an adjustment mechanism configured to adjustably couple a first dental arch to a second dental arch and displace the second dental arch in a forward position relative to the first dental arch; and

a plurality of plates each configured to removeably couple to a body of the adjustment mechanism;

wherein the plurality of plates comprise at least two plates that are not structurally identical with respect to each other;

wherein at least one of the plurality of plates is configured to couple a tensioning device to the oral appliance, the tensioning device configured to adjustably couple a mask to the oral appliance, the tensioning device comprising a flexible tension element configured to apply an adjustable tensile force between the mask and the oral appliance.