Study On Injectable Nonaqueous Calcium Phosphate Cement As Root Canal Filling

Root canal therapy (RCT) is an effective and fundmental treatment for pulposis. Properties of root canal filler determine the effects of root canal therapy. To meet the requirements of RCT, nonaqueous but water-soluble organic liquid and CPC powders were mixed to form a kind of premixed injectable nonaqueous CPC paste which is stable in syringe and hardens in vivo.First, the injectable nonaqueous CPC with different Ca/P ratio was premixed as root canal filler. The effect of Ca/P ratio on physical and chemical properties was discussed. The result showed the setting time and degradation of filler decreased with increasing of Ca/P ratio and the CPC paste with Ca/p=1.67 behaved best as a root canal filler. The effects of different aqueous setting liquid and particle size on the rheology and suspension stability of CPC paste were also measured. The result showed among glycerol, propylene glycol and PEG600, paste with propylene glycol had low viscosity, which was fitted for injection. Reduction of particle size could effectively improve suspension stability.Second, different additives were introduced into paste to improve the properties. The radiopacity of CPC pastes was improved by addition of CTSAC. The addition of 1.5wt% disodium hydrogen phosphate decreased the setting time form 14 hours to 4.5 hours.1%wt fumed silica increased suspension stability by 3 times.In isolated teeth experiment, CPC pastes showed better sealing and were compacter with detine well than Ca(OH)2 pastes as control. Cytotoxicity results showed that CPC pastes were noncytotoxic and possess good biocompatibility.CPC paste developed in this research could meet the requirements of root canal filling with a proper setting time, easy injection, improved suspension stability and high compressive strength. It is a kind of root canal filler with good perspective.