Expression analysis of α-smooth muscle actin and tenascin-C in the periodontal ligament under orthodontic loading or in vitro culture.

Although orthodontic braces apply constant force to teeth, researchers have found thatthe strain on gum tissue varies with time. To move teeth, orthodontists must apply justenough force to trigger remodelling of bone and gum tissues around tooth roots.However, these forces cannot be directly measured in living tissue. An internationalteam at Texas A&M University in Dallas, US, and Sichuan University, China, led by Xiang-Long Han used molecular markers to reveal stress in the periodontal ligament,which attaches tooth roots to gum tissue. Using cultured cells and cells from ratsundergoing orthodontic treatment, the researchers measured expression of the proteinsalpha-smooth muscle actin, which enhances tissue contraction, and tenascin-C, whichloosens tissue to prevent overstretching. Levels of both markers varied over time,corresponding to patterns of tooth movement.