Molecular Diagnosis in Orthodontics, Facial Orthopedics, and Orthognathic Surgery: Implications for Treatment Progress and Relapse

One of the expectations after orthodontic, orthopedic, or orthognathic treatment is improved orofacial function, which arises through adaptation of muscle capacity. However, some patients fail to show any improvement, whereas others may relapse. Adaptation of muscle is attributable to changes in the expression of genes and proteins within the tissue, and these changes can be measured by a variety of molecular biological techniques. As technology has advanced, so these techniques have changed, yet many have been applied to the study of human masticatory muscle harvested in association with the various functional treatments. The transcription of a gene is the first step in the production (translation) of the protein. However, it is often easier and quicker to measure the amount of gene transcription, rather than the amount of protein, although it is important to note that this does not always correlate with the amount of protein. With this caveat in mind, this article will refer to the gene expression of myosin heavy chain mRNA as an important marker for an ultimate increase in protein expression in adaptation. This review will, therefore, discuss the outcomes of various studies where such techniques have been used.