Force-induced increased osteogenesis enables accelerated orthodontic tooth movement in ovariectomized rats

Abstract

As the number of elderly orthodontic patients increases, the impact of postmenopausal osteoporosis on orthodontic tooth movement (OTM) has attracted a great deal of attention because OTM relies on alveolar bone remodeling. The question of whether OTM causes subsequent alveolar bone loss and is harmful to alveolar bone health under osteoporotic conditions remains to be answered. The present study aimed to clarify the influences of OTM on alveolar bone in osteoporotic rats. OTM was accelerated in ovariectomized (OVX) rats as a result of increased bone resorption in the pressure area. At the same time, anabolic bone formation was promoted in the tension area during OTM in OVX rats. Micro-CT analysis of alveolar bone revealed a decrease in BMD, BV/TV and Tb.Th. in the OTM group compared with that in non-OTM rats on day 21 of OTM, suggesting that OTM caused alveolar bone loss in OVX rats during OTM. However, the OTM-induced bone loss could be recovered 3 months after OTM in OVX rats. Thus, our findings suggest that increased osteogenesis may compensate for the increased bone resorption during and after OTM and enable effective accelerated OTM in OVX rats.

Tension force-induced bone formation in orthodontic tooth movement via modulation of the GSK-3β/β-catenin signaling pathway

“…However, the mechanism of orthodontic force-induced bone formation at the tension site of a moved tooth is unclear. Our results showed that proper mechanical loading significantly increased levels of ALP and osterix-positive cells, which is consistent with previous studies (Fu et al 2016 ; Dai et al 2017 ). Additionally, mechanical loading obviously increased bone volume at tension sites in the rat tooth movement model.…”

“…However, mechanical stimulation not only directly affects bone homeostasis by stimulating osteoclastogenesis, but also has positive effects on osteoblastogenesis. Recent studies demonstrated that marked upregulation of bone formation from increased osteoblast activity was a common feature of OTM at tension sites (Fu et al 2016 ; Kariya et al 2015 ; Liu et al 2017a , b , c ; Dai et al 2017 ). However, the mechanism of orthodontic force-induced bone formation at the tension site of a moved tooth is unclear.…”

Bone regeneration with bovine bone impairs orthodontic tooth movement despite proper osseous wound healing in a novel mouse model

“…After M1 extraction, the animals were given four‐week tissue healing period (the optimal period as determined in the ABR experiment), OTM was applied to the upper left second molar (M2) for 2 and 3 weeks ( n = 11 for test and control at each OTM time point). The orthodontic model was performed as detailed previously with some modifications . In brief, the mice were anesthetized with IP injection of ketamine and xylazine (9:1, respectively) and a 3 mm nickel‐titanium closed coil spring (TOMY International, Tokyo, Japan) (10 g of constant force), was inserted between the upper incisors and the M2 for 2 or 3 weeks, thereby moving M2 into the ABR site.…”

“…The orthodontic model was performed as detailed previously with some modifications. 15,22 In brief, the mice were anesthetized with IP injection of ketamine and xylazine (9:1, respectively) and a 3 mm nickel-titanium closed coil spring (TOMY International, Tokyo, Japan) (10 g of constant force), was inserted between the upper incisors and the M2 for 2 or 3 weeks, thereby moving M2 into the ABR site. To enhance the attachment of the ligature to the teeth, a 0.1 mm stainless wire was inserted into a shallow groove drilled at the incisor tooth cervix (approximately 0.5 mm from the gingiva) and fixed with dental self-adhesive resin cement (RelyX TM U200,3 M, Maplewood, MN).…”

“…To enhance the attachment of the ligature to the teeth, a 0.1 mm stainless wire was inserted into a shallow groove drilled at the incisor tooth cervix (approximately 0.5 mm from the gingiva) and fixed with dental self-adhesive resin cement (RelyX TM U200,3 M, Maplewood, MN). 15,22 To prevent spring and M2 detachment, the same adhesive resin was applied. The springs were activated once, at spring insertion day.…”