“The ledge� and it can be circumferential, interrupted or opposing.
CLASS II During mandible
centric
both
the
and
excursive
restoration
and
movements
of
the
tooth structure
are
periodically loaded both separately and jointly. This brings about different stress patterns, depending upon the actual morphology of the occluding
area of both the tooth in
question and the opposing contacting cuspal elements. For the purpose of this discussion, one can classify these loading situations and their induced stress patterns in the following way: A small cusp contacts the fossa away from the restored proximal surface, in a proximo-occlusal restoration at centric closure. A)
As
shown
in
mesio-distal
cross
section, due to the elasticity of the dentin, especially in young teeth, a restoration will bend at the axio-pulpal line angle (provided the proximal part of the restoration is self retained). This creates tensile stresses at the isthmus 15