The mean strength that has traditionally been taken as a measurement of the strength of a material does not reflect the true strength, and therefore it cannot be used as a design parameter. This explains why many brittle materials fail at unpredictable stress, either below or above the mean strength. By using Weibull statistics, the prediction and assessment of strength can be made more sensibly. The performance of a material can be predicted by considering a stress at a lower level of failure probability.
Histiocytosis X is a rare disorder with no particular predilection for race, age or sex. Since its discovery by Hand in 1893, the etiology has remained unknown, although viruses, bacteria and genetic factors have been implicated. Familial occurrence of this disease is very rare, and only a handful of such cases have been reported. The present study adds further evidence to support the influence of genetic factors in the etiology of histiocytosis X.
Two cases of either peripheral odontogenic fibroma (POF) (WHO type) or peripheral ameloblastoma are reported. Their immunohistochemical characteristics were investigated in an attempt to clarify their histogenesis. The results showed that the epithelial component of this neoplasm tended to retain its distinct odontogenic character and expressed a keratin profile different from that of the overlying oral epithelium from which both cases most probably originated. The connective tissue element of these tumors was vimentin-positive and S-100 protein negative, confirming their mesodermal nature but precluding the possibility of ectomesenchymal derivation. No reactivity for desmin was noted.
A cross-sectional exploratory survey was conducted in six West Malaysian schools involving 762 fifteen- to eighteen-year-old secondary school students. Periodontal health status was assessed using the Community Periodontal Index of Treatment Needs (CPITN), utilizing six index teeth to represent the six sextants of the mouth. The results indicated that 66.8% of the students examined had healthy gingiva (Score 0), 2.6% had bleeding of the gingiva on gentle probing, while 30.6% had calculus on their teeth. In terms of treatment needs, 35.0% of those examined needed oral hygiene education, 34.4%, on the other hand, required scaling. No student was found to require complex treatment. Sex-specific comparison revealed a slightly higher prevalence of calculus formation in male students. In terms of race, the Malays had a higher prevalence of calculus formation than either Chinese or Indians.
A survey of 303 six- to fifteen-year-old Proto-Malay children was carried out in Selangor, West Malaysia. The examinations were carried out using a chair-table and natural daylight. Periodontal status was assessed using the Community Periodontal Index of Treatment Needs (CPITN). The findings revealed a generally low prevalence of periodontal disease affecting only 25.08% of the sample examined. Of these, 15.72% were found to have a score of 1 (bleeding of the gingiva), while 9.36% had calculus on the tooth surface. In terms of treatment needs, 24.75% required dental health education. The relationship between these findings and the possible causes are discussed.