Evaluation of Distal Movement of Maxillary Dentition With Zygomatic Miniplates: a Clinical Study Using Cone Beam Computed Tomography

Premolar extraction treatment with multibracketed system and reinforced anchorage has been a common modality for correcting maxillary incisor crowding or Class II malocclusion in nongrowing patients. Treatment of Class II malocclusion without extraction frequently requires distalization of maxillary molars into Class I relation by means of extraoral or intraoral forces. Previously, it had been difficult to move maxillary molars distally after full eruption of maxillary 2nd molars. Extraoral headgear traction restricting the forward growth of maxilla and /or distalizing the maxillary dentition has been the most commonly used and oldest method to correct a Class II buccal segment molar relationship.This distalizes not only 1st molar but also maxillary 1st and 2nd premolars via transeptal fibers. Headgear is seldom an option in adults due to aesthetics and compliance concerns. The disadvantages of extraoral appliances have motivated many investigators to develop the mechanics of intraoral molar distalization.

Various intraoral non compliance appliances like nickel-titanium spring , magnets , distal jet , pendulum appliances have been used to distalize maxillary molars. However, in these appliances, anchorage loss characterized by protrusion of maxillary incisors and an increase in overjet is seen. Also considerable amount of relapse occurred when the distalized molars were used as anchorage for the retraction of anteriors and premolar teeth.

Absolute skeletal anchorage available 24 hours a day is an alternative method for molar distalization. It provides stationary anchorage for various tooth movements without the need for active patient compliance and with no undesirable side effects. Miniscrews, which are generally placed between the roots, limit the amount of distalization possible as they come in contact with surrounding roots during tooth movement. Also, proximity of miniscrews to the roots may lead to failure of screw anchorage .These disadvantages can be overcome by the use of miniplates which are fixed at a distance from the root apices, and therefore do not interfere in tooth movement.

Until now, there have been only a few clinical studies on group distalization of posterior teeth. Thus, little information is available regarding the type of tooth movement that occurs and the limitations of distal movement. An attempt was also not made to study the root resorption and the amount of distal movement or tipping of maxillary 2nd molars since lateral cephalometric radiographs do not provide a clear view of this region.

To the best of our knowledge, no previous study has been conducted on Cone Beam Computed Tomography to evaluate the amount of distal movement of entire maxillary dentition using miniplates placed in zygomatic region and assess the root resorption in all the roots of maxillary molars. The purpose of this study is to evaluate distal movement of maxillary dentition using Cone Beam Computed Tomography to overcome the shortcomings of the previous studies.