A randomized clinical trial to evaluate a newly designed 3D printed miniscrew-supported molar distalization device in comparison to the conventional miniscrew-supported distal jet appliance in correction of Class II malocclusion and upper arch crowding.

It is a multicenter randomized clinical trial with two parallel arms. The patients will be randomly divided into two groups, group one: conventional miniscrew-supported distal jet appliance will be used while for group two, new 3D printed miniscrew-supported molar distalizers is going to be utilized. Lateral cephalometric x-ray and digital models of upper arch will be taken before starting the treatment (T0) and at the end of molar distalization (T1). The effectiveness of the two appliances will be assessed and measured comparing patient's records before and after treatment.

Inclusion Criteria:

1. Class II molar relationships bilaterally, with fully erupted 2nd molar.

2. No or minor crowding on the mandible to [reserve Class I posterior occlusion after treatment.

3. Good oral health free from caries and periodontal problems at the start of treatment.

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Exclusion Criteria:

1. Previous history of orthopedic and/or orthodontic treatment.
2. Patients with cleft lip and palate and/or craniofacial syndrome
3. Patients with bad oral habit.
4. Active periodontal disease.
5. Sever rotation of maxillary molars. -](streamdown:incomplete-link)

The study will be a single blinded because both the patients and the investigator will be aware of the allocation during treatment, but the cephalograms and digital models will be scored and coded by an independent person, i.e. pre-and post-treatment cephalograms and digital models will be analyzed after replacing the patients' names with codes, and the examiner conducting the measurement analysis will be unaware of the group to which the patient has been allocated.