The purpose of this study was to investigate the effect of cytokine-induced osteoclastogenesis on tooth movement related to orthodontic force. We evaluated the cytotoxicity as well as the expression of OPG and RANKL, which influence the homeostasis of bone metabolism. Titanium particles were applied to human periodontal ligament cells and subcultured fourth generation cells. The ALP assay and the MTT assay were used to assess changes in cytotoxicity. After 48 hours, cytotoxicity increased proportionally with the concentration of titanium. With 20 mg, the cytotoxicity was the lowest. R T-PCR was u sed for assessing m R NA l evels of O PG a nd R ANKL; after 96 hours, t he m R NAs of O PG a nd R ANKL increased steeply. A western blot analysis showed that with 20 mg of titanium, the protein expression of OPG increased linearly with time, especially a fter 96 hours, while t he p rotein e xpression o f RANKL d id n ot s how significant changes with titanium processing. Given the increase in OPG expression after the initial cytotoxicity, changes in cytotoxicity with titanium may be attributable to the antagonistic effect of OPG on cytotoxicity

Hydroxyapatite(HA) has been widely used as bone substitutes to rehabilitate bone loss area by new bone formation. But there were some problem of bone formation around HAs due to a little space between HAs embedded in bone loss area. The purpose of this study was to observe morphologically new bone formation around HAs mixed with PLGA block (5.5㎜ in diameter, 4 mm in depth) in Newzealand white rabbit tibia. Before 1 week of sacrification, Alizarin red was injected intraperitoneally into rabbit. At 3 day, 1, 2, 4, 10, 18, 32 weeks, bones with HA as control group(CG)and HA mixed with PLGA block as experimental group (EG)were fixed with 10 % neutral formalin, dehydrated, and embedded with Spurr low viscosity resin. After the specimens were cut by 500 ㎛ with slow diamond wheel saw, these were coated with carbon and examined by REM, LSM and qualifative analysis of calcium and phosphorous deposition were done with EPMA. The obtained results were as follows. 1. Both group showed scattered HA around compact bone under REM and little AZ labelled bone under LSM at 3 days. 2. Both group showed active AZ labelled bone, while EG showed higher Ca(calcium) and P(phosphate) deposition than that of CG at 1 wk. 3. There was decreased AZ labelled bone of both group under LSM. REM of EG showed HA associated with new bone from compact bone, while EPMA features showed similar to Ca and P deposition at 1 wk and EG showed higher than that of CG. 4. REM features of both group showed resorbed HA associated with new bone. There was decreased AZ labelled bone of both group under LSM. EPMA features showed higher Ca and P deposition at 4 wks than that of 2 wks. 5. New bone of both group was well demarcated from compact bone under REM at 10 wks. LSM features showed various AZ labelled bone, but weak AZ labelled than that of CG. 6. LSM features of 14 wks showed discontinuous AZ labelled on osteon formation. EPMA of both group showed increased Ca deposition, while there was higher Ca deposition of EG and similar P deposition to CG. 7. REM featureless of 18 wks in EG showed similar gray color to compact bone. LSM features showed osteon formation with little concentric lamellars. EPMA of both group showed increased Ca deposition, while there was higher Ca and P deposition of EG. 8. New bone was ill demarcated from compact bone and increased otseon formation of REM features at 32 wks. There was little AZ labelled bone. EPMA features showed higher Ca and P deposition of EG than that of compact bone. From the aboving results, there was early active AZ labelled bone of both group within 1-2 weeks and since 18 weeks new bone with active osteon formation was poorly demarcated from compact bone. Calcium deposition of EG was early increased than that of CG deposition since 4 weeks after experiments. It was suggested that EG showed active and rapid new bone formation and similar bone mineralization of compact bone

This study was to verity that the uptake inhibition and accumulation of nitrogen in different potassium levels. Lettuce was used as model plant in this study and grown in pot of 10cm's in diameter and depth with mixture media of vermiculite and perlite under supply of different culture solution for three weeks. Nitrogen absorption at root was inhibited by increased potassium concentration in nutrient solution, and nitrate accumulation of plant was depended on absorption of nitrogen because nitrate content of 0 K level was 4-5 times higher than that of 2 K level, Concentration of ascorbic acid was decreased by increasing the nitrogen absorption, since ascorbic acid (AsA) content of 2K level was higher than those of OK level in both of old leaf and flesh leaf