Fracture Resistance of Zirconia Abutments with or without a Titanium Base: An In Vitro Study for Tapered Conical Connection Implants

Dental implants with tapered conical connections are often combined with zirconia abutments for esthetics; however, the effect of the titanium base on the implant components remains unclear. This study evaluated the effects of a titanium base on the fracture resistance of zirconia abutments and damage to the tapered conical connection implants. Zirconia (Z) and titanium base zirconia (ZT) abutments were fastened to Nobel Biocare (NB) implants and Straumann (ST) implants and subjected to static load testing according to ISO 14801:2016. The experiments were performed with 3 mm of the platform exposed (P3) and no platform exposed (P0). The fracture loads were statistically greater in the titanium base abutments than the zirconia abutments for the NB and ST specimens in the P0 condition. In the P3 condition of the ST specimens, the deformation volume of the ZT group was significantly greater than the Z group. The titanium base increased the fracture resistance of the zirconia abutments. Additionally, the titanium base caused more deformation in the P3 condition. The implant joint design may also affect the amount of damage to the implants when under a load. The mechanical properties of the abutment should be considered when selecting a clinical design

Dynamic interactions in the l-lactate oxidase active site facilitate substrate binding at pH4.5

The crystal structure of l-lactate oxidase in complex with l-lactate was solved at a 1.33 Å resolution. The electron density of the bound l-lactate was clearly shown and comparisons of the free form and substrate bound complexes demonstrated that l-lactate was bound to the FMN and an additional active site within the enzyme complex. l-lactate interacted with the related side chains, which play an important role in enzymatic catalysis and especially the coupled movement of H265 and D174, which may be essential to activity. These observations not only reveal the enzymatic mechanism for l-lactate binding but also demonstrate the dynamic motion of these enzyme structures in response to substrate binding and enzymatic reaction progression

Crystallization and preliminary X-ray diffraction study of l-lactate oxidase (LOX), R181M mutant, from Aerococcus viridans

An X-ray crystallographic study of a LOX mutant in which Arg181 is replaced by Met was initiated in order to understand the functions of the conserved amino-acid residues around the FMN in the enzyme active site. LOX-R181M crystals belong to the tetragonal space group I422, with unit-cell parameters a = b = 192.632, c = 200.263 Å, α = β = γ = 90°