Abstract:

Objective     To observe and evaluate the mandibular changes in growing Class Ⅲ malocclusion patients treated with protraction headgear. Methods    This study consisted of 30 adolescent Class Ⅲ malocclusion subjects treated with protraction headgear and 30 untreated controls from the Department of Orthodontic, School of Stomatology, Shandong University. All the subjects had their lateral cephlometrics taken before and after the treatment or observation period.The cephalometric data including variables assessing sagittal and vertical relationships of maxillary was analyzed and the direction of mandibular displacement was evaluated according to a structural superimposition method. Results   The results showed significant improvements in dentofacial profile after 6 months of maxillary protraction. During the treatment or observation period, the mean mandibular rotation between the treatment and control groups had significant difference (P<0.05). It was clockwise rotation for the treatment group and anticlockwise rotation for the control group. The mean rotation in the treatment and control groups were 0.8° and -0.6°, respectively. A more horizontal movement of the mandibular could be observed in the control group during the study period. Conclusion    The mandibular of the treatment group produces clockwise rotation while the control group has a trend of anticlockwise rotation after protraction headgear treatment.

Key words: Protraction headgear; Class Ⅲ malocclusion; Adolescent; Superimpositions; Mandibular rotation