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In vitro experiments on the reduction of the solubility of human dentine in decinormal lactic acid have shown that, under the experimental conditions chosen, disodium beta-glycerophosphate was less efficient than sodium fluoride alone or in combination with ammonium metavanadate and/or ammonium molybdate.
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The effect of bleaching agents on the inorganic composition of human dentin and cementum was examined. Intact teeth were crushed, pulverized, and separated to dentin and cementum powders. The pulverized tissues were exposed to treatments with 30% H2O2, 3% H2O2, 2% sodium perborate in 30% H2O2, 2% sodium perborate in 3% H2O2, and 2% sodium perborate in bidistilled water for periods of 15 min and 1, 24, and 72 h. The degree of dissolution and the percentage of inorganic material for both dentin and cementum were measured. Thirty percent H2O2 and 2% sodium perborate in 30% H2O2 treatments significantly increased the solubility of dentin and cementum. The degree of dissolutions and the percentage of inorganic material remaining in the undissolved dentin and cementum increased with time progression. The greatest increase occurred with 30% H2O2 and 2% sodium perborate in 30% H2O2 after 24- and 72-h treatments. It is concluded that 30% hydrogen peroxide treatment may cause alteration in the chemical structure of the dentin and cementum making them more susceptible to degradation.
UNLABELLED: Human osteoclasts can be efficiently generated in vitro from cord blood mononuclear cells and derived CFU-GM colonies. However, CFU-M colonies are poorly osteoclastogenic. Short-term (2-48 h) treatment with GM-CSF stimulates osteoclast formation by proliferating precursors, whereas longer exposure favors dendritic cell formation. INTRODUCTION: Osteoclasts (OC) differentiate from cells of the myelomonocytic lineage under the influence of macrophage-colony stimulating factor (M-CSF) and RANKL. However, cells of this lineage can also differentiate to macrophages and dendritic cells (DC) depending on the cytokine environment. The aims of this study were to develop an efficient human osteoclastogenesis model and to investigate the roles of granulocyte macrophage-colony stimulating factor (GM-CSF) and M-CSF in human OC differentiation. MATERIALS AND METHODS: A human osteoclastogenesis model, using as precursors colony forming unit-granulocyte macrophage (CFU-GM) colonies generated from umbilical cord mononuclear cells cultured in methylcellulose with GM-CSF, interleukin (IL)-3 and stem cell factor (SCF), has been developed. CFU-GM, colony forming unit-macrophage (CFU-M), or mixed colonies were cultured on dentine with soluble RANKL (sRANKL) and human M-CSF with and without GM-CSF. Major endpoints were OC number, dentine resorption, and CD1a+ DC clusters. RESULTS: Osteoclast generation from CFU-GM and mixed colonies treated with M-CSF and sRANKL for 7-14 days was highly efficient, but CFU-M colonies were poorly osteoclastogenic under these conditions. Pretreatment of precursors with M-CSF for 7 or 14 days maintained the precursor pool, but OCs were smaller and resorption was reduced. The effect of GM-CSF treatment was biphasic, depending on the timing and duration of exposure. Short-term treatment (2-48 h) at the beginning of the culture stimulated cell proliferation and enhanced OC formation up to 100%, independent of sRANKL. Longer-term GM-CSF treatment in the presence of sRANKL, however, inhibited OC generation with the formation of extensive CD1a+ DC clusters, accompanied by downregulation of c-Fos mRNA. Delaying the addition of GM-CSF resulted in progressively less inhibition of osteoclastogenesis. CONCLUSIONS: Human CFU-GM, but not CFU-M, progenitors have high osteoclastogenic potential. GM-CSF plays an important role in osteoclastogenesis and has a biphasic effect: Short-term treatment potentiates OC differentiation by proliferating precursors, but persistent exposure favors DC formation.
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The susceptibility of the organic matrix from permanent bovine incisor roots to proteolytic breakdown after in vitro lesion formation was investigated. Root surfaces were exposed to 0.1 M acetic acid, pH 4.0, to produce erosive lesions or to 0.1 M lactic acid, 0.2 mM methane hydroxy diphosphonate, pH 5.0, to produce subsurface lesions. After demineralization, the roots were treated with a bacterial collagenase. The quantity of enzyme-degradable collagen in the root tissue was found to be proportional to the calcium released during demineralization, until a plateau value was reached at calcium concentrations in solution of 3.3 mM at pH 4.0 and 2.7 mM at pH 5.0. The degradability of collagen was found to be substantially less in subsurface lesions than in erosive lesions. The presence of cementum-free areas did not affect the results. These findings suggest that the mineral component of the roots is composed of several fractions which differ in their solubility properties in weak acids.
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OBJECTIVE: To investigate the relationship between dentine phosphoprotein (DPP) and remineralization of demineralized dentine. METHODS: (1) Soluble DPP was extracted with 1 mol/L NaCl from demineralized dentine and was evaluated. (2) Soluble DPP was removed with 0.1 mol/L NaCl or was not removed from demineralized dentine sections in human tooth roots. Then all sections were subjected to remineralization treatment, and remineralization degrees were compared by atomic absorption spectrum, SEM and microradiography. RESULTS: (1) Soluble DPP was extracted with 1 mol/L NaCl. (2) Removal of soluble DPP resulted in significantly lower calcium concentration in remineralization solution (P < 0.01), less mean light-absorbed value in demineralized dentin sections by microradiography (P < 0.01). CONCLUSIONS: Soluble DPP may have an inhibiting effect on remineralization of demineralized dentine, this study suggests that the remove of soluble DPP from root caries lesions may enhance their remineralization potential.
An effective bonding of resin composites to dentin is generally preceded by a conditioning of the surface of the dentin. Previous studies have indicated that the intermediary or adhesive resin should have specific wetting characteristics matching those of the conditioned dentin, in order that optimum bonding can be ensured. The wetting characteristics may be expressed in terms of solubility parameter (delta) and polarity (p) of the resin. The aims of the present study were to determine these variables for a number of compounds used in adhesive resins and to investigate the effects of delta and p on the shear bond strength to dentin. Solubility parameters were obtained according to the method of Small. Fractional polarities were calculated on the basis of measurements of refractive index and dielectric constant of the resins. In the measurements of bond strength, Scotchprep, EDTA + Gluma, or Al2Ox3/glycine were used as dentin conditioners in combination with intermediary resins having various delta and p. For each conditioner, the shear bond strength (BS) could be "explained" by an exponential expression of the form BS = e(a + bx), where x = (delta + cp + d)2, and where a-d are constants depending on the conditioned dentin. It may be concluded that solubility parameter and polarity of the intermediary resins are important variables in the process of bonding to dentin.
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A scanning electron microscopic study has shown the presence of a typical layer of peritubular dentine in Hyrachyus. An homogeneous ring-shaped layer in continuity with intertubular dentine and considered as peritubular dentine despite its acid resistant character was observed around the lumens of dentinal tubules in Protungulatum, Tetraclaenodon and Propachynolophus maldani teeth; there is some evidence that the acid solubility of peritubular dentine has been altered during fossilization. No peritubular dentine was found in Phenacodus, Hyracotherium or Homogalax.
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