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Results for “Decalcification Technique”

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PubMed1997

The modulatory role of cementum matrix on osteoblastic cells in vitro.

The formation of new cementum is an important issue in clinical periodontology, as cementum is required to provide attachment for newly formed periodontal tissues to the root surface. In this study a model of cementogenesis in vitro was used in order to test the effects of root surface demineralization on the migration, attachment and formation of a cementum-like tissue by osteoblastic cells cultured on cementum and to test the specificity of cementum matrix in modulating those effects by comparison of root co-cultures with bone co-cultures. It was demonstrated that root surface demineralization did not significantly alter the orientation, number and attachment of cells to the root co-cultures. The results also demonstrated that cementum and bone matrix appear to behave differently in culture, as seen by their distinct action on the morphological profile of the attached cells and the extracellular matrix deposited by these cells. These results demonstrate that although cementum matrix appears to stimulate the production of cementum-like tissue, this action is not confined to cementum matrix alone, since a similar material was also deposited on dentine and bone surfaces. Thus, these results do not support a specific action of cementum matrix on the modulation of the cementoblast phenotype. The use of co-cultures of neonatal rat calvaria cells with root slices represents a promising model of cementogenesis in vitro; however, studies should be undertaken towards the identification of markers to distinguish between cementoblast and osteoblast phenotypes in order to further validate this model.

Animals↗
PubMed1997

The transneuronal spread phenotype of herpes simplex virus type 1 infection of the mouse hind footpad.

The mouse hind footpad inoculation model has served as a standard laboratory system for the study of the neuropathogenesis of herpes simplex virus type 1 (HSV-1) infection. The temporal and spatial distribution of viral antigen, known as the transneuronal spread phenotype, has not previously been described; nor is it understood why mice develop paralysis in an infection that involves sensory nerves. The HSV-as-transneuronal-tracer experimental paradigm was used to define the transneuronal spread of HSV-1 in this model. A new decalcification technique and standard immunocytochemical staining of HSV-1 antigens enabled a detailed analysis of the time-space distribution of HSV-1 in the intact spinal column. Mice were examined on days 3, 4, 5, and 6 postinoculation (p.i.) of a lethal dose of wild-type HSV-1 strain 17 syn+. Viral antigen was traced retrograde into first-order neurons in dorsal root ganglia on day 3 p.i., to the dorsal spinal roots on days 4 and 5 p.i., and to second- and third-order neurons within sensory regions of the spinal cord on days 5 and 6 p.i. HSV-1 antigen distribution was localized to the somatotopic representation of the footpad dermatome within the dorsal root ganglia and spinal cord. Antigen was found in the spinal cord gray and white matter sensory neuronal circuits of nociception (the spinothalamic tract) and proprioception (the dorsal spinocerebellar tract and gracile fasciculus). Within the brain stems and brains of three paralyzed animals examined late in infection (days 5 and 6 p.i.), HSV antigen was restricted to the nucleus subcoeruleus region bilaterally. Since motor neurons were not directly involved, we postulate that hindlimb paralysis may have resulted from intense involvement of the posterior column (gracile fasciculus) in the thoracolumbar spinal cord, a region known to contain the corticospinal tract in rodents.

Animals↗
PubMed1997

Effect(s) of the demineralization process on the osteoinductivity of demineralized bone matrix.

The relationships between residual calcium levels and particle size of ground demineralized bone matrix and its osteoinductive potential were investigated using in vitro and in vivo assays. The effects of variable residual calcium levels, variable particle sizes, and donor age and gender were studied using a tissue culture-based bioassay (in vitro) as well as an athymic mouse (in vivo) bioassay. The osteoinductive potential of the bone-derived biomaterial was assessed by measuring the degree of new bone formation (change in percent calcium content after 4 weeks of implantation) in the in vivo assay and levels of alkaline phosphatase activity associated with cultures of human periosteal cells (HPO cells) in the in vitro assay, respectively. Slightly demineralized bone matrix and overly demineralized bone matrix possessed a degree of osteoinductive potential whereas bone demineralized to levels of approximately 2% residual calcium provided for maximum osteoinductive potential in both assay systems. The osteoinductive potential of ground demineralized bone varied relative to the particle size such that DBM particles ranging from 500 to 710 microns provided for the highest level of calcium deposition (increase of 8.1 weight percent calcium) after 4 weeks of implantation in muscle pouches of an athymic mouse, whereas explanted particles less than 250 microns showed the lowest level of calcium deposition (increase of only 2.8 weight percent calcium). In the donor age and gender study, DBM from different donors were divided into 5 age groups for both female and male donor derived bone: less than 20, 21 to 30, 31 to 40, 41 to 50, and 51 to 60 year old age groups. This study indicated that DBM from female donors in the 31 to 40 years old age group and male donors in the 41 to 50 year age group possess the highest osteoinductive potential, whereas DBM derived from donor bone from both female and male donors in the 51 to 60 year age group presented the lowest osteoinductive potential. DBM derived from male and female donors did not in general show significant differences in osteoinductive potential.

Adult↗
PubMedDate not supplied

[Focal demineralization of the cortical plate of the jaw and its experimental reversibility based on microphotometry data].

Focal demineralization of bone tissue with local dosed vacuum (exposure of up to 20 sec) and 2% lithium chloride electrophoresis (8 sessions daily, 10 min exposure) was tried in 40 white rats (21 reference ones and 19 experimental). The maximal reduction of mineral content was achieved on days 3-7 after the end of the course and made up 76.2 +/- 15.0% (p less than 0.01) and 80.6 +/- 12.5% (p less than 0.001), respectively, as against the reference animals. Mineral content at the site of demineralization gradually normalized by day 21. This transient reduction of mineral content of bone tissue may be used in orthodontic treatment of dentition abnormalities.

Alveolar Process↗
PubMed1996

Examination of periodontal tissues by a cutting-grinding technique.

The decalcification process removes the mineralized part of the dental hard tissues, making the histologic examination of enamel-associated tissues less than optimal. The cutting-grinding technique allows preparation of histologic slides with well preserved dental hard tissues together with their surrounding soft tissue components. In this paper, the histologic appearances of undecalcified teeth and their associated periodontal tissues prepared using the cutting-grinding technique are described.

Animals↗
PubMed1991

Addition of cetyl pyridinium chloride to histological demineralizing agents to improve the demonstrability of gram-positive bacteria.

It has previously been shown experimentally using S. faecalis that the relative number of Gram-positive bacteria is reduced by demineralizing agents. To achieve better bacterial preservation after demineralization, cetyl pyridinium chloride (CPC) and neutral formaldehyde solution (NF) were added, separately and in combination, to formic acid and EDTA. The number of S. faecalis organisms in suspension was determined using a haemocytometer, and the percentage of Gram-positive bacteria was ascertained from smears. Both CPC and NF accomplished better bacterial preservation; when both substances were added together preservation was improved still further. The best results were achieved when CPC and NF were added to EDTA. If these findings could be extrapolated to tissue sections, and if it were intended to demonstrate Gram-positive bacteria, 10 per cent EDTA to which 0.5 per cent CPC and 4 per cent NF had been added would be recommended for demineralization.

Bacteriological Techniques↗