Shunting effect occurs in complete dentures:
A tipped occlusal plane will result in a shunting effect and loss of stability. That is, if the occlusal plane is lower in the molar area, there will be a tendency for the upper denture to be displaced posteriorly and the lower denture to be displaced anteriorly.
If occlusal plane is lower in molar area
If the occlusal plane is lower in incisor area
If occlusal plane is lower in molar as well as incisor area
When patient has poor muscular co-ordination