چكيده به لاتين
As the aging population in the country increases, there will be greater demand for titanium implants. So, it is necessary to increase the formation rate, strength, and structural integrity of connective tissues between the living bone and the implant surface. In recent experiments, it has been demonstrated that a bioactive glass coating on the titanium surface can increase its ability to bond to bone. However, because bioactive glasses have a higher thermal expansion coefficient than titanium, scientists have been trying to reduce the coefficient; this has led to an increase in the crystallization of neutral phases during coating, decreasing the bioactivity of these glasses.
This project aimed to develop a bioactive glass or glass-ceramic coating with a medium thermal expansion coefficient (similar to titanium), precipitating bioactive phases to make the coating more bioactive when crystallized during the coating process. Consequently, according to models for predicting bioactivity from composition, three types of glass with low thermal expansion coefficients have been developed by adding B2O3 and decreasing alkaline earth oxides of the commercialized Ceravital® glass. A sol-gel process was used to synthesize these glasses, and simultaneous thermal analysis, X-ray diffraction analysis, and scanning electron microscopy/energy dispersive X-ray spectrometry were used to analyse the three synthesized glasses. In numerous studies of sol-gel parameters and the structure of synthesized gels, the application of hydrochloric acid and chloride salts with weight ratios of (H_2 O)/(solid precursors)=20 and molar ratios of EtOH/TEOS=5 has been shown to be a simple and relatively inexpensive condition for synthesizing amorphous gels with a reasonable degree of polymerization for exemplary transparency and homogeneity. After heat treatment for stabilization and sintering, the synthesized amorphous gels were transformed into glass. Sol-gel-produced glass powders had a mesoporous morphology with a specific surface area of about 15 to 30 square meters and an average porosity of about 20 to 30 nanometers. In vitro bioactivity assessment was carried out by soaking glass powders in SBF solution at 37 °C. X-ray diffraction analysis, and scanning electron microscopy/energy dispersive X-ray spectrometry were used to examine how chemical composition affects the properties of glass. By sintering glasses at 800 °C for 30 minutes, they turned into glass-cermics. The bioactivity of glass-ceramics was evaluated, the results of which were disappointing. Therefore, the most bioactive glass composition was coated by the dip-coating technique on the titanium substrates. A study was also conducted on the effectiveness of sintering temperatures and times in creating a sticky, crack-free coating, and the optimal temperature and time were determined. Due to the conversion of glass to glass-ceramic at 830 °C for 45 minutes, the precipitated phases on the coating were detected by scanning electron microscopy/energy dispersive X-ray spectrometry and grazing incidence X-ray diffraction methods. It was demonstrated that the diffusion of titanium atoms into coatings resulted in the precipitation of bioactive phases such as titanite, chloroapatite, diopside, and a small amount of rutile phase. The bioactivity of the formed glass-ceramic coating was then assessed by immersion in the SBF solution for 21 days at 37 °C. Results from grazing incidence X-ray diffraction, and scanning electron microscopy/energy dispersive X-ray spectrometry strongly proved the formation of the bioactive phases of chloroapatite. In the following, a Pull-Off test was used to assess the adhesion of the coating to the substrate, and the results show an average failure value of 24 Mpa. Furthermore, to compare the corrosion behavior of coated and uncoated titanium specimens, electrochemical impedance spectroscopy was applied. Results showed that sample with a glass-ceramic coating demonstrated superior corrosion resistance compared to those without coating.