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At least 685 records · Page 38Linked to original sources
PubMedDate not supplied

Removable partial denture design: a photoelastic study.

Quantifiable frozen-stress photoelastic techniques were used to analyze stresses induced in mandibular models by a conventional free-end saddle removable partial denture. Four quasi-anatomical mandibular models were constructed for processing, together with their respective calibration specimens, through identical time/temperature stress-freezing cycles. After processing and slicing, an unloaded control model demonstrated some low-order fringes adjacent to the coronal third of the abutment tooth roots, but was otherwise stress free. A lower bilateral free-end saddle partial denture was constructed and fitted in turn to each of the remaining three models. Each denture/model combination was then loaded and processed through a stress-freezing cycle. After processing, 6-mm slices were cut from selected regions for analysis for the presence of stresses. Using a polariscope with circular polarized, monochromatic light, values for maximum shear stress were calculated at selected points in the slices taken from the three loaded models. Variations up to 28% of the mean were obtained for the three experimental models as compared with the consistent results for the material fringe values obtained from the calibration specimens. The study pointed out the problems involved in using photoelastic stress analysis on complicated anatomical models. The interpretation of the results from such studies should be approached with caution.

Denture, Partial↗
PubMed1999

Matrix-assisted laser desorption ionization mass spectrometry: a new tool for probing interactions between proteins and metal surfaces. Use in dental implantology.

The fixation in the bone of an artificial titanium tooth root is believed to be initiated by the rapid adsorption of the proteins present in the surgical cavity on the titanium surface. The study of this adsorption should make it possible to predict the osseointegration capacities of new implant surface treatments. We describe here a new method, based on matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS), for quantifying proteins adsorbed on titanium surfaces fully identical to these designed for implantology. The key step of this method is a new MALDI-MS sample preparation allowing the adsorbed proteins to be removed from the surface and to be homogeneously dispersed in the matrix crystals. The adsorption of a model protein (lysozyme) on two titanium surfaces (polished and sandblasted) was studied in order to evaluate the method. The absolute MALDI-MS intensity was shown to vary linearly with the amount of adsorbed lysozyme. After dipping the titanium surfaces for different times in lysozyme solutions at different concentrations, the maximum amount of adsorbed lysozyme was measured by MALDI-MS and was shown to correspond to a lysozyme monolayer, which is consistent with results described in the literature.

Adsorption↗
PubMed1987

Multiple cemental lesions in the jaw bones of a patient with Gardner's syndrome.

Unusual multiple lesions of jaws in a middle-aged woman with all classic manifestations of Gardner's syndrome are reported. Clinical examination revealed a diffuse swelling of the mandible and maxilla with bone-like hardness and numerous radiopaque lesions scattered throughout both mandible and maxilla. Impaction of the molar teeth was revealed by roentgenographic examination. Histopathologically, the multiple jaw lesions consisted of trabecular proliferation of hard-tissue which more closely resembled cementum than immature bone or osteoid. It was found to be united with the cementum of tooth-roots through obliteration of the periodontal ligament. The present lesions do not fit into any of the distinct entities of cemental lesions described.

Adult↗
PubMed1990

[Trauma in the anterior tooth area of the youthful dentition from the surgical viewpoint].

A choice of treatments is available for traumatised anterior teeth. Apicoectomy combined with pin insertion is recommended for fractures of the middle or apical part of the tooth, or in cases of loss of the whole tooth single implants. In many cases which previously did not appear to be amenable to treatment it is today possible to preserve the damaged teeth at least over a longish period.

Child↗
PubMed2006

Regulation of cementoblast gene expression by inorganic phosphate in vitro.

Examination of mutant and knockout phenotypes with altered phosphate/pyrophosphate distribution has demonstrated that cementum, the mineralized tissue that sheathes the tooth root, is very sensitive to local levels of phosphate and pyrophosphate. The aim of this study was to examine the potential regulation of cementoblast cell behavior by inorganic phosphate (P(i)). Immortalized murine cementoblasts were treated with P(i) in vitro, and effects on gene expression (by quantitative real-time reverse-transcriptase polymerase chain reaction [RT-PCR]) and cell proliferation (by hemacytometer count) were observed. Dose-response (0.1-10 mM) and time-course (1-48 hours) assays were performed, as well as studies including the Na-P(i) uptake inhibitor phosphonoformic acid. Real-time RT-PCR indicated regulation by phosphate of several genes associated with differentiation/mineralization. A dose of 5 mM P(i) upregulated genes including the SIBLING family genes osteopontin (Opn, >300% of control) and dentin matrix protein-1 (Dmp-1, >3,000% of control). Another SIBLING family member, bone sialoprotein (Bsp), was downregulated, as were osteocalcin (Ocn) and type I collagen (Col1). Time-course experiments indicated that these genes responded within 6-24 hours. Time-course experiments also indicated rapid regulation (by 6 hours) of genes concerned with phosphate/pyrophosphate homeostasis, including the mouse progressive ankylosis gene (Ank), plasma cell membrane glycoprotein-1 (Pc-1), tissue nonspecific alkaline phosphatase (Tnap), and the Pit1 Na-P(i) cotransporter. Phosphate effects on cementoblasts were further shown to be uptake-dependent and proliferation-independent. These data suggest regulation by phosphate of multiple genes in cementoblasts in vitro. During formation, phosphate and pyrophosphate may be important regulators of cementoblast functions including maturation and regulation of matrix mineralization.

Animals↗
PubMed1998

Inflammation-associated lysyl oxidase protein expression in vivo, and modulation by FGF-2 plus IGF-1.

Lysyl oxidase is the extracellular enzyme that catalyzes oxidative deamination of peptidyl-lysine residues in elastin precursors, and lysine and hydroxylysine residues in collagen precursors to form peptidyl-aldehydes. These aldehydes then spontaneously condense to crosslink collagen and elastin and thereby allow the formation of a mature and functional extracellular matrix. In the present study, cryosections made from aseptic immune-induced periapical lesions experimentally generated in laboratory rats were examined by immunohistochemistry to investigate whether lysyl oxidase protein expression is altered in inflamed oral tissues. Periapical lesions are experimentally induced endodontic lesions of tooth roots. In addition, the effect of administration of a mixture of fibroblast growth factor (FGF)-2 and insulin-like growth factor (IGF)-1 into these lesions on lysyl oxidase expression was determined. Lysyl oxidase expression was found to be increased in non-mineralized connective tissue adjacent to inflamed lesions. Morphometric analyses indicated that maximum lysyl oxidase expression occurred at a discrete distance from the lesion not exceeding 350 microm from the inflammatory cells. Staining was associated with mesenchymal cells with a fibroblastic morphology. No lysyl oxidase staining was found near teeth where no lesion was induced. Application of a mixture of FGF-2 and IGF-1 resulted in a further twofold increase in lysyl oxidase expression. These results provide a new in vivo model to study lysyl oxidase regulation, and suggest that inflammatory cells may control lysyl oxidase expression in oral tissues, possibly by a mechanism involving secretion of cytokines and other factors, probably contributing to the regulation of extracellular matrix accumulation.

Animals↗
PubMed1999

Cell proliferation and death of Hertwig's epithelial root sheath in the rat.

Hertwig's epithelial root sheath (HERS) degenerates immediately after root dentin is formed. However, odontogenic tumors or cysts may originate from residual cells, although little is known about how HERS proliferates and disappears. This study investigated whether cell death is provoked in the tissues surrounding the root during eruption of the rat upper molar. We employed the TdT-mediated-dUTP nick end labeling (TUNEL) method and transmission electron microscopy (TEM) to observe the morphological features of cell death. We examined the activity of cell proliferation immunohistochemically using proliferative cell nuclear antigen (PCNA) and the continuity of HERS using polyclonal keratin antibody (PK). Cell death resembling apoptosis and apoptotic bodies phagocytosed by neighboring mesenchymal cells were detected in only a few cells by both TUNEL and TEM. We also found cells with electron-lucent cytoplasm which contained dilated or ruptured mitochondria and remarkably dilated rough endoplasmic reticulum (rER) which lay sparsely along the root. These cells seemed to be dead HERS cells based on their ultrastructural features, location, and stage. PCNA-positive cells were found in the apical end of the HERS cells, fibroblasts of the periodontal ligament, and odontoblasts. PK reacted with HERS; however, PK-positive cells partially disappeared after the 15th postnatal day when the root dentin had formed slightly. These results may indicate that HERS cells migrate into the periodontal ligament or die immediately after root dentin is formed and that various types of cell death such as apoptosis and cytoplasmic type occur in the tissues surrounding the root during tooth development.

Animals↗
PubMed1995

Identification of osteopontin in human dental calculus matrix.

Osteopontin is a prominent non-collagenous component of bone matrix, although it is expressed in several other tissues. Recently, osteopontin was reported to be involved in urinary stone formation and atherosclerotic lesions of the aorta, suggesting that it may be a key protein associated with these types of pathological mineralization. In this study, whether or not human dental calculus contains osteopontin was investigated by immunoblotting and immunohistochemical analyses. After extraction of calculus proteins with EDTA and separation of the proteins by electrophoresis, immunoblotting analysis revealed the presence of osteopontin. Two forms of osteopontin appeared at 61 and 68 kDa on 10% polyacrylamide gel and the proteins were digested with thrombin, a highly specific protease. Moreover, immunohistochemical analysis revealed that osteopontin was localized in dental calculus adherent to tooth roots. These findings indicate that osteopontin is, in fact, present in human dental calculus and may be involved in calculus formation as the stone matrix.

Dental Calculus↗