Fibre-reinforced composites as root canal posts

Fibre-reinforced composite (FRC) root canal posts are suggested to have biomechanical benefits over traditional metallic posts, but they lack good adhesion to resin composites. The aim of this series of studies was to evaluate the adhesion of individually formed fibre-reinforced composite material to composite resin and dentin, as well as some mechanical properties. Flexural properties were evaluated and compared between individually formed FRC post material and different prefabricated posts. The depth of polymerization of the individually formed FRC post material was evaluated with IR spectrophotometry and microhardness measurements, and compared to that of resin without fibres. Bonding properties of the individually formed FRC post to resin cements and dentin were tested using Pull-out- and Push-out-force tests, evaluated with scanning electron microscopy, and compared to those of prefabricated FRC and metal posts. Load-bearing capacity and microstrain were evaluated and failure mode assessment was made on incisors restored with individually formed FRC posts of different structures and prefabricated posts. The results of these studies show that the individually polymerized and formed FRC post material had higher flexural properties compared to the commercial prefabricated FRC posts. The individually polymerized FRC material showed almost the same degree of conversion after light polymerization as monomer resin without fibres. Moreover, it was found that the individually formed FRC post material with a semiinterpenetrating polymer network (IPN) polymer matrix bonded better to composite resin luting cement, than did the prefabricated posts with a cross-linked polymer matrix. Furthermore, it was found that, contrary to the other posts, there were no adhesive failures between the individually formed FRC posts and composite resin luting cement. This suggests better interfacial adhesion of cements to these posts. Although no differences in load-bearing capacity or microstrain could be seen, the incisors restored with individually formed FRC posts with a hollow structure showed more favourable failures compared to other prefabricated posts. These studies suggest that it is possible to use individually formed FRC material with semi-IPN polymer matrix as root canal post material. They also indicate that there are benefits especially regarding the bonding properties to composite resin and dentin with this material compared to prefabricated FRC post material with a cross-linked matrix. Furthermore, clinically more repairable failures were found with this material compared to those of prefabricated posts.

The figure of the earth, determined from observations made by order of the French King, at the polar circle: by Messrs de Maupertuis, Camus, Clairaut, Le Monnier, members of the Royal Academy of Sciences, the abbé Outhier, correspondent of the Academy, and Mr. Celsius, professor of astronomy at Upsal : translated from the French of M. de Maupertuis.

Digital reproduction, The National Library of Finland, Centre for Preservation and Digitisation, Mikkeli

Liquidity and Asset Pricing in the French Stock Market

This thesis investigates pricing of liquidity in the French stock market. The study covers 835 ordinary shares traded in the period of 1996-2014 on Paris Euronext. The author utilizes the Liquidity-Adjusted Capital Asset Pricing Model (LCAPM) recently developed by Acharya and Pedersen (2005) to test whether liquidity level and risks significantly affect stock returns. Three different liquidity measures – Amihud, FHT, and PQS – are incorporated into the model to find any difference between the results they could provide. It appears that the findings largely depend on the liquidity measure used. In general the results exhibit more evidence for insignificant influence of liquidity level and risks as well as market risk on stock returns. The similar conclusion was reported earlier by Lee (2011) for several regions, including France. This finding of the thesis, however, is not consistent across all the liquidity measures. Nevertheless, the difference in the results between these measures provides new insight to the existing literature on this topic. The Amihud-based findings might indicate that market resiliency is not priced in the French stock market. At the same time the contradicting results from FHT and PQS provide some foundation for the hypothesis that one of two leftover liquidity dimensions – market depth or breadth – could significantly affect stock returns. Therefore, the thesis’ findings suggest a conjecture that different liquidity dimensions have different impacts on stock returns.