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.