Bioactive coatings on Portland cement substrates: Surface precipitation of apatite-like crystals

Chemical-Physical Properties and Bioactivity of New Premixed Calcium Silicate-Bioceramic Root Canal Sealers

The aim of the study was to analyze the chemical−physical properties and bioactivity (apatite-forming ability) of three recently introduced premixed bioceramic root canal sealers containing varied amounts of different calcium silicates (CaSi): a dicalcium and tricalcium silicate (1−10% and 20−30%)-containing sealer with zirconium dioxide and tricalcium aluminate (CERASEAL); a tricalcium silicate (5−15%)-containing sealer with zirconium dioxide, dimethyl sulfoxide and lithium carbonate (AH PLUS BIOCERAMIC) and a dicalcium and tricalcium silicate (10% and 25%)-containing sealer with calcium aluminate, tricalcium aluminate and tantalite (NEOSEALER FLO). An epoxy resin-based sealer (AH PLUS) was used as control. The initial and final setting times, radiopacity, flowability, film thickness, open pore volume, water absorption, solubility, calcium release and alkalizing activity were tested. The nucleation of calcium phosphates and/or apatite after 28 days aging in Hanks balanced salt solution (HBSS) was evaluated by ESEM-EDX, vibrational IR and micro-Raman spectroscopy. The analyses showed for NeoSealer Flo and AH Plus the longest final setting times (1344 ± 60 and 1300 ± 60 min, respectively), while shorter times for AH Plus Bioceramic and Ceraseal (660 ± 60 and 720 ± 60 min, respectively). Radiopacity, flowability and film thickness complied with ISO 6876/12 for all tested materials. A significantly higher open pore volume was observed for NeoSealer Flo, AH Plus Bioceramic and Ceraseal when compared to AH Plus (p < 0.05), significantly higher values were observed for NeoSealer Flo and AH Plus Bioceramic (p < 0.05). Ceraseal and AH Plus revealed the lowest solubility. All CaSi-containing sealers released calcium and alkalized the soaking water. After 28 days immersion in HBSS, ESEM-EDX analyses revealed the formation of a mineral layer that covered the surface of all bioceramic sealers, with a lower detection of radiopacifiers (Zirconium for Ceraseal and AH Plus Bioceramic, Tantalum for NeoSealer Flo) and an increase in calcium, phosphorous and carbon. The calcium phosphate (CaP) layer was more evident on NeoSealer Flo and AH Plus Bioceramic. IR and micro-Raman revealed the formation of calcium carbonate on the surface of all set materials. A thin layer of a CaP phase was detected only on AH Plus Bioceramic and NeoSealer Flo. Ceraseal did not show CaP deposit despite its highest calcium release among all the tested CaSi-containing sealers. In conclusion, CaSi-containing sealers met the required chemical and physical standards and released biologically relevant ions. Slight/limited apatite nucleation was observed in relation to the high carbonation processes.

Novel calcium phosphate coated calcium silicate-based cement: in vitro evaluation

Calcium silicate-based cements are known for their wide applications in dentistry and orthopedics. The alkaline pH (up to 12) of these cements limits their application in other orthopedic areas. In this study, the effect of dicalcium phosphate dihydrate (DCPD) coating on set cement on pH reduction and biocompatibility improvement was examined. Samples with 0 and 10 weight ratio DCPD were prepared and characterized by XRD, FTIR, and SEM. The DCPD coating on the set cement was performed by a 7 d immersion in 1% monocalcium phosphate (MCP) solution and characterized by XRD, FTIR, SEM, and EDX. Also, the compressive strength and cytotoxicity of the samples were tested. The results showed that DCPD coating did not significantly change the compressive strength of the cement, but by decreasing the pH of the culture medium to the physiological range, it led to enhance adhesion, spreading and proliferation of human osteosarcoma cell line (Saos-2). The novel DCPD coated calcium silicate-based cement could be served as a bulk or porous bone substitute and scaffold.

Coatings of titanium substrates with xCaO · (1 - x)SiO2 sol-gel materials: characterization, bioactivity and biocompatibility evaluation

The objective of this study has been to develop low temperature sol-gel coatings to modify the surface of commercially pure titanium grade 4 (a material generally used in dental application) and to evaluate their bioactivity and biocompatibility on the substrate. Glasses of composition expressed by the following general formula xCaO · (1 - x)SiO2 (0.0<x<0.60) have been prepared by means of the sol-gel route starting from tetraethyl orthosilicate and calcium nitrate tetrahydrate. Those materials, still in the sol phase, have been used to coat titanium substrates by means of the dip-coating technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) allowed the materials to be characterized and a microstructural analysis of the coatings obtained was performed using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated titanium was immersed in simulated body fluid (SBF) for 21 days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. To investigate cell-material interactions, mouse embryonic fibroblast cells (3T3) were seeded onto the specimens and the cell viability was evaluated by a WST-8 assay.

Improvement of bioactivity, degradability, and cytocompatibility of biocement by addition of mesoporous magnesium silicate into sodium-magnesium phosphate cement

A novel mesoporous magnesium-based cement (MBC) was fabricated by using the mixed powders of magnesium oxide, sodium dihydrogen phosphate, and mesoporous magnesium silicate (m-MS). The results indicate that the setting time and water absorption of the MBC increased as a function of increasing m-MS content, while compressive strength decreased. In addition, the degradability of the MBC in a solution of Tris-HCl and the ability of apatite formation on the MBC were significantly improved with the increase in m-MS content. In cell culture experiments, the results show that the attachment, proliferation, and alkaline phosphatase activity of the MC3T3-E1 cells on the MBC were significantly enhanced with the increase of the content of m-MS. It can be suggested that the MBC with good cytocompatibility could promote the proliferation and differentiation of the MC3T3-E1 cells. In short, our findings indicate that the MBC containing m-MS had promising potential as a new biocement for bone regeneration and repair applications.

Calcium Silicate and Calcium Hydroxide Materials for Pulp Capping: Biointeractivity, Porosity, Solubility and Bioactivity of Current Formulations

Aim

The chemical-physical properties of novel and long-standing calcium silicate cements versus conventional pulp capping calcium hydroxide biomaterials were compared.

Methods

Calcium hydroxide–based (Calxyl, Dycal, Life, Lime-Lite) and calcium silicate–based (ProRoot MTA, MTA Angelus, MTA Plus, Biodentine, Tech Biosealer capping, TheraCal) biomaterials were examined. Calcium and hydroxyl ion release, water sorption, interconnected open pores, apparent porosity, solubility and apatite-forming ability in simulated body fluid were evaluated.

Results

All calcium silicate materials released more calcium. Tech Biosealer capping, MTA Plus gel and Biodentine showed the highest values of calcium release, while Lime-Lite the lowest. All the materials showed alkalizing activity except for Life and Lime-Lite. Calcium silicate materials showed high porosity values: Tech Biosealer capping, MTA Plus gel and MTA Angelus showed the highest values of porosity, water sorption and solubility, while TheraCal the lowest. The solubility of water-containing materials was higher and correlated with the liquid-to-powder ratio. Calcium phosphate (CaP) deposits were noted on materials surfaces after short aging times. Scant deposits were detected on Lime-Lite. A CaP coating composed of spherulites was detected on all calcium silicate materials and Dycal after 28 days. The thickness, continuity and Ca/P ratio differed markedly among the materials. MTA Plus showed the thickest coating, ProRoot MTA showed large spherulitic deposits, while TheraCal presented very small dense spherulites.

Conclusions

calcium silicate-based cements are biointeractive (ion-releasing) bioactive (apatite-forming) functional biomaterials. The high rate of calcium release and the fast formation of apatite may well explain the role of calcium silicate biomaterials as scaffold to induce new dentin bridge formation and clinical healing.

β-Dicalcium silicate-based cement: synthesis, characterization and in vitro bioactivity and biocompatibility studies

β-dicalcium silicate (β-Ca₂ SiO₄, β-C₂ S) is one of the main constituents in Portland cement clinker and many refractory materials, itself is a hydraulic cement that reacts with water or aqueous solution at room/body temperature to form a hydrated phase (C-S-H), which provides mechanical strength to the end product. In the present investigation, β-C₂ S was synthesized by sol-gel process and it was used as powder to cement preparation, named CSiC. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid solutions and human osteoblast cell cultures for various time periods, respectively. The results showed that the sol-gel process is an available synthesis method in order to obtain a pure powder of β-C₂ S at relatively low temperatures without chemical stabilizers. A bone-like apatite layer covered the material surface after soaking in SBF and its compressive strength (CSiC cement) was comparable with that of the human trabecular bone. The extracts of this cement were not cytotoxic and the cell growth and relative cell viability were comparable to negative control.

Reinforced Portland cement porous scaffolds for load-bearing bone tissue engineering applications

Modified Portland cement porous scaffolds with suitable characteristics for load-bearing bone tissue engineering applications were manufactured by combining the particulate leaching and foaming methods. Non-crosslinked polydimethylsiloxane was evaluated as a potential reinforcing material. The scaffolds presented average porosities between 70 and 80% with mean pore sizes ranging from 300 μm up to 5.0 mm. Non-reinforced scaffolds presented compressive strengths and elastic modulus values of 2.6 and 245 MPa, respectively, whereas reinforced scaffolds exhibited 4.2 and 443 MPa, respectively, an increase of ∼62 and 80%. Portland cement scaffolds supported human osteoblast-like cell adhesion, spreading, and propagation (t = 1-28 days). Cell metabolism and alkaline phosphatase activity were found to be enhanced at longer culture intervals (t ≥ 14 days). These results suggest the possibility of obtaining strong and biocompatible scaffolds for bone repair applications from inexpensive, yet technologically advanced materials such as Portland cement.

Magnetic bioactive glass ceramic in the system CaO-P2O5-SiO2-MgO-CaF2-MnO2-Fe2O3 for hyperthermia treatment of bone tumor

Magnetic bioactive glass ceramic (MG) in the system CaO-SiO(2)-P(2)O(5)-MgO-CaF(2)-MnO(2)-Fe(2)O(3) for hyperthermia treatment of bone tumor was synthesized. The phase composition was investigated by XRD. The magnetic property was measured by VSM. The in vitro bioactivity was investigated by simulated body fluid (SBF) soaking experiment. Cell growth on the surface of the material was evaluated by co-culturing osteoblast-like ROS17/2.8 cells with materials for 7 days. The results showed that MG contained CaSiO(3) and Ca(5)(PO(4))(3)F as the main phases, and MnFe(2)O(4) and Fe(3)O(4) as the magnetic phases. Under a magnetic field of 10,000 Oe, the saturation magnetization and coercive force of MG were 6.4 emu/g and 198 Oe, respectively. After soaking in SBF for 14 days, hydroxyapatite containing CO(3)(2-) was observed on the surface of MG. The experiment of co-culturing cells with material showed that cells could successfully attach and well proliferate on MG.

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.

Preparation and characterization of 3D porous ceramic scaffolds based on portland cement for bone tissue engineering

There is a constant need for bone substitutes. This work was focused on developing a porous substrate based on Portland cement with air-voids introduced by outgassing reaction product from lime and aluminum powder. The structures were obtained through two routes of raw-materials and processing. Water absorption and compressive strength measurements and scanning electron microscopy, X-ray diffraction, and Fourier Transformed Infrared Spectroscopy assays were conducted in order to characterize the porous substrates. The substrates have shown pore size structure compatible with bone tissue colonization. Also, the mechanical strength exhibited by the scaffolds fall in the normal ranges for trabecular bone. These characteristics indicate potential use of the developed porous scaffold for bone tissue engineering which was endorsed by in vitro experiments via cell culture.