Effects of early and later timed cervical headgear treatment on the eruption timing and pattern of permanent upper canines and molars from 7 to 18 years of age: follow-up of a randomized controlled trial.

Background: Although cervical headgear (CH) is a widely studied method for the correction of Class II malocclusion, there is a lack of evidence regarding the effects of early versus later treatment timing on permanent upper canines and molars.

Objectives: To evaluate the differences between early versus later cervical headgear treatment to the eruption time and inclination of maxillary permanent canines and second molars, inclination of the first molars, and the overlapping between second and third molars.

Trial Design: Randomized, parallel-group, prospective controlled trial on timepoints T0-T2, follow-up study on T2-T4.

Methods: The material consisted of 67 seven-year-old children, with a Class II malocclusion, randomized into two equal-sized groups using opaque sealed-envelope randomization. In the early group (EG, n = 33), CH treatment was started at the age of 7.8 (T0) and in the later group (LG, n = 34) at the age of 9.5 (T1). Children received active CH treatment until Class I molar occlusion was achieved, after which individualized orthodontic treatment was provided at timepoints T2-T4. Dental panoramic tomographs (DPTs) were taken at five timepoints: T0-T4 (T0 = mean age 7.3 years, T1 = 9.6 years, T2 = 11.5 years, T3 = 15.3 years, and T4 = 17.8 years). The comparisons between the groups in DPT measurements were made at different timepoints using t-test and Mann-Whitney U-test and by combining the results using a linear mixed model. Due to the nature of the trial, the clinicians and children could not be blinded during the study; therefore, blinding was applied during data assessment.

Results: In the LG, the right canine erupted earlier in T1 and in T2 and in combined results both canines erupted earlier. In the LG canines were more vertically inclined in T2. The second molars in the EG were more distally tipped in T1 and on the left side in combined results. The eruption stage of the second molars was earlier in the LG than in the EG. In the EG, more overlapping of the right and left third molars with the second molars was observed in T1. All P-values were < 0.05. No harms were encountered.

Conclusion: A later treatment timing seems more beneficial, with earlier eruption and more vertically oriented canines, less distal tipping, and earlier eruption of second molars and less overlapping between second and third molars.

Trial Registration: Clinical Trials ID: NCT02010346.