Background: Chronic periodontitis could lead to alveolar bone resorption and even tooth loss. Stem cells from exfoliated deciduous teeth (SHED) are the proper seed cells for bone regeneration because of their potential in osteogenic differentiation. However tracking the survival, migration and differentiation of the transplanted stem cells is necessary to improve the transplantation success. Methods: Superparamagnetic iron oxide particles (SPIO) Molday ION Rhodamine-BTM (MIRB) were used for labeling and monitoring SHED cells in vivo by magnetic resonance imaging (MRI). Proper labeling concentration of MIRB was determined by cell viability, proliferation, osteogenic differentiation and MRI analysis in vitro after SHED cells were labeled with MIRB at different concentration of 12.5, 25, 50, 100μgFe/mL. MIRB labeled SHED were transplanted to the periodontal bone defect model in rats and tracked by MRI in vivo. The regeneration of periodontal bone were calculated with HE and immunohistochemical analysis. The survival of transplanted SHED cells in vivo was verified with Prussian blue staining.Results: After testing 25μg Fe/mL MIRB was used in vivo cells tracking. After transplanted to the periodontal bone defect model in rats, the MIRB labeled SHED could be tracked in vivo through the artifact of the low intensity signal caused by Fe3+ at 6 and 9 weeks post-surgery. HE and immunohistochemical analysis showed that both SHED labeled and unlabeled with MIRB could promote regeneration of periodontal bone defect. Prussian blue staining further verified the survival of transplanted SHED cells in vivo. Conclusions: Overall, SHED cells could promote the regeneration of periodontal bone in rats and the survival of SHED cells could be tracked by labeling with MIRB in vivo. However the distribution of the positive cells at the edge of the regenerated new bone remind us the SHED cell could promote the regeneration of new bone by factors section.

Experiments were performed to ob serve the in f lu ence of X-raj irradiation on mast ce ll s and mastoca lcergy in ïat s.Anima ls were irradiated sing l e dose of X-ray . X-ray irradiation was app lied to the who le body in doses eith er 100 rads or 15 0 rads(Cobalt-60 Teleth eraphy Unit) . O ne day after irradiation th e.rats we re injected lead acetate intravenously , followed by injection of compound 48/80 in the ba ck subcutaneously Animals were kil led by decapitation at intervals, 1 hour, 5 hours , 1 day and 6 da ys after subcutaneous in)cction.Specímens of the abdominal and ba ck sk in were f ixe d in al coh olformol solution and stained with th e fo Jl owing methods; H -E for observation of pathological changes of ti ssues, toluidin e blue for demonstration of mast cells, vo n Kossa-azure A for demonstration of carbonate and pho sphate , and chloran il ic acid for demonstration of calcium.The f ollowing co nclusions were obtained .Cal ciph ylatic wheals ar e large size in the control group , m edium size in 100 rads ir radiation group and sma Jl size i n 150 rads i .. radiation group In X-ray irradiaion groups the number of mast cell s decreases more in t h e 150 rads tha n in t he 100 rads irrad iation.In the 100 rad s X-ray irradiatio n group , histochemical study of the injection sites showed that calcium impreg nated t o mast ce ll granules an d co nn ecti ve tissue fibers in 1 day s after su bcu ta neous injection.The morphogenesis of this calcinosis was t h e same in the ra t of 5 hours after su bcu taneous injection of the co ntrol group . Whereas , 1 day after subcutaneous inection in 150 rad s X-ray irradiation group cal cium deposited more slightly than other gro ups.