Effectiveness of Two Corticotomy Techniques in Retracting the Upper Anterior Teeth by Using Miniscrews

A corticotomy is cutting of the bone involves cortical bone only, leaving intact the medullary vessels and periosteum It offers an advantage to adult patients in reduction the orthodontic treatment time. The definition of traditional corticotomy is: elevating full-thickness periodontal flaps from a coronal approach, and vertical corticotomies are made between the teeth extending from 2-3 mm apical of the alveolar crest to 2 mm beyond the tooth apices and connected by a horizontal corticotomy; this process is done on both the labial and palatal aspects.

The definition of flapless corticotomy is: a minimally invasive version of corticotomy, using a piezotome in order to inflict bone injury. This technique entails labial and palatal interproximal piezoelectric microincisions into the cortical bone, without reflecting periodontal flaps.

Prior to enrollment of each subject into the study, they will be examined completely to determine the orthodontic treatment plan. The operator will inform them about the aim of the study and ask them to provide a written informed consent.

Self-drilling titanium mini-implants (1.6mm diameter and 8mm length) will be used. they will be inserted between the maxillary second premolar and first molar at approximately 8-10mm above the archwires at the mucogingival junction and will be checked for primary stability (mechanical retention). Then the maxillary first premolar will be extracted. The maxillary arch will be levelled and aligned. The rectangular stainless steel archwires (0.019" × 0.025") with anterior 8mm height soldered hooks distal to the lateral incisors will be inserted.

The surgery will be carried out under local anesthesia. The traditional corticotomy will be handled by the same maxillofacial surgeon and the flapless corticotomy will be handled by the same orthodontist.

For traditional corticotomy, sulcular incisions the mesial aspect of one second premolar to the mesial surface of the contralateral second premolar will be placed, and full thickness flap will be elevated, 3 mm above the apical region of the tooth. piezoelectric under copious irrigation will be used for making vertical and horizontal cuts (only cortical surface). The vertical cuts will be between the dental roots in the interdental cortical surfaces ,stopping 2 mm short of the alveolar crest, occlusally. Horizontal cut will connect the vertical cuts 2 mm beyond root apex. These cuts will be performed from the mesial aspect of one second premolar to the mesial surface of the contralateral second premolar involving the anteriors. Similarly, a palatal flap incision will be raised immediately for doing the same vertical and horizontal cuts in the superficial surface of the palatal bone.

For the flapless corticotomy, The depth of gingival tissue will be determined through bone sounding using a periodontal probe. A scalpel will be used to make the incisions through the gingiva, 4mm below the interdental papilla to preserve the coronal attached gingiva. These vertical incisions will be placed from the mesial aspect of one second premolar to the mesial surface of the contralateral second premolar on the labial and palatal aspects of the maxilla through the gingiva and the underlying bone. A piezosurgery knife will be used to create the cortical alveolar incisions to a depth of 1 mm within the cortical bone.

Postoperatively, all patients will be advised to rinse with chlorhexidine mouthwash twice a day for one week. All patients will be contacted the day after the procedure to ensure no complications with surgery and will be followed up one month post-surgery to assess for signs of infection and ensure normal healing. We will assess patients' acceptance and the levels of pain and discomfort of traditional corticotomy and flapless corticotomy by asking all patients to fill out 4 questionnaires during the first month after the surgical procedure using a VAS.

The surgical procedure will be performed and (250-300) g force will be applied on each side (3-4 days) after corticotomy using two NiTi springs attached between the mini-implants and the soldered hooks in a direction approximately parallel to the occlusal plane for conducting an en-masse retraction. The force level will be measured every 2 weeks after the corticotomy . Retraction will be stopped when a class I canine relationship will be achieved and a good incisor relationship will be obtained.

Periodontal health will be assessed at the beginning of orthodontic treatment, before and after corticotomy by evaluating the following parameters: plaque index, gingival index, bleeding index, and gingival recession.

Dental casts will be used for the quantification of the anteroposterior movement of the anterior teeth and the first molars every 30 days until class I canine relationship will be achieved and a good incisor relationship will be obtained.

To evaluate the movement of the anterior teeth: we will project the canine cusp on the median line and measure the distance from this point to the projected position of a distinct medial ruga point.

To evaluate the movement of the first molars: we will project the mesial contact point of the first molar on the median line and measure the distance from this point to the projected position of a distinct medial ruga point. These measurements will be made with sliding calipers.

Inclusion criteria

• Adult patients with permanent occlusion at age 18-30 years.
• Comprehensive medical and dental history ruling out any systemic disease
• Not under any systemic medication.
• No previous orthodontic treatment
• Patients with satisfactory periodontal health and Good oral hygiene
• Need to orthodontic treatment with fixed appliances
• No congenitally missing teeth except third molars in the maxillary arch
• Mild or no anterior crowding in maxillary arch.
• Maximum anchorage, with 75% to 100% of space closure of retraction of anterior segment in maxillary arch.
• Therapeutic extraction of maxillary first premolars required.
• Patients with class Ⅱ division 1 (ANB angle ≤7 degrees) with severe overjet (5-10 mm)
• Maximum retraction of the anterior teeth was desired.

Exclusion criteria

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