The influence of toothbrush wear on the variables of plaque and gingivitis in clinical trials.

Although toothbrush wear has been shown not to be critical in ensuring optimal plaque removal, the degree of toothbrush wear occurring in a clinical trial may influence the results of the trial. The aim of this study was to determine the effects of toothbrush wear on the clinical variables of dental plaque and gingivitis. There were 107 subjects who participated in this six-month clinical trial in which plaque and gingivitis scores were assessed in relation to toothbrush wear at 2, 4, 12 and 24 weekly intervals. At each appointment, the toothbrushes being used were assessed for wear and replaced if necessary. It was found that 58% of the group were "rapid," and 42% were "slow" wearers. Of the group, 18.6% required replacement toothbrushes within two weeks from baseline with 50.9% of replacement toothbrushes being issued within four weeks of the start of the trial. Two subjects required as many as 10 replacement toothbrushes over the six-month trial period. "Slow" wearers had significantly lower plaque scores than "rapid" wearers at weeks 4 and 12, whereas the "rapid" wearers had significantly lower gingivitis scores than "slow" wearers at weeks 2 and 4. Clinical results show that significant toothbrush wear patterns of individuals participating in clinical trials should be taken into account when designing clinical trials assessing plaque and gingivitis scores. It may be necessary to exclude "rapid" toothbrush wearers from clinical trials that assess plaque and its removal. As the rate of toothbrush wear varied considerably among subjects, the simple classification of subjects into "rapid" and "slow" wearers may require further subgrouping. The surprising result that "rapid" wearers achieved lower levels of gingivitis requires further study to determine if this observation is valid in clinical trials designed for this purpose.