| Background and ObjectiveThe normal metabolism of the alveolar bone depends on the functional stimulation of teeth.If the teeth are pulled out for some reasons, the stimulus way changes and the alveolar bone will suffer persistent, progressive and non-reversible resorption,which makes the height reduced and the width narrowed down. The original form of alveolar ridge varies,which not only seriously affects the function of dentures , but also does harm to the implantation and aesthetics.The restoration of teeth extraction is complicated.The mechanism of which is still uncertain. Many experts have been in search of how to prevent the alveolar bone from being absorbed and accelerate the restoration,then people can preserve the original shape of extraction. Scholars tried to maintain the height and width of the alveolar ridge by implanting the biological materials with a function of bone guiding and the complex of growth factors which plays a critical role in bone induction into the extraction socket.This method has become a tendency due to its stable effect and having no trauma. Choukroun's platelet-rich fibrin (PRF) is a new generation of platelet concentrates which has been extracted by Choukroun and other French scientists in 2000. There are several advantages as follows:Simple preparation that can be manipulated before or during the surgery without any additives like anti-coagulate agents or blood preparation won't induce any cross contamination or immunologic rejection,and the effective process of simulating the physiological state of the fibrin clot formation makes it similar to the normal fibrin in the human blood clot. All kinds of cell growth factors in it not only increase the concentration of cytokines,but also promote the synergistic action among them. In recent years, both basic and clinical researches suggested that the PRF has a good effect on tissue healing, inflammatory regulating and anti-infection.The polymerization of PRF is slow and nature in the low-speed centrifu- gation state,which makes the fibrin a 3-dimensional organization and a more porous gel with larger pores and elasticity.As a substrate,PRF provides a favorable place for cells adhesion,migration and differentiation,those cytokines combine with the substrate in chemical bonds . The mechanisms of the tissue healing can be summarized as follows:1) to guide revascularization in the damaged tissue; 2) to guide epithelial tissue to close injuries;3) immunologic regulation; 4) to condut circulating blood stem cells to migrate,proliferate and differentiate.In this study, according to the resorption and atrophy of the alveolar ridge caused by teeth extraction and the effect of PRF in tissue healing, we compared the restoration of the remaining alveolar bone by implanting the PRF, hydro- xyapatite in the sockets and the blank control after teeth extraction by means of general observation, histological observation and radiation measurement from animal experimental studies and hoped to provide some guiding significance of PRF in the clinical application.MethodsAfter 2 weeks of feeding,we ground the right upper and lower incisors of the rabbits to 1 / 2 of their labial length for four times with the interval of 4 days.In the process ,the marrow were protected from being wore to avoid the infection. Then,we got the autologous blood of the animals through the ear marginal artery instantly and made it centrifuged to prepare the PRF membrane.After general anesthesia by Sumianxinâ…¡and local anesthesia around the mucosa,we pulled out the right upper and lower incisors. We filled PRF membrane into the experimental sockets and hydroxyapatite into the positive control one ,both of which are flush with the alveolar crest level. Then we sorted out the sockets of the blank group and made it full of blood. Gingiva were tightly sutured to closed the teeth sockets in three groups. Respectively after 1 week, 2 weeks, 4 weeks, 8 weeks and 12 weeks animals were killed ,then we produced histological specimens for general observation, X-ray and HE staining microscopic observation.We calculated the ratio of the length between the extraction and non-extraction side on the X-ray films by Digora For Windows2.5 software,and disposed the data with statistical software SPSS 13.0.ResultsGenerally we observed that there were no obvious infection and material-off phenomenon in the dental extraction.It belongs to primary bone healing.There is no difference in the surface healing among the the experimental group (PRF), the positive control group (bone meal group) and the negative control group (blank group).1-3 days after teeth extraction, the mucosa of the positive control groups and negative control groups appeared slight red,while the experimental group 's was normal. The surface of extraction wounds were completely covered by epithelial tissue after five days .The relative length of the remaining alveolar ridge observed by X-ray resulted as follows: the experimental group (PRF)> the positive control group (bone meal group) >the negative control group (control group), the difference was statistically significant ( P <0.05) after 1 week, 2 weeks and 4 weeks. After 8 weeks, 12 weeks, the experimental group (PRF) and the positive control group (bone meal group) are greater than the negative control group (control group)(P<0.05) .But there was no significant difference between the experi- mental group (PRF) and the positive control group (bone meal group)( P >0.05).The quantity and quality of new bone in the sockets of the experimental group (PRF ) were better than the positive control group (bone meal) and negative control group in the histological observation of 1 week, 2 weeks and 4 weeks . There was a large number of new bone along the nest wall which grew to the center of the sockets in the experimental group in 1 week and the experi- mental group had more lacunae and active osteoblasts than the positive control and the negative control group.There was still new bone formed in the positive control group (bone meal group) after 8 and 12 weeks,however,of which the experimental group (PRF group) and positive control group (bone meal group) had been completed remodelled, there was no significant difference on the extent of calcification in the bone lamellar structure between the two groups.ConclusionIn the experimental group,we compared the restoration of the remaining alveolar bone by implanting the PRF ,hydroxyapatite in the sockets and the blank control after teeth extraction.All in all,the conclusions were as follows:1,PRF and hydroxyapatite bioceramics (bone meal) can all preserve the height of the alveolar ridge after teeth extraction while PRF is more evident at an early stage.2,PRF can restore the alveolar ridge as a independent transplant material.34,PRF can remedy the inflammatory symptoms which can reduce post-traumatic inflammation and accelerate the healing process of wound. |
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