The Experiment Study Of The Interface Between The Bone Tissues And Self-drilling/self-tapping Microimplant Anchorage

Objective: The purpose of this study was to compare the influences on the interface of orthodontic microimplants and surrounding tissues using different modalities.The self-drilling and the self-tapping microimplants were placed on the tibias of the rabbits.Use measures like general observation,X-ray radiation,HE stain and BMP-2 immunohistochemistry and SEM to compare the effect of the two implant modalities on the osseointegration and the interface between the implant and the surrounding tissues.Methods: Thirty-two titanium alloy microimplants were placed on the tibias of eight rabbits,and the rabbits were divided into 2 groups,one group of microimplants were self-drilling,and the other group was self-tapping.For each rabbit, two self-drilling microimplants were placed on one tibia and two self-tapping microimplants were placed on the other tibia .Approximately 200g of constant force was placed immediately between the microimplants with nickel-titanium coil springs, this way was applied in four of the rabbits. And the same treatment was not applied in the other four rabbits. After 8 weeks,we killed all rabbits and obtained the tibia specimens with the implants in them.Some specimens were fixed in the fixation fluid and were dealt with decalcification in EDTA, while after the processs of HE stain and BMP-2 immunohistochemistry, we observed them under the microscope. We use the OLYMPUS(DP10) of Fuzhou General hospital in the 400 to observe them. Choose 4 visual fields on the interface between the implant and the bone tissues randomly. Use Image analysis software to determine the samples. Use the index like average gray scale and the number of masculine cell to evaluate the intensity of expression .Use SPSS 13.0 to input the data ,use the factor analysis to analyze the slides of the BMP-2 immunohistochemistry.And the other specimens were observed with SEM. Compare the the influences on the interface of orthodontic microimplants and surrounding tissues with two implant modalities .And whether the load have effect on the interface of orthodontic microimplants and surrounding tissues with two implant modalities .Results:1. The place of the implant was completely closed by the growth,the wound was not flare or hemorrhage,and all the microimplants did not loosening.2. Observed the slice of the X-ray with naked eye,the self-drilling and the self-tapping implants did not have damage to the surrounding tissues.After 8 weeks, the self-drilling implant showed sequence bone formation,and the healing between the self-tapping implant and the surrounding tissues was not as good as the self-drilling implant obviously. Comparing the slice of the X-ray, we can not confirm whether the loading has influence on the bone formation of the interface.3. On the blade of HE staining, use low power lens may observe the shape of serrature, anastomosis to the structure of the screw thread of the microimplant. On the surrounding tissues of the loaded self-drilling implant, we may observed the osteoblast,osteoclast facility.But on the surrounding tissues of the self-tapping implant, we can not discover the osteoblast easily, neither inflammation,osteoclast and osteotylus.4. The result of the slides of the BMP-2 immunohistochemistry statistical analysis displayed: the type of the microimplant all have prominent influence both on the average gray scale and the number of masculine cell. The differences all have statistic meaning(P<0.01).The loading also has prominent influence on the average gray scale and the number of masculine cell. The differences also have statistics meaning(P<0.01).The interaction of the microimplant and the loading interaction has no influence on the average gray scale and the number of masculine cell. The differences all have no statistics meaning(P>0.05). Compare the average gray scale and the number of masculine cell of different groups: loading self-drilling implant>without loading self-drilling implant> loading self-tapping implant>without loading self-tapping implant.5. The result of SEM:the section of the contact was crushed to the shape like concave-convex with the microimplant. This shape anastomosis to the structure of the screw thread of the microimplants. Through the interface between the loading self-drilling implants and the surrounding tissues,we can see many irregulary, amorphous materials and discontinuity fibrous tissues. On the interface of the unloading self-drilling implant, we can see the continuous fibrous tissues, but on the self-tapping implant, we can see little amorphous materials and fibrous tissues.Conclusion:1. The immediately loading 200g force have no side effect on the stability of the implant, meanwhile, the loading enhances the osseointegration.2. From the histological blade of experiment, we could find that the self-drilling implant more easily induces the osseointegration.3. The interface between the self-drilling implant and the surrounding tissues have more BMP-2 masculine expression. It indicated that: on the identical condition, self-drilling implant and the bone tissues have more osseointegration, but the self-tapping implant only have little osseointegration. The self-drilling implant more easily reachs to osseointegration than the self-tapping implant, and also has little damage to the surrounding tissues.4. The result of this experiment indicates that: The self-drilling implant more easily reaches to osseointegration than the self-tapping implant, the result recommends us that advocating the immediately loading self-drilling implant is necessary in orthodontic clinic, we can also use the X-ray radiation to inspect the information of the implant ,it may also help the doctor inspect the implantation of the microimplant.