iDentistry The Journal September-December 2017 | Page 22

The Journal
Haas 31 and Sandstrom et al. 32 found that
maintenance of 3 to 4 mm intercanine width and
up to 6mm intermolar width was possible when
expansion was carried out concurrently with
maxillary apical base expansion. These two
studies, however, are quite misleading. Haas’
study was based on 10 cases and primary
canines were present in the initial records for
two of these. It is questionable how one can
report on the amount of canine expansion
achieved, when in 20% of this small sample, the
permanent canines were not present at the time
of the original records.
Sandstrom’s statement that mandibular incisor
stability is increased when the mandibular
intercanine width is expanded in conjunction
with maxillary expansion is based on a sample
of 17 patients only 2 years post retention.
Moussa et al.33 reported on a sample of 55
patients who had undergone rapid palatal
expansion in conjunction with edgewise
mechanotherapy a minimum of 8 years post
retention. Their results showed good stability for
upper intercanine and upper and lower
intermolar widths. Stability of the mandibular
intercanine width, however, was poor with the
post treatment position closely approximating
the pre treatment dimension.
De La Cruz et al. 34 carried out a 10 year post
retention study on 87 patients to determine the
long-term stability of orthodontically induced
changes in maxillary and mandibular arch form.
The results showed that although there was
considerable individual variability, arch form
tended to return toward the pre treatment
shape. They concluded that the patient’s pre
treatment arch form appeared to be the best
guide to future stability. Minimizing treatment
change around the pre treatment arch form,
however, was still no guarantee of post
retention stability.
the collagen fibers. These stretched fibers have
been implicated in rotational relapse by pulling
the teeth back toward their pre treatment
35,36
position.
After the placement of a tattoo
marker on the attached gingiva in dogs,
Edwards36 also demonstrated incomplete
reorganization of gingival tissues over a 5
month post retention period. With this in mind,
various experimental approaches have been
investigated, ranging from immediate torsion
37
with surgical forceps, removal of cortical
38
bone, and removal of attached gingiva.39
40
41
Brain and Edwards advocated gingival fiber
surgery (Circumferential Supracrestal
Fiberotomy) to allow for the release of soft
tissue tension and reattachment of the fibers in
a passive orientation after orthodontic tooth
rotation. In 1971 a prospective study was
initiated by Edwards 42 with 160 patients up to 14
years post treatment. The results were
published in 1988 and show a significant
difference in the irregularity index between the
control and treatment groups at both 6 and 14
years post treatment. No significant loss of
attachment or other periodontal abnormalities
were reported, a finding that has been
confirmed by others. 43,44 The theory of stretched
collagen fibers as the cause of rotational
relapse has recently been questioned by
Redlich et al. 45 who analyzed gingival tissue
samples obtained from rotated incisors in dogs.
They found that the rotational forces caused
significant changes in the integrity and spatial
arrangement of the gingival tissues, changes
that are inconsistent with stretching. After
fiberotomy, reorganization of the fibers similar
to the control group was evident. They
concluded that rotational relapse may actually
originate in the elastic properties of the whole
gingival tissue rather than stretching of the
gingival fibers as previously believed.
Periodontal and gingival tissues
Orthodontic movement to correct tooth
rotations is proposed to result in stretching of
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Vol. 13 No. 3
Sep-Dec 2017