This RCT will include 34 patients requiring en-masse retraction of upper anterior teeth after maxillary first premolars extraction.

Patients accepted into the study will be randomly assigned to one of two groups in a 1:1 allocation ratio: the electrically stimulated en-masse retraction group (ESER) and the conventional en-masse retraction group (CER). In both groups, the upper anterior teeth will be retracted en masse by applying 250 g of force on each side using closed nickel-titanium coil springs. Mini-implants will be used to provide the maximum anchorage.

The outcomes of the study will be the external apical root resorption (EARR) and the periodontal status of the upper anterior teeth during the treatment stages.

Young adult patients who visit the Department of Orthodontics at Damascus University-Faculty of Dentistry during the sample collection period will be examined to determine the orthodontic treatment plan. Written informed consent will be obtained from all patients who meet the inclusion criteria and accept to participate in the trial.

Before starting the leveling and alignment procedures on the maxillary dental arch, skeletal anchorage will be secure on the maxillary dental arch using self-drilling mini-implants (1.6 * 8 mm; 3S screw, Hubit™, Seoul, Korea) that will apply between the roots of the maxillary first molars and the second premolars. The patients will be referred for maxillary first premolars extraction at the Department of Maxillofacial Surgery, Damascus University, Faculty of Dentistry.

This study will use fixed orthodontic appliances with an MBT prescription and a 0.022-inch bracket slot (VotionTM, Ortho Technology, Florida, USA). The two groups will follow a uniform wire sequence starting from a 0.014-inch NiTi wire until they reach the 0.019*0.025-inch stainless steel basic archwire, with a 3-week interval between each wire.

The sliding technique will be used for en-masse retraction in both study groups. An orthodontic force of approximately 500 g (250 g on each side) will be applied to the crimpable hooks using bilateral closed coil nickel titanium springs (NT3 closed coil springs, American Orthodontics, Sheboygan, Wisconsin) anchored to orthodontic mini-screws. Patients will be followed up every 2 weeks during this phase to adjust the springs to maintain a constant force. The endpoint of en-masse retraction in both groups will be determined when the maxillary canines achieve a Class I relationship with the mandible and a normal incisor relationship.

The removable electrical stimulation device utilized in the study by Shaadouh et al.. to provide the electrical stimulation will be used in this trial for the same purpose.

Each patient in the low-intensity electrical stimulation group will be asked to wear a removable device for five hours daily until the completion of the retraction of the upper anterior teeth.

To evaluate external apical root resorption (EARR), digital panoramic radiographs will be taken at three time points: before orthodontic treatment (T0), before en-masse retraction (T1), and after en-masse retraction (T2). The ImageJ software (NIH and LOCI, Madison, Wisconsin, USA) was used to analyze these radiographs. The method, originally described by Linge and Linge will be used to calculate the root resorption.

The gingival index (GI), the papillary bleeding index (PBI), and the dental plaque index (DPI) will be measured on the upper anterior teeth at the previous assessment times.

Inclusion Criteria:

1. Healthy adult patients, Male and female, Age range: 18-25 years.

2. Class II Division 1 malocclusion :

   • Mild/moderate skeletal Class II (ANB= 5-7 degrees)
   • Overjet ≤10
   • Normal or excessive facial height (Clinically and then cephalometrically assessed using these three angles: mandibular/cranial base angle, maxillary/mandibular plane angle, and facial axis angle)

3. Permanent occlusion.

4. The Existence of all the upper teeth (except third molars).

5. Good oral and periodontal health:

   • Probing depth < 4 mm
   • No radiographic evidence of bone loss.
   • Gingival index ≤ 1
   • Plaque index ≤ 1

Exclusion Criteria:

1. Medical problems that affect tooth movement, such as corticosteroid, nonsteroidal anti-inflammatory drugs (NSAIDs).

2. Presence of primary teeth in the maxillary arch

3. Missing permanent maxillary teeth (except third molars).

4. Poor oral hygiene or Current periodontal disease:

   Probing depth ≥ 4 mm Radiographic evidence of bone loss Gingival index > 1 Plaque index > 1

5. Patient had previous orthodontic treatment