Effects of lithium on orthodontically induced root resorption and tooth movement in an osteoporotic rat model

To assess the effects of lithium on orthodontically induced root resorption (OIRR) and orthodontic tooth movement (OTM) and elucidate the underlying mechanisms in an osteoporotic rat model.

Thirty 10-week-old female Wistar rats were randomly assigned to ovariectomized (OVX) or sham-operated (Sham) groups. Four weeks post-surgery, each group was further divided to receive either lithium (Li: 0.64 mM/kg) or saline via daily intraperitoneal injection. Orthodontic force was applied for 14 days using a closed-coil spring to move the maxillary first molar mesially. OTM was analyzed using micro-computed tomography on day 14. Histological analysis evaluated OIRR, apoptotic cells, osteoclasts, and odontoclasts. Immunohistochemical staining was used to assess the expression of receptor-activated nuclear factor-kappa B ligand and osteoprotegerin.

OIRR was significantly higher in the OVX group than Sham groups. Lithium markedly suppressed OIRR in OVX rats to levels comparable to the Sham + Li group. Lithium significantly reduced the number of apoptotic cells on day 3, decreased the number of odontoclasts, and increased osteoprotegerin expression by day 14. It also prevented excessive tooth tipping without affecting the overall distance of tooth movement, promoting a shift from tipping to bodily movement in the OVX group.

In an osteoporotic rat model, lithium effectively suppressed OIRR and promoted bodily tooth movement without reducing OTM distance, suggesting the therapeutic potential of lithium in patients with osteoporosis.