Orthopedic outcomes of hybrid and conventional Hyrax expanders

Abstract

Objectives: To compare the effects of a hybrid miniscrew-supported expander versus a conventional Hyrax (CH) expander in growing patients.

Materials and methods: Forty patients were randomized into two groups: a hybrid Hyrax (HH) expander group using a Hyrax expander with two miniscrews and a CH expander group. The final sample had 18 subjects (8 female, 10 male; initial age of 10.8 years) in the HH group and 14 subjects (6 female, 8 male; initial age of 11.4 years) in the CH group. Cone-beam computed tomography examinations and digital dental models were obtained before expansion and 11 months postexpansion. The primary outcomes included the orthopedic transverse effects of expansion. Intergroup comparison was performed using analysis of covariance (P < .05).

Results: Significantly greater increases in the nasal cavity width, maxillary width, and buccal alveolar crest width were found for the HH group. No intergroup differences were observed for dental arch width or shape changes.

Conclusions: The HH group showed greater increases in the nasal cavity width, maxillary width, and buccal alveolar crest width. No differences were observed for intermolar, interpremolar, or intercanine widths; arch length; or arch perimeter. Arch size and shape showed similar changes in both groups.

Keywords: Dental models; Imaging; Interceptive; Orthodontic appliance; Orthodontics; Palatal expansion technique; Three-dimensional.

Figure 1.

CONSORT flow chart.

Figure 2.

(A) Hybrid Hyrax expander group. (B) Conventional Hyrax expander group.

Figure 3.

Miniscrews installed with a 45° inclination in the paramedian anterior palate in a subject using the hybrid expander.

Figure 4.

(A) Coronal slice showing the transverse measurements (Table 1). (B) Transverse measurements performed on the digital dental models (Table 1). (C) Landmarks used for arch shape analysis.

Figure 5.

(A) Intergroup comparison of preexpansion arch shape. (B) Intergroup comparison of postexpansion arch shape. (C, D) Arch shape before (black line) and after expansion (gray) in the hybrid (C) and conventional Hyrax (D) groups.