The interaction of factors in the caries process has recently been discussed in a number of articles. Based on this, a new explanatory model has been constructed, consisting of an equilateral triangle with one of the apices on a horizontal line, along which dietary and oral hygiene habits are scaled. The triangle represents the total area of interaction. A horizontal line of resistance cuts off a tower part corresponding to the area within which caries does not occur. Through planogeometric calculations the remaining part of the triangle can be divided into areas, approximately corresponding to the relative caries values of various combinations of dietary and oral hygiene habits. The model has proved to be a useful instrument for demonstrating and creating an understanding of interactive processes among various groups of dental health personnel. The example presented is based on a pilot study of 55 4-year-old children in Malmö.