Will individual participant data (IPD) be shared publicly (including data dictionaries)?  

     Transverse maxillary deficiency associated with respiratory problems is a condition frequently seen in orthodontic practice. Maxillary constriction is commonly associated with unilateral or bilateral posterior crossbite, anterior dental crowding, high palatal vault, lowered tongue posture, and a compromised airway. Nasal breathing allows adequate growth and development of the craniofacial complex. In contrast, nasal obstruction that leads to mouth breathing results in a lower tongue posture and a constricted ‘V’ shaped maxillary arch. Rapid maxillary expansion (RME), first introduced by Emerson C. Angell in 1860, is a well-documented dentofacial orthopedic treatment procedure for correcting transverse maxillary deficiency which has been routinely used in young patients. The main goal of RME is to correct the existing posterior crossbite and to widen the maxilla and increase the maxillary dental arch length. However, a concomitant and contributing benefit of this procedure is an improvement in the upper airway which facilitates nasal respiration. RME brings about not only an increase in nasal airway dimensions but also decreases naso-respiratory problems by anteriorly positioning the tongue in the oral cavity, improving its posture, in patients with maxillary constriction and mouth breathing.

         Most investigators have analyzed the effects of RME through two dimensional radiographic techniques including lateral cephalograms and posteroanterior cephalograms. Recent advances in cone beam computed tomography (CBCT) and related software have made it possible to visualize and measure the upper airway as a solid structure. Lower costs, lower radiation dose, shorter scanning time, and overall accuracy have made CBCT technology a preferred method to assess the airway.

The purpose of this study is to assess changes in tongue posture and volume of nasomaxillary complex in patients with transverse maxillary deficiency associated with mouth breathing after Rapid Maxillary Expansion (RME) using CBCT. At the same time, increase in maxillary arch width and alveolar bending will also be assessed.