Resumo

FUENTES, G. et al. Influence of the composition on setting time and porosity in hydroxyapatite cements with alginate and chitosan. Lat. Am. appl. res. [online]. 2005, vol.35, n.4, pp.289-294. ISSN 0327-0793.

Twenty formulations of synthetic hydroxyapatite cements (HAC) of two different types are presented. The evaluation of the setting time and the porosity has been done through an experimental design. Type A cements consist in a mixture of hydroxyapatite (HA) and gypsum (GS) as a solid part (P), and a potassium phosphate solution (KP) as a liquid part (L). The sodium alginate (SA) powder was dissolved or in the solid part or in the liquid one. The setting times of the Type A cements vary from 8 to 16 min, which are similar values to report in the literature. The porosity values found (41-43 %) were not influenced by the changes evaluated. The best of type A cements was that prepared with 0.5 wt % KP and dissolving the SA in the solid part. The solid part of type Q cements consist in a mixture of HA - non sintered (ns-HA) or sintered (s-HA)- , a calcium generator -calcium oxide (CaO) or ß-tricalcium phosphate (ß-TCP)-, and an inorganic material which acts as agglutinant - zinc oxide (ZnO) or magnesium oxide (MgO)-. The liquid phase of type Q cements is formed by an acid solution of chitosan, in malic (MH) or succinic (SH) acid. The setting times observed for these cements are ranged between 2 and 24 min. The use of MgO instead of ZnO as agglutinant decreases the setting time of the cements. The same effect was observed when the succinic acid was substituted by malic acid as dissolution medium of the chitosan. The porosity values for type Q cements vary between 50 and 70 %.

Palavras-chave : Hydroxyapatite Cements; Sodium Alginate; Chitosan; Setting Time; Porosity; Polymers.

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