The goal of this controlled clinical trial is to compare the effects of two distalization methods supported by inter-radicular mini-screw for maxillary molars distalization in 20 adult patients with skeletal class I or moderate skeletal class II malocclusion, dental class II molar relationship, and full permanent dentition. The participants were randomly selected according to inclusion / exclusion criteria from the outpatient clinic of the Department of Orthodontics and Dentofacial Orthopedics, Faculty of dentistry, Ain Shams University, Cairo, Egypt. Selectees age was ranging from 18 to 25 years old.

An informed consent has been signed by each patient before his / her enrollment in this study, where the aim , methodology, and possible complications were been clearly described in details. This research has been thoroughly reviewed by the Research Ethics Committee of the Faculty of dentistry, Ain Shams University.

This study is a two-arm, parallel group, prospective randomized clinical trial with the allocation ratio of 1:1. The Consolidated Standards of Reporting Trials (CONSORT statement) were used as a guide for this study.

After reviewing the study protocol, the ethical committee at the Faculty of Dentistry, Ain-Shams University approved the study.

Before treatment was carried out, a detailed written Arabic consent was signed by all the subjects of both groups after full explanation of the aim of the study and the procedures.

This prospective clinical study was conducted on a total of 24 maxillary first molars.

No financial competing interests: This study was part of a Masters' degree in Orthodontics, Faculty of Dentistry, Ain-Shams University.

No financial conflicts of interest were declared. The study was self- funded by the principal investigator.

A sample size of 24 distalizing sites was selected and divided into two groups twelve each:

Group 1: Single coil spring. Group 2: Double coil spring.

Inclusion Criteria:

1. All subjects are free from any dental anomalies as well as periodontal and systemic diseases that may influence orthodontic treatment.
2. Adult patients with age ranging from 18 to 25 years.
3. Full permanent dentition with exclusion of third molars.
4. Both first and second maxillary molars are in occlusion.
5. Skeletal class I, mild or moderate skeletal class II malocclusion.
6. Full cusp or end to end class II molar relationship.
7. Mild to moderate crowding in the upper dental arch and / or increased overjet.
8. Normal or horizontal growth pattern.
9. Non-extraction treatment plan.

Exclusion Criteria:

1. Previous orthodontic treatment.
2. Treatment planning requiring orthognathic surgery.
3. Severe molar rotation.
4. Poor oral hygiene.

Study Protocol Statistical Analysis Plan (SAP) Informed Consent Form (ICF)