Cephalometric analysis of molar and anterior tooth movement during cervical headgear treatment in relation to growth patterns.

Objective: In this study we aimed to identify the reasons why cervical headgear treatment fails to induce bite opening or clockwise rotation of the mandible in the presence of a vertical growth pattern. In so doing, we investigated the dental effects of headgear treatment relative to growth patterns.

Materials And Methods: Records of 119 patients were analyzed, including casts and lateral cephalograms that had been obtained immediately before and after isolated cervical headgear treatment. Dental changes were determined relative to the SN line and a perpendicular line through point S. Inclusion criteria were: improvements in occlusal relationship of at least 4 mm in molar segments and treatment lasting at least 6 months. An orthodontic force of 3.5-4 N was applied in all cases through headgear featuring non-angulated outer arms. The headgear was worn for 14 hours a day during the active treatment phase. At the beginning of headgear treatment, patients were allocated into six groups according to y-axis values to quantify growth-related differences.

Results: The upper first molar was moved an average of 1.3 mm distally, while the lower first molar was moved an average of 2 mm mesially. These movements revealed no differences in terms of growth patterns. We were not able to make representative findings pertaining to upper molar extrusion due to distal tilting and the measuring point's position. We used the lower molars' movements for analysis instead, which demonstrated mean downward changes of 5.1 mm in all groups. The vertical growth pattern groups presented smaller caudal movements in the upper and lower anterior segments than did those groups with horizontal growth pattern. The occlusal plane's inclination decreased more extensively in the vertical growth pattern groups than in those with a horizontal pattern (e.g. H2: -0.1 degrees ; V3: -2.3 degrees ).

Conclusion: Our results suggest that while the upper molars extrude, the mandible rotates around the molars in a hypomochlion fashion in the presence of a vertical growth pattern, thus leading to bite deepening.