Abstract:

Objective To investigate maxillary and mandibular rotation type and characteristics in normal and Ⅱ1 malocclusion adolescents with different growth patterns. Methods 158 cephalometric films of normal occlusion and 246 cephalometric films of Ⅱ 1 malocclusion aged between 10 and 13 years old were selected. Linear regression method was used to analyze the correlation between facial height index and inclination of palatal plane, occlusal plane and mandibular plane in normal occlusion, and to establish floating norm diagram. Then maxillary and mandibular rotational types in normal occlusion and Ⅱ 1 malocclusion with different growth patterns was clarified and their proportion was counted respectively. Results Another type was found beside from traditional ones, which was characterized by that one of the palatal plane and mandibular plane remained unchanged while the other rotated either anteriorly or posteriorly, or both planes remained unchanged. In normal occlusion with different growth patterns, the proportion of five types showed no marked difference, while in Ⅱ1 malocclusion with different growth patterns, they displayed remarkable distinction: The proportion of downward rotation type in vertical growth pattern and converging type in horizontal growth pattern increased remarkably. Conclusion A new rotation type was put forward and the difference of five rotation types in Ⅱ1 malocclusion would provide reference to clinical diagnosis and treatment.

Key words: maxillary and mandibular rotation, facial growth pattern, floating norm