Abstract
Studies have revealed that severe apical root resorption during tooth movement is caused by the noninfective inflammatory reaction of apical root tissues. We hypothesized that loxoprofen can suppress apical root resorption during tooth movement. Cyclic tensile force (CTF) of 10 kPa was applied to the human pulp cells for 48 hours by the Flexcell Strain Unit. Loxoprofen (10 and 100 μM) was added to the culture cells, and expression of cyclooxygenase (COX)-1, COX-2, interleukin (IL)-1β, receptor activator of nuclear factor kappa-B ligand (RANKL), tumor necrosis factor (TNF)-α, and macrophage colony-stimulating factor (M-CSF) were examined. To determine the effects of loxoprofen sodium on apical root reabsorption during tooth movement, the upper first molars of 7-week-old rats were subjected to mesial movement by 10g force for 30 days with or without the oral administration of loxoprofen. Gene expression and protein concentration of COX-1, COX-2, IL-1β, TNF-α, RANKL and M-CSF were significantly higher in the CTF group than in the control group. However, these levels were decreased by loxoprofen administration. After orthodontic tooth movement, the expression of IL-1β, TNF-α, RANKL and M-CSF decreased in the loxoprofen group than in the control group by immunohistochemical staining. In comparison to control group, less number of odontoclasts and a decrease in the amount of apical root resorption was observed in the loxoprofen group. Many osteoclasts became visible on the pressure side of the alveolar bone in the both groups, and the amount of tooth movement did not show a significant difference. These findings demonstrate that severe apical root resorption may be suppressed by loxoprofen administration, without a disturbance of tooth movement.
Highlights
Orthodontic treatment is useful to correct malocclusion; root resorption occurs occasionally
We proved that tensile force can enhance the expression of interleukin (IL)-1β, receptor activator of nuclear factor kappa-B ligand (RANKL), tumor necrosis factor (TNF)-α, and macrophage colony-stimulating factor (M-CSF) in human pulp cells [10]
The gene expression level of COX-1 mRNA in the 10- and 100-μM loxoprofen groups decreased by 1.7- and 5.2-fold, respectively, compared with the cyclic tensile force (CTF) group (Fig 5A) and the expression of COX-2 mRNA in the 10- and 100-μM loxoprofen groups decreased by 1.3- and 2.8-fold, respectively, compared with the CTF group (Fig 5B)
Summary
Orthodontic treatment is useful to correct malocclusion; root resorption occurs occasionally. We proved that tensile force can enhance the expression of interleukin (IL)-1β, receptor activator of nuclear factor kappa-B ligand (RANKL), tumor necrosis factor (TNF)-α, and macrophage colony-stimulating factor (M-CSF) in human pulp cells [10]. The expression of these factors at the time of investigational tooth movement was high in the apical pulp tissue of rats; they were not detected in the pulp without tooth movement. We concluded that noninfective inflammatory reaction of the apical root pulp tissue may contribute to apical root resorption during orthodontic tooth movement. We investigated the effect of loxoprofen administration on apical root resorption during orthodontic tooth movement
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