tion of endotoxin and surfactants. I. Physical and biological properties of endotoxin treated with sodium desoxycholate. J. Bacteriol. 92:1493-1509. 1966.-Endotoxins from three species of gram-negative bacteria were shown to be dissociated by the bile salt sodium deoxycholate (NaD) into nontoxic subunits with molecular weights of about 20,000. When the bile salt was removed by dialysis, the subunits reaggregated in an orderly manner to form a relatively uniform population of biologically active endotoxin particles with average molecular weights of 500,000 to 1,000,000. If a small amount of human plasma was added to the dissociated endotoxin before removal of the NaD, reassociation apparently did not occur and the preparation remained nonpyrogenic. However, the plasma protein could subsequently be removed from the endotoxin subunits, and reaggregation to the toxic form would then occur. The studies on the physical nature of endotoxin performed with biophysical solution techniques were supplemented and confirmed by direct examination of the endotoxin polymers by electron microscopy. The results of these studies were consonant with the theory that the biologically active endotoxic elements are composed of micellar aggregates of linear lipopolysaccharide subunits.

Little is known about changes in dental anxiety with ageing and their association with changes in oral health. This study examined the relationship between changes in dental caries experience and dental anxiety from 15 to 18 years of age among adolescent participants in the Dunedin Multidisciplinary Health and Development Study. Dental anxiety was estimated using the Corah Dental Anxiety Scale (DAS), and individuals with a DAS score of 13+ were identified as being dentally anxious. Dental examinations were performed on 649 individuals at ages 15 and 18, and a DMFS score was computed for each. Caries prevalence among those who were dentally anxious at both 15 and 18 years was significantly higher than for those who were not at either age. Regression analysis revealed that dental anxiety predicted caries incidence between ages 15 and 18 years. Dental anxiety is likely to be a significant predictor of dental caries experience, and may be a risk factor for dental caries incidence.

Over 1000 children, participating in a longitudinal study of health and development, possess documented medical histories based on birth records and regular assessments starting at age 3. A dental examination at age 5 of 923 participants recorded their exposure to fluoride and evidence of trauma to the deciduous teeth. The prevalence of developmental defects of dental enamel in 696 of the children when aged 9 was reported as 56% (Suckling et al., 1985). For the present study, a number of illnesses, accidents, and other experiences were selected from the recorded information as possible etiological factors for any defect, demarcated and diffuse opacities, and hypoplasia. Despite extensive statistical testing, positive and strong associations were few. The prevalence of hypoplasia, seen in 15% of the sample, was higher in those children who had chicken pox before age 3 and, as reported previously, in those children with a history of trauma to their deciduous incisors. This study illustrates the difficulty of establishing the etiology of enamel defects, even when medical and dental histories are available.

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