Reducing variability and choosing ideal subjects for experimental gingivitis studies.

Introduction: This study was undertaken to test the hypothesis that male, non-smokers, aged 25-50 years, with a proven track record of developing gingivitis would provide suitable subjects for experimental gingivitis studies because the inter-subject variation would be greatly reduced.

Materials And Methods: Subjects were required to be men aged between 25 and 50 years, in good general health with at least four sound teeth in one posterior quadrant of the mandible. Subjects who were smokers, taking antibiotics, anti-inflammatory drugs or had any other medical, surgical or social condition making participation in the study inadvisable, were excluded. Subjects had previously participated in a 21-day experimental gingivitis study. Subjects with the most gingivitis at the end of the previous study were invited to participate first, moving down the list until the required number of subjects had been achieved. Subjects were randomly assigned to one of three toothpastes: Crest Gum Care, Mentadent P or a placebo (UK Signal). Subjects were asked to brush their teeth twice daily for 1 min., with the tooth-shield in place and containing 1 ml of their assigned toothpaste.

Results: Thirty-five subjects completed the study using the placebo, 36 used Mentadent P and 39 completed the study using Crest Gum Care. Both toothpastes containing active gum health ingredients (Triclosan and Zinc Citrate in Mentadent P and Stannous Fluoride in Crest Gum Care) resulted in statistically significant reductions in gingival bleeding and inflammation. Although a directional reduction, there was no statistically significant reduction in plaque scores. No significant differences between the two active groups were established.

Conclusion: The factors that were controlled or measured and analyzed in these studies were: gender, smoking status, age and chronic gingivitis level. The results add support to the hypothesis that male subjects show less variation, however there is limited evidence linking the female menstrual cycles to variations in gingivitis status. Further research in this area is required before definitive conclusions can be made. Selecting a subject population in order to decrease variation must be undertaken with caution. A subject population selected for particular attributes can be extremely valuable when assessing the anti-gingivitis potential of new agents, but this population would be as biased if used for large efficacy clinical trials. The data obtained will not necessarily be able to be generalized, that is, applicable to the whole population. However there is sufficient evidence to justify balancing for (or excluding) smokers from subject populations in experimental gingivitis studies.