Continuous force- active force that decreases little in magnitude betwwen appointments.

• Light weight appliances
• Highly flexible appliance components used which are activated at low force level.
• No interference with biological function and no harm to soft tissues.
• Direct resorption of bone

Intermittent force- active force that decays to zero before next appointment.

• High stiffness appliances
• Twice the force activation for corresponding soft tissue deformation
• Undermining resorption and corresponding tooth movement.

Interrupted force- inactive for intervals of time between appointments

• Cyclic, long term magnitude time pattern
• Heavy forces delivered
• No force decay

Reference- orthodontics bhalajhi