by Marcos C. Pitta DDS, Larry M. Wolford DMD, Reena M. Talwar DDS, PhD
Patients with retruded maxilla and mandible may have a decrease in pharyngeal airway space. This study evaluated the effects of counter-clockwise rotation of the maxillo- mandibular complex on velopharyngeal structures.
Thirty patients (22 F, 8 M) with an average age of 36.3 years (R 18 to 56) underwent maxillary and mandibular advancement with counter-clockwise rotation and rigid fixation with an average follow-up of 29.6 months (R 12 to 62). Immediate pre-op (T1), immediate post-op (T2) and long-term follow-up (T3) lateral cephalometric radiographs were taken for each patient, in a standardized head position (Quint Sectographic Corp.). The radiographs were analyzed by a single investigator for surgical changes (T2 – T1), long-term stability (T3 – T2) and long-term changes (T3 – T1). Soft tissue variables were analyzed for long-term changes (T3 – T1).
All measurements were made parallel or perpendicular to Frankfort horizontal and a posterior perpendicular vertical reference line. Statistical descriptive analysis and paired sample t-tests were used to verify significant surgical changes and long-term stability of the surgical procedures.
The mean mandibular advancement was 7.5 mm (SD 6.3 mm, p< 0.001) with long term mean change of -0.3 mm (SD 0.1), which was not statistically significant. The mean maxillary advancement was 2.0 mm (SD 3.5 mm, p<0.003) with long term mean change of 0.2 mm (SD 0.1), which was also not statistically significant. There were significant changes in all of the long term (T3 – T1) measured variables. Related to the amount of mandibular advancement the pharyngeal airway space increased an average of 79.0 % at the level of the posterior base of tongue and 48.6 % at the most inferior- posterior aspect of the soft palate.
The absolute advancement of the tongue was 88.8% of the mandibular advancement, but the posterior pharyngeal wall advanced forward a mean of 2.0mm (SD 0.6) associated with the change in head and neck posture, so the real change in PAS was 79%. The soft and hard palatal structures moved downward and forward, resulting in a 3. 5 mm increase in posterior airway space at the level of the soft palate.
Maxillo-mandibular counter-clockwise rotations produce significant changes in the position of velopharyngeal structures with an overall increase in the pharyngeal airway space.
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