Resin composites are the most commonly used material in restorative dentistry. They have been used initially for aesthetical reasons, but afterwards were modified to be used widely for their good aesthetic and mechanical properties performance. They are classified as visco-elastic materials which are composed of inorganic fillers and organic matrix. The aim of this study was to investigate some handling properties of uncured resin composites such as stickiness, consistency and rheology. Also, to measure the degree of conversion and creep behaviour under static loading of some resin composites. In the pre-cure stage, their handling properties are very essential to achieve a successful dental restoration. Therefore, dental practitioners are very critical in choosing the resin composite restorative material. A texture analyser was used to measure the stickiness and consistency of some commercial resin composites. Also, the rheology of different commercial and model resin composites were investigated using the Bohlin Rheometer in two different temperatures (room and body temperature).Moreover, Fourier transform infrared spectroscopy (FTIR) was used to determine the degree of conversion of several bulk-fill resin composites (DC) at 4 mm depth at different periods during 24 h post-irradiation. Also, the visco-elastic stability of cured resin composites with different resin matrices was investigated under static load at different maturation times (1 h and 24 h).

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study is to further investigate the effect of using six different light source types with different light output intensities on the parameters of a mathematical model that predicts the DOC in VLDC’s. In this equation: D = Dp In(E0/Ec), D is the depth of cure in millimeters, E is the curing energy in J/cm2, Ec is the critical curing energy for the composite to reach a gel layer, and Dp is a characteristic coefficient. Three LED and three halogen dental curing units with different light output intensities were used to cure three shades (B1, A3, D3) of a hybrid resin composite. The exposure duration was at the intervals of 10, 20, 30, and 40 seconds for each sample setting. ISO scraping technique was performed to measure the depth of cure of each sample. Regression analysis was used to assess the fit of the proposed mathematical model D = Dp In(E0/Ec) to the experimental data obtained in this study. 72 For all the shade-light combinations; A3, B1, and D3 had significantly different regression lines (P < 0.05) with significantly higher Dp and Ec for B1 than A3 and D3. The only exceptions were for the Ec values between B1 and D3 in Allegro, Astralis 5, and Visilux 2 groups; and the Ec between A3 and B1 in Allegro group. The Dp and Ec parameters didn’t show significant differences between A3 and D3 shades in all the groups. Also, most of the significant differences for Dp values occurred in the B1 shade-light combinations; however, none of the D3 shade-light combinations showed significant differences for Dp. Several factors play combined influential effects on the kinetics of polymerization and depth of cure in VLDC’s. The shade has a more dominant effect on both parameters Dp and Ec than the curing light type or source output intensity. As we cure lighter shades “B1,” the effect of using different lights with different output intensities on the two parameters Dp and Ec will be greater and more significant than for darker shades “A3 or D3.” The clinical significance drawn from this study is that clinicians should recognize that using curing lights w/ increased output intensities doesn’t absolutely increase the DOC of VLDC’s especially with the darker shades.

Fast-bränsle-raketer (SRM) har funnit sin plats i en stor mängd tillämpningar sedan deras framkomst mer än 2000 år sedan. En SRMs prestanda är förutbestämd av geometrin av drivmedelskrutet och är begränsad av gjutningsmetoden, som idag främst används i produktion. Forskning inom 3D-skrivning av drivmedelskrut har undersökt nya komplexa geometrier som kan öka prestandan. Studier kring 3D-skrivning med UV-härdning är få till antalet och undersöks i detta projekt. Ett bindemedel av polyuretandiakrylat (PUDA) har syntetiserats och därefter karakteriserats, med och utan diverse monomerer genom dragprovsmätningar och differentialkalorimetri (DSC). Tillsats av tvärbindarna 1,6-hexandioldiakrylat (HDDA) samt trimetylolpropantriakrylat (TMPTA) till PUDA producerade ett mer sprött material. Denna skillnaden var mer påtaglig för TMPTA än HDDA, vilket tillskrivs den högre akrylatfunktionaliteten i den förstnämnda. Den kommersiella produkten Ebecryl 113 har karakteriserats med inerta fyllmedel. Härddjupet (DOC) undersöktes med Ebecryl 113 i ett experiment, vilket påvisade en minskning av härddjupet med ökande mängder aluminium. Orsaken är troligen de reflektiva egenskaperna för UV-ljus som aluminium innehar. Reologiska studier utfördes, från vilka en minskning i viskositet påvisades till följd av en ökad polydispersitet i partikelstorlekarna. 3D-skrivning med kolvextrudering och påföljande härdning med UV-strålning utforskades. Detta visade utmaningar med tekniken som behövs bemästras. I synnerhet uppmärksammades fasseparation och residuell härdning från reflekterat UV-ljus som begränsande faktorer för fortsatt arbete. / Solid rocket motors (SRMs) have found their place in many applications since their conception more than 2000 years ago. The performance of SRMs is determined by the geometry of the propellant grain and is limited by the cast-and-mould production method typically used today. Research has been made on 3D printing propellant grains to explore new complex geometries, which may increase performance. Studies on 3D printing techniques using UV curing are limited and are in this work investigated. A polyurethane diacrylate (PUDA) binder was synthesized and then characterized, with and without various monomers by tensile testing and differential scanning calorimetry. Additions of the crosslinkers 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA) to PUDA rendered the final product more brittle. This change was more noticeable for TMPTA than HDDA, as the former has a higher acrylate functionality. The commercial product Ebecryl 113 was also characterized with inert fillers added. A depth of cure (DOC) study with Ebecryl 113 was conducted, which showed a decrease in DOC with increasing amounts of aluminium. This is attributed to the reflective properties of aluminium in the UV spectrum. Rheological studies were conducted and a decrease in viscosity could be seen as a result of increasing the polydispersity of particle sizes. A 3D printing technique using plunger extrusion followed by UV curing was explored, which highlighted challenges which need to be overcome. Most notably, phase separation and residual curing from scattered UV rays are limiting factors for future work.