Dental ceramic-bioactive glass composites support the attachment and proliferation of human periodontal ligament cells, while their immersion in a simulated body fluid (SBF) results in the precipitation of biological hydroxyapatite further supporting cell proliferation . The aim of the present study was the comparative evaluation of three dental ceramic-bioactive glass composites’ crystal structure relative to bioactive glass amount and the evaluation of their bioactivity. All composites consisted of leucite and Na2CaSi3O9 crystals dispersed in amorphous glassy matrix. Leucite and Na2CaSi3O9 crystals decreased significantly in all composites with the highest amount of dental ceramic, which did not precipitated apatite during the examined immersion time in SBF. An increase of Na2CaSi3O9 crystals in the composites with the highest amount of bioactive glass resulted in faster apatite formation. Increased bioactivity was linearly correlated to increased amount of bioactive glass.