Bioactividad de cementos de fosfatos cálcicos sustituidos con estroncio y su aplicación en regeneración ósea

Resumo

The use of bone grafts in the repair of defects in dentistry has a long history of success, primarily with the use of autologous bone. With increasing technologic advances, researchers have been able to broaden the spectrum of grafting materials to allografts, xenografts, and synthetic materials. Osteoconductive and biocompatible calcium phosphate bone substitutes are widely used for the treatment of osseous defects caused by infection, tumors and trauma. A bone graft to function adequately must have a sufficient strength to withstand applied stresses and good cohesion, especially, when used in highly blood-perfused regions. Calcium phosphate cements are being used as bone graft substitutes. They are classified into hydroxyapatite and dicalcium phosphate dihydrate (DCPD or brushite) cements according to their final product. These cements are too weak to be used in load bearing areas, even though hydroxyapatite cements are stronger than brushite cements. However, brushite is metastable under physiological conditions and, in vivo studies have shown that brushite cement is highly resorbable. Brushite crystal-growth inhibition results in smaller crystals size allowing them to pack closely together and improving brushite cement mechanical properties. Furthermore, increasing brushite cement density improves the cement mechanical properties by reducing the cement porosity that is inversely proportional to the cement strength. This can be achieved by increasing the conversion of ?-tricalcium phosphate (?-TCP) to brushite during the cement setting reaction.