Subjects

The subjects were 14 patients (two men and 12 women; average age 25.9 ± 10.6 years) with dentofacial deformities, who had skeletal class III malocclusion with or without open bite and asymmetry. The patients underwent SSRO in the department of oral and maxillofacial surgery of the study hospital. Patients who underwent Le Fort I osteotomy were excluded. All subjects received preoperative and postoperative orthodontic treatment. SSRO was performed according to the Obwegeser and Dal Pont method. The fragments were fixed with the use of titanium plates (Würzburg Titanium Plating System; Stryker Leibinger GmbH, Freiburg, Germany) and resorbable fixation devices (Super Fixsorb-MX; Takiron Co., Osaka, Japan). Each subject received a preoperative dose of dexamethasone (mean dose 4.5 mg) immediately prior to surgery, followed by postoperative treatment with dexamethasone (mean dose 2.1 mg/day) for 2 days to control postoperative swelling. The average amount of mandibular setback was 7.65 ± 3.23 mm. Intermaxillary fixation with the use of elastics or steel wires was maintained for 4–6 days postoperatively.

Informed consent was obtained from all subjects after explaining the study procedures in detail. The protocol was approved by the institutional ethics committee.

Cephalometric analysis

Morphological changes were evaluated on lateral cephalometric radiographs that were taken with the Frankfort horizontal plane (FH plane) parallel to the floor and with the patient in centric occlusion. Evaluations were performed before surgery (T0) and at 7–10 days (T1), 3 months (T2), and 6 months (T3) after surgery. All cephalograms were traced and analyzed by the same examiner. Fig. 1 shows the landmarks and contours that are commonly used for orthodontic analysis, as well as additional variables that were used to evaluate the pharyngeal airway. Four angles and three linear distances were measured to assess dentoskeletal morphological changes. Five linear distances were calculated to evaluate the pharyngeal airways.

Cephalometric linear and angular measurements. (1) sella–nasion–A point (SNA) angle. (2) sella–nasion–B point (SNB) angle. (3) A point–nasion–B point (ANB) angle. (4) HSN angle: angle between nasion, sella, and hyoid bone (lowest point of hyoid bone). (5) S–H: distance from sella to hyoid bone. (6) C3–H: distance from the most antero-inferior point of the third cervical vertebra to the hyoid bone. (7) D1: distance from posterior nasal spine (PNS) to the dorsum of the tongue on a line perpendicular to the S–N line. (8) PPS: distance from posterior pharyngeal wall to the PNS on a line parallel to the Frankfort horizontal (FH) plane. (9) SPPS: distance from the posterior pharyngeal wall to the middle of the line from PNS to PSP (tip of the soft palate) on a line parallel to the FH plane. (10) MPS: distance from the posterior pharyngeal wall to the dorsum of the tongue on a line parallel to the FH plane that runs through PSP. (11) IPS: distance from the posterior pharyngeal wall to the surface of the tongue on a line parallel to the FH plane that runs through C2 (the most antero-inferior point of the second cervical vertebra). (12) EPS: distance from the posterior pharyngeal wall to the tip of the epiglottis on a line parallel to the FH plane.

Videofluorography

Swallowing was assessed by videofluorography in all patients. Videofluorography was performed before SSRO, at 4–6 days after the release of intermaxillary fixation, and at 3 and 6 months after surgery to qualitatively and quantitatively analyze deglutition. The contrast material used was 10 ml of liquid barium. Images were recorded, converted digitally, and analyzed with InterVideo WinDVD Creator software (InterVideo, Inc., Fremont, CA, USA). Qualitative assessments included lingual movement, barium inflow into the pharynx before swallowing, soft palate movement, epiglottic movement, stasis in the epiglottic valleculae, and stasis in the oral cavity after swallowing.

Swallowing was also assessed quantitatively. The oral transit time, pharyngeal transit time, and total transit time were measured before and after SSRO, and the values were compared. The oral transit time was defined as the time required for the barium to move through the oral cavity, measured from the first backward movement of the barium until the head of the barium passed the lowest point of the mandibular ramus. The pharyngeal transit time was defined as the time required for the barium to move through the pharynx, measured from the time that the head of the barium passed the lowest point of the mandibular ramus until the tail of the barium left the cricopharyngeal region. The oral transit time and pharyngeal transit time were summed to derive the total transit time.

Data analysis

Data were analyzed by conventional statistical methods. The mean, range, and standard deviation were calculated for each variable. Values obtained before and after SSRO were adjusted with the use of the Bonferroni correction. A significance level of 5% was used throughout the study. The statistical analysis was performed using SPSS statistical software (Dr. SPSS II for Windows; SPSS Japan Inc., Tokyo, Japan).