by Richard Dean

Title of paper:  A Biomechanical Representation of the Relationship between Mandibular Cross-bite and Spinal Scoliosis.

When the midline of the lower jaw is aligned symmetrically with the midline of the upper jaw, the forces generated by the dental occlusion are centred in the mid-line.  In the case of a cross-bite relationship where there is a mandibular deviation to one side, there is unequal distribution of the load. In the joints, the side to which the mandible is deflected is under a greater compressive load than the opposite side that is under tension.  The unequal force within the fossa of the temporal bone causes an internal rotation of the compressed side and an external rotation of the opposite side.

This imbalance in the relative positions of the temporal bones causes a tipping of the occiput, so that the level of the occiput is down on the side towards which the mid point of the chin is deflected.  Tipping of the occipital base causes a compensatory scoliosis throughout the spine. This can be readily observed or palpated.

Correction of the cross-bite by bringing the midline of the lower jaw into alignment with the midline of the upper jaw can produce an immediate correction of the spinal compensations.  If the cross-bite has been present for a long time or is present in an adult, supportive osteopathic/chiropractic work is necessary to allow de-compensation of the spine and pelvic girdle.

Understanding the body’s response to skeletal misalignment is important, as it underlines the need for a multidisciplinary approach to treatment. Understanding that the body can get stuck in a compensation pattern after correction of the primary misalignment emphasises the importance of early diagnosis and early recognition of the problem. As the twig is bent, so groweth the tree, hence it is much better to treat the cross bite as early as possible.