Ultrasound stimulation attenuates root resorption of rat replanted molars and impairs tumor necrosis factor-α signaling in vitro.

BACKGROUND AND OBJECTIVE: A therapeutic protocol to minimize root resorption induced by tooth replantation has not yet been universally established. In this context, noninvasive modality such as ultrasound therapy have been a focus of increased interest. This study aimed to evaluate the inhibitory effect of ultrasound therapy on root resorption of replanted rat molars. In addition, the study aimed to promote insights into the mechanism through which ultrasound mediates the metabolism of periodontal cells in vitro. MATERIAL AND METHODS: An experimental model of tooth replantation in rats, involving luxation and immediate replacement of the maxillary first molars, was used to assess the inhibitory effect of an ultrasound-therapy regimen (15 min of exposure to ultrasound, each day for 21 d) on root resorption. Moreover, the effect of ultrasound on osteoclastogenesis/cementoclastogenesis was examined in vitro using a mouse osteoblastic stromal cell line (ST2) and a mouse cementoblastic cell line (OCCM-30). RESULTS: The area of root resorption lacunae was statistically decreased (p < 0.01) in the ultrasound-treated sample. In addition, immunohistochemical staining, using murine TNF-α polyclonal antibody, failed to detect tumor necrosis factor-α (TNF-α) protein in the ultrasound-treated sample compared with the control. An in vitro study showed that the lipopolysaccharide (LPS)-induced expression of Tnfalpha mRNA was significantly reduced by ultrasound therapy in both osteoblastic and cementoblastic cells. Moreover, the TNF-α-induced up-regulation of Rankl mRNA was also inhibited by ultrasound. CONCLUSION: Ultrasound may contribute to the reduction of the trauma-induced inflammatory reaction through impairment of the TNF-α signaling pathway. It is therefore suggested that ultrasound shows potential as a therapeutic tool to optimize the regenerative potential of periodontal tissues on replanted teeth.

Effects of ultrasound on the proliferation and differentiation of cementoblast lineage cells.

BACKGROUND: The purpose of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) stimulation on the proliferation and differentiation of cementoblast lineage cells. METHODS: An immortalized human periodontal ligament cell line (HPL) showing immature cementoblastic differentiation was used. Cultured HPL cells were subjected to LIPUS exposure (frequency = 1 MHz; pulsed 1:4; intensity = 30 mW/cm(2)) or sham exposure for 15 minutes per day. Expression levels of alkaline phosphatase (ALP), type I collagen (Col-I), runt-related gene 2 (Runx2), bone sialoprotein (BSP), osteocalcin (OCN), and osteopontin (OPN) mRNA were analyzed with real-time polymerase chain reaction analysis. Furthermore, ALP activity, collagen synthesis, and protein level of Runx2 were examined after 6 days of LIPUS exposure. RESULTS: mRNA and protein levels of ALP, Col-I, and Runx2 were significantly increased by LIPUS exposure compared to controls, whereas BSP, OCN, and OPN mRNA expression could not be detected in HPL cells, irrespective of LIPUS exposure. CONCLUSION: LIPUS enhanced ALP activity, collagen synthesis, and Runx2 expression of HPL cells, which provides important insight into the promotion of early cementoblastic differentiation of immature cementoblasts.