The purpose of this study was to use cone-beam computed tomography (CBCT) to assess changes in the volume and cross sectional areas of the upper airway in children with maxillary constriction treated by rapid maxillary expansion (RME).
The study group consisted of 5 males and 9 females with mean age of 12.93 years with posterior cross bite and constricted maxilla who were treated with hyrax expander as part of their comprehensive orthodontic treatment. Pre and post RME CBCT scans were analyzed with 3D Dolphin 11.0 software to measure the retropalatal (RP) and retroglossal (RG) airway changes including volume and cross sectional areas. The transverse width changes were evaluated from the maxillary inter 1st molar and inter 1st pre molar mid lingual alveolar plate points. Pre and post RME scans were compared with paired t test and Pearson correlation test was done on data reaching significance.
Only the cross sectional airway measured at posterior nasal spine (PNS) to Basion (Ba) level showed a statistically significant increase (P=0.0004). The minimal cross sectional area (MCA) was always found within the RP airway. The inter-molar and inter-premolar mid lingual alveolar plate distances increased equally by 4.76 mm and were statistically significant (P\u3c 0.0001). The percentage increase at the 1st premolar level was significantly larger than at the 1st molar level (P= 0.035). PNS-Ba cross sectional area increase was highly correlated with the maxillary 1st molar mid lingual inter alveolar plate width (p=0.0013).
In conclusion, RME produced a numerically equal amount of expansion between the mid inter-lingual plates of maxillary 1st molars and 1st premolars. However, when the percentage change was calculated, a greater opening was observed at the 1st premolar level suggesting a triangular shape of opening. In regard to the upper airway, a moderate increase of the cross sectional area adjacent to the hard palate was found and this increase was deemed to be highly dependent on the expansion between the maxillary 1st molars. Further studies with a larger sample size and incorporating breathing evaluations are needed to estimate the real impact of the RME on the airway
