Background: A Kloehn-type cervical headgear (CH) aims to correct skeletal jaw discrepancy in Class II children. A few studies have reported CH treatment effects on airway dimensions, but none of them have been randomized according to timing.
Objectives: To evaluate related craniofacial structures and pharyngeal airway dimensions in children with a Class II occlusion treated with CH and randomized into early and late treatment groups.
Trial design: Randomized, parallel-group, prospective controlled trial.
Methods: The material comprised 67 seven-year-old children with a Class II occlusion. Sealed-envelope randomization in 1:1 ratio was used to divide the children into two equal groups. In the early group (EG, n = 33), CH treatment was started immediately or after eruption of the first maxillary molars. In the second, late group (LG, n = 34), the active CH treatment was started about one and half year later. The active CH treatment was continued in both groups until normal Class I occlusion on first molars was achieved. Cephalometric radiographs were taken from both groups at the beginning of follow-up (T0), at the beginning of CH treatment of the second group (T1), and at the end of CH treatment of the second group (T2). Changes in cephalometric measurements were used as primary outcomes. Blinding was applicable for outcome assessment.
Results: Fifty-six children completed the study. The posterior change in the position of the maxilla was significant for early treatment males at T0-T1 (SNA; P < 0.001, ANB; P = 0.009) and T0-T2 (SNA; P = 0.012). The palato-mandibular angle (PL-ML) decreased during T0-T1 in early treatment females (P = 0.018) and early treatment males (P = 0.037). The retroglossal airway increased (P = 0.010) in early treatment males at T0-T1. Highly significant positive correlations (P < 0.001) between skeletal and upper airway dimensions during early CH treatment were found in males. No harms were encountered.
Conclusions: Despite the effective CH treatment, no harmful upper airway changes were found.
Clinical registration: NCT02010346.