CBCT of skeletal changes following rapid maxillary expansion to increase arch-length with a development-dependent bonded or banded appliance

Abstract

Objective: To assess the three-dimensional (3D) skeletal response to a standardized 5 mm of rapid maxillary expansion (RME) in growing children (6-15 years) with maxillary width deficiency and crowding.

Materials and methods: A bonded appliance was used prior to the eruption of the maxillary first premolars (Mx4s), and a banded appliance was used thereafter. A consecutive sample of 89 patients (29 boys and 60 girls) from a large pediatric dentistry and orthodontics practice was divided into four groups: 1) 6-8 years old (n = 26), 2) 9-11 years old with unerupted Mx4s (n = 21), 3) 9-11 years with erupted Mx4s (n = 23), and 4) 12-15 years (n = 19). For all patients, the 3D evaluation of dental and skeletal effects was performed with cone-beam computed tomography (CBCT).

Results: For both appliances in all patients, CBCT confirmed a triangular pattern of expansion in both the frontal and sagittal planes. Overall, both appliances produced significant maxillary expansion (>80% of the 5-mm activation), but older children showed a progressively more dental (less skeletal) response. Comparison of the two types of expanders in the crossover sample, children aged 9-11 years, showed that the bonded RME produced the most efficient skeletal expansion in the preadolescent sample. Increased maxillary width at the level of the zygomaticomaxillary suture was the best indicator for development of maxillary arch circumference.

Conclusion: Development-dependent appliances (bonded RPE before Mx4s erupt, and a banded device thereafter) provided optimal RME treatment for all children from age 6-15 years.

Figure 1.

Left: McNamara-type (bonded) appliance; right: Hyrax (banded) appliance.

Figure 2.

CBCT image shows the three reference planes: axial, sagittal, and frontal (coronal), which correspond to the reference box that defines planes relative to superior (S), inferior (I), and lateral (L).

Figure 3.

Distance between bilateral landmarks: (a) maxillary first molar central pits, (b) palatal alveolar crests, (c) greater palatine foramena, (d) nasal width, (e) inferior margin zygomaticomaxillary suture, (f) infraorbital foramena, (g) superior margin zygomaticomaxillary suture, (h) the anterior border frontozygomatic suture, (i) and the lateral border frontomaxillary suture.