AIM To evaluate the effects of a preflaring method on the determination of working length in the curved mesial canals of mandibular molars. MATERIALS AND METHODS Ninety mandibular molars with apical curvature of 30 to 40° were selected and randomly divided into two groups; each containing 45 teeth. In the first group, the initial instrumentation was performed with preflaring on the mesiobucca...

Cotton fibers arise through highly anisotropic expansion of a single seed epidermal cell. We obtained evidence that apical cell wall synthesis occurs through examining the tips of young elongating Gossypium hirsutum (Gh) and G. barbadense (Gb) fibers. We characterized two tip types in Gh fiber (hemisphere and tapered), each with distinct apical diameter, central vacuole location, and distributi...

The operation of the STM on metallic surfaces from the tunneling to the contact regime has been explored with a combination of first-principles total energy methods and a calculation of the electronic currents based on nonequilibrium Keldish-Green’s function techniques. Our calculations for the behavior of the total energy, forces, atomic relaxations, and currents for an Al tip on an Al(111) su...

BACKGROUND This in vitro study was conducted to compare the accuracy of two digital image receptors in identifying the location of tip of a fine endodontic file and radiographic apex in mandibular posterior teeth. METHODS Fourteen human cadaver mandibles with retained molars were selected. These molars were prepared for access to the canals and an endodontic file #10 was introduced into the c...

Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface...

A non-contact atomic force microscopy-based method has been used to map the static lateral forces exerted on an atomically sharp Pt/Ir probe tip by a graphite surface. With measurements carried out at low temperatures and in the attractive regime, where the atomic sharpness of the tip can be maintained over extended time periods, the method allows the quantification and directional analysis of ...