Dento-Alveolar Changes in Maxillary Incisors After En-Masse Retraction Using Two Power-Arm Heights

Malocclusion, Angle Class II, Division 1

En-masse retraction Power arm lenghth CBCT Bone remodeling

This study aims to evaluate the dento-alveolar changes associated with en-masse retraction of the maxillary anterior teeth using two different power-arm lengths to produce two distinct levels of force application. Twenty patients were randomly assigned into two equal groups. Group I received en-masse retraction using a 5-mm power arm, while Group II was treated using a 9-mm power arm. Cone-beam computed tomography (CBCT) was used to measure changes in buccal bone thickness at 3 mm, 6 mm, and 9 mm levels before and after retraction. The purpose of the study is to assess the influence of power-arm length on force direction, bone remodeling, and the safety of anterior tooth movement.

The study was conducted to assess the dento-alveolar changes that occur during the en-masse retraction of maxillary anterior teeth when using two different power-arm lengths. Twenty orthodontic patients who required extraction of the maxillary first premolars as part of their treatment plan were included. Patients were selected according to well-defined inclusion criteria to ensure uniformity in skeletal pattern, dental status, and oral health. Any patients with previous orthodontic treatment, periodontal problems, or systemic conditions that could influence bone metabolism were excluded. After obtaining approval from the Research Ethics Committee, participants were randomly divided into two equal groups. In Group I, retraction was carried out using a 5-mm power arm, while Group II was treated with a 9-mm power arm incorporated into the main archwire. All patients were treated with the same fixed orthodontic system, and temporary anchorage devices (TADs) were placed bilaterally to provide maximum anchorage. The archwire sequence, appointment intervals, and force application protocol were standardized for both groups to reduce variability. Cone-beam computed tomography (CBCT) scans were taken for each patient before initiating retraction and after the completion of space closure. Buccal bone thickness was measured at three levels along the root (3 mm, 6 mm, and 9 mm from the cementoenamel junction). Measurements were recorded on the right and left sides and averaged. Additional clinical parameters-including the amount of anterior tooth movement, changes in incisor inclination, and any alterations in the occlusal plane-were evaluated to understand the mechanical implications of each power-arm length. The main focus of the study was to determine how the length of the power arm affects the direction of force, the biomechanics of retraction, and the subsequent pattern of alveolar bone remodeling. All measurements were analyzed using appropriate statistical tests to compare differences between groups and between pre- and post-treatment values. The study aims to provide practical clinical guidance regarding the optimal choice of power-arm length to achieve effective, controlled anterior retraction while maintaining alveolar bone health.

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