The aim of this study is to evaluate the accuracy of clear aligners on the amount of the maxillary molar distalization.

Inclusion Criteria:

1. Age more than15 years.
2. Gender; male or female.
3. Skeletal Class I or Class II malocclusion and a bilateral half-cusp class II molar relationship that require molar distalization.
4. Mild crowding in the upper arch (≤ 4 mm).
5. Absence or previous extraction of the upper third molars.
6. Good compliance during the treatment

Exclusion Criteria:

1. Transversal dental or skeletal discrepancies.
2. Extraction treatment (except for the third molar).
3. Periodontal disease. .
4. Prosthodontics rehabilitation of the maxillary molars.