Background: Rapid maxillary expansion (RME) may improve the nasal respiratory pattern. This study was performed to evaluate the effect of RME on the nasal cavity by acoustic rhinometry and computed rhinomanometry and to determine nasal and maxillary width by posteroanterior cephalometric radiography, up to 30 months after the orthodontic procedure.
Methods: Twenty-seven children with oral breathing, ranging in age from 7 to 10 years, and with mixed dentition were selected. The children had uni- or bilateral posterior crossbite involving deciduous canines and the first permanent molars. All subjects were submitted to nasofibroscopy, acoustic rhinometry, and computed rhinomanometry and posteroanterior cephalometric radiography at four different times, i.e., before expansion, immediately, 90 days and 30 months after expansion.
Results: The mean linear left-to-right nasal cavity lateral prominence and left-to-right jugal points cephalometric measures increased considerably after expansion and this increase was maintained throughout the period of evaluation. There was an immediate significant decrease in nasal resistance, up to 90 days after RME, but the nasal resistance increased 30 months after the procedure. The acoustic rhinometry results did not show any difference in values throughout time.
Conclusion: RME significantly increased nasal and maxillary width as measured by frontal cephalometry, but the nasal mucosal effects were more subtle. Also, the influence of RME on nasal resistance was not stable, and nasal resistance values returned to close to the initial ones after 30 months.