Comparison of effects of cervical headgear treatment on skeletal facial changes when the treatment time is altered: a randomized controlled trial.

Background: There is a lack of evidence based on longitudinal information in the field of Class II malocclusion management with cervical headgear (CH), especially in a randomized setting. Objectives: The main objective of this study was to evaluate skeletal facial changes, particularly in vertical dimensions, after Kloehn-type CH treatment in children when the timing of treatment is altered. Trial design: Prospective, parallel-group, randomized controlled trial. Methods: Screened children with Class II malocclusion were randomized in 1:1 ratio to two groups of equal size by sealed-envelope randomization: the early group (EG), where active CH treatment was started at the age of 7.8 years, and the late group (LG), where CH treatment was started at the age of 9.5 years.The active treatment was continued until normal Class I occlusion on first molars was achieved. Cephalograms were taken at three different time points. Changes in cephalometric measurements were compared between groups and genders. Blinding was applicable for outcome evaluation. Results: Of 67 randomized children, 56 completed the study. Upper face height increased during the CH treatment phase, as the parameter N-ANS increased significantly during the active treatments of EG (P < 0.05) and LG (P < 0.05). Also, the parameter NSL-PL increased significantly during the treatment of EG (P < 0.01) and during the treatment of LG (P < 0.01). The Gonial angle decreased significantly in the early CH treatment group compared to the later treatment group (T-0-T-2: P < 0.01). CH improved the antero-posterior jaw relationship. No harms were encountered. Conclusions: Although the upper face height increased, the mandible showed anterior rotation after CH treatment. The Gonial angle was significantly decreased in the EG compared to the LG. There were gender-specific differences in both sagittal and vertical dimensions when examining interrelations in dimensional changes. The differences found between the early and later treatment groups were not clinically important when the cephalometric results are considered.