Characteristics of polymethyl-methacrylate enriched with zinc-oxide nanoparticles in complete dentures

Doktorska disertacija se bavi sintezom novog kompozita polimetil-metakrilata (PMMA) obogaćenog sferičnim nanočesticama cink-oksida (ZnO Nč), tehnikama karakterizacije i analizom dobijenih rezultata. Postavljena je hipoteza da totalne zubne proteze (TZP) izrađene od PMMA obogaćenog ZnO Nč mogu imati bolje fizičke i mehaničke karakterisatike u odnosu na TZP izrađene od konvencionalnog PMMA. U cilju potvrde postavljene hipoteze ove doktorske disertacije u prvom delu istraživanja je sintetisan novi kompozit PMMA/ZnO Nč, sa različitim zapreminskim delovima ZnO nanočestica (2 i 3 vol.%) u matriksu PMMA. Metodom dinamičkog rasejavanja svetlosti (DLS) izmerena je distribucija ZnO Nč u matrixu PMMA. Istraživanje je sprovedeno na pločicama dimenzija 42 mm x 7 mm x 3 mm, kojima je prvo određena gustina piknometrom. Na uzorcima je odrađena mikrostrukturna karakterizacija uz pomoć metoda: skenirajuće elektronske mikroskopije (SEM), energijski disperzivne rendgenske spektroskopije (EDX), Zeta Potencijala, termogravimetrijske analize (TGA), dinamičke mehaničke analize (DMA), flash diferencijalne skenirajuće kalorimetrije (Flash DSC), a kao kontrola su korišćeni uzorci čistog PMMA. Na osnovu dobijenih rezultata i njihove analize iz prvog dela istraživanja urađeni su konkretni modeli zuba (oblika prvog gornjeg stalnog kutnjaka) i TZP kako bi se identifikovala mehanička svojstva koja su potrebna u kliničkoj praksi. Dobijeni uzorci su bili testirani na otpornost na habanje korišćenjem simulatora žvakanja i otpornost na lom sa klasičnim mehaničkim testom opterećenja. Prvom analizom je dobijen uvid u mikrostrukturu novog kompozita PMMA/ZnO Nč prateći distribuciju ZnO Nč u matriksu PMMA. U suspenziji metil-metakrilata (MMA) sa ZnO Nč prosečna vrednost veličine nanočestica bila je 2.21± 0.10 μm, ali 42.1% nanočestica je bilo u opsegu 21,04 nm...The Doctoral Dissertation presents the development and synthesis of a new composite material, polymethyl-methacrylate (PMMA), enriched with spherical zinc-oxide nanoparticles (ZnO NPs), characterization techniques, and analyses of the results. The work hypothesis was that acrylic dentures made by PMMA enriched with ZnO NPs could have better physical and mechanical properties than dentures made by pure PMMA. To confirm this thesis in the first part of the investigation, a new composite, PMMA/ZnO NPs, was synthesised and tested with a different volume fraction (2 and 3 vol.%) of these nanoparticles into a matrix of PMMA. The DLS technique was used for chaking ZnO NPs' distribution into a PMMA matrix. Investigation was done on samples, in the shape of laminae with dimensions 42 mm x 7 mm x 3 mm, on which density had first measured with a picnometer. Microstructural characterization was made - SEM, EDX, Zeta Potential, TGA, DMA, Flash DSC) and, as a control, samples were made from pure PMMA. According to the results from the first part of the investigation, in the second step a concrete samples of a real model of teeth (in the shape of the first upper molar) and complete dentures had made, to identify which mechanical properties are required in clinical practice. These samples were tested for a wear resistance in a chewing simulator and for a fracture resistance in a classical mechanical tensile strength test. With the first analysis an insight was got into the microstructure of the new composite material PMMA/ZnO NPs, and followed the distribution of these nanoparticles in the PMMA matrix. In suspension with MMA, the average value of ZnO NPs was 2.21± 0.10 μm, but 42.1% of the nanoparticles were around 21,04 nm. The problem with irregular distribution was solved with a different kind of mixture dry phase (PMMA powder and powder of ZnO NPs) for a 2h in contolled vacuum conditions for a precise synthesis of the new material. Density measurement in a new composite confirmed indirectly the loss of residual monomer, the most often the cause of allergyc reaction and porosity, which could lead to worse mechanical properties..