Tooth size (Mesiodistal, Buccolingual and Occluso-gingival) has an important role in pediatric dentistry as it helps for fabrication of appropriate sizes of zirconia crowns for primary anterior teeth and Stainless-Steel crowns for primary posterior teeth. Tooth size differs among and within populations.

Inclusion Criteria:

1. Children aged 4-6 years
2. Fully erupted first and second primary molars
3. Sound interproximal & buccal / lingual walls with or without minimal occlusal pits & fissure incipient caries.
4. No previous interproximal & buccal / lingual restorations
5. Intact mesial and distal marginal ridge

Exclusion Criteria:

1. Children with gross carious lesions.
2. Children with hypo-mineralization, hypoplasia and fracture.
3. Children with mental disability.

Egyptian children from the outpatient clinic of pediatric dentistry department Cairo University