Crystallization and Ability of Hydroxyapatite Formation in Some Trivalent Oxides Containing Na-Ca-Silicate Glass-Ceramics

The formation of glass-ceramics based on Na₂O–CaO-silicates containing P₂O₅ with minor additives of some trivalent oxides (e.g. La, In, Ga, and Al), has been investigated. Different crystalline phases including sodium-orthosilicate containing lanthanum, or aluminum were formed together with Na₂Ca₂Si₃O₉, NaInSi₂O₆, and Na₃Ga₂Si₃O₁₀. The nature and mechanism of HA formed in the glass-ceramics are considered. In general, the presence of trivalent oxides in the glass-ceramics progressively reduced the ability to form a calcium phosphate layer on the surfaces of the materials. The addition of In₂O₃ decreased the crystallization of the hydroxyapatite layer. However, in the presence of either Ga₂O₃ or Al₂O₃ only the amorphous calcium phosphate layer was formed after the immersion of the crystallized specimens in the SBF solution.