EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

correction in order to sever these tissue attachments that are thought to
contribute to the relapse (Thompson 1959; Edwards 1970, 1988; Boese 1980).
Redlich et al. (1996) also examined the posttreatment relapse tendencies of
rotated teeth, but contrary to Reitan and Edwards, came to different conclusions
regarding stretched collagen fibers. Redlich et al. had the benefit of scanning and
transmission electron microscopes to analyze control and experimentally rotated
tissue samples. Results indicated that the rotational forces produced gingival
tissue changes that were inconsistent with stretching. Following resection of
these tissue fibers, many of these periodontal fibers assumed positions similar to
their pretreatment positions and the positions of the control groups.
Mandibular Incisor Dimensions and Approximal Contacts
Theories have been put forth concerning the association between
mandibular incisor dimensions and crowding. Begg (1971) proposed that the
interproximal surfaces of teeth, particularly the incisors, become worn over time
due to function. As this attrition takes place, the interproximal contacts between
adjacent teeth evolve from a smaller, point type contact to a broader and flatter
contact that he proposes to be a natural aid to stability. This interproximal
attrition also reduces the mesiodistal width of the teeth, which allows for the
mesial migration of teeth in response to the constant mesial forces present on
them. In essence, Begg attributes dental stability to changes in shape and size of
the approximal contacts of mandibular incisors.
Moore (1956) compared the mandibular dental arch with the staves of a
barrel; as long as all of the staves in a barrel are in contact with one another, the
barrel remains intact. He noted that the lingual and distal functional forces
acting on the lower incisors must be offset or resisted by what he termed the
“contained arch principle” (p 53) and possibly pressure exerted by the tongue.
This contained arch principle depends on each of the lower incisors having solid,
broad contacts with each other, thus balancing the opposing forces without
slipping. Like Begg, Moore suggested that flat, worn contacts were better able to
balance opposing forces and minimize slippage than were smaller, point
contacts.
According to Huckaba (1952), Dewey and Anderson (1942) also suggest
that approximal contacts are important, natural forces of retention. They made
the comparison of the dental arch to a masonry arch in which each unit exerts a
passive force to maintain itself and its fellows in alignment. In just the same
manner, if a unit of the dental arch is removed or distorted by a faulty
restoration, a lack of stability will occur. All the active muscle forces that are
15