The disadvantage of bite correction using an anterior bite plane for long periods of time is:

An ANTERIOR BITE PLANE (flat anterior splint) disoccludes the posterior teeth. When posterior teeth are disoccluded for extended periods, they lose their vertical stop and tend to SUPRA-ERUPT (over-erupt — move toward the opposing arch). This INCREASES the vertical dimension and can worsen open bite. This is the major disadvantage of long-term use. Anterior teeth may be slightly intruded (B — but this is often the goal for deep bite, not a disadvantage per se). A is correct.