Size of the primary enamel knot (day 2) and cusp number (day 7) for Eda null, Eda null + 10 ng ml−1 EDA, Eda null + 50 ng ml−1 EDA, and wild-type teeth. Reduced major axis regression for square root of μm2 are 0.0533 × −0.791, r2 = 0.613, P < 0.0001, n = 46. Enamel knot size does not increase substantially with higher EDA concentrations.