Development of new sol-gel tricalcium silicate cements in endodontic applications
Date Issued
2011
Date
2011
Author(s)
Wang, Wei-chuan
Abstract
An ideal repair material plays an important role in the success of endodontic repair therapy including retrograde filling, perforation repair and vital pulp therapy. There are many repair materials have been used in endodontic applications, but none of these could fit the requirements of ideal material. Mineral trioxide aggregate (MTA) has been currently considered as a potential material used in endodontic repair treatments with promising results, which may caused by its major component - the tricalcium silicate (C3S). However, several disadvantages of MTA have been reported such as long setting time, difficulty in handling, and the high arsenic levels contained. Calcium silicate ceramics (CSCs) without toxic ingredients, developed by our research team, are surface bioactive ceramics presenting the similar behaviors in hydration, cell-material interaction and bioactivity to MTA. But the large amount of CaO remained in the high temperature sintering CSCs caused the low chemical reactivity and long setting time. In this study, we developed the porous C3S to enhance their setting reaction by applying sol-gel process, and further investigated their potential using in endodontic applications. This study was conducted to two sections. In the first section, we synthesized tricalcium silicate via sol-gel process (sC3S) following Tsai’s protocol, and evaluated its physical-chemical and clinical properties with commercial MTA and conventional-sintered C3S as compared groups. The results of X-ray diffraction (XRD) analysis showed the similar patterns in sC3S and C3S powders. After hydrated, peaks corresponding to reactants decreased, and peaks corresponding to hydration products of calcium hydroxide and calcium carbonate were recorded by XRD in both groups. Furthermore, the microstructures of C3S and sC3S hydrates were similar, which became more compact structure when time increased. Scanning electron microscope indicated the smaller particle size and porous texture of sC3S powder. In addition, sC3S presented the significant short setting time (12±0.8min) than those of C3S (177±10min), WMTA (172±8min) and GMTA (114±5min) gourps. In the push-out bonding test, there was no significant difference between sC3S (12.96±4.1 MPa), C3S (11.11±3.9MPa), WMTA (16.2±4.5 MPa) and GMTA (15.78±3.8 MPa). To consider the high level content of residual calcium oxide and unacceptable compressive strength (20.21±3.26 MPa) of previous synthesized sC3S, the protocols of sol-gel process were be modified by changing the mixing order (r ratio) and the concentration of catalyst to improve the properties of the material in the second section. The results showed that the changes in r ratio and the concentration of catalyst would not affect the porous texture and crystal phases of the produced sC3S powder, except the decline of the intensities of the peaks corresponded to calcium oxide. After hydration, the crystals over the outer surface changed their shapes form bar-like crystals to plate-like crystals with 3D structure when the catalyst decreased in concentration. In comparison to the previous synthesized sC3S in first section, the modification of sol-gel process by changing the r ratio and the concentration of catalyst would slightly prolong the setting time of products (28min~34min), but still significantly shorter than that of commercial MTA (p<0.001). Meanwhile, the decrease of the concentration of catalyst in sol-gel process would also improve the compressive strength of products (68.14±7.12MPa), which was much better than that of MTA (p<0.001). In conclusion, sol-gel process could produce porous sC3S with a clinical significant short setting time. Furthermore, the modification of r ratio and the concentration of catalyst in sol-gel process could improve the gelation and the purity of products, and enhance their compressive strength after hydration. Based on these findings, sol-gel synthesized tricalcium silicate is a potential ideal material in endodontic applications.
Subjects
tricalcium silicate
sol-gel process
porous
setting time
compressive strength
push-out test
Type
thesis
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