Rotation of the upper first molar in Class I, II, and III patients

OBJECTIVE The aim of this study was to evaluate the mean rotation of the upper first molar (U1(st) M) in cast models from nontreated patients presenting: Class I, skeletal Class II, dental Class II, and skeletal Class III, comparing with Class I orthodontically treated patients. MATERIALS AND METHODS One hundred cast models were evaluated with five groups, composed of nontreated Class I (n = 20), dental Class II (n = 20), skeletal Class II (n = 20), skeletal Class III (n = 20), and treated Class I (n = 20). Measurements were taken from photocopies of the upper arches. The angle formed between a line crossing the mesiopalatal and the distal-buccalcusps of the U1(st) M and a line traced on mid palatal junction were measured in all samples. RESULTS One-way variance analysis showed that dental Class II group presented great mean rotation of the 1(st) molar (x = 78.95°, SD = 6.19) (P < 0.05), and in 85% of the patients from this group this angle was higher than 73°. CONCLUSIONS The skeletal Class II and skeletal Class III groups showed similar mean position of the 1(st) molar, presenting rotation in approximately 50% of the patients. It can be concluded that upper molar rotation occurs mainly in dental Class II patients and shows higher mesial rotation angle.