| Objective To study the anchorage ability and stability of different loading time micro-implant anchorage by establishing hyperthyroid rat model, and discuss that whetherhyperthyroid rats can use micro-implants and the appropriate implant loading time,providing theoretical guidance and experimental basis for the clinical application.Methods Using a random number table, forty3-month-old female wistar rats weredivided into four groups: normal immediately-loading group, normal two-weeks-loadinggroup, hyperthyroid immediately loading group and hyperthyroid two-weeks-loadinggroup. Two micro-implants were implanted into left tibia of the two-weeks-loading groupafter the hyperthyroid rat model is established. The same micro-implants were implantedinto the immediately-loading group after two weeks, then each group were loaded with100g orthodontic force in the same time. After that, X-ray taken to observe the micro-implant position and check the degree of micro-implant loosening. All animals werekilled4weeks later, before the rats were sacrificed, respectively labeled tetracyclinehydrochloride and calcein bone formation fluorescent on the14th,13thday and4th,3thday.Measured the distance between the micro-implant and measured the bone mineral densityat the time of loaded and sacrificed. collected their bilateral tibias. Production of bonetissue slices, observed bone tissue morphology and micro-implant bone combination ofcircumstances. Data was analyzed and processed by SPSS17.0.Results1. Model established: After being gavaged28days, the levels of serum T3, T4,TSH between hyperthyroid group and the normal control group were statisticallysignificant. Compared with normal control group, the hyperthyroid groups’ serum T3, T4levels were significantly increased （P<0.05）, TSH levels were significantly lower（P<0.05）. It prompted that hyperthyroid model successfully established.2. Generalcondition: Successfully established the hyperthyroid model, rats showed typicalsymptoms of hyperthyroidism. There were occasionally infected in soft tissue around themicro implant anchorage. Micro-implant anchorages were no loosing and shedding in allgroups. After the implant surgery completed, the X-ray results show that the micro-implants’ position in the tibia was good and no spot around the micro-implants.3. Bone-mineral density: As the experiment progresses, the BMD of hyperthyroid group hasdecreased, compared with the normal group it has statistically significant （P<0.01）.4.Moving distance of micro-implant: After forcing4weeks, Micro-implants have takeplace move. There was statistically significant （P<0.05） between hyperthyroid groupand the normal control group in distance of micro-implant. The moving distance ofmicro-implant anchorage in hyperthyroid immediately loading group and hyperthyroidtwo-weeks-loading group has not statistically significant （P>0.05）. It also has not statistically significant （P>0.05） between normal immediately-loading group andnormal two-weeks-loading group.5. Fluorescence analysis: there are double fluorescencelabeling among the four groups, and fluorescence mainly in the bone-microimplantinterface and bone trabecula. There was not statistically significant （P>0.05） betweenthe four groups.6. Bone-implant contact ratio （BIC） calculation: BIC ofhyperthyroid group was higher than the normal group, a statistically significant（P<0.05）. BIC of hyperthyroid immediately loading group and hyperthyroid two-weeks-loading group has not statistically significant （P>0.05）. It also has notstatistically significant （P>0.05） between normal immediately-loading group andnormal two-weeks-loading group.7. Micro-implant bone tissue around the morphologicaland histological: four groups of micro-implant and bone tissue close contact,hyperthyroid immediately loading group and hyperthyroid two-weeks-loading group havenew bone formation, hyperthyroid immediately loading group tension side mainlyosteogenic, the small number of osteoclasts. The pressure side could seen osteoblasts andosteoclasts, the more osteoclasts tension side and poor continuity. hyperthyroid two-weeks-loading group can be seen the phenomenon of bone formation and resorption inboth tension side and pressure side, and more osteoclasts in the pressure side; Normalimmediately-loading group and normal two-weeks-loading group: the phenomenon ofbone formation can be seen in both groups, normal immediately-loading group tensionside mainly osteoblasts, the pressure side has small number of osteoclasts, normal two-weeks-loading group tension and pressure sides can observe the phenomenon of boneformation and resorption, but the pressure side of the bone resorption stronger than boneformation.Conclusions1. With a dose of60μg/（100g d） of Euthyrox formulated liquid ig28d, can establish hyperthyroid rat model.2. Hyperthyroid can reduce the BMD of rats,resulting in bone loss, having a tendency to osteoporosis.3. Micro-implants ofhyperthyroid rats were stable and shown good biocompatibility, indicating that the micro-implant anchorage in hyperthyroid rats are feasible.4. The micro-implant anchorage inhyperthyroid rats load immediately or two-weeks are feasible, but should be use lightforce. |
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