Comparison of Nasal Cavity Effects of Haas versus Hyrax Expanders

Introduction: Rapid Maxillary Expansion (RME) is one kind of orthopedic treatment used to expand the maxilla. Since the maxilla is the floor of the nose and it is directly connected to the lateral walls of the nasal cavity, it is hypothesized that RME also affects the nasal cavity. Acoustic Rhinometry (AR) is an objective method employed to assess the nasal cavity’s geometry. Objectives: To compare the effects of Haas (tissue-born) versus Hyrax (teeth-born) expanders on the nasal cavity of growing patients receiving RME. Methods: Sixteen subjects who received RME with Haas-type (HA) expander and 15 subjects who received the Hyrax-type (HY) were tested with the AR (Eccovision system, Hood Laboratories) before (T1) and after expansion (T2). Results: Independent student t-test was used to compare HA and HY groups at T1 and T2. The results demonstrated that subjects in both groups presented with similar nasal resistance, volume and area values before and after treatment. Paired t-test was used to analyze the outcomes of expansion in each group. The results revealed that the mean airway resistance (cmH2O/L/sec) was reduced in both groups but was statistically significant only in the HY group. Nasal cavity volume (cm³) and minimal cross-sectional area (cm²) were enlarged after expansion therapy in both groups with statistical significance only in the HY group. Conclusion: In this study, RME affected the geometry and function of the nasal cavity by reducing the airway resistance, increasing the volume and enlarging the minimal crossectional area of the nasal cavity. In our sample, the tooth-born appliance (Hyrax) demonstrated better performance over the tissue-born appliance (Haas) in all variables.