Signaling molecules and genetic mechanisms involved in orthodontic tooth movement

ABSTRACT

The objective of this review is to highlight recent developments in cellular, molecular, tissue, and genetic reactions in response to orthodontic force application. Histologic, histochemical, and immunohistochemical studies in the 20th century and the early 21st century demonstrated that many phenomena, both physical and biologic, are involved in tooth movement. When mechanical forces are applied, cells, as well as the extracellular matrix [ECM] of the [periodontal ligament] PDL and alveolar bone, respond concomitantly, resulting in tissue remodeling. During the early phases of orthodontic tooth movement, PDL fluids are shifted, and cells and ECM are strained. In areas where tension or compression evolves under the influence of the orthodontic appliance, vasoactive neurotransmitters are released from distorted nerve terminals. In the PDL, most terminals are near blood-vessel walls. Therefore, the released neurotransmitters interact first with capillary endothelial cells. In response, the endothelial cells express receptors that bind circulating leukocytes, promoting their migration by diapedesis out of the capillaries. These migratory cells secrete many signal molecules, including cytokines and growth factors, some of which might be categorized as inflammatory mediators, that stimulate PDL and alveolar bone lining cells to remodel their ECM. This force-induced remodeling facilitates movement of teeth to areas in which bone had been resorbed