RPD Review Questions
According to the Kennedy Classification, the partially edentulous arch shown is a Class I, Modification 0. There are bilateral posterior extension areas with no other modification (edentulous) space(s) present.
All class I RPDs have an axis of rotation. To be very specific, the axis of rotation will pass through the rigid metal closest to the edentulous space that lies above the survey line (height of contour). If the design is correct and the laboratory and clinical procedures are carried out properly, the axis of rotation should pass through the most distal rests on each side. The axis of rotation for this case is indicated by the black line.
Class I and Class II RPDs always have an axis of rotation. Class III RPDs never have an axis of rotation. Class IV RPDs seldom have an axis of rotation---some people consider that Class IV RPDs have an axis of rotation if all the incisors and both canines are missing, creating an "anterior extension" area.