Nova zlatna dentalna legura za metalkeramiku

Introduction: Porcelain to metal fused alloys with Au content are most frequently used in dentistry. Their characteristic is high biocompatibility and well fusion to ceramics. Aim of the study: The aim of this study was to present the procedure of production and technology of developing the new dental alloy with high gold content (Au). Materials and Methods: The dental alloy was melted and cast in a vacuum-induction melting furnace. Casting was followed by subsequent thermo-mechanical treatments (the procedures of profile and polish milling, and thermal treatment) and the cutting strips into regular shapes. Testing of the new Au dental alloy included an examination of alloy’s final condition. The measurement of hardness was carried out according to standard 6507-1:1998, and static tensile testing was performed for determination of the mechanical properties. Microscopic analysis of the dental alloy and the finished metal-ceramic bridge included an observation of the polished surface, and by performing qualitative and quantitative micro-chemical analyses. Results: The mechanical properties and hardness of new dental gold alloy was: Rp0.=630 [N/mm2], Rm =710 [N/mm2], A= 9%, 170 HV and CTE (25-600°C) about 14,55×10-6K-1. Macro-inspection of the finished metalceramic bridge showed that there was no porosity. However, during scanning electron microscopic examination, one of the tested sample shows porosity in one alloy region and in the ceramic layer. Detailed examination of the ceramic layer’s surface showed that there were two types of air or gas bubbles - larger with distinct bubbles (type I) and smaller with clearly porous microstructure (type II). Conclusions: According to the results of this study, it can be concluded that this new dental alloy from Zlatarna Celje satisfied all the required standards regarding mechanical properties and hardness. The application of new dental alloy with high gold content depends on the adequate technology when firing ceramics. It is necessary to obtain accurate oxidation temperature and cooling rates of metal-ceramic restorations because, otherwise, different defects may appear.Uvod: Visoko plemenite legure za metal-keramiku (PFM legure - porcelain fused to metal alloy) su najviše korišćene legure u stomatologiji a odlikuje ih visoka biološka prihvatljivost i dobro vezivanje sa keramikom. Cilj: Cilj ovog rada bio je da prikaže postupak dobijanja i tehnologiju razvoja i izrade nove dentalne legure sa visokim sadržajem zlata (Au). Materijal i metod: Pretapanje komponenti dentalne legure izvedeno je u vakuumskoj peći. Tome je sledila naknadna termo-mehanička obrada odlivka (postupcima profilnog i polirnog valjanja, toplotna obrada) kao i sečenje dobijene trake u propisani oblik. Testiranje nove Au dentalne legure uključivalo je testiranje izlaznog stanja legure. Merenje tvrdoće sprovedeno je po standardu 6507-1:1998, dok je za određivanje mehaničkih karakteristika upotrebljeno statično istezanje. Mikroskopska analiza dentalnih legura i završenog metal-keramičkog mosta uključivala je posmatranje polirane površine i izvođenje kvalitativne i kvantitativne mikro-hemijske analize. Rezultati: Mehaničke karakteristike i tvrdoća nove dentalne legure sa visokim sadržajem zlata iznosi Rp0.=630 [N/mm2], Rm =710 [N/mm2], A= 9%, 170 HV, a CTE (25-600°C) iznosi oko 14,55×10-6K-1. Makroskopski na površini metala i potom sinterovane keramike nije uočena poroznost dok je mikroskopskim pregledom ustanovljeno da je na pojedinim mestima jednog uzorka vidna poroznost metalne konstrukcije mosta kao i keramičke površine u vidu većih mehurića (tip I) i manjih sa izrazito poroznom mikrostrukturom (tip II). Zaključak: Na osnovu dobijenih rezultata može se zaključiti, da nova dentalna legura Zlatarne Celje odgovara propisanim standardima u pogledu mehaničkih karakteristika i tvrdoće. Neophodno je primeniti pravilnu temperaturu oksidacije i režim hlađenja fiksne zubne nadoknade, jer u suprotnom može doći do nastanka različitih defekata

Mechanical properties and microstructure characterisation of Au-Pt dental alloy

Development of a dental alloy with high Au content is based on the ternary system of Au-Pt-Zn with a nominal composition of 86,9Au-9,9Pt-1,5Zn, and about 1,5 wt.% micro-alloying elements (in, Ir, Rh). The results analyses of different heat-treated states showed that the optimal mechanical properties and hardness of an Au-Pt-Zn alloy can be reached with combinations of heat treatment for 20 minutes at 723 K and then slowly cooling, if the alloy was annealed at 1223 K for 30 minutes and the water quenched. Research results confirmed that the microstructure of the Au-Pt-Zn alloy consists of two phases: alpha(1)-phase rich in Au (main phase) and alpha(2)-phase rich in Pt (minor phase). During XRD analysis and use of the Rietveld method, it was found that the alpha(1)-phase content is about 98,5 wt.% while the content of alpha(2)-phase is 1,5 wt.%. STA analyses show that the Au-Pt-Zn alloy has a solidus temperature of about 1292 K and a liquidus temperature of about 1412 K

Karakterizacija nove dentalne zlitine z visoko vsebnostjo Au

The basis for developing a new dental alloy with high Au content is appropriate chemical composition and manufacturing technology. This new Au dental alloy is based on the ternary system of Au-Pt-Zn with a nominal composition of 88.5Au-8.7Pt-1.5Zn-0.5In-0.4Ir-0.3Rh. The alloy was melted and cast in a vacuum-induction melting furnace in Zlatarna Celje. Casting was followed with subsequent thermo-mechanical treatment (procedures of profile and polish milling, thermal treatment) and cutting-off strips to form a regular shape. The heat treatments of Au alloy samples were carried out in a tube furnace under different temperatures, and over different times. Testing of the new Au dental alloy included examining the initial cast, and the different heat treated conditions of the Au alloy. The optical properties of Au-dental alloy were investigated by means of spectrophotometric colourimetry. Finally the test of cytotoxicity of new Au based dental alloys using standard in vitro assays for testing the biocompatibility with establishing new, more sensitive, in vitro tests on cell lines was done.Osnovo razvoja nove dentalne zlitine z visoko vsebnostjo Au predstavljata pravilna določitev kemijske sestave in tehnologije izdelave. Nova dentalna zlitina temelji na ternarnem sistemu of Au-Pt-Zn z nominalno kemijsko sestavo 88,5Au-8,7Pt-1,5Zn-0,5In-0,4Ir-0,3Rh. Izdelava dentalne zlitine je potekala s pretaljevanjem zelo čistih komponent v vakuumski indukcijski peči v Zlatarni Celje. Temu je sledilo odlivanje taline v ustrezno formo, postopek termo-mehanske obdelave odlitka in razrez zlitine v ustrezno obliko. Toplotna obdelava je bila izvedena pri različnih temperaturah in za različne čase. Testiranje dentalne zlitine je vključevalo določitev lastnosti začetnega stanja in stanja po različnih toplotnih obdelavah. Optične lastnosti dentalne zlitine so bile raziskane s spektro-fotometrično kolorimetrijo. Na novi Au dentalni zlitini so bili narejeni še testi citotoksičnosti z uporabo standardain vitro analize za testiranje biokompatibilnosti z uvajanjem novih, bolj občutljivih in vitro testov na celični liniji

Internal oxidation of microalloying gold for medical application

V doktorski disertaciji je obravnavana problematike izdelave mikrolegiranega disperzijsko utrjenega zlata z disperzijo oksidov (La2O3), redko zemeljskega elementa (La) s procesom notranje oksidacije ter študija biokompatibilnosti materiala.. V prvem delu raziskav smo izdelali zlitino Au – 0,5 ut.% La, s postopkom klasičnega litja. Rezultati karakterizacije so pokazali, da že zelo majhna količina mikrolegirnega elementa lantana v zlati zlitini, povzroči tvorbo intermetane faze Au6La, ki pomembno izboljša mehanske lastnosti mikrolegiranega zlata, v primerjavi s čistim zlatom. V drugem delu smo s tehnologijo hitrega strjevanja in valjanja, izdelali trakove z metastabilno mikrostrukturo. S hitrim strjevanjem zlitine Au - 0,5 ut.% La smo dosegli spremembo morfologije strjevanja. Mikrostruktura hitro strjenih trakov sestoji iz zelo finih zrn αAu, s premerom do nekaj mikrometrov ter homogeno razporejeno intermetalno fazo (Au6La), po celotnem preseku traku. Izmerjena trdota trakov je pokazala, da se je v primerjavi z litim stanjem, trdota povečala za skoraj 20 %. Valjane trakove smo rekristalizacijsko žarili in ugotovili, da že majhen dodatek 0,5 % La, zvišuje temperaturo rekristalizacije do 200 K in povzroči rekristalizacijski zastoj. Karakterizacija materiala, je pokazala, da intermetalna faza Au6La v valjanih trakovih tvori neprekinjeno mrežo po mejah zrn, ki dodatno niža hitrost rekristalizacije. Sledila je notranja oksidacija zlitine v litem, valjanem in hitro strjenem stanju. Rezultati notranje oksidacije zlitine v litem ter valjanem stanju so pokazale, da proces notranje oksidacije poteče le po mejah kristalnih zrn z oksidacijo lantana iz intermetalne faze (Au6La). Med tem ko notranja oksidacija hitro strjenih trakov poteče s oksidacijo lantana iz trdne raztopine in tvorbo CNO ter delno po mejah zrn s oksidacijo lantana iz intermetalne faze (Au6La) . Na osnovi rezultatov smo identificirali mehanizem notranje oksidacije in postavili model notranje oksidacije zlitine Au- 0,5 ut.% La, ki rezultira v disperzijskem utrjanju mikrolegirane zlate zlitine v površinskem sloju, kljub temu, da je topnost kisika v kristalni mreži zlata zelo majhna. V zaključni fazi smo potrdili, da je material Au-0,5 ut.% La biokompatibilen, kar daje možnost njegove uporabe v obliki tankih nanosov na medicinske implantate.This Doctoral Dissertation presents the production of micro-alloyed dispersion hardened gold, by internal oxidation, with oxides of the rare earth element La (La2O3), which are dispersed homogeneously across the volume of gold. In the first stage, in order to achieve our objective, we produced an alloy of Au – 0.5 wt.% La with a classical casting procedure. The characterization results have shown that a very small amount of the micro-alloying element La in the Au alloy causes the formation of an intermetallic Au6La phase, which improves the mechanical properties of micro-alloyed gold in comparison with pure gold. In the second stage, using a technology of rapid solidification and rolling, we produced strips with a metastable microstructure. With rapid solidification of the alloy Au – 0.5 wt% La, we achieved a change in the solidification morphology. The microstructure of rapidly solidified ribbons consists of very fine grains with a diameter of up to a few micrometers were formed with a nanosized intermetallic phase, which is dispersed homogeneously throughout the volume of the strips. The measured hardness of the strips is 90 HV, which is 20 % higher when compared with the casted alloy. The rolled strips were recrystallization annealed, where we found that even a small addition of 0.5% La increased the recrystallization temperature by 200 K and caused a halt in recrystallization. Namely, the intermetallic phase Au6La in the rolled strips forms a continuous network across the grain boundaries, which further decreases the rate of recrystallization. The next step was to perform an internal oxidation in the as cast alloy, rapidly solidified and rolled strips. The results of internal oxidation of alloy in as cast and rolled state showed that the international oxidation occurred only at the grain bounders, with oxidation La from the intermetallic phase. On the other hand, during internal oxidation of rapidly solidified ribbons the internal oxidation zone was formed by oxidation of La from solid solution and partially with oxidation of La from intermetallic phase. Based on these results, we have identified the mechanism of internal oxidation and set up a model of internal oxidation for micro-alloyed gold in a metastable state, which results from dispersion hardening of the Au alloy, even though the solubility of oxygen in the crystal lattice of Au is very low. In the final stage we confirmed that the alloy Au-0.5 wt.% La is biocompatible, which gives it the possibility for use in the form of thin coatings on medical implants, improving their surface and tribological properties significantly

Razvoj 3D-tiskalnika za termoplastično modeliranje

Additive technologies are entering the market in all price segments and the development of new machines and materials is rapidly growing. Machines under 2000 EUR are more and more interesting for home and educational use. This paper presents the development of a 3D printer that shapes the parts layer by layer by depositing the material on a predefined position. The development is presented from the engineering point of view. The construction steps, the control and the actuator solutions are presented. The ABS plastic was analysed for its material properties. The 3D printer evolved from a prototype to the pre-production phase.Dodajalne tehnologije vstopajo na trg v vseh cenovnih segmentih, razvoj novih naprav in materialov pa je v konstantnem teku. Naprave s ceno pod 2000 EUR so vse bolj zanimive za uporabo doma in v izobraževalne namene. Članek prikazuje razvoj 3D-tiskalnika, ki izdela izdelek s ciljnim nalaganjem materiala na določena mesta posameznega sloja. Prikazan je inženirski pogled na razvoj. Predstavljeni so konstrukcijski koraki in rešitev vodenja. Analizirane so bile lastnosti materiala ABS. Izdelek je prešel prototipno fazo in je sedaj v predproizvodni fazi

Mehanička svojstva i mikrostrukturna karakterizacija Au-Pt dentalne slitine

Development of a dental alloy with high Au content is based on the ternary system of Au-Pt-Zn with a nominal composition of 86,9Au-9,9Pt-1,5Zn, and about 1,5 wt.% micro-alloying elements (In, Ir, Rh). The results analyses of different heat-treated states showed that the optimal mechanical properties and hardness of an Au-Pt-Zn alloy can be reached with combinations of heat treatment for 20 minutes at 723 K and then slowly cooling, if the alloy was annealed at 1223 K for 30 minutes and the water quenched. Research results confirmed that the microstructure of the Au-Pt-Zn alloy consists of two phases: α1-phase rich in Au (main phase) and α2-phase rich in Pt (minor phase). During XRD analysis and use of the Rietveld method, it was found that the α1-phase content is about 98,5 wt.% while the content of α2-phase is 1,5 wt.%. STA analyses show that the Au-Pt-Zn alloy has a solidus temperature of about 1292 K and a liquidus temperature of about 1412 K.Razvoj dentalne slitine s visokim sadržajem zlata zasnovan je na ternarnom sustavu Au-Pt-Zn s nominalnim sastavom 86,9Au-9,9Pt-1,5Zn i oko 1,5 mas. % mikrolegirajučih elemenata (In, Ir, Rh). Rezultati analize su pokazali da se u slučaju slitine odžarene kod 1223 K u trajanju od 30 minuta i zakaljena u vodi optimalna mehanička svojstva i tvrdoća Au-Pt-Zn slitine mogu postići kombinacijom toplinske obrade na 720 oC u trajanju 20 minuta s naknadnim sporim hlađenjem. Rezultati istraživanja su potvrdili da se mikrostruktura Au-Pt-Zn slitine sastoji od dvije faze: α1-faze bogate sa zlatom (primarna faza) i α2 - faze bogate s platinom (sekundarna faza). Tijekom XRD analize i primjenom Rietveldove metode utvrđeno je da je sadržaj α1-faze oko 98,5 mas. %, dok je sadržaj α2-faze iznosio oko 1,5 mas. %. STA analiza je pokazala da je Au-Pt-Zn slitina imala solidus temperaturu oko 1292 K, a likvidus temperaturu oko 1412 K

Layered additive manufacturing in clinical medicine

The use of contemporary technologies of Computer Assisted Design (CAD), combined with latest rapid prototyping, tooling and manufacturing, with traditional CT scanning techniques and high medical skills are used as instruments for better diagnostic visualization, simulation of procedures and treatment of patients with craniofacial deformities. They also improve the overall performances of medical and nursing staff thus influencing the quality of medical service. Patients with congenital defects, orthognathic deformities, deformities after malignancy treatment or after craniofacial traumatic injuries of different severities are of particular interests due to both aesthetic and functional alterations. The paper presents two clinical cases - a patient with scull bone defect after brain hemorrhage and brain edema as well as a patient with hemifacial microsomia treated by surgery followed by implantation of titanium angular implant prepared by means of computer tomography scans, Computer Aided Design and Rapid Manufacturing technologies