In most people, the maxilla is misaligned to the left (Left YAW). This is caused by a misalignment of the sphenoid bone. If the sphenoid bone is twisted to the left, the contact between the palatal bone and the sphenoid bone is loosened, resulting in asymmetrical expansion with more left side instead of bilateral expansion. In particular, when expanding using MARPE, the left side moves more and moves backward. The way to reduce this is to treat the Left YAW of the sphenoid bone before any treatment to prevent asymmetric expansion.

In other words, it is possible to prevent the asymmetric expansion of the maxilla and distortion of the sphenoid bone by performing cranial osteopathy or mcb splint treatment.