Σχεδιασμός, σύνθεση και χαρακτηρισμός νέων υαλοκεραμικών υλικών για εφαρμογές στην οδοντιατρική προσθετική (Master thesis)

Κουβόπουλος, Ευριπίδης

Many research groups, that are dealing with bioactive biomaterials, like dental biomaterials, have turned their attention to the development of novel substances of glasses and glass-ceramic materials. Thus the aim of this thesis was to develop and characterize novel glass-ceramic materials in the ternary system CaO-MgO-SiO2 in order to be used on modern dental clinic applications as dental implants. That is, in this paper we are trying to find out whether we can efficiently produce, from the composition of glass 1d (CaO-MgO-SiO2-Na2O-P2O5-CaF2), a new glass-ceramic material in order to increase the mechanical strength to the desired limits, but at the same time maintain its bioactivity at a level that it would permit its usage as a dental implant. Parent glass was developed in the aforementioned system with the addition of P2O5, Na2O and CaF2 by melting the components in a platinum crucible at 1400 °C and by quenching the melt in cold water. The sample which was obtained was in the form of glass-frit. The kinetics of crystallization of the glass before the sintering process, was studied using thermal analysis methods (DSC, dilatometry) and the temperatures at which crystallization was feasible was estimated. Powder from glass-frit was created by applying pressure. Using a metal matrix, parallelepiped bar specimens were produced. The sintering process took place at 800 °C, 850 °C and 900 °C, and dense white crystalline materials were obtained. The characterization of the glass-ceramic material was carried out using XRD and SEM methods, and it was found that the material consisted of diopside-wollastonite and fluoroapatite crystals, coexisting with residual glass phase. The physical and mechanical properties of the samples, such as density, linear shrinkage, flexural strength, modulus of elasticity, hardness and fracture toughness, were also studied. Furthermore, in order to evaluate the in-vitro bioactivity, the glass ceramic samples were immersed in SBF for 7, 14, 21, 60 and 90 days, and then were characterized by XRD and SEM / EDX so that to determine the formation of a HA (hydroxyapatite) surface layer. The experimental results showed that the specimen sintered at 850 °C exhibited the most desirable mechanical properties with values of bending strength 170,82 MPa, modulus of elasticity 26,57 GPa and fracture toughness 1,67 MPa-m0,5. The in vitro bioactivity results showed that the glass-ceramic material had formed HA surface layer and this was evaluated firstly by X-ray diffraction, as the peaks that appeared fitted perfectly with the peaks of the HA card (01-086-0740). HA formation was also evaluated by observing its surface using scanning electron microscopy / energy dispersive X-ray spectroscopy, where the evolution of bioactive surface formation over time was clearly apparent, as well as the Ca/P ratio was 1,65. The main conclusions drawn from the present study are that the composition 1d resulted in a diopside-wollastonite-fluorapatite glass-ceramic material, with modulus of elasticity and fracture toughness values that were close to those of the human cortical bone. The color of the glass ceramic material was aesthetically acceptable as it resembled that of the root of the natural tooth. Finally, the glass-ceramic material after remaining in SBF proved to be bioactive.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Πολυτεχνική Σχολή. Τμήμα Μηχανικών Επιστήμης Υλικών
Subject classification: Οδοντικά εμφυτεύματα
Keywords: Υαλοκεραμικά,Βιοενεργότητα,Οδοντικά εμφυτεύματα,Υδροξυαπατίτης,Glass ceramic,Bioactivity,Dental implants,Hydroxyapatite
URI: https://olympias.lib.uoi.gr/jspui/handle/123456789/29405
http://dx.doi.org/10.26268/heal.uoi.375
Appears in Collections:Διατριβές Μεταπτυχιακής Έρευνας (Masters)

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