To compare the effect of digital fabricated Nance and transpalatal arch appliances versus conventional fabricated Nance and transpalatal arch appliances.

measuring arch parameters: arch perimeter, anterior segment perimeter, maxillary width, anterior segment length, right molar rotation angle, left molar rotation angle, palatal vault depth

Inclusion Criteria:

• Healthy children aged 8-9 years
• Bilateral, prematurely extracted maxillary primary molars within a period not more than one month were selected.
• Fully erupted maxillary permanent first molars.
• Angle's class I occlusion.
• Adequate space for premolar eruption according to Moyer's arch length analysis.

Exclusion Criteria:

• Children with congenitally absent permanent successors.
• Children with successors not covered by bone.
• Children with successors with two-thirds or more of their roots formed.