Uticaj tehnološkog procesa proizvodnje na biofunkcionalne osobine nikl-titanijum legure za primenu u stomatološkoj protetici
The influence of technological production process on the biofunctional properties of nickeltitanium alloy for use in prosthodontics
Докторанд
Miličić-Lazić, MinjaМентор
Radović, KatarinaЧланови комисије
Rudolf, RebekaLazić, Vojkan
Đorđević, Igor
Grgur, Branimir N.
Метаподаци
Приказ свих података о дисертацијиСажетак
Nikl-titanijum legure predstavljaju napredne funkcionalne materijale koji mogu pokazati različite
mehaničke, hemijske i biofunkcionalne osobine zavisno od procesa proizvodnje. U ovoj doktorskoj
disertaciji primenjena je metoda kontinualnog livenja za dobijanje nikl-titanijum legure i sprovedene su
metode za ispitivanje biofunkcionalnih osobina dobijenih odlivaka. Osobine dobijene legure poređene
su sa komercijalno dostupnom nikl-titanijum legurom dobijenom klasičnim postupkom livenja,
odnosno pretapanjem u vakuum peći sa elektrootpornim zagrevanjem i finalnim livenjem u različite
ingote.
Hemijska karakterizacija uzoraka vršena je metodama semikvantitativne i kvalitativne analize
skenirajućom elektronskom mikroskopijom obogaćenom energijsko–disperzivnom rendgenskom
spektroskopijom (SEM–EDX), rendgenskom fluorescentnom spektoskopijom (XRF) i difrakcijom
povratnog raspršenja elektrona (EBSD). U okviru analize mehaničkih osobina legura, tvrdoća površine
uzoraka ispitivana je statičkom meto...dom po Vikersu. Koroziono ponašanje kontinualno i klasično
livene legure analizirano je kroz standardizacijom regulisanu grupu testova za ispitivanje korozije
dentalnih legura (ISO 10271-2011). Postojanost uzoraka u pH neutralnoj i kiseloj sredini ispitivana je
statičkim testom uranjanja i naknadnom analizom migracije jona u medijum metodom induktivno
spregnute plazme (ICP). Sklonost legura ka tamnjenju ispitana je testom sulfidne matrice, nakon čega
je vršeno elektrohemijsko ispitivanje metodom potenciodinamičke polarizacije. Da bi se ispitao udeo
određenih hemijskih elemenata novoformiranog površinskog sloja nakon testova korozije vršeno je
ispitivanje topografije i sastava površine uzoraka fokusiranim jonskim snopom elektronske
mikroskopije.
U cilju ispitivanja citotoksičnih svojstava nikl-titanijum legure dobijene metodom klasičnog i
kontinualnog livenja sproveden je MTT test ćelijske vijabilnosti kroz dve vrste kontakta materijala i
ćelija fibroblasta humanog porekla. Pri direktnom kontaktu analizirana je toksičnost same površine
materijala, dok je indirektni kontakt podrazumevao analizu toksičnog efekta molekula materijala
otpuštenih u medijum za ćelijsku kulturu.
Dobijeni rezultati pokazali su da su najvažnije prednosti kontinualnog nad klasičnim livenjem:
mogućnost dobijanja odlivaka malih dimenzija, što eliminiše potrebu za daljim postupcima hladne ili
tople obrade, stabilnija mikrostruktura i bolja koroziona postojanost legure u kiseloj sredini...
Nickel-titanium alloys represent smart, functional materials that can exert different mechanical,
chemical, and biofunctional properties depending on the manufacturing process. In this doctoral
dissertation, nickel-titanium alloy was produced by the continuous casting method (NiTi-2).
Biofunctional properties of continuous cast alloy were compared with commercial nitinol (NiTi-1)
manufactured by the classical process, i.e., from remelting in a vacuum furnace with electro-resistive
heating and final casting into ingots.
The chemical composition of the samples was analyzed via semiquantitative and qualitative analysis
methods using scanning electron microscopy enriched with energy-dispersive X-ray spectroscopy
(SEM-EDX), X-ray fluorescence spectroscopy (XRF), and electron backscatter diffraction (EBSD). In
order to evaluate the mechanical properties of tested samples, the hardness was measured using the
static Vickers test. The corrosion behavior of continuous and conventional cast alloy...s was evaluated
according to the standard for corrosion testing of dental alloys (ISO 10271-2011). The release of metal
ions in pH neutral and acidic solutions was measured by static immersion test. The chemical content of
the suspensions was overseen by the inductively coupled plasma (ICP) method. The surface
discoloration of the tested alloys was evaluated using a sulfide tarnish test. Corrosion potentials were
investigated using polarization measurements. Finally, the formed corrosion layers on all samples were
characterized with the focused ion beam (FIB) technique.
An MTT assay was performed to evaluate the biocompatibility testing of the NiTi-1 and NiTi-2
samples. During direct exposure, the toxicity of the sample's surface was examined, while indirect
contact included the cell's contact with ion-enriched supernatants.
The results of our research showed that the most important advantages of continuous casting over
classical casting are: the ability to produce strands of small diameter, which eliminates the need for
further cold or hot processing procedures, a more stable microstructure, and better corrosion resistance
in an acidic solution. Increased mitochondrial activity of cells grown directly on the tested samples was
recorded, showing that contact with the oxide layer on the surface of the samples leads to increased
mitochondrial activity and, thus, cell proliferation. Over time, in the indirect test, a slight decrease in
cell viability was observed, but the number of viable cells did not indicate subtoxic doses of molecules
released into the cell culture medium. During both types of cell contact with the investigated alloys,
their satisfactory biocompatibility was demonstrated...