Does headgear treatment in young children affect the maxillary canine eruption path?

Objective: To test whether early headgear (HG) treatment and space conditions in the dental arch affect the eruption pathway of the maxillary canines in young children with mixed dentition. Subjects and methods: Data from two randomized controlled trials studying the effects of early HG treatment were pooled, yielding a study sample comprising 99 children (38 girls and 61 boys, mean age 7.6 years) with Angle Class II occlusion. Fifty-one children were treated with HG and 48 children served as an untreated control group (CG). Digital 3D models and panoramic radiographs were taken before (T0) and after (T1) treatment, and changes in the maxillary canine eruption angle and interdental spaces were measured at T0 and T1. A paired samples t-test was used to assess changes in maxillary canine angulation, and an independent samples t-test was used to evaluate the effect of HG treatment on spacing in the dental arch. Associations between intra-arch space conditions and changes in maxillary canine angulation were estimated with linear regression models. Results: The eruption pattern of the permanent canine was significantly more vertical in the HG group than in the CG. The linear regression models showed a statistically significant association among the intercanine distance, crowding in the anterior part of the maxilla, and changes in the maxillary canine eruption angle. The maxillary canine eruption pattern changed significantly more to a vertical direction in spaced dental arches than in crowded dental arches in the HG group. Conclusion: This study shows that early HG treatment in children with Angle Class II occlusion may change the eruption pattern of permanent maxillary canines to a more vertical direction. This change appears to be related to space conditions in the maxillary arch, especially in the intercanine region, with more effect in children with spaced dental arches than in children with crowded dental arches.