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In situ cariogenicity-testing models must show evidence of compliance with valid clinical parameters, and this has been achieved with respect to pyrophosphate-, monofluorophosphate-, and zinc citrate trihydrate-containing dentifrices, where earlier in vitro studies failed to predict clinical efficacy. Parameters for validity testing should include the use of enamel fluoride uptake, plaque and/or saliva fluoride assessments, re-/demineralization assays of appliance-borne enamel slabs or slices, and plaque microbial, biochemical, and pH studies. Model reliability must be capable of withstanding repeat calibration experiments where the dosage, frequency of application, and/or duration of exposure to a new product may be varied. Furthermore, the number of enamel slabs/slices carried per appliance (and the number of artificial caries lesions per enamel insert) requires to be defined. Such studies should be repeated, but whether in the same or different subjects, or with or without cross-over, has to be determined. However, the capability of reproducing a clinically proven dose-response is essential. Models must be sensitive enough to detect changes in any test product F concentration, but only equivalence claims should be permitted. Thus, superiority cannot be established, since accuracy may not be assumed beyond the upward limits of a clinically validated range. Finally, models should not be so exclusive in design as to preclude independent verification of their findings. more...

The hypotheses to be tested were: (i) that chewing sugar-free gum frequently and for long periods would be associated with higher amounts of supragingival calculus, and (ii) that there would be no site-specificity of calculus deposition on the lingual surfaces of the 6 lower anterior teeth. Subjects, 436 in Glasgow and 191 in Winnipeg, were scored for calculus at mesial, lingual, and distal sites on the lingual surface of each of the 6 lower anterior teeth, by the Volpe-Manhold method. They also answered questions on the time since the last prophylaxis, the frequency of gum chewing, the type of gum chewed, and the length of a typical gum-chewing episode. A subset (233) of the Glasgow subjects were scaled and re-scored for calculus 3 months later. When the data for the logarithmic transformations of the initial calculus scores were subjected to stepwise multiple-regression analysis, the only factor which correlated significantly with initial calculus scores in both cities was the time since the last prophylaxis. In the Glasgow subjects scored 3 months after a prophylaxis, there was a negative correlation between chewing sugar-free gum and calculus scores, whereas in the Winnipeg subjects, age and the chewing of sucrose-containing and sugar-free gum were positively correlated with calculus scores. Thus, the results were contradictory with respect to the first-tested hypothesis. The calculus distribution patterns were very similar in the subset of Glasgow subjects and the Winnipeg subjects, with the amounts on the lateral incisors and canines averaging 70.2% and 44.5%, respectively, of those on the central incisors. Thus, the second hypothesis was disproved. more...

Erupting first permanent molars of 5 1/2 to 6 1/2 year-olds are eminently suited for the clinical testing of potential caries-inhibiting techniques. Due to the rapid onset of caries in these teeth, accurate monitoring of new materials/regimes can be instituted and meaningful data obtained within one year of trial commencement. In addition, by concentrating on this age-group and by also stratifying for socio-economic status, deciduous caries experience and three-month wide age-bands, different trials' data can be readily compared. A further benefit is that these most caries-prone teeth can be protected thus saving the need for block injections in young subjects and alleviating later orthodontic problems. more...