Types of screw:
• Two dimension expanding screw. ( used in patient with bilateral posterior crossbite)• Three dimension expanding screw. (used in patient with bilateral posterior crossbite and anterior crossbite)
• Fan type expanding screw.
Quarter turn activation of the screw will produce 0.25mm expansion
Uses of orthodontic screw• 1. Expansion.
• a. Bilateral expansion.
Fan type expander
Uses of orthodontic screwb. Unilateral expansion.
Uses of orthodontic screw2. Distal movement.
Distalization of molar is very easy if 6/6 are driftedmesially due to early loss of deciduous molars.
Uses of orthodontic screw3. In mild class III malocclusions with a slight upper arch crowding.
DISADVATAGES:• Bulky appliance.
• Patient cooperation is needed since relapse is quick and may elongate treatment time.
• Over activation may lead to difficulty during insertion.