2019. Additive manufacturing of ceramics from preceramic polymers: A versatile stereolithographic approach assisted by thiol-ene click chemistry. Additive Manufacturing,27, AbstractHere we introduce a versatile stereolithographic route to produce three different kinds of Si-containing thermosets that yield high performance ceramics upon thermal treatment. Our approach is based on a fast and inexpensive thiol-ene free radical addition that can be applied for different classes of preceramic polymers with carbon-carbon double bonds. Due to the rapidity and efficiency of the thiol-ene click reactions, this additive manufacturing process can be effectively carried out using conventional light sources on benchtop printers. Through light initiated cross-linking, the liquid preceramic polymers transform into stable infusible thermosets that preserve their shape during the polymer-to-ceramic transformation. Through pyrolysis the thermosets transform into glassy ceramics with uniform shrinkage and high density. The obtained ceramic structures are nearly fully dense, have smooth surfaces, and are free from macroscopic voids and defects. A fabricated SiOC honeycomb was shown to exhibit a significantly higher compressive strength to weight ratio in comparison to other porous ceramics. 2019. Additive manufacturing of ceramics from preceramic polymers: A versatile stereolithographic approach assisted by thiol-ene click chemistry. Additive Manufacturing,27,

The topical literature lacks any comparison between stereolithography (SLA) and direct light processing (DLP) printing methods with regard to the accuracy of complete denture base fabrication, thereby utilizing materials certified for this purpose. In order to investigate this aspect, 15 denture bases were printed with SLA and DLP methods using three build angles: 0°, 45° and 90°. The dentures were digitalized using a laboratory scanner (D2000, 3Shape) and analyzed in analyzing software (Geomagic Control X, 3D systems). Differences between 3D datasets were measured using the root mean square (RMS) value for trueness and precision and mean and maximum deviations were obtained for each denture base. The data were statistically analyzed using two-way ANOVA and Tukey’s multiple comparison test. A heat map was generated to display the locations of the deviations within the intaglio surface. The overall tendency indicated that SLA denture bases had significantly higher trueness for most build angles compared to DLP (p < 0.001). The 90° build angle may provide the best trueness for both SLA and DLP. With regard to precision, statistically significant differences were found in the build angles only. Higher precision was revealed in the DLP angle of 0° in comparison to the 45° and 90° angles.

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In this study, high-resolution transmission electron microscopy (HRTEM) was employed to characterize the nanostructure of strontium-substituted hydroxyapatite (Sr-HA) and its evolution following in vitro immersion in physiological solutions. HRTEM images showed that the substitution of Sr induced local distortions in the hydroxyapatite (HA) lattice: minor levels of edge dislocations were detected at low doping contents of Sr ions (1 at %); when the Sr content exceeded 10 at%, the density of grain boundaries increased notably and triple junctions were clearly observed. The dissolution of undoped HA was initiated at crystallite surfaces, whereas the dissolution of Sr-HA started around grain boundaries. Acicular nanocrystal reprecipitation was observed on grain surfaces immersed in simulated body fluid (SBF), while not in dilute hydrochloric acid (HCl). These findings suggest appropriate levels of Sr incorporation can introduce imperfections in the crystal structure of apatite and thus enhance its dissolution rate towards enhanced physicochemical performance in biomedical applications.

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