ABSTRACT
The use of phosphates in dental glasses and ceramics for the application as biomaterial is merging. Hydroxy apatite is characterized by its solubility in the oral fluids. Studying the effect of the dissolution process of hydroxy apatite added to conventional dental porcelain on its mechanical strength was our aim in this work. Five formulations were prepared from Egyptian raw materials and the mechanical strength of each investigated formulation was measured. It is found that addition of bone ash in amounts not exceeding 10% raised the tensile strength of the investigated dental porcelain. The rate of dissolution of dental porcelain containing bone ash increases with percentage of bone ash added, as the values of mechanical strength were lowered. The pH of the solution was affected by time of immersion. Calcium ions released from the dissolution of tricalcium phosphate readily react with silicon ions giving calcium silicate which render the solution alkaline.
Subject(s)
Biocompatible Materials/chemistry , Dental Porcelain/chemistry , Durapatite/chemistry , Chemistry, Pharmaceutical , Hydrogen-Ion Concentration , Immersion , Materials Testing , Microscopy, Electron, Scanning , Solubility , Surface Properties , Tensile Strength , X-Ray DiffractionABSTRACT
The continued experience of testicular biopsy application in 861 cases of azoospermia and 152 cases of severe oligospermia is reported adding to the previously published cases of 1075 patients with azoospermia. The most common finding in the whole series was that of normal testis denoting obstruction (48%), while among cases of functional azoospermia, Sertoli cell only and spermatogenic arrest were the most frequent (66%).
