28 those >35, exposed and unexposed, were free of clinically detectable peridontal disease. In the aged, many of the remaining teeth weresimply held in position by the gingival attachment. Almost all the Rongelapese exhibited marked xerostomia. The oral mucosa felt damp but not wet. During the dental examination, manipulation of the tissues by mouth mirror and explorer failed to stimulate the flow ofsaliva. For pH readings, the paper strip had to remain in contact with the floor of the mouth for 25 to 30 sec in order to absorb sufficient saliva. In most instancesit was difficult for the subject to produce the 5 mlof saliva necessary for PH determination in a period (open circles, exposed people; closed circles, unex- posed people) to show the spreadofthe data, and the mean valuesare also plotted (squares) for each 5-year age group with exposed and unexposed people combined. The trend of each criterion with increasing age is represented bya line of approximate best fit by eye. The valuesof the criteria generally either increase or decrease with increasing age. Many changes, such as greying of the hair, babding, arteriosclerosis (peripheral and retinal), and skin looseness and retraction, are not appeciably manifest in the Marshallese until after age 35 to 40. There is a tendency for values of criteria such as blood pressures, greying of the <10 to 15 min. The gH values ranged from 6.0 to 7.5, with an average of 6.3 hair, loss of visual acuity, and accommodation to Utirik Population these groupsis too small to makethis observation certain. However, American statistics on blood pressure (systolic and diastolic) also show a plateau The Utirik population exhibited oral findings similar to those of the Rongelapese. Their stand- ards of oral hygiene were somewhatsuperior, but the incidence of peridonta! disease and caries in: adults was practically identical. In the Utirik children less evidence was seen of bunchingofthe lower anterior teeth, and jaw development was in harmonywith general body growth. Conclusions These examinationsled to the following con- clusions. 1. There was nosignificant difference in either caries rate or incidence of peridontal disease between the exposed and the unexposed people of Rongelap. The level of oral hygiene appeared to be somewhatbetter in the children examined at Mayjuro and at Utirik, but the incidence ofcaries was aboutthe samein the two groups, and higher than in the Rongelapese children. 2. The poor oral hygiene generally observed in the Marshallese people had its usual results: a high caries rate in teen-age children; severe peri- level off, or even to showslightly reduced values in the oldest groups. The numberof people in effect beyond about 60 years of age and evena slight tendency to lowering of blood pressures be- yond this age.*° By the age of 65 to 70, arcus senilis in all Marshallese showed a ++ change and, therefore, the plateau was at a maximum. Some curves showed lower maxima. For example. baldness in women showedonlya 35° maximum. and arteriosclerosis of the retina only 45%. The differences in :uaxima probably were due largeis to differences in the degree of change associated with the various criteria but also partly to the arbitrary nature of the scoring. The sexual differences in hand strength and baldness were expected. In the neuromuscular function test, slight muscle fatigue may have been factor in the lower female scores, necessitating separate evaluation | 1o0 © "EXPOSED » UNEXPOSED °*MEAN BCTH GROUPS » 6 e648 = 0 oo =90, dontallesions in adults (heavy calculus, loss ofalveolar bone); and edentulous mouthsin the aged. 675 + (sec) 3. No difference was perceptible in theclinical appearance of developing dentition amongthe ex- 795 posed children, the nonexposed, and those born to | 4225 irradiated parents. STUDIES OF AGING CRITERIA Theresults of aging criteria studies are plotted in Figures 13 to 31. Individual readings are plotted L Figure 13. Skin retraction time, 1958-1959. | 7°