the study aimed to evaluate the effect of different types of Micro-osteoperforation on the rate of distal movement of maxillary first molars as a primary out come. Besides, it was aimed to study secondary effect on the first molars by evaluating root resorption, bone density, and level of the pain during performing the procedures.

in the study, investigators tried to evaluate two methods to accelerate tooth movement by comparing them with control group. the first method was to apply one-time micro-osteoperforation. the second method was to apply the micro-osteoperforation repeatedly till reaching the end of the phase one treatment.

Inclusion Criteria:

• Space deficiency in the upper arch > 5 mm, and < 8 mm.
• Non-extraction lower arch.
• Full upper dentition up to the second molars.
• Third molar present in both sides, not yet erupted.

Exclusion Criteria:

• Systemic disease or syndrome.
• Evidence of root resorption.
• Poor oral hygiene.
• Previous orthodontic treatment
• Evidence of bone loss.
• Active periodontal disease.
• Pregnant females.
• Presence of oral habits

sexual hormones could affect the study outcomes. aiming to minimize the factors that might cause bias of the results.

single blinded, the assessor of the out comes did not participate in the study