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[Induced hematopoietic foci in mice. I. Induction of extraskeletal hematopoietic areas using demineralized tooth matrix].

Conditions of formation of induced osteo-hemopoietic foci in mice, in response to ectopic implantation to them of homologous demineralized tooth matrix, have been studied. It is shown that the hemopoietic tissue of the induced foci is similar to the bone marrow of the skeletal bones by the morphological parameters and cellular composition; differentiation of precursor cells takes place in all three directions of myelopoiesis. Induced foci formation under the capsule of the kidney occurs much later (after 5-8 months) than under the skin of muscular fascia (1-1.5 months). The induced hemopoietic foci functioning continues at least for one year.

Animals

Transformation of fibroblasts by allogeneic and xenogeneic transplants of demineralized tooth and bone.

Xenogeneic transplants of powdered, dehydrated, demineralized matrix of bone and tooth were well tolerated in three species of rodents. Differences between the species were found in competence of fibroblasts to be transformed into cartilage and bone in vivo by these preparations. Rat fibroblasts were most susceptible to transformation of this sort; they were transformed by demineralized dentin of guinea pig, mouse, and rat, and to a limited extent, by a specimen of decalcified human bone.

Alkaline Phosphatase

Prevention of sucrose-induced demineralization of tooth enamel by chewing sorbitol gum.

Measurements were made of the effect of chewing sorbitol gum on the intra-oral demineralization induced by rinsing with 10% sucrose solutions. Blocks of bovine enamel were covered with a layer of Streptococcus mutans IB1600, and mounted on palatal appliances that were worn by five subjects for defined periods of time. Enamel demineralization was determined by following changes in iodide penetrability (delta Ip) of the enamel surfaces. Delta Ip increased to a maximum of about 15 units between 30 and 45 min, while the pH of the S. mutans plaque dropped to below 4 by 15 min. Plaque pH returned to 4.9 by 60 min. Chewing sorbitol gum after the sucrose rinse minimized further increases in delta Ip and brought about a more rapid return of the S. mutans plaque pH toward neutrality. The effect of chewing gum was greater when chewing was initiated earlier so that, when gum was given at five min after the sucrose rinse, demineralization was only 37% of that obtained without gum. The findings confirm earlier reports on the effect of gum on plaque pH, and directly demonstrate the profound protective effects that chewing sorbitol gum can have on tooth enamel.

Adult

Dissociative extraction and partial purification of osteogenin, a bone inductive protein, from rat tooth matrix by heparin affinity chromatography.

Implantation of demineralized tooth matrix in subcutaneous sites results in new bone formation locally. The osteoinductive activity of the tooth matrix was dissociatively extracted in 4.0 M guanidine hydrochloride and the residue was devoid of biologic activity. The bone inductive protein, osteogenin, was partially purified by heparin affinity chromatography. The heparin binding fraction initiated the bone differentiation cascade when implanted with guanidine extracted, inactive bone or tooth matrices. These results imply a cooperative interaction between the soluble osteogenin and collagenous substratum in bone induction.

Animals

Three-dimensional changes in direction and interrelationships among enamel prisms in the dog tooth.

This study describes the three-dimensional features of enamel prisms and their arrangement in dog teeth. Tangential semithin sections of demineralized tooth germ were serially cut from the enamel surface to the enamel-dentin junction. Straight rows of enamel prisms parallel or perpendicular to the meridian were selected at the enamel-dentin junction; these prisms were reconstructed from micrographs with a personal computer. Near the enamel-dentin junction, the arrangement of enamel prisms appeared regular. Viewed from the enamel surface, the cut-ends of the enamel prisms that were parallel to the meridian at the enamel-dentin junction appeared as a sine curve, with 16 enamel prisms forming one period. The enamel prisms in a row perpendicular to the meridian were parallel to each other and deflected to the left or right from the enamel-dentin junction. Away from the enamel-dentin junction, the periodicity of the prisms gradually disappeared. The sine curve formed by the cut-ends of prisms in a row parallel to the meridian became irregular, and prisms in rows perpendicular to the meridian crossed each other. The semithin sections showed belt-like zones arranged perpendicular to the meridian. Each belt-like zone consisted of enamel prisms oriented in the same direction, those in neighboring zones being oriented in opposite directions. The disappearance of the regular arrangement of prisms was related to changes in their location in the belt-like zones.

Animals

Tooth enamel softening with a cola type drink and rehardening with hard cheese or stimulated saliva in situ.

The in-situ remineralization effect of hard cheese was compared with that of saliva on tooth enamel in man. The intra-oral test of softening enamel surfaces by a cola type drink followed by rehardening by chewing hard cheese and/or parafilm was assessed by microhardness and SEM measurements. Cheese consumption significantly increased the enamel hardness, whereas stimulated saliva did not have this effect. The remineralizing effects are presumably due to uptake of calcium and phosphate salts by the surface enamel. Morphologically, the enamel surfaces did not return to their original state.

Carbonated Beverages

A random effects model for some epidemiological features of dental caries.

We describe a random effects model for caries lesion development and progression based on considering the effects of the pH fluctuations over time in microbial dental plaque as a Wiener process with a single absorptive barrier. The model predicts that the period of greatest risk to developing caries occurs shortly after eruption, but thereafter the longer a surface survives without developing a lesion, the less likely will it be that a lesion will subsequently develop. The model is able to anticipate why the effect of water fluoridation on caries prevalence is most pronounced when caries is diagnosed at cavity level. This model offers one way in which the variability which characterizes the complex ecosystem associated with dental caries may be considered a subject of interest for enhancing our understanding of its pathogenesis and epidemiology.

Absorption

Influence of fluoride and pH on in vitro remineralization of bovine enamel.

Subsurface lesions in bovine enamel slices were remineralized. The remineralization solutions contained either 0.03, 0.3, or 1.0 ppm fluoride at either pH 5.5 or 6.8. The amount of remineralization was determined after periods of up to 610 h, using quantitative microradiography. The results showed that after 126 h of remineralization in the presence of 0.03 ppm fluoride significantly (p less than 0.05) more remineralization occurred at pH 6.8 than at pH 5.5. At 0.3 and 1.0 ppm fluoride no significant differences between pH 5.5 and pH 6.8 were observed. An interaction between fluoride and pH was observed. The observed differences in the rates of remineralization are explained by the formation and subsequent transformation of the precursors octacalcium phosphate (pH 6.8) and brushite (pH 5.5) into (fluor)apatites.

Animals

A flexible and rapid pH cycling procedure for investigations into the remineralisation and demineralisation behaviour of human enamel.

A rapid and flexible model system has been developed to study human enamel behaviour under conditions of oscillating pH similar to those experienced in the mouth. The model uses realistic time intervals and operates at in vivo temperatures (35-37 degrees C). Mineral loss or gain is measured quantitatively on a volume basis. Results indicate that for single 1-day periods with three 20-min exposures to acid, 1% v/v of enamel mineral was lost. These results, together with the histological appearance of the tissue, are in close agreement with previous studies of enamel caries.

Calcium

Noncariogenicity of maltitol in specific pathogen-free rats infected with mutans streptococci.

The effect of maltitol on caries development was examined in an experimental caries system employing specific pathogen-free (SPF) Sprague-Dawley rats. Fourteen strains of oral streptococci, including mutans streptococci, did not utilize the maltitol nor produce sufficient acid to demineralize tooth enamel. Furthermore, maltitol did not serve as a substrate for glucosyltransferases of either Streptococcus mutans MT8148R or Streptococcus sobrinus 6715 to synthesize water-insoluble glucan. Maltitol induced no significant dental caries in SPF rats infected with these mutans streptococci, and replacement of the dietary sucrose content with maltitol resulted in a trend towards caries reduction in SPF rats.

Animals

Effect of hard cheese exposure, with and without fluoride prerinse, on the rehardening of softened human enamel.

The in situ rehardening effect was compared between Cheddar cheese consumption and saliva secretion with and without a fluoride pretreatment on softened human enamel. Ten volunteers wearing prostheses which held slices of human enamel participated in this study. Average microhardness of enamel was determined on the surface at baseline, after exposing to an acidic beverage, after exposing to saliva and mastication of cheese, with and without a mouth F prerinse (10 ml Meridol containing 0.025% F). The rehardening was increased in the groups consuming cheese compared to the saliva controls. The effect was increased by an F prerinse; the initial hardness of the intact enamel surface, however, was not reached.

Amines