Introduction: This case report presents a case of skeletal Class I malocclusion characterized by maxillary transverse deficiency (MTD) resolved by using a hybrid rapid palatal expander (h-RPE). To avoid undesired effects and promote pure skeletal expansion, especially of the anterior palate, anchorage was shifted from hybrid to bone-borne.
Case Report: A 13-year-old girl with Class I malocclusion and an anterior open bite tendency sought treatment for anterior dental misalignment. Intraorally, she presented with a bilateral Class I molar relationship and a bilateral Class II edge-to-edge canine relationship. The maxilla exhibited MTD with a V-shaped form, although no posterior crossbites were present; the maxillary canines were high displaced and ectopic, and the maxillary lateral incisors were palatally positioned. After an initial phase of expansion conducted by h-RPE (21 activations), both arms of the RPE were cut, shifting from hybrid to bone-borne anchorage, and a further 14 activations were prescribed. Subsequently, fixed vestibular appliances were placed in both arches to achieve adequate alignment, leveling, and arch coordination, followed by additional activations of the bone-borne RPE (total of 45 turns).
Conclusions: Use of a hybrid RPE represents a viable option for correcting MTD in adolescent patients with advanced skeletal maturity. Precise planning of digital miniscrew insertion to ensure bicortical anchorage facilitates the transition from hybrid to bone-borne anchorage, thereby preventing undesired dental effects and maximizing skeletal effects. Moreover, it enables an increase in the transverse dimension of the anterior palate without inducing iatrogenic scissor bites.