Effects of rapid vs slow maxillary expansion on nasal cavity dimensions in growing subjects : a methodological and reproducibility study

Aim To evaluate the methodological feasibility of a RCT comparing skeletal changes of nasal cavity size obtained with RME and SME, assessed via CBCT. Methods Twenty Caucasian children with a mean age of 10.4 years were recruited and allocated to receive RME (10 subjects, mean age 10.4 years) or SME (10 subjects, mean age 10.5 years). Inclusion criteria: constricted maxillary arch, upper and lower first molars erupted, unilateral or bilateral posterior crossbite. Exclusion criteria: age above 15 years, history of previous orthodontic treatment, periodontal disease, systemic disease affecting craniofacial growth, or craniofacial congenital syndrome. CBCT examinations were performed before treatment (T0) and 7 months after expander removal (T1). Changes of nasal width (NW), palatal width (PW) and total nasal volume (TNV) were assessed; palatal and nasal expansion was also calculated as a percentage of the increase of intermolar width IMW (PW% and NW%). Results The correlation between the first and the second readings ranged from 0.991 to 0.995 for linear measurements and was of 0.915 for volumetric measurements. The method error, as described by the value of s, was in general less than 0.3 mm for linear measurements and 0.372 cm3 for volumetric measurements. All linear transverse skeletal and dental measurements and the nasal volume increased with both RME and SME protocols. Conclusions The reported methodology can be reasonably used to investigate the transverse dimension of nasal cavity. The PW% and NW% parameters more accurately described the efficacy of the two expansion protocols as compared to their corresponding absolute measurement (PW and NW).