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CHANGES IN ARCH WIDTH AFTER ORTHODONTIC
TREATMENT: A LITERATURE REVIEW
HYO EUN KIM
DAEGU, KOREA
It is a well established fact that increases in dental
arch width during orthodontic treatment tend to return
toward pretreatment values during and after retention.
However, changes in arch width inevitably occur
during and after orthodontic treatment as a result
of growth or treatment. In this literature review the
historical background of maintenance of arch width is
studied and some consequences of changing of arch
width during treatment are also discussed.
MAINTENANCE OF ARCH WIDTH DURING ORTHODONTIC
TREATMENT
In the middle 1920s, the apical base school formed
around the writings of Axel Lundström who suggested
that the apical base was one of the most important
factors in the correction of malocclusion and
maintenance of a correct occlusion. Nance noted that
“if a stable result is to be attained, mandibular teeth
must be positioned properly in relation to basal bone.”
McCauley made the following statement, “since these
two mandibular dimensions, molar width and cuspid
width, are of such an uncompromising nature, one
might establish them as fixed quantities and build the
arches around them.” After measuring a large number
of cases, including successes and failures, Strang drew
certain conclusions and said, “Stable results can only
be gained when the width of the mandibular denture in
the canine and molar areas is maintained inviolate.”
The ‘lateral limit’ is referred to as one of four
basic premises defined by Merrifield’s ‘diagnostic
concept of dimensions of the dentition’. Vaden said,
“lateral expansion works if you believe in permanent
retention.” and “the dentitions that exhibited the most
relapse are, in most instances, the ones that have
undergone the most mandibular canine expansion.”
COMPARISONS OF THE ARCH WIDTH CHANGES BETWEEN
EXTRACTION AND NON-EXTRACTION TREATMENT
Motivated by a question that concerned the
possibilities of dental arch expansion and the
maintenance of such expansion, Walter investigated
50 non-extraction cases and 50 extraction cases.
Intercanine width and intermolar width were measured
before treatment, following completion of active
treatment, and at least one year following removal of
retainers. In 31 or 62% of the non-extraction cases, an
increase of 2.0 mm of intercanine width was obtained
and maintained. And in the extraction cases 31 or
62% showed an increase of 1.4 mm of intercanine
width which was also obtained and maintained. In
36 or 72% of the cases in the non-extraction group
an average increase of 1.8 mm was obtained and
maintained in intermolar widths. Conversely, in the
extraction sample intermolar widths, 35 or 70% of
the cases demonstrated a contraction or decrease of
2.9mm. Overall, the intercanine distances behaved
the same in the non-extraction and extraction cases:
the intermolar distances of the non-extraction cases
tended to increase and those of the extraction cases to
decrease.
Bishara et al. evaluated treatment and posttreatment
changes in the dental arches of patients with Class II,
division 1 malocclusions. Half the patients (N=46)
were treated with a non-extraction approach; treatment
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