Compensation trends of the angulation of first molars: retrospective study of 1403 malocclusion cases.
We investigated the compensatory trends of mesiodistal angulation of first molars in malocclusion cases. We compared differences in the angulation of first molars in different developmental stages, malocclusion classifications and skeletal patterns. The medical records and lateral cephalogrammes of 1403 malocclusion cases taken before treatment were measured to evaluate compensation of molar angulation in relation to the skeletal jaw. The cases were stratified by age, Angle classification and skeletal patterns. Differences in the mesiodistal angulation of the first molars were compared among the stratifications. We observed three main phenomena. First, angulation of the upper first molar varied significantly with age and tipped most distally in cases aged <12 years and least distally in cases aged >16 years. The lower first molar did not show such differences. Second, in Angle Class II or skeletal Class II cases, the upper first molar was the most distally tipped, the lower first molar was the most mesially tipped, and opposite angulation compensation was observed in Class III cases. Third, in high-angle cases, the upper and lower first molars were the most distally tipped, and opposite angulation compensation was observed in low-angle cases. These data suggest that the angulation of the molars compensated for various growth patterns and malocclusion types. Hence, awareness of molar angulation compensation would help to adjust occlusal relationships, control anchorage and increase the chances of long-term stability.
Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China.
Hong
H
Su
Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China.
Bing
B
Han
Department of Stomatology, Shenzhen People's Hospital, Shenzhen, China.
Sa
S
Li
Graduate from School and Hospital of Stomatology, Peking University, Beijing, China.
Bin
B
Na
Arrail International Dental Clinic, Beijing, China.
Wen
W
Ma
Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China.
Tian-Min
TM
Xu
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D059925:Anatomic Landmarks / Q000473:pathology; D002508:Cephalometry / Q000379:methods; D002648:Child; D015331:Cohort Studies; D003818:Dentition, Mixed; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000145:classification / Q000473:pathology*; D008311:Malocclusion, Angle Class I / Q000473:pathology; D008312:Malocclusion, Angle Class II / Q000473:pathology; D008313:Malocclusion, Angle Class III / Q000473:pathology; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D008445:Maxillofacial Development / Q000502:physiology; D008875:Middle Aged; D008963:Molar / Q000473:pathology*; D010159:Palate / Q000473:pathology; D012189:Retrospective Studies; D055815:Young Adult