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At least 991 records · Page 55Linked to original sources
PubMed1982

A stereologic analysis of collagen phagocytosis by periodontal ligament fibroblasts during occlusal hypofunction in the rat.

Maxillary molars were extracted unilaterally from 4 young male rats so as to leave the agonist mandibular molars in hypofunction. The mandibular molars on the opposite side of the mouth acted as controls. Three days later, the animals were killed by perfusion and all mandibular molars removed en bloc. After demineralization, each block was trimmed, prepared for electron microscopy and embedded in Epon. The Epon blocks were trimmed so as to comprise the middle-third of the buccal periodontal ligament of the mesio-buccal root of the first molar together with some cementum and alveolar bone as landmarks. Two light-gold sections were cut from each trimmed block and systematically photographed in the electron microscope. The photographs were analysed stereologically so as to quantitate phagocytosed collagen (ICC), cytoplasm (CC) and extracellular fibrillar collagen (ECC). The results for the hypofunctional and contralateral control ligaments were compared with each other and with earlier results from similar but untreated (baseline) animals. The results were expressed as mean values for ICC, CC and ECC, and as the ratios ICC/ECC (the fraction of extracellular collagen phagocytosed), ICC/CC (collagen phagocytic activity per unit cytoplasm) and CC/ECC (cell density per unit extracellular collagen fibril). Significant differences were found for all measurements except ICC/ECC which remained the same in the three states of the ligament. The hypofunctional ligaments had the lowest collagen phagocytic activity and the highest cell density, whereas the ligaments from the untreated animals had the highest collagen phagocytic activity and the lowest cell density. The values for the contralateral control ligaments were intermediate between those for the other two states of the ligament. There was also a significant loss of recognizable, extracellular fibrillar collagen in the hypofunctional ligament. It is suggested that this loss of ECC and its replacement by less organized, pre-fibrillar forms of collagen may be an important mechanism in tooth eruption.

Animals↗
PubMed1983

Electron microscopy of dentinal tubule sclerosis in the enamel-free region of the rat molar.

Ultrastructural changes in dentinal tubule contents were followed for periods up to 6 weeks following tooth eruption into the mouth. Characteristic odontoblast processes were observed in some tubules throughout the enamel-free dentine. Many dentinal tubules contained shrunken odontoblast processes, large collagen fibres and/or accumulations of mineral in various forms. The mineralization patterns suggest mechanisms of tubule occlusion other than simple formation of peritubular dentine. Both the degenerating odontoblast processes and collagen fibres appear to provide an organic framework for deposition of mineral. This region of rat molar dentine is recommended as useful for study of naturally-occurring tubular sclerosis.

Animals↗
PubMed1984

Energy-dispersive X-ray microanalysis and scanning electron microscopy of developing and mature cat enamel.

Calcium and phosphorus distribution in forming, maturing and mature enamel of cat teeth and the microstructures manifest in all these were examined in fractured enamel from the dentine-enamel junction toward the enamel surface. concentrations of both Ca and P increased gradually from the forming enamel, through the maturing enamel and into the mature enamel. The innermost layer, adjacent to the dentine-enamel junction showed the greatest and the superficial layer the lowest concentration of Ca. Still the mature enamel of the erupted tooth was not yet completely mineralized and Ca and P concentrations only slightly higher than those in maturing enamel. Molar Ca:P ratio of each enamel stage was lower than that of pure crystalline hydroxyapatite. Simultaneously-performed SEM observations revealed microstructural changes in the enamel: in the forming-front layer of the forming enamel, the enamel was a rough, immature structure but began to show more compact, tighter structures as concentrations of Ca and P altered. The results suggest that the enamel organ exercises intense cellular control over increases of Ca and P concentration during the formation and maturation stages of amelogenesis.

Amelogenesis↗
PubMed1985

The effects of preventing movement of the rat incisor on the structure of its periodontal ligament.

A quantitative, ultrastructural study was made on the periodontal ligaments of rat mandibular incisors immobilized for 18 days. Fibroblasts and their organelles (i.e. endoplasmic reticulum, mitochondria, microtubules, microfilament bundles, lysosomes, intracellular collagen profiles and intercellular contacts), oxytalan fibres, collagen fibrils and ground substance were quantified. There was re-orientation of tissue at the lateral borders of the ligament and an apparent increase in size of epithelial cell rests. Within the matrix, the mean collagen-fibril diameter decreased and the amount of ground substance increased. No change occurred in oxytalan fibres. Within the cells, effects were seen only in cell contacts and in the relative volume of intracellular collagen, lending no support to the view that fibroblast activity generates the force responsible for tooth eruption.

Animals↗
PubMed1990

Tooth type as indicator of exposure to lead of adults and children.

One hundred and forty-two teeth of children and adults were analysed for lead content by graphite furnace atomic absorption spectrophotometry. The results showed that, for children, tooth age is an important factor that has to be taken into consideration when lead levels are evaluated. In adults tooth type may be ignored, as it is not a major factor affecting lead accumulation.

Adolescent↗
PubMed1994

Immunohistochemical evidence for the presence of nerve fibres with substance P- or calcitonin gene-related peptide-like immunoreactivity in the proliferating epithelium in the developing teeth of rats.

By immunohistochemistry using the avidin-biotin peroxidase complex method, nerve fibres with substance P- or calcitonin gene-related peptide (CGRP)-like immunoreactivity (IR) were examined in the dental lamina, cells external to the reduced ameloblasts and oral epithelium in the developing upper first molars of postnatal rats. At birth, very few varicosities with substance P- or CGRP-IR were found in the dental lamina over the mesial cusp of the dental germ. In 5-day-old rats, nerve fibres with substance P- or CGRP-IR in the dental lamina over the mesial cusp gradually increased in number. In 7-day-old rats, over the mesial portion of the dental germ, the oral half of the dental lamina began to thicken on the buccopalatal side, in which many nerve fibres with substance P- or CGRP-IR were observed. A few nerve fibres began to penetrate the cells external to the reduced ameloblasts over the middle buccal cusp. In 10-day-old rats, the oral epithelium over the mesial cusp gradually thickened, and nerve fibres with substance P- or CGRP-IR were found especially in its basal layer. In 13-15-day-old rats, a great many nerve fibres with substance P- or CGRP-IR were distributed all over the fused, thickened dental lamina and cells external to the reduced ameloblasts proliferated over the middle and distal cusps. Nerve fibres with substance P- or CGRP-IR formed a plexus in the thickened oral epithelium, which spread to the mesiopalatal end of the mesial cusp.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1980

Fractures of the mandible involving the impacted third molar tooth: an analysis of 47 cases.

An attempt is made to correlate mesio-angular, horizontal, disto-angular and vertical tooth impaction with the incidence, displacement and management of fractures in the region of the mandibular third molar. Evidence was taken principally from a radiographic study of 47 cases of fracture of the mandible at this site. No particular single mandibular third molar angulation showed itself more commonly in this series of fractures. However, fractures involving unerupted mesio-angular third molard tended to remain undisplaced and could, therefore, be treated by simpler measures.

Adolescent↗
PubMed1977

The mandibular posterior fixed partial denture.

Absence of a mandibular posterior tooth, particularly the first molar, is the basic common denominator in a wide range of dental disorders. Despite their awareness of this fact, many dentists are deterred from the routine construction of mandibular posterior fixed partial dentures because of several technical difficulties. An attempt has been made to show how these difficulties may be overcome to give a predictable and satisfactory result.

Bicuspid↗
PubMed1985

Drifting, tipping, supraeruption, and segmental alveolar bone growth.

Drifting, tipping, supraeruption, and segmental alveolar bone growth are the four major forms of nonorthodontic intraoral tooth movement. They may occur separately but usually occur in combination (Fig. 6). They can occur at any age but tend to be most devastating in their effects on the dentition of the young adult and the elderly. They may represent nonrestorable occlusal situations if combined and present in both arches. Clear diagnosis is therefore essential prior to the formulation of a treatment plan.

Adolescent↗