Scott & Turner (1997)
# The normative form of the cervical enamel line on the lingual & buccal surface of the molar crown is horizontal.
# An enamel extension is distinguished as a line directed apically toward the bifurcation of the roots (Pederson 1949; Lasker 1950).
# These extension can deviate from 1 to more than 4 mm from the horizontal axis of the cervical enamel line.
# The enamel extensions are expressed on both upper & lower molars & premolars
# While enamel extensions can be buccal or lingual most workers score their presence on the buccal surface of the molars. Turner et al (1991) recommend scoring these lines on the UM although LM expressions should also recorded. The focal tooth for enamel extensions is the UM1 & LM1
# Eskimos have a high freq of enamel extension (Pederson 1949).