Three-dimensional evaluation of upper airway following rapid maxillary expansion: a CBCT study

Abstract

Objectives: To evaluate, by using cone beam computed tomography, the skeletal, dental, oropharyngeal (OP) airway volume, and nasal passage (NP) volume changes that occur after rapid maxillary expansion (RME).

Materials and methods: Two groups were selected, each with 35 patients (15 males, 20 females), an RME group (mean age, 14.02 ± 1.46 years) and a control group (mean age, 14.10 ± 1.44 years). The RME group consisted of patients with maxillary constriction who were treated with Hyrax palatal expanders, and the control group comprised age- and sex-matched patients who underwent comprehensive orthodontic treatment without the use of a rapid maxillary expander.

Results: All of the transverse skeletal (medial orbital width, lateral nasal width, maxillary width, and mandibular width) and interdental (intermolar, interpremolar, and intercanine) parameters were significantly enlarged in the RME group. A statistically significant increase in airway variables was seen in both groups between pretreatment (T0) and final records (T1). The mean increase of NP airway volume for the RME group (1719.9 ± 1510.7 mm(3)) was twofold compared with the control group (813.6 ± 1006.7 mm(3)), and no intergroup significant difference was found for the OP volume.

Conclusions: Rapid maxillary expansion creates a significant increase in nasal passage airway volume but no significant change in the oropharyngeal airway volume.

Figure 1.

Cephalometric tracing illustrating measurements performed. 1, SNA in degrees; 2, SNB in degrees; 3, ANB in degrees;, 4, maxillary depth (FH-NaPerp) in degrees; 5, maxillary skeletal (A-NaPerp) in millimeters; 6, skeletal profile convexity (NaApOG) in degrees; 7, midface length (Co-A) in millimeters; 8, effective mandibular length (Co-Gn) in millimeters; 9, lower facial height (ANS-Me) in millimeters, 10, GoGnSN in degrees; 11, palatal plane-facial height in degrees; 12, palatal plane-mandibular plane in degrees.

Figure 2.

Three-dimensional measurements of transverse skeletal variables. MoL-Mor (medial orbital width in millimeters), LnL-LnR (lateral nasal width), JL-JR (most superior aspects of the concavity of the maxillary bone as it joins the zygomatic process (maxillary width) in millimeters), AgL-AgR (mandibular width in millimeters).

Figure 3.

Interdental measurements performed using the coronal view. (A) Intercanine width, or the distance between the cusp tips of canines (B) Interpremolar width, or the distance between the buccal cusp tips of first premolars. (C) Intermolar width, or the distance between the mesiobuccal cusp tips of the right and left first molars.

Figure 4.

Superior and inferior limits of OP and NP volume, PAS, and minAx (area of the most constricted region at the base of the tongue). The circle on the left illustrates the last axial slice before the nasal septum fuses with the posterior wall of the pharynx. In the center image, the top line represents the mentioned axial slice on the sagittal view (superior border of NP). In the lower right image, the area in evidence represents the PAS on the axial view; pp (line passing from palatal plane), 2cv (line passing from the most anteroinferior aspect of the second cervical vertebrae and parallel to pp).