Notes

MATERIALS AND METHODS: A total of 88 maxillary first molar denture teeth were evaluated: C (Classic; Dentsply Sirona, York, PA), DCL (SR Postaris DCL; Ivoclar Vivadent, Schaan, Liechtenstein), IPN (Portrait IPN; Dentsply Sirona, York, PA), and F (Denture Teeth A2 Resin 1 L; Formlabs, Somerville, MA)
The 3D printed denture tooth specimens were fabricated from a methacrylate-based photopolymerizing resin using stereolithography (SLA). Denture teeth were subjected to a three-body wear test with a poly(methylmethacrylate) (PMMA) abrasive slurry. A Leinfelder-style four station wear apparatus with custom bullet-shaped milled zirconia styli was utilized with a load force of 36-40 N at 1 Hz for 200,000 cycles. Maximum depth of wear was measured using a lab grade scanner and analyzing software program. Data were analyzed using a one-way ANOVA followed by the Tukey's Multiple Comparisons post hoc test (α = 05).RESULTS: A statistically significant difference in depth of wear was found between denture tooth materials (p < 001).

The mean vertical depth of wear for the 3D printed denture teeth (016 ± 010 mm) was statistically significantly less than the prefabricated denture teeth. The highly cross-linked denture teeth, DCL (036 ± 011 mm) and IPN (035 ± 014 mm), exhibited statistically significantly less wear than the conventional acrylic denture teeth. The conventional acrylic denture teeth demonstrated the greatest wear (058 ± 014 mm). No significant difference in depth of wear was found between CONCLUSIONS: Denture tooth material significantly influences the depth of wear. The 3D printed denture teeth demonstrated superior wear resistance compared to the commercially available prefabricated denture teeth when opposed to zirconia. Denture teeth fabricated with SLA technology may have a promising future in Oxygen, sulfur and selenium terminated single-walled heterocyclic carbon nanobelts (SWHNBs) as potential 3D organic semiconductors.Carbon nanomaterials such as polyaromatic hydrocarbons (PAHs), graphene, fullerenes and nanotubes are on the frontline of materials research due to their excellent physical properties, which in recent years, have started to compete with conventional inorganic materials in charge transfer based applications.

Recently, a variety of new structures such as single-walled carbon nanobelts (SWCNBs) have been conceived, however, to date only one 'all-phenyl' example has been synthesised, due to problems with their stability and the challenging synthetic methodologies required. This study introduces a new class of phenacene-based SWCNBs and their chalcogenide derivatives, forming the new sub-class of single-walled heterocyclic carbon nanobelts (SWHNBs) which are expected to be both more stable and easier to synthesise than the all carbon analogues. Subsequent theoretical examination of the structure-property relationships found that unlike the small-molecule acene homologues (tetracene, pentacene etc.) which become more reactive with addition of oxygen, an increase in the molecular size of the SWCNBs actually stabilises the HOMO energy level, in correlation with the increasingly negative nuclear independent chemical shift (NICS) calculations of their cylindrical aromaticities. The FMO energies of the phenacene SWCNBs are similar to that of the nanobelt reported by Itami and co-workers, but those of the SWHNBs are deeper and thus more stable. The sulfur derivative of one SWHNB was found to give hole-charge transfer mobilities as high as 12 cm2 V-1 s-1, which is three orders of magnitude larger than the corresponding unsubstituted SWCNB (3 × 10-3 cm2 V-1 s-1). Seebio Photolyzable Acid Precursor suggest the candidates are air-stable and potentially high-performing organic semiconductors for organic thin film transistor (OTFT) devices, while the structure-property relationships uncovered here will aid the design and synthesis of future three-dimensional organic nanomaterials.

Structural insight into a CE15 esterase from the marine bacterial metagenome.The family 15 carbohydrate esterase (CE15) MZ0003, which derives from a marine Arctic metagenome, has a broader substrate scope than other members of this family. Here we report the crystal structure of MZ0003, which reveals that residues comprising the catalytic triad differ from previously-characterized fungal homologs, and resolves three large loop regions that are unique to this bacterial sub-clade. The catalytic triad of the bacterial CE15, which includes Asp 332 as its third member, closely resembles that of family 1 carbohydrate esterases (CE1), despite the overall lower structural similarity with members of this family. Two of the three loop regions form a subdomain that deepens the active site pocket and includes several basic residues that contribute to the high positive charge surrounding the active site. Docking simulations predict specific interactions with the sugar moiety of glucuronic-acid substrates, and with aromatically-substituted derivatives that serve as model compounds for the lignin-carbohydrate complex of plant cell walls. Molecular dynamics simulations indicate considerable flexibility of the sub-domain in the substrate-bound form, suggesting plasticity to accommodate different substrates is possible.

The findings from this first reported structure of a bacterial member of the CE15 family provide insight into the basis of its broader substrate specificity.
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