The aim of this study is to evaluate dentoskeletal changes concomitant with different three levels of force application for maxillary protraction in growing patients with skeletal class 3 malocclusion.

Nanda reported that numerous experimental studies on primates have shown orthopedic changes in response to extraoral forces; however, very few studies have made an attempt to analyze the different force variables and their relationship to facial sutures. In consideration of the variables, experimental and clinical studies were initiated in their laboratory in 1972. A study on protraction of midfacial bones on primates reported that the point of force application significantly influences the center of rotation of the maxilla in rhesus monkeys. Our unpublished data also show that centers of rotation are influenced by the magnitude of force. The study showed that the maxilla can be successfully protracted by means of carefully controlled forces.

Based on the aforementioned data, we can hypothesize that the point of force application for maxillary protraction in relation to the center of resistance of maxilla could be utilized in order to correct skeletal class 3 malocclusions with different vertical dimension discrepancies.

Inclusion criteria:

The patients will be included in the study if they have the following:

1. An age range from 7 to 10 years.
2. Patients diagnosed to have skeletal class 3 malocclusion due to retruded maxilla and/or combined maxillary retrusion with mild mandibular protrusion. (based on cephalometric analysis)
3. No serious systemic diseases and/or medical treatment that could interfere with orthodontic tooth movement such as analgesics, non-steroidal anti-inflammatory drugs, and hormone supplements or antibiotics.
4. Good oral hygiene and periodontal conditions.
5. No evidence of craniofacial anomalies, such as cleft lip and palate or previous history of trauma, bruxism or parafunctions.
6. No previous orthodontic or orthognathic treatment.

Exclusion criteria:

The patients will be excluded from the study if they have the following:

1. Systemic diseases or medications that could interfere with orthodontic treatment.
2. Poor oral hygiene or periodontally compromised patients.
3. Craniofacial anomalies or previous history of trauma, bruxism or parafunctions.
4. Previous orthodontic treatment.