X-ray diffractometric determination of crystalline phase content in bioactive glasses.

A rapid routine determination of the content of crystalline CaF(2) and Al(2)O(3) inclusions in bioactive glass ceramics is performed using X-ray diffractometry with a standard addition technique. Multiple ratio analysis, even using peaks with different broadenings, indicates that differences in crystallite properties (e.g., crystal imperfection, particle size and morphology, preferred orientation) between the unknown sample and standard do not bias the result. In this respect, an exact match between their crystallographic integrities does not seem to be required for a reliable estimation of the crystalline content with a relative standard deviation of 7%.

Is systemic treatment of osteoporosis and mandibular resorption possible?

It is argued that mandibular resorption can be considered as osteoporotic in nature. This calls for a systemic approach in its treatment. One aspect mostly neglected is the tendency of bone to bind calcium and phosphate ions. A direct measure for this tendency is the difference in pH between the bone extracellular fluid and blood plasma with octocalcium phosphate. Calculation of these degrees of saturation of about 2000 data of blood plasma compositions given in the literature learned that calcitonin injections, estrogen replacement and magnesium supplementation increase the tendency of bone to bind calcium and phosphate ions and, hence, should be used in the therapy of mandibular resorption and of bone resorption in general.

A systemic approach to the oral problem of mandibular resorption.

It is argued that mandibular resorption can be considered as osteoporotic in nature. This calls for a systemic approach in its treatment. One aspect mostly neglected is the tendency of bone to bind calcium and phosphate ions. A direct measure for this tendency is the difference in pH between the bone extracellular fluid and blood plasma. This pH difference is directly reflected by the degree of saturation of blood plasma with octocalcium phosphate. Calculation of these degrees of saturation of about 2000 data of blood plasma compositions given in the literature indicates that calcitonin injection, estrogen replacement and magnesium supplementation increase the tendency of bone to bind calcium and phosphate ions and hence should be used in the therapy of mandibular resorption and of bone resorption in general.

Effects of acid-base status and fluoride on the composition of the mineral in developing enamel and dentine in the dog.

Developing molar teeth of the dog were sectioned, embedded in copper containing polymethyl methacrylate, polished and their Ca/P and Ca/Na molar ratios investigated with the electron microprobe. The teeth were obtained at 30 days from 9 pups fed regimes of different acid-base status with or without fluoride supplementation from birth to sacrifice at 30 days. No clear trends in their Ca/P or Ca/Na ratios with variation in the diet were observed. However, evaluation of the Ca/P ratio of the enamel as a function of depth revealed that this ratio was 0.80 +/- 0.15 at the mineralization front. This suggests that in enamel brushite rather than octacalcium phosphate is the precursor phase of the mineral.

The dynamics of bone mineral in some vertebrates.

In the literature octocalcium phosphate as well as brushite have been proposed as the precursor phase for bone mineral in the higher vertebrates. In this study it is shown that the situation is more complex. A sodium and carbonate containing apatite (NCCA) and a magnesium whitlockite (MWH) are present from the beginning of mineralization together with octocalcium phosphate. Upon further bone development the NCCA and the MWH phase are deposited in amounts proportional to the amount of mineral deposited. However, the octocalcium phosphate is transformed slowly in a heavily carbonated defective hydroxyapatite. From the available experimental data it can be derived that the time of this transformation is smaller than four weeks under in vivo conditions.

Screening of chelating agents for chemolysis.

The solubility of calcium oxalate monohydrate and calcium hydroxyapatite was calculated as a function of pH in the presence of different chelating agents and was compared with the solubilities in EDTA- or CDTA-containing solutions. An analysis of the solubility curves for 19 chelating agents showed that 5 of the complexing agents considered result in a high solubility for calcium phosphate and oxalate at pH 8 or higher. For these complexing agents the solubility curves of struvite were also calculated. EGTA and HEDTA showed rather low solubilities for struvite due to their low tendency to form complexes with magnesium. On the basis of the calculated solubility curves, the expected litholytic effectiveness for the inorganic kidney stone compounds could be classified in the following decreasing order: CDTA approximately equal to EDTA approximately equal to EGTA greater than EEDTA greater than DTPA greater than UDA approximately equal to HEDTA. With the exception of EGTA and HEDTA for struvite stones, solutions based on these compounds show high solubilities for all the inorganic kidney stone compounds at a solution pH of 8 or higher and therefore have good prospects as litholytic agents.