ABSTRACT
Early treatment of functional unilateral posterior crossbite during the mixed dentition stage is extremely important, as it provides the correct positioning of osseous bases, teeth, and the temporomandibular joint when the stomatognathic system is in growth and development. This article reports on a 9-year-old patient who presented with functional unilateral posterior crossbite and was treated with a modified Hyrax expander. The case report highlights a simple, low-cost, effective treatment protocol. The malocclusion was corrected with 15 days of active use of the appliance, 5 months of use for retention purposes, and 5 years of post-treatment follow-up. The stability in the long-term treatment is highly dependent on early diagnosis by the clinician and the elimination of the etiological factor through use of the proper appliance.
