[Mathematical classification of root canal curvature of human teeth].

Endodontic research requires a mathematically based classification method of root canal forms. The aim of this study was to give a mathematical description of root canal forms using differential geometrical pattern analysis and computer graphics. The measurements of 433 extracted human roots were carried out on isometric radiographs taken from clinical view. Seven points of root canal axis of the same radiographs were approximated using fourth degree polynomial functions describing the imaginary axis of canals. The Schneider's angle of each root was also measured for grouping the samples according to this parameter. The classification of root canal form on the basis of Schneider's angle differs from the classification of geometrical pattern analysis. This type of classification of root canals is suitable for standardizing test specimens, including natural human teeth used for testing root forms: I (straight), J (apically curved), C (continuously curved) or S (multicurved).