Study on the self-setting property and thein vitro bioactivity of ?-Ca2SiO4

Properties of anti-washout-type calcium silicate bone cements containing gelatin

Novel washout-resistant bone substitute materials consisting of gelatin-containing calcium silicate cements (CSCs) were developed. The washout resistance, setting time, diametral tensile strength (DTS), morphology, and phase composition of the hybrid cements were evaluated. The results indicated that the dominant phase of beta-Ca(2)SiO(4) for the SiO(2)-CaO powders increased with an increase in the CaO content of the sols. After mixing with water, the setting times of the CSCs ranged from 10 to 29 min, increasing with a decrease in the amount of CaO in the sols. Addition of gelatin into the CSC significantly prolonged (P < 0.05) the setting time by about 2 and 8 times, respectively, for 5% and 10% gelatin. However, the presence of gelatin appreciably improved the anti-washout and brittle properties of the cements without adversely affecting mechanical strength. It was concluded that 5% gelatin-containing CSC may be useful as bioactive bone repair materials.

Environmental scanning electron microscopy connected with energy dispersive x-ray analysis and Raman techniques to study ProRoot mineral trioxide aggregate and calcium silicate cements in wet conditions and in real time

INTRODUCTION

ProRoot mineral trioxide aggregate (MTA) and calcium silicate cements are able to set in a moist environment. The aim of the study was to examine the surface structure and composition of a cement paste under wet conditions and in real time during setting by environmental scanning electron microscopy connected with energy dispersive x-ray analysis (ESEM-EDX) and micro-Raman techniques.

METHODS

White ProRoot MTA and experimental white tetrasilicate cement (wTC) and wTC containing bismuth oxide (wTC-Bi) were studied. Cement disks were analyzed 10 minutes after powder-liquid mixing (freshly prepared samples) and after immersion in Dulbecco phosphate-buffered saline at 37 degrees C for 24 hours (24-hour-aged samples).

RESULTS

Freshly prepared wet cements at ESEM-EDX exposed an irregular surface (displaying calcium, silicon, aluminum, chlorine reflexes, and bismuth traces in MTA and wTC-Bi) with needle-like and cubic-hexagonal shaped crystals. Aggregates of spheroidal Ca-P-rich crystals (spherulites) appeared on the surface of 24-hour-aged samples. The starting unhydrated powders displayed the typical Raman bands of Portland cement components: alite, belite, and calcium sulfate (only as anhydrite in MTA and as both anhydrite and gypsum in wTC and wTC-Bi). MTA powder showed higher amount of calcium carbonate and lower quantities of anhydrite and higher crystallinity of the silicate component, leading to a slower hydration reaction. Products/markers of hydration reactions were present on fresh samples; ettringite formed on the surface of all the cements; calcium hydroxide (portlandite) was detected only on the surface of wTC, but no conclusion can be drawn on wTC-Bi and MTA because of the interference of bismuth oxide. Calcium phosphate and calcite/aragonite bands were detected on all 24-hour-aged cements; portlandite was no longer detected on wTC.

CONCLUSIONS

ESEM and micro-Raman are powerful and suitable techniques to investigate endodontic calcium silicate hydrated cements in real time and in their humid state without inducing artifacts by sample preparation. The formation of apatite spherulites on calcium silicate cements might have clinical relevance.

Dislocation resistance of ProRoot Endo Sealer, a calcium silicate-based root canal sealer, from radicular dentine

AIM

To examine the dislocation resistance of three root canal sealers from radicular dentine with and without immersion in a simulated body fluid (SBF), using a modified push-out test design that produced simulated canal spaces of uniform dimensions under identical cleaning and shaping conditions.

METHODOLOGY

Sixty single-rooted caries-free human canine teeth were used. Standardized simulated canal spaces were created using 0.04 taper ProFile instruments along the coronal, middle and apical thirds of longitudinal tooth slabs. Following NaOCl/ethylenediamine tetra-acetic acid cleaning, the cavities were filled with ProRoot Endo Sealer, AH Plus Jet or Pulp Canal Sealer. After setting, half of the cavities were tested with a fibre-optic light-illuminated push-out testing device. The rest were immersed in SBF for 4 weeks before push-out evaluation. Failure modes were examined with stereomicroscopy and field emission (FE)-scanning electron microscopy.

RESULTS

Location of the sealer-filled cavities did not affect push-out strengths. ProRoot Endo Sealer exhibited higher push-out strengths than the other two sealers particularly after SBF storage (P < 0.001). Failure modes were predominantly adhesive and mixed for Pulp Canal Sealer and AH Plus Jet, and predominantly cohesive for ProRoot Endo Sealer. Spherical amorphous calcium phosphate-like phases that spontaneously transformed into apatite-like phases were seen in the fractured specimens of ProRoot Endo Sealer after SBF storage.

CONCLUSIONS

When tested in bulk without a main core, both 'sealer type' and 'SBF storage' were significant in affecting push-out results. The ProRoot Endo Sealer demonstrated the presence of spherical amorphous calcium phosphate-like phases and apatite-like phases (i.e. ex vivo bioactivity) after SBF storage.

Microscopic appearance and apical seal of root canals filled with gutta-percha and ProRoot Endo Sealer after immersion in a phosphate-containing fluid

AIM

To investigate the sealing quality of ProRoot Endo Sealer, a calcium silicate-based sealer and its morphologic characteristics after immersion in a phosphate-containing fluid (PCF).

METHODOLOGY

Single-rooted canals were filled with gutta-percha and either ProRoot Endo Sealer or two commercially available zinc oxide eugenol (ZOE)-based and epoxy resin-based sealers. The sealers were allowed to set for 6 days and the filled teeth were immersed in PCF for 24 h before fluid leakage evaluation. After initial leakage evaluation at the 7th day, each filled root was restored and reimmersed in PCF for 28 days before the second phase of leakage evaluation at 35 days. Cryofractured specimens of additional teeth filled with the three sealers were examined using scanning electron microscopy after immersion in PCF for the two periods.

RESULTS

One-way repeated measures anova and Tukey test revealed significant differences between the ZOE-based sealer at 35 days and the calcium silicate-based sealer at 35 days (P < 0.001), and between the ZOE-based sealer at 7 days and the calcium silicate-based sealer at 35 days (P = 0.001). No difference was found between the epoxy resin-based sealer and the calcium silicate-based sealer after both storage periods. Cryofractured calcium silicate-based sealer specimens demonstrated apatite-like crystalline deposits along the apical and middle thirds of the canal walls via transformation from amorphous calcium phosphate-like precursors.

CONCLUSIONS

ProRoot Endo Sealer is comparable in sealing quality to the epoxy resin-based sealer and seals better than the ZOE-based sealer after immersion in PCF. The calcium silicate-based sealer also demonstrates ex vivo bioactivity when it comes into contact with phosphate ions.

Stimulating effect of silica-containing nanospheres on proliferation of osteoblast-like cells

Silica and silica-based materials have been found widespread application for medical purposes, especially in the fields of bone tissue engineer. Nano-sized silica has been developed too and been considered to be used in bone regeneration. In this study, we observed the biological response of osteoblast-like cells to three kinds of silica nanospheres: SNs-A (30-40 nm), SNs-B (70-80 nm), and Silica/OCP (70-80 nm). Cells treated with three kinds of nanospheres always showed higher cell viability than control cells. ALP activity of cells treated with three kinds of silica nanospheres was higher than that of control cells at early time. Both of the two effects were not in a concentration-dependent manner. Silica/OCP had better effect on MG-63 cell activity and proliferation than SNs-A and SNs-B. The three kinds of silica nano material all have biological validity on osteoblast-like cells, especially Silica/OCP.

Self-setting properties of a β-dicalcium silicate reinforced calcium phosphate cement

Beta-dicalcium silicate was used to reinforce the injectable calcium phosphate cement (iCPC) for the first time in this study. The influence of the content of beta-dicalcium silicate on the mechanical properties, setting time, rheological properties, injectability, phase evolution, microstructure, and biodegradability of iCPC was systematically investigated. The results demonstrated that the addition of 8 wt % beta-dicalcium silicate obviously enhanced the compressive strength of the CPC from 26.5 to 47.5 MPa, and did not significantly influence the biodegradability, setting time, injectability, phase evolution, and microstructure of the CPC. The beta-dicalcium silicate-reinforced iCPC with relatively high mechanical property should have potential prospects for the wider applications in surgery such as orthopedics, oral, and maxillofacial surgery.

Novel tricalcium silicate/monocalcium phosphate monohydrate composite bone cement

In this paper, we obtained a novel bone cement composed of tricalcium silicate (Ca(3)SiO(5); C(3)S) and monocalcium phosphate monohydrate (MCPM). The weight ratio of MCPM in the cement is 0, 10, 20, and 30%. The initial setting time was dramatically reduced from 90 min to 30 min as the content of MCPM reached 20%. The workable paste with a liquid/powder (L/P) ratio of 0.8 mL/g could be injected for 2-20 min (nozzle diameter 2.0 mm). The pH variation of the composite cement in simulated body environment was obviously lowered. The compressive strength of the composite cement after setting for 4-28 days was slightly lower than that of the tricalcium silicate paste. The in vitro bioactivity was investigated by soaking in simulated body fluid for 7 days. The result showed that the novel bone cement had good bioactivity and could degrade in tris-(hydroxymethyl)-aminomethane-hydrochloric-acid (Tris-HCl) solution. Our result indicated that the Ca(3)SiO(5)/MCPM paste had good hydraulic properties, bioactivity, and degradability. The novel bone cement could be a potential candidate as bone substitute.