RESUMO
In the aim of optimizing implantable slow-release systems for the local delivery of antibiotics, the stability of tetracyclines was studied in water at 37 degrees C or under gamma irradiation. Four tetracyclines in their chlorhydrate form were chosen depending on their hydrophilic/hydrophobic balance. Their chemical stability was established by HPLC, and biological stability by bacteriological tests. It was shown that methacycline and doxycycline are stable in water for three days. Tetracycline and minocycline exhibit limited decomposition (less than 10%) under the same conditions. So, in vitro drug release for at most three days, appears to be possible. Besides, all four tetracyclines either in powdered form or included in a calcium phosphate matrix, kept their bacteriological activity after gamma irradiation at 32.4 kGr. Consequently, the in vivo study of these implantable slow drug release systems, can be carried out.
RESUMO
OBJECTIVES: The work was carried out with a view to identifying the elements composing the glass ionomer under study, and then to characterising the interactions occurring between this particular glass ionomer and the dentin substrate on which it was placed and with which it interacted. METHODS: The samples studied were sections of healthy human dentin on which a very thin film of auto-polymerisable cement, composed of a powder and a liquid, was deposited under para-clinical conditions. After separation, the interfaces on the dentin side and on the glass ionomer side were studied using X-ray Photoelectron Spectroscopy (XPS). RESULTS: This study showed that the dentin and glass ionomer cement exchanged mineral and organic elements. The acid contained in the liquid showed a certain degree of aggressivity, despite the presence of the glass ionomer. The dentin protein was, in fact, rapidly denuded from the very first minute. Migration of the mineral elements from one substrate to the other led to the formation of an intermediate layer on the surface of the materials. SIGNIFICANCE: This layer, which forms an interphase, enables the material to adhere to the dentin.
