Cephalometric study of the upper airways and dentoalveolar height in open bite patients

Open bite is related to various etiological factors and, in many cases, is difficult to diagnose. The present study is aimed at evaluating, through cephalometric analysis, the dimensions of the upper airways and dentoalveolar heights in open bite (OB) patients versus normal overbite patients. The relationship between the width of the upper airways and the lack of overbite is also studied, in order to differentiate between dental open bite (DOB) and skeletal open bite (SOB).

Eighty X-rays were selected from files of orthodontic patients to form the control sample (n=40) and open bite sample (n=40). Dimensions of the upper airways and dentoalveolar heights were measured in both samples, using 16 linear measurements, two angle values and one ratio.

In OB patients, anteroposterior narrowing of the upper airways, mainly in the nasopharynx and oropharynx, was observed, together with forward displacement of the hyoid bone and increased maxillary and mandibular dentoalveolar heights, and anterior facial height. In SOB, the overbite was more negative and facial growth was more clockwise-oriented than in DOB. Greater narrowing of the airways in the anteroposterior orientation was also noted. In DOB, there was evidence of muscular adaptation, as shown by increased values of the hyoid bone displacement to a more anterior and lower position, and increased values of the vertical dimensions of the airways. An increase in posterior facial height was also observed allowing anterior rotation of the mandible.

The results suggest that the airway's dimensions reflect a tendency to open bite. The variable vertical airway length (Val) and the position of the hyoid bone allow the adaptive potential of these individuals to be determined and make the treatment of open bites more predictable.