Three-Dimensional Assessment of Pharyngeal Airway Space by MRI in Class II Division 1 Patients Treated
by Twin Block Appliance
ZC20-ZC23
Correspondence
Dr. Tulika Tripathi,
Department of Orthodontics, 4th Floor, MAIDS, MAMC Comnplex, BSZ Marg, Delhi-110002, India.
E-mail: drtulikatripathi@yahoo.com
Introduction:A close relationship exists between pharyngeal airway and dentofacial structures. Retrognathic mandible is an anatomic predisposing factor for narrow pharyngeal airway. Twin Block appliance improves the patency of pharyngeal airway by correction of mandibular retrognathia in growing patients.
Aim: To assess changes in pharyngeal airway space by MRI in Class II Division 1 subjects treated by twin block appliance.
Materials and Methods: A total of 12 patients (two females and ten males) in the age group of 12-14 years were treated by Twin-Block appliance for correction of Class II Division 1 malocclusion. All the orthodontic records and MRI were collected at two stages, T1 (Pre-treatment) and T2 (Post-treatment). Three-dimensional analysis of pharyngeal airway space was performed. Normality of the data was checked by Kolmogorov Smirnov test. Paired-t test was performed to compare the means at T1 and T2.
Results: Following Twin Block treatment, MRI showed statistically significant increase in pharyngeal airway space in all three dimensions. Maximum increase in volume was seen in oro-pharynx (240±92.75 mm3, p<0.05) followed by hypo-pharynx (207±139.62 mm3, p< 0.01) and naso-pharynx (111.51±137.03 mm3, p< 0.05). Laterally and sagitally, maximum increase of 1.61±.55 mm and 1.92±0.89 mm respectively was seen in oro-pharynx (P<0.001). Vertically, total increase of 3.73 mm was observed in pharyngeal airway with the highest increase in hypo-pharynx (1.421mm, p< 0.05) followed by oro-pharynx (1.392 mm) and naso-pharynx (0.917 mm).
Conclusion: There is a positive impact of Twin Block treatment on pharyngeal airway dimensions. When narrow airway is suspected clinically or on cephalograms, MRI is useful for dynamic pharyngeal airway space analysis, as transverse and volumetric changes cannot be appreciated by two-dimensional imaging.