Cu-containing glass polyalkenoate cements (GPCs) were developed by modification of the glass composition, and were characterized by their physical, mechanical and biological behavior. In vitro biological behavior was initially evaluated by studying the solubility profiles of the glass composites and the resulting cements.
B ONE T ISSUE
- Bone Microstructure
- Bone Tissue Diseases
- Vertebral Augmentation
- Hip and Knee Arthroplasty
Blood vessels in these canals supply blood to osteons deeper in the bone and tissues of the marrow cavity. The cement is used to create immediate stability of the femoral stem to allow early load bearing (Figure 2.5).
PMMA B ONE C EMENT
Issues with Current Bone Cements
The cement is bonded to the bone by a mechanical interlock formed by applying pressure to the cement during surgery46. Modulus mismatch or stress shielding can also occur because the mechanical properties of the cement and the bone are different48.
G LASS P OLYALKENOATE C EMENTS
- Historical Development
- Clinical Applications
- Chemistry of Glass Polyalkenoate Cements
- Setting Reaction
- The Glass Component
- Polyacrylic Acid
- Adhesion of GPCs to Tooth Structure
- Transition from Dental to Skeletal Adhesive GPCs
The glass components play a critical role in the chemistry and physical properties of resulting cements. One of the primary concerns with the use of conventional GPCs in skeletal applications is the presence of Al3+ in the glass composition86.
C OPPER I NCORPORATED G LASS P OLYALKENOATE C EMENTS
To investigate the surface crystallization of heat-treated glass particles, to modify the cross-linking mechanism in the curing reaction and to improve the mechanical properties of the resulting GPCs. The first part of the next chapter describes the chemistry and morphology of the glasses, and the structural effects of Cu incorporation into glasses, using DTA, MAS-NMR, XPS.
R EFERENCES
Rehman, I., Effects of incorporating hydroxyapatite and fluoroapatite nanobioceramics into conventional glass ionomer cements (GICs). Guida, A.; Towler, M.; Wall, J.; Hill, R.; Eramo, S., Preliminary work on the antibacterial effect of strontium in glass ionomer cements.
A BSTRACT
I NTRODUCTION
Therefore, the solubility of the glass particles is crucial to promote the desired bioactive response. The concentration of NBO (Si-NBO) has previously been found to have a significant effect on glass solubility, and these NBO species are formed by the incorporation of alkali/alkaline earth cations into the glass.
M ATERIALS & M ETHODS
- Glass Synthesis
- X-Ray Diffraction (XRD)
- Differential Thermal Analysis (DTA)
- Scanning Electron Microscopy & Energy Dispersive X-ray Analysis
- Advanced Surface Area and Porosity (ASAP)
- Particle Size Analysis (PSA)
- X-Ray Photoelectron Spectroscopy (XPS)
- Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR)
- Ion Release Profiles
- pH Measurements
- Glass Polyalkeonate Cements Formulation
- Rheological Evaluation
- Compressive Strength
- Shear Bond Strength Test
- Antibacterial Testing
When the glass component is mixed with polyacrylic acid (PAA) and water, the surface of the glass partially breaks down and releases cations that serve to cross-link the ionized PAA chains43. The setting times (Ts) of the cement series were tested in accordance with ISO991751, which specifies the standard for dental water-based cement.
R ESULTS
Working (Tw) and setting (Ts) times of GPC were performed according to ISO9917 and the results are presented in Figure 3.10 and also in Table 3.4. Pressure testing was performed after 7 days of immersion in deionized water, taking into account 40 wt. %, 50 wt. % and 60 wt. % PAA, and the results are presented in Figure 3.11. The shear bond strength was measured after a 24-hour incubation in water and the results are presented in Figure 3.12.
Agar diffusion testing was performed using GPCs formulated with 40 wt% PAA and the results are shown in Figure 3.13 and Figure 3.14.
D ISCUSSION
The MAS-NMR data presented in Figure 3.6 and Figure 3.7 also show that with the addition of 12 mol% CuO, the concentration of bridging oxygen in the glass increases as this technique probes the local environment of the Si atom. In addition, the solution pH of the glass series was found to be slightly higher for the control glass compared to CuG6 and CuG12. This effect may be related to changes in the local pH of the cement matrix through the dissolution of glass particles in response to PAA.
The failure of the mechanical properties in these GPCs is probably due to the reduced dissolution rate of the glass particles.
C ONCLUSION
The overuse of these antibiotics has led to the development of resistant strains of microbes that pose serious problems in immunocompromised patients62-64. The mechanical properties of GPCs will be analyzed using compressive, flexural and shear strength tests. In addition, to analyze the bond strength, the fracture surface will be analyzed using laser profilemetry.
Later, the in vitro biocompatibility of GPCs will be studied using different approaches, such as ion release proliferation, simulated body fluid traces, antibacterial efficacy in agar and broth, and finally the cytotoxicity of osteoblast cells will be evaluated.
R EFERENCES
G.; Schubert, J., Comparison of the bond strength of selected adhesive dental systems to cortical bone under in vitro conditions. Rheological evaluation of GPCs determined that the addition of Cu reduces the working time (Wt) and setting times (St) of the cements. The compressive strength (CS) of the cements was found to be between 21-36 MPa, with Cu6C having the highest CS.
Bioactivity testing was performed using Simulated Body Fluid (SBF), which revealed CaP precipitants on the surfaces of each of the GPCs.
I NTRODUCTION
During the hardening reaction, and in the presence of water, the surface of the glass particles is attacked by hydrogen ions from the acid chains. Degradation occurs on the surface of the glass particles, while the core remains intact and exists as filler in the hardened cement (Figure 4.1). One of the primary concerns with the use of conventional GPCs for skeletal applications is the presence of aluminum (Al3+) in the glass.
Zn2+ offers an alternative to Al3+ in the glass with a similar structural role as a network intermediate.
M ATERIALS & M ETHODS
- Glass Synthesis
- Cement Formulation
- Rheological Evaluation
- Compressive Strength
- Biaxial Flexural Strength
- Shear Bond Strength
- Laser Profilometry
- Ion Release Profile
- Simulated Body Fluid Trial
- Scanning Electron Microcopy (SEM)
- Antibacterial Analysis - Agar Diffusion
- Antibacterial Analysis - Bacterial Broth
- Cytotoxicity - MTT assay
- Statistical Analysis
The setting time (St) of the series of cements was tested in accordance with ISO991745, which defines the standard for water-based dental cements. Ion release profiles of liquid extracts were measured using inductively coupled plasma–optical emission spectroscopy (ICP–OES) on a Perkin-Elmer Optima 3000DV (Perkin-Elmer, MA, USA). The antibacterial activity of the cements was evaluated against three strains of bacteria using the bacterial slurry method.
The MTT test was then added in an amount equal to 10 % of the culture medium volume/well.
R ESULTS
To determine the effects of curing time on mechanical properties, each cement was tested for CS after 1, 7, 14 and 21 days of incubation in DI water at 37°C and the results are shown in Figure 4.2b. The 3D microtopography of the fracture surface of ConC and Cu6C after 1 and 21 days of incubation in DI water is shown in Figure 4.5, where the smooth blue background represents the HaP surface and the circle mark illustrates the fractured surface of the cement cylinders. Optical microscope images of the fracture surface of Cu6C cement after 1 and 21 days of incubation in DI water are shown in Figure 4.7.
As shown in Figure 4.9, all three GPCs had similar morphology of spherical deposits on the surface after 21 days of incubation in SBF.
D ISCUSSION
This effect can be attributed to the continuous dissolution of the glass particles, resulting in increased cross-linking. The rough fracture surface of ConC and Cu6C after 21 days in Figure 4.5 and Figure 4.6 indicates this. The similar morphologies of the precipitants indicate that ConC and Cu-GPC behave similarly when incubated in SBF.
The antibacterial efficiency of Cu-GPC is greatly enhanced by the incorporation of Cu ions into the glass phase.
C ONCLUSION
The analysis of the behavior of the cements over different periods also shows that the cell viability of the ConC cement decreases significantly (p=0.000) over the 1 to 21 day incubation period. Solutes of the glass and acid component of the GPCs can significantly change the pH of the surrounding solution and consequently affect the number of viable cells. Specifically, the results of antibacterial testing of the cement were promising indicators of their potential in orthopedic bone cements.
The first part of the next chapter will mainly investigate the surface characteristics of the annealed glasses using SEM, Raman and XRD.
R EFERENCES
E.; Gore, D., Glass Ionomer Cements: A Review of Composition, Chemistry, and Biocompatibility as a Dental and Medical Implant Material. W.; Czarnecka, B., Review paper: The role of aluminum in dental ionomer cements and its biological effects. Selimovic-Dragaš, M.; Huseinbegović, A.; Kobašlija, S.; Hatibović-Kofman, Š., A comparison of the in vitro cytotoxicity of conventional and modified glass ionomer resin cements.
This work outlines the formation of flexible organic-inorganic polyacrylic acid (PAA)–glass hybrids, commercial forms are known as glass ionomer cements (GICs).
I NTRODUCTION
Structural analysis of the glass using Raman suggests the formation of CuO nanocrystals on the surface. The mechanical properties of Cu-containing adhesives exhibited higher strength and flexibility compared to the control composite. The formulation of its main ingredients plays a critical role in the properties of the resultant cement.
Water deprotonates the COOH groups on the acid chain, which further crosslink with ions released from the surface of the glass.
M ATERIALS & M ETHODS
- Synthesis of Glass Powders
- Fabrication of Glass/PAA Hybrid Adhesives
- Scanning Electron Microscopy & Energy Dispersive X-ray Analysis
- X-Ray Diffraction (XRD)
- X-Ray Photoelectron Spectroscopy (XPS)
- Raman Spectroscopy
- ATR-FTIR Spectroscopy
- Rheological Evaluation
- Mechanical Properties
Raman analysis was performed using an Alpha300 R – Confocal Raman spectrometer (Alpha300 R, WITec, Germany) in the wavenumber range between 200 cm−1 to 1200 cm−1 using a continuous wave diode laser with an excitation wavelength of 488 nm and power of 1 mW. The infrared spectra were recorded on a Bruker Invenio R – FTIR spectrometer with an A225/Q-Pt ATR Multiple Crystals CRY Diamond accessory. The setting times (Ts) of the adhesive series were measured by lowering a 400 g mass attached to a Gilmore needle into an adhesive fillet mold measuring 8x9x10 mm internal diameter.
37oC during fixation and Ts was taken as the time when the needle failed to make a complete dent in the adhesive surface, (where n = 3).
R ESULTS
However, the surface images of annealed Cu-BG (Figure 5.2) show different morphologies, with inhomogeneous microstructure of fine crystals of high density and uniform size (~100 nm) embedded in the surface of the amorphous glass phase. Raman spectra of glass powders in the frequency region between 200 and 1200 cm-1 are shown in Figure 5.5a. In contrast, the compressive stress–compressive stress curve for CuG/PAA in Figure 5.7b shows a different behavior.
The average compressive strength for corresponding strain amplitude in each time period is summarized in Figure 5.8c.
D ISCUSSION
Thus, also in our prepared nanoparticles, we are confirmatory in obtaining CuO phase, formed on the outer amorphous structure of the glass particles. This is consistent with the previous results suggesting formation of the Cu-rich domain in the surface and nanocrystallization of CuO. The curing reaction of the adhesives is an in-situ reaction between the glass powder and the PAA solution, which takes place immediately after mixing different components59.
The mechanical properties of glass-based adhesives are well understood due to the formation of a continuous network bond.
C ONCLUSION
R EFERENCES
Neve, A.; Piddock, V.; Combe, E., Effect of heat treatment of glass on the properties of a new polyalkenoate cement. Wetzel, R.; Eckardt, O.; Biehl, P.; Brauer, D.; Schacher, F., Effect of poly(acrylic acid) architecture on setting and mechanical properties of glass ionomer cement. Valliant, E.; Dickey, B.; Price, R.; Boyd, D.; Filiaggi, M., Fourier transform infrared spectroscopy as a tool to study the hardening reaction in glass-ionomer cements.
Future work may include analysis of the mechanical properties of these cements under cyclic conditions and determination of the fatigue strength.
A PPENDIX A - P UBLICATIONS
Germanium-based glass polyalkenoate cements for skeletal applications: glass characterization and physical and bioactive properties. Copper-based glass polyalkenoate bone cements: effect of copper replacement on physical, mechanical and antibacterial properties.
