Correlation Between Hyoid Bone Position, Width Of Pharynx and Swallowing Function Before-After Orthognathic Surgery for Mandibular Deficiency

Shunsuke Namaki DDS, PhD, Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan
Norio Maekawa , Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan
Jun Iwata , Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan
Mitsuyo Namaki DDS, PhD, Department of Oral and Maxillofacial Surgery, Juntendo University Faculty of Medicine, Tokyo, Japan
Yoshiyuki Yonehara MD, PhD, Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan
Study objectives: Sagittal split ramus osteotomy (SSRO) is a common treatment for the mandibular deficiency and results in functional and aesthetic improvements. In some cases, a combination of maxillary and mandiblar osteotomies to achieve the best possible occlusal, functional, esthtic result and improvement of Obstructive Sleep Apnea. Mandibular advancement alters the positions of the tongue, hyoid bone position and width of pharynx. The aim of this study was to determine the correlation between the hyoid bone position, width of pharynx and swallowing function as evaluated before and after maxillary and mandibular orthognathic surgery.

  Methods and material: The subjects were 10 patients (2 males, 8 females; mean age, 25.6 years) with dentofacial deformities who had skeletal class Ⅱ malocclusions. 4 patients underwent bilateral SSRO. 6 patients underwent Le Fort Ⅰ+ bilateral SSRO. Morphological changes were evaluated on cephalometric radiographs, and swallowing function was evaluated by videofluorography. Evaluations were performed before surgery and 7 to 10 days after surgery. Swallowing function was assessed quantitatively. Oral transit time, pharyngeal transit time, and total transit time were measured before and after surgery, and the values were compared.

 Data analysis: Data were analyzed by conventional statistical methods. For each variable, the mean, range, and standard deviations were calculated. Values before and after orthognathic surgery were compared with the Wilcoxon signed-rank test. Statistical analysis was performed using SPSS statistical software (Dr. SPSS II for Windows, SPSS Japan Inc, Tokyo, Japan).

  Result: HSN degree and the distances of the sella and mandible to the hyoid bone position no significantly changed after surgery. Width of pharynx were significantly wider after surgery than before surgery. On videofluorographic assessment, oral transit time, pharyngeal transit time and total transit time were significantly shorter 7 to 10 days after surgery than before surgery. There were positive correlations between the hyoid bone position and hypopharynx, there was a negative correlation between width of pharynx and the pharyngeal and total transit time.

  Conclusion: We conclude that orthognathic surgery for mandibular deficiency influences hyoid bone position, width of phrynx and swallowing function.

 References:

  1. Jakobsone G, Neimane L, Krumina G, Latvai R. Two- and three-dimensional evaluation of the upper airway after bimaxillary correction of ClassⅢmalocclusion. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010: 110: 234-242.
  2. Namaki S, Tanaka T, Hara Y, Ohki H, Shinohara M, Yonehara Y Videofluorographic evaluation of dysphagia before and after surgical flap and scar modification in patients with oral cancer. - Surgical procedure for dysphagia improvement -. J Plast Surg Hand Surg 2011: 45: 136-142
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