Effects of rapid maxillary expansion with a memory palatal split screw on the morphology of the maxillary dental arch and nasal airway resistance.

The purpose of this study was to investigate the effects of rapid maxillary expansion (RME) with a memory palatal split screw on the morphology of the maxillary dental arch and nasal airway resistance (NAR). The material consisted of the rhinomanometric records and study models of 15 patients (8 females and 7 males) with mean age of 12.89 ± 1.20 years. Data were collected before expansion (T1), immediately after expansion (T2), and after a retention period of 6 months (T3). Maxillary expansion was completed within 8 days in all subjects. The data were analysed by analysis of variance. The least significant difference test was also used to determine between which periods the changes in the measurements were significant. Statistical analyses showed that NAR decreased (P < 0.01) and intermolar and interpremolar distances increased (P < 0.001) significantly at all observation periods, except between T2 and T3. RME using a memory palatal split screw is effective for improvement of nasal respiration via a widening effect on the nasal cavity.