What is the different between the incisal ridge and incisal edge?

it might be good at this point to differentiate between the two term incisal ridge and incisal edge the incisal ridge is that portion of the crown which makes up the complete incisal portion. when and incisor is newly erupted , the incisal portion is rounded and merges with the mesioincisal and distoincisal angles and the labial and lingual surfaces. this ridge portion of the crown is called the incisal ridge. the term edge implies an angle formed bye the margin of two flat surfaces. therefore an incisal edge does not exist on an incisal until occlusal wear has created a flatten surface linguincisally, which surface forms an angle with a labial surface. the incisal edge is formed by the junction of the linguincisal surface, sometimes called the incisal surface, and the labial surface. Wheeler's Dental Anatomy Physiology and occlusion Ninth edition