Effects on Maxillary Anterior Dentition Following En Masse Retraction Using Mini-implants and Various Heights of Anterior Power Arm.

The controlled three dimensional movement of anterior dentition during orthodontic treatment is a desire of every orthodontist. Maxillary en masse retraction with mini implants has been reported to provide absolute anchorage thus utilizing the complete extraction spaces thereby enhancing patient's esthetics. Power arm or anterior retraction hook permits the application of force close to a desired direction thereby warranting better anterior dentition control. Various heights of power arms and proposed centre of resistance for six maxillary anterior teeth have been estimated through finite element model and also from a very limited number of clinical studies. For a set of teeth, the determination of centre of resistance is complex in actual clinical scenario and response of force applied from certain level for better anterior dentition control requires sufficient clinical evidence suggestive of further clinical studies to endow orthodontists to hasten treatment due to less time consumption during finishing stage of orthodontic treatment.

This Randomized Control Trial will be conducted to compare the effects of various heights of anterior power arm on maxillary anterior dentition following en masse retraction with mini-implants by participation of thirty patients meeting eligibility criteria. The participants will be divided in three groups through software generated randomization table. Group I (control group; height of anterior power arm 6 mm), Group II and Group III (experimental groups; height of anterior power arm 3 mm and 9 mm, respectively). Ten patients will be allocated in each group. En masse retraction with mini implants and various heights of anterior power arm will be carried out immediately after bilateral maxillary first premolar extractions using continuous arch sliding mechanics. Horizontal, vertical and angular dimensions will be measured on lateral cephalograms while the transverse effects will be measured on maxillary dental cast. Both lateral cephalograms and dental casts will be obtained at two different point of time; T1, before retraction and T2, after complete extraction space closure. The data will be assessed with-in and among groups.

Eligibility Criteria:
Inclusion criteria

* Patients between ages 18-30 years.
* Good oral hygiene and healthy periodontal tissues.
* Patients having overjet ≥ 7 mm and ≤ 10 mm and overbite of 2-3 mm.
* Pt with molar relation angle's full cusp Class II requiring symmetric extractions of maxillary 1st premolars and maximum anchorage.
* Patients having coincident maxillary midline with the facial midline.

Exclusion criteria

* Patients with maxillary anterior teeth have dilacerations, fusion, hyper-cementosis, shorter roots or any other tooth anomaly.
* Patients with traumatized or impacted teeth in the anterior maxilla.
* Patients with moderate to severe crowding in maxillary and mandibular arch.
* History of bone metabolic disorders or patients receiving drugs that alter bone metabolism.
* History of systemic diseases or hormonal imbalance that hinders orthodontic tooth movement.