Resistance form in
endodontics
Carmen Cohn
When a GP root filling is being
condensed, there is a tendency
to be pushed through the apex.
Resistance form is a natural
consequence of a tapered
canal preparation.
Carmen Cohn
Resistance form in endodontics
AAtapered
canal with
canal
parallel
shape
walls
will has
help
to spread
no resistance
the downward
formforces
to the walls of the canals and
lateral canals.
Carmen Cohn
Tapered canal shape

Cone fit

Vertical condensation

Lateral forces

No extrusion
Because more force is
transmitted laterally, less filling is
squeezed through the apex.
Carmen Cohn
Parallel walls

Cone fit

Vertical condensation

Vertical forces

Extrusion
There is little resistance to
pushing the filling and sealer
through the apical constriction.
Carmen Cohn