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At least 613 records · Page 34Linked to original sources
PubMed2003

Age-related changes in blood capillary endothelium of human dental pulp: an ultrastructural study.

AIM: To describe the ultrastructural changes that occur in pulpal blood capillaries as a result of ageing. METHODOLOGY: Thirty samples of healthy dental pulps were obtained from functional human permanent teeth. Two age groups were examined: young (10-17 years) and old (>60 years). The teeth were extracted under local anaesthesia using mepivacaine without adrenaline (Scandonest 3%, Septodont, Saint-Maur des Fossés, France) and split longitudinally in a bench press. The pulps were gently removed, immersed in fixative solution, sectioned and processed by conventional transmission electron microscopic techniques. Micrographs were taken from the endothelium, and the whole capillary area of each vessel was examined. RESULTS: In young pulps, the endothelial cell layer was characterized by the presence of numerous pinocytotic vesicles and microvesicles, RER cisterns, free ribosomes, a small Golgi complex, centrioles, microtubules, microfilaments and mitochondria. In the endothelial cell cytoplasm of older pulpal vessels, pinocytotic vesicles and microvesicles, as well as microfilaments, were more numerous. In addition, lipid-like vacuoles, monogranular glycogen granules and extensive Golgi complexes with dilated cisterns were also present. Weibel-Palade bodies were observed in both age groups without showing variations related with age. CONCLUSIONS: The results obtained in capillaries of aged pulpal tissue suggest that the endothelium experiences morphological changes that could be associated with advancing age.

Actin Cytoskeleton↗
PubMed1989

[Dental x-ray pictures made by parallel and right-angle technics].

The long cone and its belonging film holder-centralizing system made by the Kentzler-Kaschner Dental GmbH (Ellwangen-Jagst, GFR) is well suitable to the right-angle technique. The system can simply be adapted to a number of X-ray apparatus. These technique decreases the distortion, the magnification and the radiation dose, increases the contrast of the pictures. The pictures are well reproducable.

Dental Equipment↗
PubMed1992

Demonstration of amelogenin in the enamel-free cusps of rat molar tooth germs: immunofluorescent and immunoelectron microscopic studies.

The enamel-free cusps of 1-4 day-old rat mandibular first molars were investigated using the monoclonal antibody En3 against rat amelogenin at light and electron microscopic levels in order to clarify whether the enamel-free cusp is virtually devoid of enamel. At 1 day after birth, there were presecretory ameloblast-like cells (PALCs), which were short and were not polarized, at the cusp tips. They were close to the outer enamel epithelium. Hematoxylin positive enamel matrix was not distinctly observed in the enamel-free cusp by light microscopy, but almost continuous immunofluorescence for amelogenin was detected at the interface between PALCs and dentin. The penetration of immunopositive material toward the dental pulp was also observed in the enamel-free cusp. At 4 day after birth, both in the frontal section and in the horizontal section, almost continuous immunofluorescence was recognized at the interface between PALCs and dentin in the enamel-free cusp. The penetration of amelogenin toward the dental pulp was not seen in the enamel-free cusp. By immunoelectron microscopy, immunolabelling was recognized in the Golgi apparatus of PALCs, in a layer of amorphous material at the interface between PALCs and dentin, and in stippled material-like substance in the intercellular space between PALCs. Although no basement membrane was observed beneath PALCs, they did not have Tomes' processes. These investigations suggest that PALCs in the enamel-free cusp differentiate into the secretory cells and that they can synthesize and secrete the amorphous material containing amelogenin at the interface between PALCs and dentin. The penetration of amelogenin toward the dental pulp might play a role in the interaction between PALCs and odontoblasts in the enamel-free cusp and/or the initiation of mineralization of predentin.

Ameloblasts↗
PubMed2006

Mechanical and fracture behavior of veneer-framework composites for all-ceramic dental bridges.

OBJECTIVES: High-strength ceramics are required in dental posterior restorations in order to withstand the excessive tensile stresses that occur during mastication. The aim of this study was to investigate the fracture behavior and the fast-fracture mechanical strength of three veneer-framework composites (Empress 2/IPS Eris, TZP/Cercon S and Inceram-Zirconia/Vita VM7) for all-ceramic dental bridges. METHODS: The load bearing capacity of the veneer-framework composites were evaluated using a bending mechanical apparatus. The stress distribution through the rectangular-shaped layered samples was assessed using simple beam calculations and used to estimate the fracture strength of the veneer layer. Optical microscopy of fractured specimens was employed to determine the origin of cracks and the fracture mode. RESULTS: Under fast fracture conditions, cracks were observed to initiate on, or close to, the veneer outer surface and propagate towards the inner framework material. Crack deflection occurred at the veneer-framework interface of composites containing a tough framework material (TZP/Cercon S and Inceram-Zirconia/Vita VM7), as opposed to the straight propagation observed in the case of weaker frameworks (Empress 2/IPS Eris). SIGNIFICANCE: The mechanical strength of dental composites containing a weak framework (K(IC)<3 MPam(1/2)) is ultimately determined by the low fracture strength of the veneer layer, since no crack arresting occurs at the veneer-framework interface. Therefore, high-toughness ceramics (K(IC)>5 MPam(1/2)) should be used as framework materials of posterior all-ceramic bridges, so that cracks propagating from the veneer layer do not lead to a premature failure of the prosthesis.

Aluminum Oxide↗
PubMed1984

[Pitfalls in the treatment of periodontitis].

The author point out that periodontitis is a disease of multiple aetiology and indicate two types of pitfall: traps in conceiving the plan of treatment and traps in carrying out treatment. The treatment plan may be incomplete. The authors show that the deepest types of vertical alveolysis are always related to occlusal or functional imbalance and that treatment based only upon hygiene and periodontal surgery represents a pitfall. They stress the importance of functional treatment. However such complex functional treatment itself has a number of pitfalls when it is being carried out. It is essential to restore balance of the oro-facial musculature before any treatment of occlusion. These are also types of non-occlusal musculo-dental imbalance which may plan an important role in the course of periodontitis. In conclusion, the authors note that functional treatment of the manducatory apparatus is as important as controlling inflammation. This must not be underestimated nor be allowed to go unrecognised.

Alveolar Process↗
PubMed1988

Treatment of endodontically and periodontally involved teeth. A case report.

Treatment of endodontically and periodontally involved teeth requires accurate diagnosis to determine the primary cause. The case presented involves a deep periodontal pocket associated with a necrotic tooth. The cause was diagnosed as being primarily endodontic and regeneration of the attachment apparatus occurred after endodontic therapy.

Adult↗
PubMed1989

[Conserving silicoater treated surfaces with primers for use in adhesive prostheses].

UNLABELLED: To achieve permanent bond strength to enamel adhesive fixed partial dentures can be coated for example by a SiOx-C-layer followed by a silane primer (Silicoater system). Now and then these resin bonded restorations will be incorporated some days later. The object of this in-vitro-study was to investigate the possibility of preserving metal surfaces treated by the Silicoater system. RESULTS: Metal surfaces coated in the described manner can be preserved by unfilled Bis-GMA-, PMMA-adhesives or a light curing opaquer (PMMA monomer) for later bonding without loss of bond strength. To cure the opaquer a special light curing apparatus is needed.

Adhesives↗
PubMed1979

[Possibilities of healing of periodontal injuries in the apical region--an animal experimental study].

A histologic study of the healing of periodontal injuries in the area of the roots was carried out using beagle dogs. Mucobuccal injuries were inflicted in the dentoaveolar region with a saw. Polychromatic fluorescence labeling was selected to observe the reparative processes. Combined with polarization, it was possible to obtain a good evaluation of the unstained microsection. The course of healing was favorable, and the original condition was completely restored. When pure saw injuries were limited to the periodontium, we found that saw cuts extending into the dentin always left defects in the hard substance which, under favorable conditions, functionally adapted to the attachment apparatus of the teeth.

Animals↗
PubMed1978

[Principles and indications for prosthetic restorations].

Once it has been explained and defined what a prosthesis and what the masticatory apparatus and its function are, the author defines the three principles of a prosthetic restauration: --Any prosthetic restauration should be conceived and realized only after a complete study of the odontostomatognathic system. --Any prosthetic restauration must reestablish the health of the masticatory apparatus. --Any prosthetic restauration must assist in the conservation of the remaining teeth. Six corollaries are deduced from those principles and are equally defined and analysed. The indication of a prosthetic restauration comes from those principles and their corollaries. A possible fixed restauration is to be studied first, then comes the possibility of a semifixed construction. When both those solutions are impossible, the planning of a removable prosthesis, even simple, must be studied with method. This prosthesis must be composed of a cast metallic framework. If the planned prosthetic restauration can not be beneficial to the whole masticatory apparatus, it is better to renounce to do it.

Biomechanical Phenomena↗