Comparison of different orthognathic surgeries impact on pharyngeal airway space in CL III patients

Aims:  This study sought to compare the changes in the pharyngeal airway space, hyoid bone position, tongue, soft palate, and retro-lingual soft tissues by three common orthognathic surgeries on class III patients after three different types of orthognathic surgeries. Methods and material: This quasi-experimental study was conducted on 75 skeletal class III patients. The predictor variable was the type of orthognathic surgery namely mandibular setback, maxillary impaction & mandibular setback and maxillary advancement & mandibular setback (25 patients in each group). The primary outcome variables were the dimensions of the pharyngeal airway space and retrolingual region, measured preoperatively and at least one year postoperatively.     Cephalometric landmarks were also measured. Pre- and post-operative cephalograms were superimposed based on SN line with registration at the S-point. The mean, standard deviation (SD) and range of the variables were calculated and compared using paired t-test . Repeated-measures analysis of variance was used for inter-group comparisons. The Tukey’s HSD test was used for post hoc analysis (P<0.05). Results:  When considering the changes in the whole sample (75 cases) significant changes were found in oropharyngeal length (UMPW, VLPW), tongue height (H-VT), horizontal position of vallecula (V_C3) and horizontal position of the hyoid bone. The only significant difference noted, was the tongue height and vertical position of hyoid between the three groups. Conclusion: Orthognathic surgery significantly affects the oropharyngeal space and position of the tongue and hyoid bone. The three types of Orthognathic surgeries on class III patients caused different effects on oropharyngeal space, tongue and hyoid position with a significant impact on tongue height in maxillary advancement plus mandibular setback.