IADR Abstract Archives
Orthodontic Force on Irradiated Rat Jawbone: Micro-CT and Histomorphometric Analyses
Objectives: Irradiation affects bone metabolism - a key feature for orthodontic tooth movement (OTM). We assessed OTM changes in irradiated jawbones by micro-CT and histomorphometry.
Methods: Heads of 14-week-old rats received a single 5Gy dose (n=11). Orthodontic force (NiTi spring 25g, 2 weeks) created mesial movement of the left maxillary first molar (RAD-OTM); the right side was only irradiated (RAD). The same orthodontic procedure was performed in the controls (non-irradiated, n=10): CON-OTM (left), CON (right). MicroCT scans assessed the distance of the OTM (µm), trabecular thickness (Tb.Th; mm), trabecular bone volume fraction (BV/TV; %), volumetric bone mineral density (vBMD; mgHA/cm3) and porosity volume fraction (PoV/TV; %) on the pressure and tension sides. Histomorphometry corresponded to the scanned regions and included the mean relative volume of bone, mean number of osteoblasts (OB), bone-resorbing osteoclasts (OC) and external root resorption.
Results: OTM distance in RAD-OTM was 30% lesser than in CON-OTM (p<0.05). In RAD, Tb.Th, BV/TV and vBMD were higher (0.10±0.01mm, 49.5±5.0%, 695.85±38.74mgHA/cm3, respectively; p<0.05) and PoV/TV was lower (50.5±5.0%) than in CON (0.09±0.01mm, 41.2±6.2%, 622.39±53.31mgHA/cm3, 58.8±6.2%, respectively; p<0.05). In CON-OTM, on pressure and tension sides, Tb.Th, BV/TV and vBMD significantly decreased and PoV/TV increased compared to CON. However, differences in these parameters between RAD-OTM and CON-OTM were non-significant. Histomophometrically, irradiation (RAD & RAD-OTM) had an effect of increasing the mean relative bone volume on the tension side (36.9±19.0%) compared to non-irradiated CON & CON-OTM (24.3±14.6%), while orthodontic force (CON-OTM & RAD-OTM; 24.1±16.3%) decreased it compared to CON & RAD (37.0±17.4%). OTM, but no radiation, increased the number of OC and the degree of root resorption on the pressure side in both irradiated and non-irradiated rats.
Conclusions: Our data indicate that orthodontic force had a similar impact on the microarchitecture of irradiated and non-irradiated bones, and may rescue the radiation effects on bone metabolism.
Methods: Heads of 14-week-old rats received a single 5Gy dose (n=11). Orthodontic force (NiTi spring 25g, 2 weeks) created mesial movement of the left maxillary first molar (RAD-OTM); the right side was only irradiated (RAD). The same orthodontic procedure was performed in the controls (non-irradiated, n=10): CON-OTM (left), CON (right). MicroCT scans assessed the distance of the OTM (µm), trabecular thickness (Tb.Th; mm), trabecular bone volume fraction (BV/TV; %), volumetric bone mineral density (vBMD; mgHA/cm3) and porosity volume fraction (PoV/TV; %) on the pressure and tension sides. Histomorphometry corresponded to the scanned regions and included the mean relative volume of bone, mean number of osteoblasts (OB), bone-resorbing osteoclasts (OC) and external root resorption.
Results: OTM distance in RAD-OTM was 30% lesser than in CON-OTM (p<0.05). In RAD, Tb.Th, BV/TV and vBMD were higher (0.10±0.01mm, 49.5±5.0%, 695.85±38.74mgHA/cm3, respectively; p<0.05) and PoV/TV was lower (50.5±5.0%) than in CON (0.09±0.01mm, 41.2±6.2%, 622.39±53.31mgHA/cm3, 58.8±6.2%, respectively; p<0.05). In CON-OTM, on pressure and tension sides, Tb.Th, BV/TV and vBMD significantly decreased and PoV/TV increased compared to CON. However, differences in these parameters between RAD-OTM and CON-OTM were non-significant. Histomophometrically, irradiation (RAD & RAD-OTM) had an effect of increasing the mean relative bone volume on the tension side (36.9±19.0%) compared to non-irradiated CON & CON-OTM (24.3±14.6%), while orthodontic force (CON-OTM & RAD-OTM; 24.1±16.3%) decreased it compared to CON & RAD (37.0±17.4%). OTM, but no radiation, increased the number of OC and the degree of root resorption on the pressure side in both irradiated and non-irradiated rats.
Conclusions: Our data indicate that orthodontic force had a similar impact on the microarchitecture of irradiated and non-irradiated bones, and may rescue the radiation effects on bone metabolism.