Transverse effect of Haas and Hyrax appliances on the upper dental arch in patients with unilateral complete cleft lip and palate: a comparative study.

Objective: The aim of the present study was to evaluate the transverse effect of rapid maxillary expansion in patients with unilateral complete cleft lip and palate while comparing the Haas and Hyrax appliances.

Methods: The sample consisted of 48 patients divided into two groups: Group I = 25 patients treated with modified Haas appliance (mean age: 10 years and 8 months); and Group II = 23 patients treated with Hyrax appliance (mean age: 10 years and 6 months). Cast models were taken during pre-expansion and after removal of the appliance, at the end of the retention period. The models were scanned with the aid of the 3 Shape R700 3D scanner. Initial and final transverse distances were measured at cusp tips and cervical-palatal points of maxillary teeth by using the Ortho Analyzer 3D software.

Results: The mean expansion obtained between cusp tips and between cervical-palatal points was, respectively: for inter-canine width, 4.80 mm and 4.35 mm with the Haas appliance and 5.91 mm and 5.91 mm with the Hyrax appliance; as for first deciduous molars or first deciduous premolars, the values obtained were 6.46 mm and 5.90 mm in the Haas group, and 7.11 mm and 6.65 mm in the Hyrax group; with regard to first molars, values were 6.11 mm and 5.24 mm in the Haas group, and 7.55 mm and 6.31 mm in the Hyrax group.

Conclusion: Rapid maxillary expansion significantly increased the transverse dimensions of the upper dental arch in patients with cleft palate, with no significant differences between the Hass and Hyrax expanders.