The Spahl Split Vertical Appliance is very effective at closing posterior open bites -- after the mandible has been properly and thoroughly advanced by a functional appliance (such as a Bionator, an Orthopedic Corrector, the Clark Twin Block, the Levandoski Mandibular Stabilization Appliance, etc.). The Spahl Split Vertical consists of separate upper and lower devices.

The upper has a simple bite plane that is designed to hold the arches at the ideal vertical relationship. This bite plane is placed on a lingual wire attached to the first molar bands via a vertical removable bracket assembly. Because the upper is to be worn 24 hours per day, the bite plane should be kept to a minimum (to allow for comfort and ease of speech).

The lower is a wire-bodied appliance composed of an anterior bite block that covers the four lower anteriors and a pair of posterior bite blocks which cover the last molar on each side of the arch. Bonded hooks, buttons, or brackets are placed on the upper and lower cuspids, bicuspids, and first molars. When the lower appliance is in place, vertical elastics are used to initiate eruption of these teeth. By wearing this device a minimum of 12 hours a day (evenings and during sleep) eruption will occur much faster than it could through passive eruption alone.