Kev Kho Hniav Kev Kho Hniav Txhuam Hniav Tus Kws Qhia Ntawv A2 yog ua los ntawm polyurethane ruaj khov, thiab tsim nyog rau kev ua rau me ntsis malocclusion. A2 cov khoom ruaj khov tau tsim los siv tom qab A1, thiab ua kom muaj kev sib koom ua ke ntau dua ntawm cov hniav tom ntej.