Journal of Dental Research, Vol 72, 947-952, Copyright © 1993 by International & American Associations for Dental Research Online Journals
An in vitro and in vivo study of toothbrush bristle splaying
H. R. Rawls, R. Casella and N. J. Mkwayi-Tulloch
Gillette Company, Boston, Massachusetts 02106-2131.
The extent to which a toothbrush is worn out, as evidenced by bristle
splaying, is an important determinant of cleaning efficacy. In order for
this aspect of oral hygiene to be studied, an accelerated means of
producing a life-like pattern of bristle splaying was investigated and
compared with splaying induced by a human test-panel. Porcelain denture
teeth were brushed under a static applied load in a slurry of dentifrice,
by means of a revolving "figure 8" motion, for up to 12,000 revolutions.
This was found to induce an increase in the degree of splaying (as measured
by "wear index") that was well-fitted (R2 = 0.96) by a second-order
expression of the form: WI = WIi + Ritj - Ctj2 where WI = wear index, WIi =
initial wear index, Ri = initial rate of increase in WI, tj = brushing time
measured in either machine revolutions (tr) or weeks of human use (tw), and
C = a separate constant for each brushing mode (machine or human panel).
The rate of splaying was found to be strongly influenced by the quality of
the bristle filament, but not by small differences in toothbrush design.
The splaying pattern induced by the machine could not be distinguished
visually from that in a set of brushes used at home by human volunteers. A
strong correlation was found between the splaying produced by
machine-brushing and by a panel who brushed free-style at home for 13
weeks.(ABSTRACT TRUNCATED AT 250 WORDS)
