A three-dimensional evaluation of the effects of functional occlusal forces on the morphology of dental and periodontal tissues of the rat incisor.

We examined the effect of function on tooth and periodontal ligament (PDL) morphology in 40 lower incisors of adult female rats. Ten teeth were exposed to occlusal hyperfunction for three months, ten to hypofunction for three weeks, ten to hypofunction for three months, while ten teeth in normal occlusion served as control. Transverse ground sections were cut at various levels perpendicular to the tooth long axis, and their distances from the apex were calculated. The outlines of the tissues were traced and fed into a computer. We plotted the measurements according to their location and fitted them by second-order polynomials. We calculated tissue volume for the proximal 18 mm of bone-embedded tooth. Hyperfunction affected tooth shape, in that it became more rounded. The volumes of the dental tissues remained unchanged, while width and volume of the cementum-bordering PDL increased. Hypofunction did not alter tooth shape, but influenced its size: After three weeks, tooth circumference decreased, and after three months, it expanded. Dentin width was reduced, with concomitant increase of pulp size. The amount of enamel diminished initially, but after three months returned to normal values. The PDL bordering enamel expanded proportionally to the duration of hypofunction. The changes in socket size reflected the total dimensional variations in the tooth and its PDL. The results demonstrate that the shape and size of growing teeth and their periodontium are influenced by functional occlusal forces.

Terrorist bombing experience during 1975-79. Casualties admitted to the Shaare Zedek Medical Center.

During a period of 4 1/2 yr, 24 terrorist explosions occurred in Jerusalem. Of the 511 casualties, 340 were evacuated to the Department of Emergency in our hospital. A total of 272 admissions were graded by the "Injury Severity Score" (1), with a breakdown into light injuries (87%), medium (3%) and severe (10%). The high proportion of light injuries may be explained by the evacuation of all casualties to the nearest hospital without on-site triage. Injuries to the head and neck comprised 19.3%, and to the extremities 39% of all injuries.