Subdividing a digital dentition model

A computer-implemented method for use in creating a digital model of a tooth in a patient's dentition, the method comprising:

• (a) receiving a 3D dataset representing at least a portion of the patient's dentition, including at least a portion of a tooth and gum tissue surrounding the tooth;
• (b) applying a test to the 3D dataset to identify data elements lying on a gingival boundary that occurs where the tooth and the gum tissue meet, wherein applying the computer-implemented test includes;
• identifying elements of the data set that represent the gingival boundary, and
• labeling those data elements as belonging to the gingival boundary;
• and
• (c) applying a test to the data elements lying on the boundary to identify other data elements representing portions of the tooth, wherein applying the test to identify data elements on the gingival boundary includes creating a series of roughly parallel 2D planes, each intersecting the dentition roughly perpendicular to an occlusal plane of the dentition, and each including data elements that represent a cross-sectional surface of the dentition.