Relationship between rapid maxillary expansion and nasal cavity size and airway resistance: short- and long-term effects.

INTRODUCTION The availability of new, reliable, objective, and 3-dimensional techniques to assess the effects of rapid maxillary expansion on the morphology of the maxillary dental arch, nasal cavity dimensions, and nasal airway resistance led to the development of this research. METHODS Thirty-eight subjects participated in this study (mean age, 13 years). Data were collected before expansion, when the expander was stabilized, when the expander was removed, and 9 to 12 months after the expander was removed. Subjective assessment of improvement in nasal respiration was obtained when the expander was stabilized. Three-dimensional imaging and acoustic rhinometry were used to assess the virtual cast and the nasal cavity, respectively. RESULTS AND CONCLUSIONS The statistically significant short-term effects of RME were (1) mean increases in palatal area, volume, and intermolar distance; (2) a mean reduction of nasal airway resistance; and (3) mean increases in total nasal volume and nasal valve area. Our long-term findings were the following: (1) mean palatal area and intermolar distance were reduced, while palatal volume was stable, and (2) nasal airway resistance was stable, whereas mean nasal cavity volume and minimal cross-sectional area increased. Additionally, 61.3% of our subjects reported subjective improvement in nasal respiration. Weak correlations were found between all variables analyzed.