Use of conventional tomography to evaluate changes in the nasal cavity with rapid palatal expansion

Introduction: The relationship between nasal airway resistance and the use of rapid palatal expansion appliances remains controversial. The purpose of this study was to use conventional tomography to determine the anatomical changes in the nasal cavity after maxillary expansion. Methods: Nineteen patients (aged 8–15 years) were included in the study. Tomograms were taken before expansion (T1), immediately after expansion (T2), and 3 months after expansion (T3). Areas for the left and right anterior, middle, and posterior nasal cavity and total volume were calculated by using the computer software, AutoCAD LT 2005. Data were analyzed with paired t tests. Results: Significant increases in area were found in the anterior nasal cavity from T1 to T2 (0.85 ± 1.19 cm2, 11.7% increase), T2 to T3 (1.18 ± 1.2 cm2, 22.2% increase), and T1 to T3 (2.6 ± 1.7 cm2, 35.7% increase) (P <.05). Similar increases were found in the middle and posterior nasal cavity. Significant increases in volume were found from T1 to T2 (2.1 ± 2.7 cm3, 10.7% increase), T2 to T3 (4.9 ± 2.3 cm3, 22.6% increase), and T1 to T3 (6.99 ± 2.45 cm3, 27.8% increase). No significant differences were found in the area or the volume of the left and right sides of the nasal cavity. Individual variations in response to maxillary expansion were large for most of the parameters tested. Conclusions: These data suggest that rapid palatal expansion is usually accompanied by increases in area and volume of the nasal cavity, and these changes remain stable 3 months after maxillary expansion.