This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability.The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

Introduction/Objective The objective of this paper is to describe the microstructure and mechanical properties of sintered Co-Cr alloy and to emphasize its advantages and disadvantages with respect to the microstructure and mechanical properties of cast Co-Cr alloy. Methods Base Co-Cr alloy, EOSint M EOS Co-Cr SP2 (EOS GmbH, Munch, Germany), was used for the purpose of this research as the base material for sintering metal structures of metal-ceramic restorations. Metal sintering was conducted by using EOSint M 280 device of German origin in a stream of neutral gas-argon. After that, the alloy was heated over a period of 20 minutes at the temperature of 800°C. The chemical composition of the alloy was determined by energy dispersive spectroscopy. Microstructure of the tested alloy samples was examined under an optical metallographic and scanning electron microscope. Physical and mechanical properties were measured in a universal testing machine. The samples were prepared according to the standard ISO 527-1:1993. Results Chemical composition of the sintered Co-Cr alloy, determined by applying energy dispersive spectroscopy, indicated the same qualitative but different quantitative composition compared to cast Co-Cr alloys. The microstructure of the sintered Co-Cr alloy is lamellar in nature, with two dominant phases: ξ-Co and/or ξ-Cr (fcc-face-centered cubic) and γ-Co (hcp-hexagonal close-packed). Mechanical properties of the Co-Cr alloy obtained by applying selective laser melting technology compared to the cast Co-Cr alloy are superior or approximately the same. Conclusion Selective laser melting of the Co-Cr alloy is a good example of new technologies based on digitization. Together with other digitized procedures, this technology is an introduction to a new era in dentistry popularly called Dentistry 4.0. The advantages of the selective laser melting technology with respect to the conventional technology of casting Co-Cr alloy metal structures are precise metal structure fitting and eco-friendly technology.

Composites with the addition of alumina nanofillers show improvement in mechanical properties.Poly(methyl methacrylate), PMMA, was used as a matrix and two different types of nanofillers having extremely different shapes were added into the matrix to form the composites. The reinforcements were based on alumina nanoparticles having either a spherical shape or whiskers with a length to diameter ratio of 100. The influence of the size and shape of the alumina fillers and the loading on the mechanical properties of the prepared composite were studied using nanoindentation measurements and dynamic mechanical analysis. It was observed that both alumina whiskers and spherical alumina nanoparticles added in the PMMA matrix improved the mechanical properties of the composites, but the improvement was significantly higher with reinforcement by alumina whiskers. The concentration of the reinforcing spherical alumina nanoparticles and alumina whiskers in the PMMA matrix varied up to 5 wt. %. The best performance was obtained by the addition of 3 wt. % of alumina whiskers in the PMMA matrix in terms of the mechanical properties of the obtained composite.

Predmet ovog istraživanja je kvantitativna procena adhezije između fotopolimerizujućeg kompozitnog filma na bazi Bis-GMA (Bisfenol A glicidilmetakrilata)/TEGDMA (trietilen glikol dimetakrilata) kao matrice i čestica na bazi aluminijum oksida dopiranih gvožđem na metalnoj podlozi. Korišćene su dve različite metalne podloge, jedna od srebra (u daljem tekstu "srebro") i jedna pozlaćena mesingana pločica sa međuprevlakom od nikla (u daljem tekstu "zlato"). Adhezija je merena korišćenjem mikroindentacije i upoređena je sa izmerenim uglom kvašenja kompozita na datim podlogama. Pokazalo se da se podloge, iako sličnih mehaničkih svojstava koje se ogledaju u veoma bliskim vrednostima tvrdoće, razlikuju po ostvarenoj adhezivnoj vezi sa polimernim fotopolimerizujućim filmom. Dodatak keramičkih čestica u polimernu matricu dodatno je povećao adheziju kompozitnog filma na obe podloge, dok je trend adhezije u zavisnosti od tipa podloge održan.

Summary Background: Free radicals (FR) occur in oral cavity where lot of food was transferred to through entire life under specific saliva conditions. Many enzymes, microorganism, alcohol beverages, nicotine and other harmful or indifferent substances when in contact to oral tissues might provoke oxidation process under specific condition creating FRʼs. The similar role might have various dental materials.Aim: Of the study was to record the level of antioxidant (AO) activity of several permanent (P) luting cements alone or combined with quercetin AO substance.Materials/Methods: P cements were Zn-phosphate, Zn-polycarboxilate, GIC and composite resin cement. They were prepared as original prescription and their variant by 1%weight addition of quercetin. AO activity of cements was measured by HPMC test evaluated by Student t test.Results: There were statistically significant differences among Zn-phosphate, Zn-polycarboxilate and resin dental cements (p ˃ 0,05). GIC displayed significantly higher AO values (p < 0,01) versus other three cements. There were no difference in AO capacity between sample of original P cements and their corresponding quercetin variants (p ˃ 0,05).Conclusions: Conventional GIC displayed the most powerful AO activity among P luting cements. Addition of 1% antioxidant quercetin did not improve AO capacity of investigated cements.