Associations of sagittal malocclusions with dental arch characteristics and crowding in Northern Finland Birth Cohort 1966.

Objective: To analyse the associations between the widths and forms of dental arches, malocclusions and crowding in middle-aged adult population.

Materials And Methods: The study material is part of the Northern Finland Birth Cohort 1966 (NFBC1966); the subjects were examined at the age of 46 years. A total of 781 adults with full dentition and no orthodontic treatment history were included. Overjet, overbite, cross-bite and scissor bite were examined during clinical examination. The widths and forms of dental arches, molar relationships and crowding were measured using three-dimensional (3D) dental models.

Results: Dental arches were significantly larger in males than in females. Class II (CII) occlusion and increased overjet (≥6 mm) were associated with narrow maxilla (P < .001, P < .05 respectively). Subjects with lateral cross-bite had significantly narrower maxilla and wider mandible (P < .05) than subjects with normal lateral occlusion. In subjects with CII occlusion, square or tapered maxilla and tapered or ovoid mandible were significantly more frequent compared to subjects with Class I (CI) occlusion (P < .05). CII occlusion was significantly associated with crowding in the maxilla (P < .01).

Conclusion: Narrow and tapered-shaped maxilla was related to CII occlusion, which was associated with dental crowding in the maxilla. Malocclusions were more likely to be found together with other malocclusions than alone.