Posterior crossbites in children: Developmental-based diagnosis and implications to normative growth patterns

Posterior crossbites are one of the most common malocclusion problems observed in primary and mixed dentitions, with a prevalence of approximately 5–8% in children aged 3–12 years. Upwards of 90% of posterior crossbites in the developing dentition exhibit lateral shifts of the mandible on closure associated with a transverse width discrepancy between the dentoalveolar relationships of the maxilla and mandible. The rotational shift of the mandible results in the appearance of a unilateral posterior crossbite involving multiple buccal segment teeth in centric occlusion, midline deviation of the mandibular arch, asymmetric condylar positioning, asymmetric Class II subdivision malocclusion in A-P relationships of the buccal segments, and a chin deviation towards the crossbite side. The transverse discrepancy may be associated with etiological factors producing constriction of the maxillary intercanine width to include non-nutritive sucking habits, mouth-breathing/airway problems, localized anatomical tooth interferences, atypical eruption sequence, and trauma. Assessments of structural anatomy changes in children across age groups consistently demonstrate the asymmetric patterns in condylar positioning and neuromuscular movements associated with posterior crossbites may result in long-term mandibular asymmetric length differences, differential EMG loading patterns between sides, and asymmetric maxillary dentoskeletal adaptations. Given these findings, correction of posterior crossbite by redirecting developing teeth into more normal functional positions while correcting asymmetries of condylar position is indicated whenever the discrepancy is noted in the developing occlusion. Restoration of normal closure patterns of the mandible with elimination of functional deviations, usually through maxillary expansion to harmonize the transverse discrepancy, makes beneficial dentoskeletal changes during periods of dynamic growth and minimizes malocclusion factors that are detrimental to long-term dentofacial cosmetics and function. In addition, early primary and mixed dentition correction allows treatment approaches that are less complex, less time consuming, and more physiologically tolerable than treatment demands in the older patient.