The Effect of Extracorporeal Shock Wave (ESW) on Cementoblasts In Vitro

Root resorption is an adverse consequence of orthodontic treatment, and currently no effective treatment method exists. Extracorporeal shock wave (ESW) has been applied to enhance angiogenesis, growth and healing of bone, but the effects of ESW on root resorption have not been studied. Cementoblasts are the cells responsible for forming and repairing cementum covering the dental root, and ESW may enhance this reparative process. The purpose of this study was to investigate the effects of ESW on cementoblasts to determine if ESW could potentially be used to treat root resorption. OCCM.30 cementoblasts were prepared in suspension at a density of 107/ml and placed in Eppendorf tubes which were held in a specially designed apparatus to focus the shock waves at the cells. Using the focused shock wave stimulator (Storz Medical AG, Switzerland), the cells were subjected to a single dose of 2000 impulses of ESW at their assigned energy level (0.1mJ/mm2, 0.25mJ/mm2 or 0.5mJ/mm2). Controls were set under identical conditions without ESW application. Immediately after ESW stimulation, the amount of ATP release was measured since ATP is an early messenger in bone modeling regulation. Cell viability was tested to determine if any dose level caused cell death. After 24 hours of post stimulation incubation, the cells were lysed to test functional protein productions of sclerostin (SOST), a negative regulator of bone formation, receptor activator NFkB ligand (RANKL), a direct stimulator of bone resorption, and osteopontin (OPN), a regulator of osteoclastogenesis. After ESW application, ATP levels in the medium and high-dose groups were found to be significantly increased in a dose-dependent manner. High-dose ESW significantly decreased cell viability. SOST protein was significantly decreased only at the dose level of 0.25mJ/mm2 (n=3, p\u3c0.05). OPN was significantly increased at 0.1mJ/mm2 and 0.5mJ/mm2 (n=3, p\u3c0.01), but not at the 0.25mJ/mm2 energy level. RANKL was not significantly changed with any of the doses. Our data suggest that ESW at an energy level of 0.25mJ/mm2 anabolically modulates bone remodeling by decreasing SOST production but not affecting RANKL and OPN production significantly. These findings suggest that ESW could potentially be used to treat root resorption in orthodontics