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The aim of this study was to investigate the effects of TiO2/CaO addition on the crystallization and flexural strength of leucite glass-ceramics (GC). Synthesis of translucent and high strength GCs is important for the development of aesthetic and durable dental restorations. To achieve this, experimental aluminosilicate glasses (1–3 mol% TiO2 and CaO (B1, B2, B3)) were melted in a furnace to produce glasses. Glasses were ball milled, screened and heat treated via crystallization heat treatments, and characterized using XRD, differential scanning calorimetry, dilatometry, SEM and biaxial flexural strength (BFS). Increasing nucleation hold time (1–3 h) led to a reduction in crystallite number for B2 and B3 GC, and significant differences in leucite crystal size at differing nucleation holds within and across test groups (p < 0.05). A high area fraction of leucite crystals (55.1–60.8%) was found in the GC, with no matrix microcracking. Changes in the crystal morphology were found with higher TiO2/CaO addition. Mean BFS of the GC were 211.2–234.8 MPa, with significantly higher Weibull modulus (m = 18.9) for B3 GC. Novel glass compositions enriched with TiO2/CaO led to crystallization of leucite GC of high aspect ratio, with high BFS and reliability. The study's findings suggest a potential high performance translucent leucite GC for use in the construction of dental restorations. [ABSTRACT FROM AUTHOR]

Two underlying problems of the Late Quaternary history of the Scandinavian Ice Sheet (SIS) are reviewed in the paper: the position of the southeastern SIS boundary at the Late Glacial Maximum (LGM), which is still widely "migrating" depending on authors' concepts, and the formation of associated proglacial lakes (i.e. their dimensions, drainage and chronology) in the valleys of Severnaya Dvina River basin. The position of maximum ice limit in the northwest of the Russian Plain remains debatable and is the least reliable compared to the other SIS sectors. Most of the recent reconstructions concerning ice-dammed lakes (water overflows, restructuring of river valleys etc.) exploited the geological survey results of mid-20th century: since then no geological studies have been conducted of the proposed spillways, their filling sediments and age using the modern sedimentological and geochronological techniques. As a result, the majority of the above-mentioned reconstructions have to be considered hypothetical. Here we present new results on two valley sites that allow to suggest that: 1) the SIS did not advance through the lower and middle Vychegda valley at LGM as suggested in some recent publications; 2) the LGM glacier-dammed lake had a very limited extension in the Severnaya Dvina valley and did not exceed to the Vychegda River mouth. [ABSTRACT FROM AUTHOR]

The commercial calcium phosphate cement, HydroSet™, was investigated in vitro, studying phase formation, compressive strength and setting time, followed by an ovine in vivo study to measure osseointegration, bone apposition and bone-to-graft contact. The X-ray diffraction and 31P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) results showed the initial formation of octacalcium phosphate and hydroxyapatite at one hour. Over 7 days the octacalcium phosphate transformed to apatite, which was the only crystalline phase of the cement at 28 days. This apatite phase is thought to be a calcium deficient apatite. In the scanning electron microscopy, histological images of 12-week ovine in vivo results showed a high degree of osseointegration, 92.5%. Compressive strength comparisons between in vitro and in vivo measurements showed a dramatic difference between the in vitro measurements (highest 25.4 MPa) and in vivo (95 MPa), attributed to bone ingrowth into the cement in vivo. To the best of our knowledge this is the first time phase evolution of HydroSet™ and the properties studied in vitro complement the in vivo evaluation of the cement in a publication. The significance of the new finding of initial formation of octacalcium phosphate in this cement is discussed. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 21-30, 2018. [ABSTRACT FROM AUTHOR]