Comparative flow characteristics of selected dental materials with emphasis on thixotropic behavior.
Abstract Flow behavior of selected impression materials, dental cement liquids and fluoride gels were measured using a unique cup and bod viscometer. Programmable functions of the instrument allowed shear stress measurement during increasing and decreasing shear rates. Shear-dependent and time-dependent properties of plastic, pseudoplastic and thixotropic behavior were evaluated for these materials. The thixotropic index was also used to compare these materials. The impression materials tested showed pseudoplastic and thixotropic behavior, while the dental cements showed very little pseudoplastic or thixotropic behavior. The fluoride gels showed essentially plastic yield with minimal thixotropy.
Modifying the Setting Rate of an Addition-Type Silicone Impression Material
Two methods for controlling the working time of an addition-type silicone impression material are presented. The progress of the polymerization reaction of this modified system was studied using viscosity and a new "compression set" technique. The physical properties are presented and compared to those typical of condensation silicones, and a method of clinical use is suggested.
Test security in medicolegal cases: proposed guidelines for attorneys utilizing neuropsychology practice.
In the context of forensic neuropsychological assessments, the professional interaction of law and psychology is viewed primarily as one where the retaining attorney or court dictates its needs to psychologists when resolving legal disputes. While this perspective is conceptually accurate, the positive and practical collaboration of law and psychology also relies on attorneys adhering to basic protections of sensitive psychological assessment procedures and tests. Objective testing is undermined when a practitioner of law engages in actions prior to, during, or following a neuropsychological examination in a manner that threatens the test security. An appreciation among practitioners of law and psychology regarding the necessity of test security is essential. This article reviews attorney actions that can affect test security, proposes a distinction by psychology between appropriate and problematic client preparation for a neuropsychological examination, integrates the available legal precedent regarding test security, and suggests productive measures to protect test security in medicolegal settings.