EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

Sinclair and Little (1983, p 114) assessed the dental casts of 65 untreated
normal adolescents to determine “the nature and extent of the developmental
maturation process of the normal dentition.” A normal occlusion was defined as
occurring in untreated individuals with dental and skeletal Angle Class I
relationships. The sample was obtained from records of children in the
Burlington Growth Center Study, Ontario, Canada. Six variables (irregularity
index as described by Little in 1975, mandibular intercanine width, mandibular
intermolar width, mandibular arch length, overbite, and overjet) were evaluated
in the mixed dentition (9 to 10 years), early permanent dentition (12 to 13 years),
and early adulthood (19 to 20 years). The results showed decreases in arch
length and intercanine width; minimal overall changes in intermolar width,
overjet, and overbite; and increases in Incisor Irregularity. It was also noted that
females exhibited more severe dental changes than males.
More recently, Eslambolchi et al. (2008) documented the longitudinal
dental changes in seen in 15 untreated children and 18 untreated adults who had
been participants in the original Burlington Growth Research Project at the
University of Toronto. In both groups, Little’s irregularity index continued to
increase 2.0 to 4.0 mm with age, while intercanine and interpremolar widths
continued to decrease. Arch length also decreased up to 2.0 mm in the children
and 1.0 mm in the adults over time.
Most orthodontic patients are treated in their adolescence, leaving ample
opportunity for subsequent growth of the maxillary and mandibular complexes
to move the teeth into unstable positions (Vaden, Harris and Gardner 1997;
Gardner, Harris and Vaden 1998; Harris, Gardner and Vaden 1999). Conflicting
reports exist in the literature as to the potential effects that continued craniofacial
growth may have on incisor stability. Riedel (1960, p 187) admitted that,
“Growth may be an aid in the correction of many types of orthodontic problems
and it also may be of such character as to cause relapse of treated orthodontic
patients.”
Ricketts et al. (1972) reported that continued posttreatment growth may
contribute to an increased pressure on the mandibular incisors as they are forced
in a lingual direction with the advancement of the mandible. This occurs to a
greater extent in patients whose incisors were tipped during treatment, as these
teeth will have a greater tendency to be forced lingually. Similarly, Perera (1987)
reported a relationship between mandibular growth and lower anterior
crowding in untreated subjects (n = 29). Perera indicated that forward rotational
growth in the mandible is closely related to lower incisor crowding that
commonly occurs after the adolescent years. He suggested that as the mandible
rotates forward, the lower incisors can become retroclined relative to the face.
Similarly, Siatkowski (1974) conducted a longitudinal study that consisted of two
20