AIM To evaluate the effect of rotational speed and the angle and radius of curvature of root canals on the fracture of two types of nickel-titanium rotary instruments: K3 and ProTaper. METHODOLOGY A total of 240 root canals of extracted human maxillary and mandibular molars were divided into two groups of 120, according to the angle of the canal curvature (group A: <30 degrees, group B: >30 d...

Characteristic numbers of compact hyper-Kähler manifolds are expressed in graphtheoretical form, considering them as a special case of the curvature invariants introduced by L. Rozansky and E. Witten. The appropriate graphs are generated by “wheels,” and the recently proved Wheeling theorem is used to give a formula for the L 2-norm of the curvature of an irreducible hyper-Kähler manifold in te...

Using the visual search method, we show that stimuli that contain curvature discontinuities (i.e., points where the second derivative along an image contour is not defined) are easily found among stimuli containing only smooth changes in curvature. Curved stimuli that lack curvature discontinuities, however, are difficult to find among distractors that have them. These results suggest that the ...

Background and Aim: Maintaining the original central canal path during cleaning and shaping of the root canal system plays an important role in the success of endodontic treatment. This study sought to compare canal transportation and centering ability of WaveOne and SafeSider rotary files using cone-beam computed tomography (CBCT). Materials and Methods: This in-vitro, experimental study was ...

We find a unique torsion free Riemannian spin connection for the natural Killing metric on the quantum group Cq[SL2], using a recent frame bundle formulation. We find that its covariant Ricci curvature is essentially proportional to the metric (i.e. an Einstein space). We compute the Dirac operator D/ and find for q an odd r’th root of unity that its eigenvalues are given by q-integers [m]q for...

Cyclic fatigue of nickel-titanium, engine-driven instruments was studied by determining the effect of canal curvature and operating speed on the breakage of Lightspeed instruments. A new method of canal curvature evaluation that addressed both angle and abruptness of curvature was introduced. Canal curvature was simulated by constructing six curved stainless-steel guide tubes with angles of cur...

The aim of the present study was to compare the root canal preparation ability of rotary nickel-titanium (NiTi) Hero 642 and K3 files in curved mandibular or maxillary molars. A total of 40 extracted mandibular molars with two separate mesial canals, an apical width of approximately size ≤15 and a root canal curvature of 15-30° were randomly divided into two groups and instrumented using Hero 6...

INTRODUCTION This study evaluated the working length (WL) modification after instrumentation with WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) reciprocating files and the incidence of overinstrumentation in relation to the initial WL. METHODS Thirty-two root canals of permanent teeth were used. The angles of curvature of the canals were calculated on digital radiographs. The ...