Figure 1. Mutans streptococcal (MS) colonization of humans in the first three years of life. The percentage of children colonized with mutans streptococci is indicated on the ordinate. Percentages reflect children under modest maternal challenge (approximately 50% colonized) or children exposed to high maternal levels (approximately 90% colonized). If high maternal MS levels (dose) are combined with significant exposure to dietary sucrose, initial dental colonization with MS occurs at a younger age.