Standard reference has means and standard deviations by gender [Moyers et al, 1976]. It is easy to measure the width of teeth, for which reason the definition of microdontia can be made with reference to the width of the tooth. However, microdontia means that the overall size of the tooth is decreased. In microdontia, the gaps between the teeth, particularly the anterior upper and lower teeth, are increased, creating diastemata. This should be assessed and coded separately.