Discussion
Orthodontists must gain a greater awareness that crowding is an
increasingly common type of malocclusion2 caused by
abnormalities in the dentition, jaws, or both.1 The
severity of this tooth size-arch length discrepancy is typically
measured by visual examination methods and classified as mild, moderate,
or severe crowding.7
Dental7 and skeletal8 measurements
reveal that crowding is caused by excess tooth size, decreased arch
width, or a combination of large teeth and narrow jaws. Three well-known
treatment options for this type of malalignment in adolescent patients
are interproximal reduction,9extractions,4, and expansion.2Interproximal reduction is typically only used to treat patients with
mild-to-moderate crowding, whereas extraction and expansion are standard
treatment options for patients with all types of crowding. In patients
with standard arch width and excess tooth size, extractions are
recommended, especially for those with severe mandibular crowding
(>6 mm).4 In contrast, in the presence of
a normal-sized dentition and decreased arch width, expansion is the
treatment of choice because it enables widening of the dental arches,
which predictably increases the arch perimeter3 and
provides a given amount of transverse expansion and accommodates
existing teeth. Predicting this relationship helps promote rapid palatal
expanders in patients with crowding; these expanders facilitate
non-extraction orthodontic treatment, which is the treatment preference
for most modern orthodontists.10 In addition, to
achieve more significant orthopedic skeletal change, especially in a
growing patient, a miniscrew-assisted rapid maxillary
expander5,6 can be used in patients with a true
skeletal transverse discrepancy,8 rather than a tooth
tissue-borne rapid palatal expander. Subsequent widening of the dental
arches from this treatment protocol is generally considered
stable,6 as it exhibits minimum relapse, especially in
patients with fixed prolonged retention.
In this case report, severe mandibular crowding was caused by a
decreased arch length due to a narrow maxilla (transverse skeletal
discrepancy) that was diagnosed via posterior-anterior cephalometric
radiography: the skeletal width of the maxilla and mandible was measured
based on skeletal landmarks and norms, as developed by
Ricketts.8 This decrease in maxillary arch width also
restricted the mandibular arch width, resulting in severe mandibular
crowding and collapsed mandibular posterior segments. Treatment was
initiated with the expansion of the maxillary arch, thereby widening
dental arches and creating an increased arch perimeter; this unraveled
the crowding and allowed uprighting of the collapsed mandibular buccal
segments with routine orthodontic treatment. The key to the alleviation
of crowding in this patient was increasing the transverse dimension by
using a miniscrew-assisted rapid maxillary
expander,5,6 rather than a tooth tissue-borne rapid
palatal expander, which enabled a 4 mm increase in the width of the
maxillary dental arch to be achieved by solid orthopedic expansion. The
success of this maxillary expansion increased the mandibular intermolar
width by 4 mm, which created sufficient space to relieve severe crowding
without extraction. In order to ensure the post-treatment long-term
stability of these widened arches, the retention protocol included a
combination of fixed and removable prolonged retention procedures.
Therefore, this case report highlights the importance of increasing the
arch width and arch perimeter3 to alleviate dental
crowding during orthodontic treatment, thereby avoiding extractions and
facilitating the maximum preservation of dental units.