Preparation And Properties Of Calcium Silicate-based Root Canal Filling Material

Root canal therapy is an effective treatment for pulpal and periapical diseases, properties of root canal filling material determine the effects of root canal therapy. Two kinds of calcium silicate based root canal filling materials were made to overcome shortcomings of MTA. such as long setting time, low early strength. One was modified MTA(MMTA) prepared by mixing citric acid and calcium chloride, acting as modifier, with MTA and another was calcium phosphate silicate cement(CPSC) prepared by adding CPC into MTA. Properties had been discussed including the performance during gelation, solubility, ion release, bioactivity in vitro.In this experimental study, MTA and TTCP were prepared via solid state sintering method and XRD was employed to characterize the crystal structure. The influences of liquid concentration, ratio of liquid and solid, modifier and CPC on setting time and compressive strength were evaluated according to the YY0717-2009so as to determine the optimal formula. Then the hydration mechanism was systemic analyzed via XRD, SEM and microcalorimeter. The weight loss ratio and pH at various periods were recorded and the concentrations of Ca2+and Si4+were tested by ICP, then the mineralization of apatite at the surface of MMTA and CPSC in the PBS solution was examined by XRD. SEM-EDS and FT-IR to evaluate the mineralization ability. The results showed that:High-purity TTCP could be obtained at1450℃for8h. The working time of MTA containing citric acid was prolonged and the initial compressive strength growth was restrained, on the other hand, the setting time of MTA was shorten sharply and the initial compressive strength was enhanced when adding calcium chloride into it. MMTA containing0.05wt%citric acid and1.0wt%-1.5wt%calcium chloride might meet the clinical needs, with the working time (4-6min), setting time (18-24min). compressive strength (78.96-117.14MPa). With the increase of CPC’s content, the setting time of CPSC decreased and the compressive strength of CPSC setting for24h increased, while the growth of the compressive strength of CPSC in late ages became smaller. When the percentage of CPC was40%and L/P ratio was set to0.28(g/g). CPSC mixed with0.4mol/L Na,8H1.2PO4expressed a better comprehensive performance, which the setting time of CPSC was30.9min and the compressive strength setting for24h was42.16MPa. The weight loss ratio of MTA, MMTA and CPSC within28days was lower than1.03%and the samples had no visual decomposition which was in accord with YY0717-2009. The concentration of Si4+maintained within3.0mg/L to4.5mg/L and the value of Ca2+fluctuated around90mg/L. The deposition formed by the cement-PBS system on the surface of MMTA and CPSC was HA, in addition, CaCO3existed as another deposition of CPSC, which showed that both MMTA and CPSC had certain biological activity.Both MMTA and CPSC, two kinds of silicate-based materials, show proper setting time and compressive strength which are adjustable to a certain extent, so they can be used as root cancal filling materials.