Lateral cephalometric radiographs of adult orthodontic patients referring for orthodontic consultation at the Unit of Orthodontics and Pediatric Dentistry, Section of Dentistry, Department of Clinical, Surgical, Diagnostic and Pediatric Sciences, University of Pavia, 27100 Pavia, Italy, will be collected for the study according to the inclusion criteria.~For each lateral cephalometric radiograph, a cephalometric tracing will be performed with DeltaDent software (version 2.2.1, Outside Format, Spino d'Adda, Italy). Riedel's ANB angle [Riedel 1952] has been adopted to determine patients' skeletal class. Steiner's SN^GoGn angle [Steiner 1953] will be used to evaluate skeletal divergence. Biprotrusion will be assessed for SNA > 84° and SNB > 82°, while biretrusion for SNA < 80° and SNB < 78°.~Sample size calculation was performed with soft palate length as primary outcome. Considering alpha = 0.05 and power = 95%, an expected mean value of 31.05 with a standard deviation of 4.16 was hypothesized, with an expected mean difference of 3.34 [Sprenger et al. 2017], therefore 40 patients per group were required.~Statistical analysis will be conducted with R® software (version 3.1.3 R Development Core Team, R Foundation for Statistical Computing, Wein, Austria). For each cephalometric measure belonging to the three skeletal classes, descriptive statistics (mean and standard deviation) will be calculated. Appropriate statistical tests will be used to assess data normality and multiple comparisons. Linear regressions will be performed between upper airways diameters and SNA, SNB, ANB, SN^GoGn, ANSPNS^GoGn, PT, PL, sex and age.
The aim of the present study is to investigate the baseline upper airways dimensions in adult patients belonging to all skeletal classes