Dose response relationships for acute ionizing-radiation lethality.

A review and analysis of the dose response relationship for the probability of acute lethality from prompt or short-term exposure to ionizing radiation is presented. The purpose of this analysis is to provide recommendations concerning estimates of casualties expected from radiation accidents, the use of nuclear weapons, or possible terrorist activities. Previous work on acute ionizing radiation-induced lethality risk together with a collection of dose response relationships are analyzed and presented based on historical case data and expert opinion that have evolved from whole-body radiation therapy experience, radiation exposure accidents, nuclear weapon detonations, and animal experimentation. The nature of the data reviewed ranges from direct individual events to those offered according to collective expert opinion and consensus published as journal articles and in various technical documents and reports. The dose response relationships are expressed as two-parameter (median exposure level and slope) probability distribution models as a function of radiation exposure in terms of a free-in-air dose. Twelve different dose response relationships are presented and discussed, including the impact of some medical care.

Orthodontists' perceptions of the impact of phase 1 treatment for Class II malocclusion on phase 2 needs.

The most appropriate timing for the treatment of Class II malocclusions is controversial. Some clinicians advocate starting a first phase in the mixed dentition, followed by a phase 2 in the permanent dentition. Others see no clear advantage to that approach and recommend that the entire treatment be done in the late mixed or early permanent dentition. This study examines how orthodontists, blinded to treatment approach, perceive the impact of phase 1 treatment on phase 2 needs. The sample consisted of 242 Class II subjects, aged 10 to 15, who had completed phase 1 or observation in a randomized clinical trial (RCT). For each subject, video orthodontic records, a questionnaire, a fact sheet, and a cephalometric tracing were sent to five randomly selected reviewing orthodontists blinded to subject group and study purpose. Reviewing orthodontists were asked to assess treatment need, general approach, need for extractions, priority, difficulty, and determinants. Orthodontists agreed highly on treatment need (95%) and moderately on treatment approach (84%) and extraction need (80%). They did not perceive differences in need, approach, or extractions between treated and control groups. Treated subjects were judged as less difficult (p = 0.0001) and to have a lower treatment priority (p = 0.0001) than controls. In ranking problems that affect treatment decisions, the orthodontists ranked dental Class II (p = 0.005) and skeletal relationships (p = 0.004) more highly in control than in treated patients. These data indicate that orthodontists do not perceive phase 1 treatment for Class II as preventing the need for a second phase or as offering any particular advantage with respect to preventing the need for extractions or other skeletal treatments in that second phase. They do view early Class II treatment as an effective means of reducing the difficulty of and priority for phase 2.