Nonsurgical treatment of an adult patient with severe transversal skeletal discrepancy: Tooth bone-borne tandem expander and hybrid aligner approach

Background: Although they have proven effective in the resolution of mild to moderate malocclusions, aligners demonstrate substantial limitations. More complex malocclusions therefore require a combination of auxiliaries, or a hybrid approach involving both aligners and fixed appliances, such as miniscrew-supported appliances or sectionals. This case report presents a 25-year-old female patient with a severe transversal discrepancy associated with an anterior open-bite tendency effectively treated with a tooth bone-borne palatal expander characterized by two expansion screws (tandem expander) and a hybrid treatment with aligners. Methods: After accurate matching between the pretreatment cone-beam computed tomography scan and digital models, four self-drilling miniscrews were inserted palatally using a computer- aided design and computer-aided manufacturing surgical template to guide their correct and safe placement, and a tooth bone-borne appliance was fitted. After this first phase, the hybrid clear aligner approach was used to obtain alignment, leveling, and arch coordination, with the use of a partial lingual fixed appliance. Results: Transverse maxillary deficiency was corrected, crowding has been resolved, Class I molar and canine relationship were obtained, and marginal ridges has been aligned. Conclusions: Double jackscrew of the tandem expander enabled effective expansion of both the posterior segments as required to correct the skeletal discrepancy and the anterior region, thus relieving the dental crowding. Lingual sectional appliances have been shown to increase the effectiveness of clear aligners which, on the other hand, have been shown to be effective in closing the anterior bite by retroclination of the maxillary and mandibular incisors and, only minimally, by extrusion movements.