J. Soc. Cosmetic Chemists 18 473-491 (1967) ¸ 1967 Soctety of Cosmetic Chemists of Great Britain The laboratory evaluation prophylactic dentifrices of W. H. BULL* Presented at the Symposium on "Product Testing", organised by the Society of Cosmetic Chemists of Great Britain in Eastbourne, Sussex, on 14th November, 1966 $]/nop$1$--The need for laboratory methods of assessing dental prophylactic products is discussed and a review of some of the methods used to evaluate fluorine containing tooth- pastes given. The techniques mentioned include in vitro and in vivo solubility studies using chemical, physical and electron microscopical techniques to evaluate the action of the pro- ducts. The advantages of establishing in vitro methods which do not depend directly on acid solubility, e.g. some form of artificial mouth, are explained. INTRODUCTION From writings which have survived from the Ancient World it is apparent that dental products designed to care for teeth have been made by man from earliest times. In Chinese and Indian records of ca. 3000 B.C. and in Egyptian manuscripts of ca. 1500 B.C. there are references to dental topics including anatomy, treatments with drugs and by acupuncture, dentifrices, etc. The Romans were also versed in such matters and Pliny records the formula for a dentifrice which includes the ashes of oxen hooves, myrrh, burned eggshells, pumice, etc. The formulator of today may not recognise all of these as ingredients which he might want to use in tooth- paste but such a mixture is likely to have an abrasive, and therefore clean- ing, action on teeth. That cleaning the teeth is desirable for other than social reasons has been shown by Fosdick (1) and Mansbridge (2) who found that children about 12-14 years of age, practising good oral hygiene, i.e. *UnileVer Research Laboratory, Isleworth, Middlesex. 473

474 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS regular tooth brushing, experienced a lower caries incidence than those with poor habits in this respect. The greatest contribution so far made by manufacturers of dental products has been to provide the public with toothbrushes and dentifrices which are reasonably efficient and pleasant to use. However, with increase in knowledge and in sophistication additional attributes, such as sweet breath, healthy gums and freedom from caries, have been claimed. These have been based, usually, upon some scientific fact or hypothesis but their efficiency has not necessarily, in the past, been proved rigorously. A genuine desire on the part of the manufacturer to make his product as effective as possible and the explicit demand of bodies such as the Indepen- dent Television Authority that his claims be related to user experience has resulted in industrial organisations undertaking in vitro and in vivo studies on problems of oral health and hygiene. The only satisfactory method for testing products designed to improve dental health is a clinical trial. Because the changes achieved by prophy- lactic agents may be difficult to assess and indeed may be small, large numbers of subjects are required if a statistically significant result is to be obtained. Thus a full scale clinical trial to demonstrate, say, the effectiveness of a caries inhibitory agent will be expensive, not only in terms of time and money, but also in the numbers of highly trained research workers required to conduct it. The thorough screening of potential agents by whatever laboratory means are available or can be devised, is therefore essential if we are to be sure that these expensive, cumbersome and sometimes scarce facilities are used to the best advantage. The crucial factor, of course, is the selection of appropriate tests, the results of which will correlate with user experience. In this field the results which will permit correlation are acquired only slowly and so at the start of a project the experimenter is left with the problem of selecting tests which, on his knowledge at that time, are likely to be most relevant to the mode of action of the active ingredient. As this knowledge is often scanty, a battery of tests to cover all possible modes of action, whether likely or not, may be the safest way of dealing with this problem. A further requirement for laboratory methods is the need to test hypotheses which might involve the use of materials which could never be employed in the mouth for reasons of toxicity but which might establish principles and therefore, lead to the development of safe derivatives. Prophylactic toothpaste means any product which has a specific action