|dc.description.abstract||The investigations described in this thesis originated from my experiences in treating periodontal disease in mentally retarded patients at the Levin Hospital and Training School. This is a hospital of the Division of Mental Health and has approximately 800 patients in permanent residence. In 1957 when I was appointed as the first dental officer, there were 450 patients. At that time the general standard of dental health was poor, and although a few parents had private arrangements for their children to be treated by local dentists, the majority were receiving emergency dental treatment only. Many patients had ulcerated, bleeding gingivae and heavy deposits of calculus and debris. The periodontal condition of the mongoloid patients appeared to be worse than that of the non-mongoloids – indeed several mongoloid children under 10 years of age had lower permanent incisors exfoliated because of advanced periodontal disease.
With regular dental care and improved oral hygiene, the periodontal health of both mongoloid and non-mongoloid patients improved, but a greater susceptibility of the mongoloid children to severe periodontal disease was still apparent. Periodontal disease in mongoloids has been described in several reports, but the full natural history and the aetiology of the condition is not known. The reasons for this susceptibility are of considerable importance, not only in prevention and treatment of the condition in mongoloid subjects, but also by adding to the knowledge of the aetiology of periodontal disease in general.
The purpose of the investigation was to obtain a fuller understanding of the nature of the condition, to add to the knowledge of its natural history, and to investigate some of the factors which might account for its severity.
Three investigations are described. A cross-sectional study compares the prevalence and severity of periodontal disease in mongoloid and non-mongoloid retarded subjects living under similar hospital conditions. A longitudinal study of periodontal disease in mongoloid subjects follows. This includes results of periodontal examinations made at 4-monthly intervals over a 2-year period, and describes changes in individual subjects over periods of from 2 to 5 years. Six case histories are presented in detail, and because of their bulk are in Volume 2.
Periodontal disease was observed clinically to be particularly severe in the lower incisor region of mongoloid subjects and it was noted that the roots of the mongoloid lower incisor teeth were often short. Comparisons of the root lengths, root/crown ratios, and the shapes of the crowns (crown height and the ratio of the labia-lingual/mesio-distal dimensions) of lower incisor teeth of mongoloid, non-mongoloid retarded and normal subjects were therefore made.
A toothbrushing study was also conducted, my assistant and I brushing daily the teeth of an experimental group of mongoloid subjects. However as the results were inconclusive, this study is not included. Other studies, carried out in association with the Dental Research Unit, Medical Research Council of New Zealand, are described in the review of the literature, and are placed in the Appendix as Supplementary Papers.
The thesis is divided into review of the literature, methods, results and discussion. Small tables and figures are inserted into the text where possible, but the larger tables are placed in the Appendix. Such tables and figures are identified in the text by an -A following the table or figure number.
Throughout the thesis the term mongolism is used and a person with this condition is described as a mongoloid subject, or for simplicity, a mongoloid. Other names such as Down's syndrome, trisomy 21 and trisomy G are synonymous with mongolism, but as none of these terms is in universal usage, my preference remains with the long-accepted term mongolism. A non-mongoloid subject refers in the thesis to a person mentally retarded for reasons other than mongolism.
These investigations were carried out in addition to my normal duties as dental officer at the hospital and Principal Dental Officer (Psychopaedic) in the Department of Health. Because of limitations of time, my research was confined to studies which could readily be combined with my clinical and administrative duties. However the need for further research into periodontal disease in mongoloid subjects, particularly into the anatomical, histological, and biochemical aspects of the condition, is fully recognized.||en_NZ