Differential Scanning Calorimetry (dsc) Analyses Of Esthetic Nickel-Titanium Wires As-Received And After Clinical Use

Introduction: The demand for esthetic orthodontics has increased rapidly over the past few decades, and much progress has been made in the development of esthetic clear and translucent brackets for labial orthodontics. However, the majority of wires used with these clear brackets are still the traditional alloys. Recently, American Orthodontics (Sheboygan, WI) and Opal (Ultradent; South Jordan, UT) have released epoxy resin coated nickel-titanium archwires that give a tooth-colored appearance. American Orthodontics has released EverWhite and Opal has released Via Pearl. The goal of this study was to compare the thermal properties of these new archwires with their uncoated counterparts before and after clinical use via differential scanning calorimetry (DSC). Materials and Methods: Four types of nickel-titanium orthodontic archwires were evaluated in this study. The four types consisted of two epoxy coated wires and two comparable control wires of the same .016 x 0.022 inch dimension. The transformation temperatures and phase transformations of these wires were determined in the as-received condition and after 4 to 12 weeks in the oral cavity by differential scanning calorimetry. In addition, the amount of coating lost for each coated archwire after clinical use was determined using a scanned image of the wire and matlab software. Results: There were no statistically significant differences in thermal properties when comparing archwires before and after clinical use. However, significant differences were observed between the as-received uncoated and coated counterparts from both manufacturers. Both wire types lost a significant amount of esthetic coating after use, but the Opal Via Pearl wire maintained significantly more coating compared to the EverWhite type. Conclusions: The significant differences between as-received uncoated and coated wires from the same manufacturer indicate that these wires may perform differently in clinical situations contrary to the manufacturers\u27 claims. In addition, improvements to the coating processes or alternative wires are needed to provide a more esthetic archwire with limited coating loss

The Closed Orbit Controllability Criterium

We prove that every closed "general" trajectory of the control system $\Sigma_M$ has an open neighborhood on which $\Sigma_M$ is controllable if 1) this orbit contains some point where the Lie algebra rank condition ($LARC$) is satisfied, and 2) the set of control vectors is "involved" at $q$. In particular, for the control systems $\Sigma_M$ on the compact connected manifold $M^n$ with an open control set this gives the following "Closed Orbit Controllability Criterium": The dynamical system $\Sigma_M$ of the considered type is controllable on $M^n$ if and only if for an arbitrary point $q$ of $M^n$ there exists a closed trajectory of the control system going through this point. We also present examples which show that our conditions are necessary.Comment: 16 pag

Gauge Transformations For Self/Anti-Self Charge Conjugate States

Gauge transformations of type-II spinors are considered in the Majorana-Ahluwalia construct for self/anti-self charge conjugate states. Some speculations on the relations of this model with the earlier ones are given.Comment: ReVTeX file, 7pp., accepted in "Acta Physica Polonica B

The Barut Second-Order Equation: Lagrangian, Dynamical Invariants and Interactions

The second-order equation in the (1/2,0)+(0,1/2) representation of the Lorentz group has been proposed by A. Barut in the 70s. It permits to explain the mass splitting of leptons (e,mu,tau). Recently, the interest has grown to this model (see, for instance, the papers by S. Kruglov and J. P. Vigier et al). We continue the research deriving the equation from the first principles, finding dynamical invariants for this model, investigating the influence of potential interactions.Comment: 8 pages, no figures. The talk given at the Int. Conf. on Clifford Algebras and Applications (ICCA7), Toulouse, France, May 19-29, 2005. To be published in the Proceeding