Cone-beam computerized tomography (CBCT) evaluation of the upper airway in the context of orthognathic surgery

Upper airway analysis has become a key focus of investigation in the fields of Orthognathic Surgery and Orthodontics. This is due to the well-acknowledged relationship between a narrow upper airway and sleep-disordered breathing, and to the association between airway configuration and specific craniofacial phenotypes. As a result of the advancement of the skeletal insertions of the suprahyoid and velopharyngeal muscles, maxillomandibular advancement with counterclockwise rotation has established itself as an effective strategy to increase the pharyngeal airway volume, with subsequent improvement in sleep-disordered breathing symptomatology. These changes can be assessed objectively with cone-beam computerized tomography (CBCT), which has provided a paradigm shift in cranio-maxillofacial imaging due to its capacity to obtain a thorough two- and three-dimensional evaluation of the upper airway at relatively modest costs, with greater accessibility, lower radiation, and shorter scanning times. The most important contributions of this PhD Thesis are the following: 1) Paper one provides the first systematic review of the literature concerning upper airway imaging and analysis with CBCT. Results confirm that CBCT is indeed an accurate and reliable tool for upper airway analysis. Nevertheless, specific problems related to the image acquisition process and to image processing and analysis persist. 2) Paper two is a preliminary CBCT evaluation of the effect of mono- and bimaxillary advancement on the volume of the upper airway. Results showed a systematic volumetric increase for all groups. However, bimaxillary and mandibular advancement achieved a greater percentage increase than maxillary advancement alone. These results suggest the influence of mandibular advancement on the posterior airway space’s dimensions is greater than the effect of the forward movement of the maxilla. 3) Based on the results of the previous two papers, paper three was aimed at providing clinical three-dimensional anatomical limits for the upper airway subregions, translating them into accurate and reliable cephalometric landmarks in CBCT data, and validating the proposed measuring protocol. Our proposed protocol for upper airway subregion analysis proved to be anatomically logical, technically feasible, and statistically reliable