Effect of Class III bone anchor treatment on airway

Abstract

Objectives: To compare airway volumes and minimum cross-section area changes of Class III patients treated with bone-anchored maxillary protraction (BAMP) versus untreated Class III controls.

Materials and methods: Twenty-eight consecutive skeletal Class III patients between the ages of 10 and 14 years (mean age, 11.9 years) were treated using Class III intermaxillary elastics and bilateral miniplates (two in the infra-zygomatic crests of the maxilla and two in the anterior mandible). The subjects had cone beam computed tomographs (CBCTs) taken before initial loading (T1) and 1 year out (T2). Twenty-eight untreated Class III patients (mean age, 12.4 years) had CBCTs taken and cephalograms generated. The airway volumes and minimum cross-sectional area measurements were performed using Dolphin Imaging 11.7 3D software. The superior border of the airway was defined by a plane that passes through the posterior nasal spine and basion, while the inferior border included the base of the epiglottis to the lower border of C3.

Results: From T1 to T2, airway volume from BAMP-treated subjects showed a statistically significant increase (1499.64 mm(3)). The area in the most constricted section of the airway (choke point) increased slightly (15.44 mm(2)). The airway volume of BAMP patients at T2 was 14136.61 mm(3), compared with 14432.98 mm(3) in untreated Class III subjects. Intraexaminer correlation coefficients values and 95% confidence interval values were all greater than .90, showing a high degree of reliability of the measurements.

Conclusion: BAMP treatment did not hinder the development of the oropharynx.

Keywords: Airway; Class III; Skeletal anchorage.

Figure 1.

Elastic traction is applied from the upper bone plates to the lower bone plates for 24 hours a day over a period of 1 year.

Figure 2.

Surface models are oriented to Frankfort horizontal/transverse planes using the following reference lines: (A) porion–orbitale in the sagittal view, (B) trans-orbitale in the coronal view, and (C) Crista Galli–middle of basion in the transverse view.

Figure 3.

Borders of airway volume are shown. The superior border includes the most posterior point of the bony posterior nasal spine to basion, while the inferior border is defined by a line from the inferior edge of C3 to the base of the epiglottis.

Figure 4.

Three-dimensional image of a segmented airway from bone-anchored maxillary protraction–treated patient. The volume of the hypopharynx is shown, while the minimum cross-section area (choke point) is designated as the circle.