A

Rapid (instantaneous) tooth separation is produced by driving a wooden or plastic wedge between adjacent teeth; the wedging force pushes the crowns apart immediately, so it relies on the wedge principle rather than on prolonged orthodontic traction, which is used for slow separation [Qualtrough & Wilson, 1991, PMID 1915992; VanderWeele et al., 1999, PMID 10202490].