An electron microscopic comparison of bristle end-rounding of three commercial toothbrushes

The results from three separate examinations using SEM photomicrographs and shape factor (SF) measurements show that Oral-B P-35 brushes have a highly significant difference in bristle end-rounding when compared to Colgate Precision and Crest Complete toothbrushes. The proportion of Oral-B P-35 bristles with highly rounded ends was substantially greater than that for Colgate Precision and Crest Complete toothbrushes. Oral-B also had fewer bristles in the very sharp-edged category than both Complete and Precision toothbrushes. Each toothbrush sample in these studies was purchased from geographically dispersed retail outlets throughout the United States. Scanning electron micrographs were made from a representative random sample of bristles, then digitized and evaluated using image analysis software. The comparisons were made on the basis of the number and distribution of bristles having varying degrees of roundness as determined by shape-factor analysis. Previous studies asserted that low shape-factor values indicate sharp bristle edges that are less conducive to good oral hygiene than end-rounded bristles with high SF values. In separate studies, Oral-B P-35 had a significantly higher number of highly end-rounded bristles than did either the Colgate Precision or Crest Complete toothbrushes. The averages for end-roundness fall in the order of Oral-B P-35 > Complete > Precision. Thus we conclude that the potential for harming dental tissues is less for the Oral-B P-35 toothbrush than for either the Colgate Precision or Crest Complete toothbrushes.