Cell biology in orthodontic tooth movement: the known and the unknown.

This review is aimed at providing, at the cellular level, a concise and complete overview of the important knowledge on the mechanism of orthodontic tooth movement to orthodontists and postgraduates who are involved or interested in basic research. The construction of this article was oriented to the following key questions: Where an osteoclast starts to its first resorption site? When the cascade of a resorption cycle starts? What are the factors involved in bone remodeling and how they orchestrate? What happens before and after the formation of a resorption pit? Major findings in these aspects were summarized and discussed. In addition, related biological phenomenon such as orthodontically induced root resorption was intensively reviewed. By means of an updated and systematic review, the author intended to introduce more biological evidence to orthodontic intervention and to encourage evidence-based treatment in daily orthodontic practice.