Evidence for putting the calculus: caries inverse relationship to work.

Objectives: To report previously unpublished data from three different types of clinical study to show the strength of the evidence purporting to demonstrate the existence of an inverse relationship between subjects' calculus and caries experience.

Methods: Data have been analysed from: a 3-year caries clinical trial of six toothpastes conducted in Lanarkshire, Scotland that involved 3000 children, Study 1; a caries epidemiological study in the Isle of Lewis that involved 228 children, Study 2; a calculus formation study carried out at Port Sunlight using a wide age range of adults, Study 3.

Results: Baseline data taken from Study 1 show that caries prevalence is highly significantly lower in calculus-prone than in calculus-free subjects (P < 0.0001). The inverse relationship is also demonstrated by the 3-year caries increment data for subjects who had used non-zinc toothpastes. Results from Study 2 show that a similar association arose for 8-year olds over a 6-year period, based on their erupting teeth alone. Finally, data from Study 3 show that whilst the extent of caries and calculus experience are both positively linked to age, within specific age groups the relationship between the two dental conditions on an individual subject basis is clearly of an inverse nature.

Conclusions: The present work confirms that calculus status has a direct bearing on both current and future caries experience. Baseline calculus status could be, and has subsequently been demonstrated to be, a useful stratifying factor for caries clinical trials.