Biomedical subjects

M Dard

Publications and source records attributed to M Dard.

26 records · Page 2Linked to original sources

PubMed1989

Effects of synthetic calcium phosphates on the 3H-thymidine incorporation and alkaline phosphatase activity of human fibroblasts in culture.

Gingival fibroblasts were cultured with four different calcium phosphate minerals (hydroxyapatite, whitlockite, beta-tricalcium phosphate, and octocalcium phosphate). 3H-thymidine incorporation into DNA and alkaline phosphatase specific activity were determined after different incubation periods. As a consequence of the phagocytosis of calcium phosphates crystals, we pointed out, compared to control, a stimulation of the rate of 3H-thymidine incorporation and sharp decreases in alkaline phosphatase activity. The magnitude of the alkaline phosphatase activity inhibition was observed to be increased with the solubility of the materials. We propose that the effects of calcium phosphates on alkaline phosphatase and 3H-thymidine incorporation could be calcium-mediated events, resulting from intracellular dissolution of phagocytized materials. We suggest that in vitro determination of 3H-thymidine incorporation and alkaline phosphatase activity, which are highly sensitive tests, could be involved in evaluation procedures of calcium phosphates biomaterials.

Adult↗

PubMed1989

A transmission electron microscope study of fibroblast changes in human deciduous tooth pulp.

The coronal pulps of four primary canines, free from radicular resorption, and of three primary teeth, with roots entirely resorbed, were prepared for electron microscopy. Mature fibroblasts, similar to those reported in the pulps of permanent teeth, were present in the pulps of the clinically mature teeth. Regression of fibroblasts, evident in the pulps of deciduous teeth at the root resorption stage, was characterized by cytoplasmic changes, modifications in the cytoskeleton and dissociation of cells and fibrils. Deciduous teeth might provide a model for studying pulp fibroblast ageing.

Actin Cytoskeleton↗

PubMed1989

Cytoskeleton and calcium. A review.

The aim of the present paper was to summarize the main features about cytoskeleton in order to understand the possible interactions between this system of filamentous, microfilaments structures (including microtubules, intermediate filaments, microfilaments) and calcium in mesenchymal cells of the oral cavity.

Actin Cytoskeleton↗

PubMed1988

Transmission electron microscopy of the morphological relationship between fibroblasts and pulp calcifications in temporary teeth.

Calcifications found in the coronal pulps of primary teeth extracted in an 8-year-old child were studied by TEM. Different types of relationship were observed between fibroblasts and pulp calcifications: extension of cell processes towards calcifications, modelling of the cells upon calcifications, internalizing process of calcifications. Fibroblasts proved to be able to enclose small pulp calcifications within intracytoplasmic vesicles. There was no evidence of any active role played by fibroblasts in the genesis of pulp calcifications. It was shown that collagen fibres could be involved or not in the mineralizing process. It is suggested that mitochondria might provide an adequate environment for initial mineralization. It is likely that the role played by the cytoskeleton in the internalizing process of calcifications is important.

Child↗

PubMed1986

[Dental enamel pearls: histopathological study].

Enamel pearls are small rounded or egg-shaped nodules which most frequently develop in the furcation area of molars. They may consist of enamel only or enamel containing a small core of tubular dentin. They often sit upon strands of cementum or Tomes granular layer. Histologically, the enamel surface of enamel pearls resembles immature enamel and may be covered with cementum. Small calcoglobules presenting varying degrees of organization are often found related to enamel pearls. Some of them, which have the same radiodensity as the enamel of the pearl and of the affected tooth, may be considered as an enamel-type of calcifications. Others, which present a concentric structure revealed by a polarization cross when viewed between cross polars, may be similar to cementicles. All calcifications located in contact with enamel pearls or at a distance, from them are dystrophic calcifications.

Calcinosis↗

PubMedDate not supplied

Biomimetic coatings functionalized with adhesion peptides for dental implants.

A complete biological integration into the surrounding tissues (bone, gingiva) is a critical step for clinical success of a dental implant. In this work biomimetic coatings consisting either of collagen type I (for the gingiva region) and hydroxyapatite (HAP) or mineralized collagen (for the bone interface) have been developed as suitable surfaces regarding the interfaces. Additionally, using these biomimetic coatings as a matrix, adhesion peptides were bound to further increase the specificity of titanium implant surfaces. To enhance cell attachment in the gingiva region, a linear adhesion peptide developed from a laminin sequence (TWYKIAFQRNRK) was bound to collagen, whereas for the bone interface, a cyclic RGD peptide was bound to HAP and mineralized collagen using adequate anchor systems. The biological potential of these coatings deduced from cell attachment experiments with HaCaT human keratinocytes and MC3T3-E1 mouse osteoblasts showed the best results for collagen and laminin sequence coating for the gingiva region and mineralized collagen and RGD peptide coatings for regions with bone contact. Our concept opens promising approaches to improve the biological integration of dental implants.

Journal Article↗

PubMedDate not supplied

Alveolar ridge repair using resorbable membranes and autogenous bone particles with simultaneous placement of implants: an experimental pilot study in dogs.

The aim of this experimental study was to evaluate the use of autogenous bone harvested during preparation of implant sites in combination with resorbable membranes for vertical ridge augmentation under 2 different defect site conditions. Combined vertical/horizontal alveolar bone defects were created by experimentally induced periodontal infections around all premolar teeth in the mandibles of 3 dogs (group 1). In another 3 dogs, fresh surgical defects were created after extraction of all premolar teeth in the mandibles (group 2). In all dogs, 2 implants were placed on each side of the mandible into the defect areas. One implant on each side of the mandible received augmentation with autogenous bone particles, and both implants on one side of the mandible were covered with polylactic acid membranes. After 5 months, the material was evaluated histologically. There was a small but significant increase in bone regeneration in the defects augmented with bone particles with and without membrane coverage in group 1. In group 2, no significant difference was seen between the controls and the augmented sites. The major limiting effect for bone regeneration appeared to be insufficient stability of the bone material to withstand the overlying soft tissue pressure. It was concluded that the placement of autogenous bone particles, either with or without membrane coverage, had little effect on the regeneration of peri-implant bone defects.

Absorbable Implants↗

PubMedDate not supplied

Histology of alveolar bone and primary tooth roots in a case of cleidocranial dysplasia.

Cleidocranial dysplasia is commonly reported as an autosomal dominant inherited condition with defective formation of clavicles, malformation of the craniofacial bones, very slow exfoliation of the primary teeth and failure of the eruption of the permanent dentition. Lack of clinical resorption of the roots of the deciduous teeth and/or surrounding bone, lead to eruption failure of permanent teeth. Histopathological study (light and scanning electron microscopy), in a case of cleidocranial dysplasia, gives prominence to the hypothesis of abnormal remodelling of bone and cementum.

Alveolar Process↗