Maxillary skeletal expander with 6 miniscrews and tadlock: A case report

Miniscrew-assisted rapid palatal expansion (MARPE) devices offer an alternative to orthognathic surgery for postpubertal patients, but a limitation of MARPE is the possible migration of miniscrews during maxillary expansion. This becomes critical when palatal bone is thin at the miniscrew insertion sites, potentially leading to miniscrew failure. In this article, a maxillary skeletal expander (MSE), a particular type of MARPE appliance, was adopted to skeletally expand the maxilla in a postpubertal patient with a thin palatal bone. To reinforce the skeletal anchorage, the MSE was modified by adding 2 lateral miniscrews in the palatal slope between the second premolar and first molar. A virtual model of the MSE with 4 miniscrews was imported into the merged model of the patient's cone-beam computed tomography and maxillary dental arch. Then, a computer-aided design/manufacturing structure with appliance arms, 2 bushings for additional lateral miniscrews, and molar bands was 3-dimensionally designed and manufactured with selective laser melting technology and was laser welded to the MSE body to produce the modified MSE with 6 miniscrews. Because appliance arms tend to slide along the additional lateral miniscrews during maxillary expansion because of the lateral force vector, a steel ligature (the “tadlock”) is tied between the miniscrew head and the bushing pin present on the appliance arms to eliminate the problem. The digital workflow to fabricate the MSE with 6 miniscrews and the tadlock mechanism are presented along with the procedure to expand the maxilla in a postpubertal patient with a thin palatal bone.