The Relationship between the Angulation of the Roots and the Rate of Approximal Drift of Cheek Teeth in Adult Monkeys

The angulation of the roots of cheek teeth in nine adult monkeys (Macaca irus) were measured from lateral radiographs taken after death. The angle formed by seventy pairs of teeth was compared with the horizontal distance these teeth were known to have migrated relative to each other during the last few weeks of life. It was found that no significant correlation was present between these parameters nor with the direction of horizontal drift. This was true when the teeth were in normal occlusion, the opposing teeth were extracted or the interdental soft tissues were scraped away. This evidence together with specimens of mammalian skulls showing lack of association of angulation of the roots and presence or absence of approximal contacts indicates that the inclination of the roots is not an important factor in the causation of approximal drift in adult animals.