly, choanal atresia, midnasal stenosis, and congenital nasal pyriform aperture stenosis. SMMCI can also be a feature of recognized syndromes or associations or a finding in patients with specific chromosomal abnormalities. We performed a molecular study on a cohort of 13 SMMCI patients who did not have HPE. We studied two genes, Sonic Hedgehog (SHH) and SIX3, in which mutations have been reported in patients showing SMMCI as part of the HPE spectrum. A new missense mutation in SHH (I111F), segregating in one SMMCI family, was identified. Our results suggest that this mutation may be specific for the SMMCI phenotype since it has not been found in the HPE population or in normal controls. Published 2001 Wiley-Liss, Inc.

Abnormalities, Multiple↗
PubMed1979

A scanning electron microscope study of aberrations in the prism pattern of rat incisor inner enamel.

The prism pattern in the inner enamel of adult rat incisors was studied with the SEM in unfixed tissues that had been sectioned, ground, polished, and etched. Six different types of aberrations in the prism pattern were encountered: 1. Prism lamellae may be shorter than the mesio-lateral width of enamel. 2. Prism lamellae may deviate from a transverse orientation. 3. Prism lamellae may "fuse" or "bifurcate." 4. Prisms of two adjacent lamellae may pursue a common course. 5. Prisms may change direction. 6. Variations exist in the outline of transversely cut prism profiles. Aberrations were observed at any distance from the dentino-enamel junction. These observations were used as a basis for an analysis of the movement of ameloblasts during rat incisor amelogenesis. It was concluded that it is physically possible for the ameloblasts to create the observed aberrations as they move along the path of the prisms. However, the aberrations seem to make it more difficult to understand the factors controlling ameloblast movement. Occasionally crystallite bridges connecting adjacent prisms were observed. A configuration resembling a bifurcating prism is pesented.

Ameloblasts↗