This study aims to assess the dental changes, periodontal health and the pulp vitality in mini-screw supported en-masse retraction associated with traditional or flapless corticotomy techniques.

40 adult patients exhibiting class II division 1 malocclusion requiring upper first premolar extractions followed by en-masse retraction will participate in the study. They will be randomly and equally distributed into two groups: traditional corticotomy (20 patients) versus flapless corticotomy (20 patients). The corticotomy procedure will be performed pre-retraction. The dental changes will be assessed using dental casts. The impressions will be taken after finishing the leveling and alignment phase and before starting the en-masse retraction (T0), 1 month (T1), 2 months (T2), 3 months (T3), 4 months (T4), and 5 months (T5) following the onset of en-masse retraction. The final impression will be considered at the end of the en-masse retraction (when the canines reach Class Ι relationship).

One of the most important challenges in daily practice is prolonged orthodontic treatment duration. For that lots of therapeutic procedures have been introduced to minimize orthodontic treatment time such as surgical interventions. Even though the traditional corticotomy with flap elevation proved to be effective in accelerating different types of tooth movement, it has been deemed aggressive. Therefore, minimally invasive surgical techniques have been proposed and labeled 'flapless corticotomies'.

In flapless corticotomy group, vertical soft-tissue incisions will be made on the buccal and palatal gingiva by using a blade N.15. One incision will be made between the roots of the six upper anterior teeth, and two incisions will be made between the upper canines and second premolars. The incisions will be 5 mm long and started 4 mm apical to the interdental papilla. Then a piezosurgery knife will be inserted to perform the cortical alveolar incisions with 3-mm in-depth and 8-mm in length. No suturing will be needed.

In traditional corticotomy group, a full-thickness mucoperiosteal flap will be elevated including the interdental papilla, and extended from the distal side of the second premolar on the right side to the same position on the left side without performing any vertical releasing incisions. The full-thickness flap will be extended 3 mm above the root apices, from the buccal and palatal sides, knowing that the incision in the incisal papilla region will be done around it with a (V) or (U) shape. Then, one vertical incision between the roots of upper anterior teeth and two vertical incisions in the site of first premolar extraction will be made by the piezosurgery knife. The vertical incisions will be connected by a horizontal incision using the piezosurgery knives. The vertical incisions will be 3 mm in depth, starting 2-3 mm apical to the alveolar crest, and extending 3 mm beyond the root apices. The interrupted technique of suturing will be done using a non-absorbent 3-0 black silk.

The en-masse retraction will be begun 4 days after carrying out the corticotomy procedure using 0.019×0.025-inch SS archwires with 8-10-mm long soldered hooks located distal to the lateral incisors. NiTi closed coil springs with 9-mm long will be extended from the mini-screws to the soldered hooks and applied 250-g of force per side. The patients' follow-up appointments will be every 2 weeks. The force will be measured on every appointment and adjusted if needed. The endpoint of the monitoring period will be the session when canines reached a class Ι relationship.

Inclusion Criteria:

1. Age range between 18 and 30 years.
2. Class II division 1 malocclusion requiring extraction of upper first premolars.
3. Mild to moderate skeletal class II malocclusion.
4. Normal or excessive anterior facial height.
5. No or mild crowding (tooth-size arch-length discrepancy ≤3 mm).
6. Overjet >5 mm and <10 mm.
7. Completion permanent dentition (regardless of third molars).
8. No previous orthodontic treatment.
9. No drug use or systematic disease that would affect the bone and tooth movement rate.
10. Healthy periodontium and good oral hygiene.

Exclusion Criteria:

1. Patients with previous orthodontic treatment.
2. Patients with severe skeletal dysplasia in all three dimensions.
3. Patients suffer from systemic diseases or syndromes
4. Patients on medication for systemic disorders, pregnancy or steroid therapy.
5. Patients showing any signs of active periodontal disease
6. Patients with severe crowding (≥ 3.5 mm) in maxillary arch
7. Patients with missing or extracted teeth in maxillary arch except third molar.