Biomedical subjects
B de Liefde
Publications and source records attributed to B de Liefde.
The decline of caries in New Zealand over the past 40 years.
In New Zealand, as elsewhere, caries prevalence has declined since the 1950s; this has been accompanied by a change in the intra-oral pattern of the disease. This is illustrated by analysis of data for 12-year-old children. However, because treatment services for children in New Zealand are so comprehensive, the DMF index is primarily a count of restorations placed. This treatment overlay can distort the true caries prevalence and has been a confounding factor in assessment of the change in caries over time. Measurement of the fine gradations of ongoing change in the present low-caries-prevalence population requires the use of a more sensitive indicator than the DMF indices. When the timing of various forms of fluoride supplementation is correlated with the decline in caries, the decline continues beyond the time of maximum population coverage with fluoridated water and fluoridated toothpaste. Thus an explanation of the convergance of caries prevalence in fluoridated and non-fluoridated areas since the 1970s may require a re-assessment of the fluoride effect. This convergence, and the overall decline during the last decade without known additional fluoride supplementation, suggest that factors other than fluoride, such as food additives and antibiotics, may have contributed.
The prevalence of development defects of enamel and dental caries in New Zealand children receiving differing fluoride supplementation, in 1982 and 1985.
Seven hundred and twenty-seven 9-year-old children resident in Hawke's Bay were examined in 1985, 3 years after a baseline survey of a cohort of the same age group. Children were allocated to one of four fluoride-history groups on the basis of the responses of parents to a questionnaire, which also gave information on infant feeding and household water source. Examination conditions were duplicated, and children were examined by the same examiner using a modification of the DDE Index. The prevalence of diffuse defects in the low fluoride (LF) group (24.3 percent) was lower (P less than 0.001) than in the fluoridated water (WF) group (50.8 percent), the PT group who had used tablets to 5 to 6 years of age (53.1 percent), and the CT group who had used tablets continuously (54.7 percent). There were 2.9 percent of children with contralateral pairs of teeth with diffuse opacities in the LF group compared with 22.9 percent in the WF group, 18.7 percent in the PT group, and 36.0 percent in the CT group. For European children, 9.7 percent had post-eruptive defect sub-types. Defect prevalence could not be related to infant feeding or water source in unfluoridated areas. There had been a significant increase in the prevalence of diffuse defects in the WF, PT, and CT groups, but not the LF group since the baseline survey. There was also an increase in the numbers of children considered to have an unsatisfactory appearance due to either continuous or diffuse opacities--from none in 1982, to 24 (3.7 percent) in 1985. In the 3 years since the baseline survey there had been considerable reductions in the caries prevalence in all groups (P less than 0.001).
Identification and preventive care of high caries-risk children: a longitudinal study.
A method of identifying high caries-experience children to participate in a mouthrinsing programme was tested. Children aged 9 to 12 years were assigned into high and low caries-risk groups using caries experience in the deciduous dentition and a clinical lesion on the occlusal surface of a first permanent molar within 2 years of eruption as indicators of risk. There were 273 high caries-risk children (101 in the fluoride rinse group, F, and 172 in the placebo rinse group, P); in the low caries-risk group, L, there were 648 children. After 5 years there were differences in the caries experience in the permanent dentition of the high and low caries-risk groups P and L. The high caries-risk group P had mean DMFT and DMFS scores of 2.7 and 3.2 respectively compared with 0.4 for both indices for the low caries-risk group, L. Most lesions occurred on occlusal surfaces. Caries experience was accurately predicted for 87 percent of the children when a DMFT score equal to or greater than 3 was used as the criterion of high caries experience. Accuracy was greater for the low caries-risk group (96 percent) than for the high caries-risk group (51 percent). Similarly the proportion of low caries-experience children identified in the low caries-risk group was greater than the proportion correctly identified in the high caries-risk group. When a DMFS score equal to or greater than 4 was used, there was little change. This method of prediction provided a practical method of identifying groups of children in need of special preventive care. Fortnightly mouthrinsing with 0.2 percent sodium fluoride solution was tested as a preventive measure for half the high caries-risk children (group F); the control group, P, used a placebo rinse. There were no significant differences in the caries scores of the two groups at the end of the study. Mouthrinsing was an ineffective preventive measure for high caries-risk children in this study.
Longitudinal survey of enamel defects in a cohort of New Zealand children.
Enamel defects are being used increasingly to monitor fluoride use. In New Zealand in 1982 a survey of the prevalence of enamel defects in 9-yr-old children was carried out. Children who had enamel defects on the labial surfaces of their maxillary incisors were re-examined after 3 yr together with an equal number of children without defects. The same examiner using the same examination methods and the DDE index carried out both examinations but at the second examination was unaware of the results for individual children at the first examination. There was little difference in the group prevalence of the main defect categories except for the tooth prevalence of hypoplasia. There was an increase in discolouration and hypoplasia occurring in combination with diffuse fluoride-related opacities. There was no evidence that defects had faded with time. This longitudinal survey showed that some increase in defect severity occurred over a relatively short time span in initially mild defects. In some children these changes were sufficient to cause a deterioration in tooth appearance. Age and tooth specific enamel defect data are necessary in surveys monitoring the public health use of fluoride since posteruptive changes can affect prevalence and severity.
Dental care and health outcome in the Dental Benefit Scheme.
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Prevalence of hepatitis B among school dental nurses.
A survey of hepatitis B serological markers and associated risk factors was carried out among school dental nurses in 1985. A postal questionnaire provided information on demography, years worked and residential history from birth to 10 years of age. A blood sample was provided by 1015 subjects (95% response). All sera were tested for HBsAg, anti-HBs and anti-HBc, and HBsAg positive sera for HBeAg and anti-HBe. Twenty-three percent of subjects were both anti-HBs and anti-HBc positive, 2% were anti-HBs positive and 3% anti-HBc positive only. Less than 1% were HBsAg positive. Prevalence varied with geographic area--40% in the north and east of the North Island, 25% in the south and west of the North Island and 5% in the South Island. There was a linear increase in marker prevalence with age group in subjects under 45 years. Only in the north and east of the North Island was there a relationship (inverse) between the proportion of Europeans treated and marker prevalence. Childhood residence had little effect on prevalence (p less than 0.001). The results suggest that infection occurred during adult life, whether as a result of occupation or area of residence cannot be determined without a control group.
A study of the chemical treatment of early caries of occlusal pits and fissures.
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Prevalence of developmental defects of enamel and dental caries in New Zealand children receiving differing fluoride supplementation.
A survey of the prevalence of dental caries and developmental enamel defects in 666 New Zealand children aged 9 years and with differing histories of fluoride supplementation was carried out in 1982. In the LF (low fluoride) group 22.8% of children had diffuse white opacities compared with the WF (water fluoridation) group, 36.7%, and the CT (continuous use of fluoride tablets) group 49.4% (P = 0.0018). When the tooth prevalence was determined, the differences were more marked with 4.9% of teeth affected in the LF group and 24.7% in the CT group. Dental caries prevalence in the fluoride history groups displayed an inverse relationship with fluoride supplementation, the LF group had a DMFT of 2.4, the WF group, 1.7 and the CT group, 1.2. The prevalence of both diffuse opacities and of dental caries in the PT group where tablets had been used to 5-6 yr of age was anomalous. The survey confirmed that diffuse opacities occur in children with a low fluoride intake but the prevalence increases in groups of children given fluoride supplements.
Evaluation in dental public health in New Zealand.
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The dental care of pregnant women.
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Identification of high-caries-risk children.
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Dental caries: diagnosis and treatment planning.
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Painless dentistry and prevention.
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