Toothbrush wear and cleaning performance 431 The condition of the brush does not drastically affect the ability of a toothpaste to remove cosmetic stains from extracted teeth. Some deterioration was observed for severely worn brushes. Our experience of evaluating the cleaning performances of tooth- pastes in vivo (3, 10) strongly suggests that this effect would not lead to any serious increase in the severity of stains on the teeth for the great majority of a population. The function of a toothbrush is to remove dental plaque and food particles as well as help remove cosmetic stains and it does not follow that while the condition of the brush does not unduly influence the ability of a dentrifrice to keep teeth free from stains, that similar relationships hold for dental plaque and other soft deposits. This may be parti- cularly true for dental plaque retained in the spaces between the teeth. Filaments of a badly worn brush may well be unable to penetrate into these regions, with important consequences in terms of gingival health. REFERENCES 1 Manly, R. S. A structureless recurrent deposit on teeth. J. Dent. Res. 22 479 (1943). 2 Kitchin, P. C. and Robinson, H. B. G. How abrasive need a toothpaste be? J. Dent Res. 27 501 (1948) 3 Bull, W. H., Callender, R. M., Pugh, B. R. and Wood, G. D. The abrasion and cleaning properties of dentifrices. Br. Dent. J. 125 331 (1968). 4 World Workshop in Periodontics (1966) The University of Michigan Press, Ann Arbor. 5 Frandsen, A. (ed.) Oral Hygiene (1972) Aalborg Stiftsbogtrykkeri, Denmark. 6 A survey into the state of the nation's toothbrushes: A British Dental Health Foundation Survey. (1975) British Dental Health Foundation, London. 7 McKendrick, A. J. W., McHugh, W. D. and Barbenel, L. M. H. Toothbrush age and wear. An analysis. Br. Dent. J. 130 66 (1971). 8 Bergstrom, J. Wear and hygiene status of toothbrushes in relation to some social background factors. $ven. Tandlak, Tidskr. 66 383 (1973). 9 Heath, J. R. and Wilson, H. J. Forces and rates observed during in vivo toothbrushing. BiomedEng. 9 61 (1974). 10 Wilkinson, J. B. and Pugh, B. R. Toothpastes: cleaning and abrasion. J. $oc. Cosmet. Chern. 21 595 (1970). 11 Robinson, H. B. G. Toothbrushing habits of 405 persons. J. Am. Dent. Ass.33 1112 (1946).

J. $oc. Cosmet. Chem. 29 433-440 (1978) Techniques for the evaluation of emollients and keratoltios R. MARKS Department of Medicine, Welsh National School of Medicine, Heath Park, Cardiff, Wales Presented at the Symposium on 'Product Evaluation', 18 April 1958, at Eastbourne Synopsis Established and new technologies were evaluated to assess the efficacy of emollients and keratolytics. The newer techniques included the use of (a) an instrument designed to measure in vivo intracorneal cohesion, (b) an instrument to assess the point penetrability of the stratum corneum in vivo and (c) an instrument designed to apply a standard stimulus in order to quantRate the number of squames' that are released in vivo. The established methods used included surface contour analysis of skin surface replicas and morphological assessments using macrophotography and scanning electron microscopy. The kera- tolytics so far evaluated included preparations of salicylic acid and urea and the emollients evaluated included three commercially available preparations. The results thus far showed that keratolytics are difficult to evaluate in entirely normal skin but that morphological assessments are best in abnormal skin and physical measurements are of more help in abnormally scaly skin. Emollients have proved much easier to evaluate and their effects can be detected by all the techniques described. Emollients and keratolytics account for a large proportion of the topical applications prescribed by dermatologists and a not inappreciable proportion of products that are directly available to the public for skin care It is, therefore, astonishing that com- paratively little atter•tion has been paid to methods for the assessment of the effectiveness of these products. This has been in part due to the intrinsic difficulties in quantitating events taking place at the skin surface, in part due to lack of understanding of how emollients and keratolytics work and in part due to the empirical approach previously adopted by dermatologists and cosmetic scientists. The subject is now, however, of considerable widespread interest and the author would point out the excellent review of Quattrone and Laden (1) which concentrated on in vitro methods for evaluation of emollients. It is the purpose of this paper to discuss several of the techniques available for assessment, to point out those in vivo techniques that appear to be most useful and at the same time to document the author's experience in this subject. TERMS AND DEFINITIONS It is worth while at the outset to define some terms. The term 'emollicnt' implies (from the Latin derivation) a material designed to soften the skin. The only true emollients in this sense are destructive agents that chemically change the usually hard stratum corncum into a softer less protective substance. What we actually mean by the term 'emollient' is a material that 'smooths' the surface to the touch (and makes it look smoother to the eye). 0037-9832/78/0400-0433 :$02.00 ¸ 1978 Society of Cosmetic Chemists of Great Britain 433