Dissertation--Marburg (Ad novi prorectoris inaugurationem). / Bibliographical foot-notes.

Thesis (Ph. D.)--University of Queensland, 2003. / Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains vi, 38 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 35-37).

Delayed diagnosis of dental anomalies in the permanent dentition can lead to severe occlusal, functional and aesthetic problems. Early diagnosis is not feasible in the primary dentition stage without screening radiography, which is controversial due to possible mutagenic effects. However, some dental anomalies in the primary dentition of Caucasians have been found to be followed by anomalies of the permanent successors. Therefore, identifying individuals at high risk of having anomalies of their permanent teeth by screening children for dental anomalies in the primary dentition, will facilitate early diagnosis and appropriate treatment. The objectives of this study were to determine the prevalence of dental anomalies in the primary dentition of a southern Chinese child population, and to investigate the relationship between the presence of a talon cusp, missing or supernumerary tooth in the primary dentition and the number of the permanent successor teeth. A total of 1513 children from 12 kindergartens were invited to participate in the prevalence study. School children visiting a regional school dental clinic during a four-year period and having talon cusp, supernumerary tooth or congenitally missing tooth in the primary dentition were included in the study to determine the relationship to the permanent successors. A total of 1333 children, aged from 2 years 11 months to 5 years 5 months (mean age 4 years 4 months) were included in the prevalence study. The prevalence of the commonest dental anomaly, double tooth, was 4.28%. Almost 95% of which were in the mandibular anterior region; one third of the double teeth involved the central and lateral incisors while the other two-thirds involved a lateral incisor and canine. The prevalence of congenitally missing teeth was 3.53%; all but one were mandibular incisors, the majority of which were lateral incisors. Girls were affected twice as often as boys. Both talon cusp and a supernumerary tooth occurred rarely (0.15%) and they were only found in the maxillary incisor region. A study of 57 cases of talon cusp on primary maxillary incisors showed that, when there was a talon cusp on the lateral incisor, 78.3% of the permanent successors exhibited odontogenic abnormalities; mostly in the form of supernumerary teeth. However, a talon cusp on a maxillary central incisor had no effect on the permanent successor. A study of 30 children with supernumerary primary teeth revealed that half of the children with supernumerary primary maxillary lateral incisors also had supernumerary permanent successors. A further study of 182 children with missing primary mandibular incisors showed that normal permanent successors were present in 50% of the cases with missing central incisors but only 8.5% of cases with missing lateral incisors. The prevalence of dental anomalies in the primary dentition of a local southern Chinese population differed from that of Caucasians. Children with talon cusp on primary maxillary lateral incisors, missing mandibular incisors and supernumerary maxillary lateral incisors were found to be at high risk of having an odontogenic abnormality in the permanent dentition. Clinicians should be aware of these anomalies and prepared to implement appropriate treatment. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

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Several investigators have suggested that "upper" neural tube defects (NTD's)--anencephaly, encephalocele, and thoracic spina bifida--are etiologically different from "lower" NTD's (lumbo-sacral spina bifida). This hypothesis was primarily based on the observations that the two types have different sex ratios and recurrence rates and that the NTD cases within one sibship are concordant for NTD type. In order to test this, the above figures were calculated in a sample of NTD probands from Montreal and Newfoundland. The findings were not consistent with the hypothesis. However, a previously unreported finding was observed: the frequency of twinning was significantly higher in the near relatives of upper NTD probands than in those of lower NTD probands or of controls. This curious association between upper NTD's and twinning may be explained by a familial factor predisposing to a delay early in development. This delay could also explain any differences observed in upper and lower NTD groups.

The purpose of this research was to examine four selected human population groups, institutionalized and normal, to determine the prevalence of the 47, XYY chromosome abnormality among adult males.

No description available.