Preparation of Sol-Gel Synthesized Partial-Stabilized Cement (PSC) and Evaluate the Feasibility as Dental Retrograde-Filling Material

Conventionally, Partial-Stablized Cement (PSC), which is a kind of calcium silicate cement, is prepared through powder mixing method and have to prepare each component separately. Low reaction efficiency in conventional process leads to a very time- and energy-consuming preparation process. Moreover, low initial strength of conventional PSC limited the application of PSC as a dental root-end filling material. This study provides a one-step sol-gel process for the synthesis of PSC for more simple and economic preparation process. First part of this study will focus on the preparation and characterization of sol-gel synthesized PSC. Because of inconsistency between alkoxide and metal salts used in the sol-gel process, complexing ligand (acetylacetone) is used for tuning down the activity of aluminum sec-butoxide (ASB) in order to avoid possible self-polymerization and phase separation. After the modification with complex ligand, ammonia water is used instead of nitric acid as catalyst in the process because of better reaction efficiency. Each component of PSC is identified and more active monoclinic phase is formed in the product according to the result XRD, FTIR, and MAS NMR. This fact of more active product is also in agreement with result of hydration product formation and microhardness test. The initial strength of sol-gel-synthesized PSC achieves detectable level 24 hours which is 72 hours earlier than PSC synthesized by conventional process. Moreover, the microhardness value of sol-gel-synthesized PSC at 7th day is 27.26 HV which is much higher than conventional PSC which is 2.05 HV. Second part is the in vitro evaluation of PSC. PSC synthesized by sol-gel will not alter the proliferation ability, mitochondria activity, and cytoxicity of the target cells according to result of crystal violet, MTT and LDH assays. Cell phenotype is maintained when incubated with medium extract from PSC (both groups) according to the result of alkaline phosphatase and osteocalcin. Moreover, cell apoptosis is also delayed according to the PI cell cycle and Annexin V-FITC cell apoptosis test. This phenomenon is due to the higher Ca2+ ion and OH- group content in the extract medium. Ca2+ ion plays a very important in the regulation of osteoblast maturation and cell apoptosis. Higher content of OH- group in the medium can not only favors the function of alkaline phosphatase but also delays acidized tendency due to the cell metabolites. Sol-gel synthesized PSC remains its biocompatibility and similar cell response as conventional PSC. Moreover, more active monoclinic phase and much faster hydration rate are observed in PSC synthesized by sol-gel process. The results above suggest that sol-gel prepared PSC is a potential candidate as dental retrograde-filling materials.