AcceleDent^® Altered Transcript Expression in PDL Cells

Objectives: During orthodontic tooth movement, compression of the periodontal ligament (PDL) induces bone resorption, and tension of the PDL causes bone deposition. The PDL monitors mechanical tension and regulates bone deposition and resorption by secreting many proteins; including bone morphogenic proteins (BMPs) and proteins associated with osteogenesis. AcceleDent^® is a device marketed to orthodontists to accelerate tooth movement. It achieves this by oscillating the teeth at 30 Hz. Daily treatment for 20 minutes has been reported to reduce orthodontic treatment time by up to 50%. However, the cellular mechanism of this process is unknown.
Methods: PDL cells were stretched over a flexible membrane and vibrated using the AcceleDent^® device for 20 minutes a day for three days. RNA was isolated from the cells 24 hours after treatment and was used to synthesize cDNA, and Reverse Transcriptase-PCR analysis was conducted. Alternatively, cells were treated once with AcceleDent^® for 20 minutes, and then harvested for PCR analysis after 3, 6 or 12 hours. Densitometric analysis was used to compare the relative levels of transcript expression.
Results: Following three daily exposures to AcceleDent^®, no change was detected in the expression of any growth factors (BMP2, BMP4, BMP7, GDF5 and TGFβ1). In addition, this treatment induced no change in transcripts associated with osteogenesis (Periostin, alkaline phosphatase, osteomodulin, osteonidogen and collagen Type I). Finally, transcripts involved with the regulation of osteoclasts (RANKL and osteoprotegerin) were not altered by treatment with AcceleDent^®. However, AcceleDent^® treatment did induce a transient increase in the expression of RANKL after 3 hours that rapidly decreased by 6 hours.
Conclusions: Based upon our in vitro studies, AcceleDent^® induced transient changes in RANKL transcript expression. This supports the concept that AcceleDent^® treatment will transiently activate osteoclasts and enhance remodeling of the alveolar bone.