A comparison of the bone-like apatite formation potency between hydroxyapatite and β-tricalcium phosphate in glass ionomer dental luting cement

Previous studies have shown that hydroxyapatite increases the bonding strength of dental luting cement with human teeth by forming bone-like apatite when it is added to cement. However, due to the low solubility of the hydroxyapatite, its ability to form bone-like apatite decreases in protein-free acellular simulated body fluid with ion concentrations nearly equal to those of the human blood plasma. The purpose of this experiment was to increase the formation of bone-like apatite by mixing hydroxyapatite with β-TCP of high solubility. RelyX™ glass ionomer cement(3M/ESPE, USA) was used as dental luting cement. Film thickness, setting time, and compressive strength was measured for each group of 15% hydroxyapatite, 15% β-TCP, and 15% mixed hydroxyapatite and β-TCP (85:15). Every specimen of each group was immersed in the simulated body fluid for four week before measuring bonding strength, and then their sectional surface was observed under SEM. The most noteworthy result was that the group containing β-TCP produced more amount of bone-like apatite compared with the group composed of only hydroxyapatite.