The Spahl Split Vertical (SSV) appliance allows doctors to open the bite in order to gain the necessary vertical dimension to support the TMJ in its new relocated position. The SSV functions the same as the Biofinisher, but more doctors prescribe the SSV because it does not require an additional appliance (like the Biofinisher often does) and it interferes less with speech. The SSV was created by Dr. Terrance Spahl, who co-authored three orthodontic and TMJ books with Dr. John Witzig.