Search

Suvremena restaurativna dentalna medicina još uvijek je suočena s problemom rubne pukotine i mikropopuštanja. Dimenzijske promjene, odnosno konačno skupljanje restaurativnih materijala, izravno utječu na pojavu rubne pukotine s posljedičnim mikropopuštanjem i mogućnošću razvoja sekundarnog karijesa, upalne reakcije pulpe i gubitka restauracije. Svrha ovog rada bila je ispitati dimenzijske promjene materijala tijekom stvrdnjavanja [konvencionalni staklenoionomerni cementi, smolom modificirani staklenoionomerni cemenati (autopolimerizirajući, svjetlosno polimerizirajući), giomeri] i utjecaj polimerizacijskih programa (visoki, postupni, niski) Bluephase G2 LED polimerizacijskog uređaja na dimenzijske promjene svjetlosno polimerizirajućih materijala tijekom stvrdnjavanja. Također, cilj je bio odrediti mikrotvrdoću materijala s obzirom na vrstu materijala [konvencionalni staklenoionomerni cementi, smolom modificirani staklenoionomerni cemenata (autopolimerizirajući, svjetlosno polimerizirajući), giomeri], te utjecaj polimerizacijskih programa (visoki, postupni, niski) Bluephase G2 LED polimerizacijskog uređaja i sazrijevanja materijala na mikrotvrdoću. Postupak digitalne laserske interferomerije, korišten u ovom istraživanju, omogućuje bilježenje promjena i izračunavanje linearne dimenzijske promjene staklenoionomernih cemenata i giomera tijekom stvrdnjavanja. U ovom istraživanju svi materijali imali su početnu ekspanziju te posljedično skupljanje. Ekspanzija kovencionalnih staklenoionomernih cemenata, što smanjuje neto iznos skupljanja, bila je veća i duža u odnosu na smolom-modificirane staklenoionomerne cemente. Skupljanje smolom modificiranih staklenoionomernih cemenata i giomera bilo je veće nego konvencionalnih staklenoionomernih cemenata. Najmanje skupljanje imali su konvencionalni Ketac Molar Aplicap i Ketac Molar Quick Aplicap. Utjecaj polimerizacijskog programa na skupljanje smolom modificiranih staklenoionomernih cemenata nije bio značajan. Razlike su bile statistički značajne samo za B2 između visokog i niskog programa. Poboljšanje mikrotvrdoće zabilježeno je kod svih materijala nakon umjetnog starenja od 14 dana. Najveću mikrotvrdoću konvencionalnih SIC-eva nakon četrnaest dana imali su Ketac Molar Quick Aplicap i Fuji IX Fast. Beautifil II imao je značajno veću mikrotvrdoću od Fuji II LC i Photac Fil Quick u svim vremenskim razmacima i svim polimerizacijskim programima. Vrijednosti mikrotvrdoće dobivene različitim polimerizacijskim programima u pozitivnom su odnosu s energijom zračenja koja je dospjela na površinu uzorka. Usprkos tome što su statistički značajne, razlike polimerizacijskih programa mogu se smatrati zanemarivima s kliničkog stajališta. The Purpose: Bioactive restorative materials due to chemical activity with enamel and dentin achieve direct chemical bonding, and thanks to their ability to release fluoride remineralize dental tissues. This group includes glass ionomer cements (GIC) and giomers which, in their composition, have already incorporated glass ionomer component. Furthermore, modern restorative dentistry is still faced with a problem of marginal gaps and consequent microleakage. Microleakage of the restoration may lead to serious problems as postoperative sensitivity and due to penetration of bacteria, secundary caries, inflammatory reaction of the pulp and loss of the restorations. The purpose of the present study was to evaluate the linear dimensional chages of conventional glass ionomer cements during the setting time period [Ketac Molar Aplicap (KM), Ketac Molar Quick Aplicap (KMQ), Fuji IX Extra (FIXE), Fuji IX Fast (FIXF)], autocured resin-modified glass ionomer cements [Fuji PLUS (FP) and Fuji VIII (FVIII)] and to assess the influence of three curing modes of LED unit on dimensional changes of resin-modified glass ionomer cements [Fuji II LC (FIILC), Photac Fil Quick Aplicap (PFQ)], conventional GIC [Fuji Triage PINK (FTP) and giomer [Beautifil II (BII)] during the setting time period. One of the aims was to evaluate the microhardness of conventional GICs (KM, KMQ, FIXF,FIXE), light curing resin-modified glass ionomer cements (FIILC,PFQ), autocured resin-modified glass ionomer cements (FP,FVIII) and giomer (B2). It was also important to evaluate the impact of polymerization programs (low, soft-start, high) of the Bluephase G2 LED curing unit and maturation of materials on the microhardness. Methods: The digital laser interferometry method (DLI) was used to measure linear dimensional changes during the setting time of tested materials. The DLI used in this study is a method that measures the linear dimensional changes of glass ionomer cements and giomers during the recommended curing time. All tested materials were of shade A3, while all of the GICs were encapsulated. For each tested material (and curing mode, for light-curable materials), 10 discoid specimens (d=10 mm, h=0.85 mm) were prepared. Microhardness measurements were performed using the Vickers test. 100g loads were applied for 10s in the Leitz Miniload2 Microhardness Tester. The Bluephase LED curing unit was used. Hardness was evaluated in intervals, starting immediately after a recommended cure (RC) and repeated after 1 day (1d), 7 days (7d) and 14 days (14d). Five samples (d=4 mm, h=2 mm) were prepared for each combination of curing mode and tested material. Results: All tested materials show an initial setting expansion and following setting shrinkage KM showed a significantly lower shrinkage than FIXE and FIXF (p ˂ 0,01) and KMQ showed a significantly lower shrinkage than FIXF (p ˂ 0,01). FIILC and PFQ showed a higher shrinkage than conventional GICs. The resin-modifed GIC showed an increase of microhardness during the time and for all polymerization programs. The values of microhardness measurements for FIILC with the high polymerization program were higher, compared to the values obtained using the soft-start and low programs, but the difference was not statistically significant. PFQ showed higher microhardness values after 14d for samples polymerized with the high polymerization program, compared to low program. The highest values of microhardness of conventional GIC after 14d showed two highly viscous cements KMQ and FIXF. The BII showed significantly higher microhardness than FIILC and PFQ during the time and for all polymerization programs. Conclusion: Unlike other methods, which are limited to finding information about the final dimensional changes, the laser interferometry method provides information in discrete increments of time during the desired period. In particular, Ketac Molar Quick Aplicap exhibited the highest expansion, while Ketac Molar Aplicap showed the lowest contraction. The measured microhardness values showed significant dependence on the polymerization program (low, soft-start, high) and storage time for tested materials. An improvement in MH was identified in all materials after an artificial aging of 14 days, reflecting the long-term continuation of the setting reaction. The MH values attained by different curing modes were positively related to radiant energy delivered to the specimen surface. Despite being statistically significant, the differences among curing modes can be considered negligible from the clinical standpoint. Material composition exerted a stronger effect on MH values, suggesting that the choice of material had more impact on the mechanical properties than the curing mode.

Da bi se dobio odgovor na pitanje postavljeno u naslovu ovog diplomskog rada trebalo je prethodno riješiti nekoliko zadataka iz raznih područja: prvo, odabrati materijal te pripremiti uzorke za mjerenja, drugo, ovladati tehnikom mjerenja mikrotvrdoće, treće, ovladati tehnikom holografske interferometrije s mikroskopskim postavom i na kraju dati interpretaciju svih dobivenih rezultata. Odabrani materijal je PLA plastika za koju mnogo mehaničkih svojstava još nije dovoljno istraženo, a jedna je od termoplastika koje se koriste kao materijal za 3D ispis. U novije vrijeme tehnologija 3D ispisivanja doživljava pravi procvat pa je mjerenje svojstava mikrotvrdoće 3D struktura načinjenih od PLA plastike od praktičnog interesa za mnoge primjene. Korišten je 3D pisač Instituta za fiziku, Forcebook UltraPrint 3D. Za mjerenje mikrotvrdoće upotrijebljen je Leitz mikroskop i Vickersova metoda. Istraženo je kako se mijenja Vickersova mikrotvrdoća ispisanih 3D modela u ovisnosti o raznim parametrima ispisa gdje je posebna pažnja posvećena ispunjenosti modela dizajniranih za ovu priliku. Holografska interferometrija općenito daje uvid u topografiju nastalih promjena na nekoj površini. U ovom slučaju, superpozicija dvaju holograma površine uzorka snimljenih prije i nakon indentacije rezultira 3D informacijom u vidu interferencijskih pruga. Interpretacijom dobivenih interferograma dolazi se do odgovora na pitanje postavljeno u naslovu diplomskog rada. Pored tablica s vrijednostima mikrotvrdoće izračunatim Vickersovom metodom, dodatno je ustanovljeno sljedeće: indentacija je plitka s istisnutim materijalom na njenim rubovima i stranama blago savinutim prema središtu utisnute kvadratne piramide. Ova kvalitativna informacija dobivena holografskom interferometrijom lako se može kvantificirati te tako doprinijeti novim saznanjima o proučavanom materijalu. To answer the question posed in the title of this graduate thesis, a number of tasks from different fields had to be resolved: first, select the material and prepare the samples for measurements, second, master the microhardness measurement technique, third, master the holographic interferometry technique with a microscopic setting and finally give an interpretation of the obtained results. The selected material is PLA plastics for which many mechanical properties have not yet been sufficiently explored and is one of the thermoplastics used as a 3D printing material. More recently, 3D printing is experiencing a true blossoming, so measuring the properties of microhardness of a 3D structure made of PLA plastic is of practical interest with many applications. 3D printer available at the Institute of Physics (Forcebook UltraPrint 3D) was used. For microhardness measurement, Leitz microscope and Vickers method were used. How Vickers microhardness of the printed 3D models changes depending on the various print parameters was explored, with a special attention on the infill of models designed for this occasion. Holographic interferometry generally provides an insight into the topography of changes on a surface. In this case, the superposition of the two holograms of the sample surface recorded before and after the indentation results in 3D information in the form of interference lines. By interpreting interferograms, the answer to the question posed in the title of graduate thesis was achieved. In addition to the tables with microhardness values calculated by Vickers method, the following is further established: the indentation is shallow with the piled up material on its edges and sides slightly bent towards the center of the squared pyramid. This qualitative information obtained by holographic interferometry can easily be quantified and thus contribute to new knowledge of the studied material.

Thin films of Al-W alloys were prepared on sapphire substrate by the magnetron cosputtering . By X-ray diffraction it was revealed that within a composition range Al80W20 to Al67W33 the films were X-ray amorphous. The increase of tungsten content in the films (Al60W40 and Al50W50) resulted in the appearance in a mixture of two or three metastable crystalline phases. Apparently the mixture of crystalline phases coexisted with a small fraction of amorphous one. Vickers microhardness of the as-prepared films varied from ~11 GPa for completely amorphous up to ~20 GPa for the films consisting of a mixture of phases. The thermal stability of films was investigated after isochronal annealing the samples for 1 h in a temperature range from 293 K to 1273 K. It was revealed that there was slight increase in the microhardness during annealing up to a temperature chosen within interval ~(773 -848) K, and such annealing has a small influence on the XRD patterns. In contrast, the annealing above this temperature interval induced detectable changes in the microhardness and a significant changes in X-ray diffraction patterns. The results of analysis of XRD patterns demonstrated that amorphous thin films do not disintegrate directly into the ordered equilibrium (a-W, Al4W, and Al5W) coexisting phases, but the metastable (a-W(Al), b-W(Al), and Al(W) ) intermediary phases were observed to appear in the films before the former phases were observed. Thus, for the microhardess behaviour during isochronal annealing of Al-W thin films an explanation given for the metallic glasses investigated earlier can be offered, and this explanation is based also on the results of the XRD investigation we performed.