2) Z – Spring with posterior bite plane
a. For developed crossbite

POSTERIOR CROSSBITE
 Reasons — narrow maxillary jaw
 Rx plan
o Expansion of maxillary arch
o Maxillary expansion device
o At or above 7 years of age
o Max suture growth ends at 15 years
o Both unilateral and bilateral posterior crossbite
 Function of expansion device —bilateral expansion
 Effect seen when midline diastema appears
 This diastema closes as a result of relapse
 No Rx required for midline diastema

UNILATERAL CROSSBITE
1. LAERTOGNATHY / TRUE CROSSBITE
The center of the mandible and the facial midline does not coincide in both rest and in occlusion
2. LATEROCCLUSION
The center of the mandible and the facial midline coincide in rest position butttt in occlusion the