Methods and models to study nickel–titanium instruments
Over the past two decades, nickel–titanium (NiTi) instruments have become an important part of the armamentarium for root canal treatment. They are increasingly used by generalists and specialists to facilitate the cleaning and shaping of root canals. Despite the advertising claims of superiority of design for some NiTi rotary systems, few have been supported by objective well-designed studies in the literature. A variety of experiments with different models and methods have been developed for studying the properties of NiTi instruments and how they fulfil these mechanical goals. One of the main issues is how to make a rational choice for the best study model that is relevant. This article aims to present an overview of those methods and devices that have been used in endodontic literature for studying NiTi files.
The dependence of the differential cross section ${\mathrm{d}\sigma}/{\mathrm{d}p_{\perp}}$ of inclusive heavy quark production in pp and $\bar{\mathrm{p}}$p collisions on the renormalization and factorization scales is investigated. The implications of our results for experiments at TEVATRON and LHC are discussed. In particular, it is shown that the NLO QCD predictions for $\bar{t}t$ production at the LHC based on the Principle of Minimal Sensitivity are by 30-50% higher than the standard ones.