| [Objective] As is known that in dental implants the lack of the oral soft tissue will affect the function and appearance of the implant. In order to solve this problem, the purpose of this study is, with the same principle of the skin expansion, to apply water-swelling material placed in the bottom of the oral soft tissues to make it incremental. Polyvinyl alcohol (PVA) hydrogel has been prepared experimentally and the characteristics and cytotoxicity of water-swelling properties of the gel and been researched so as to provide experimental basis for the increment applied to the oral soft tissues.[Material and methods]1. PVA hydrogel was obtained by using the freezing/thawing method to crosslink physically the PVA solution;PVA hydrogel water content was soaked for48hs as an evaluation to explore the PVA hydrogel swelling in deionized water factors.2. Dry PVA hydrogel was soaked in SBF to make it swell again so as to observe the swelling laws of different concentrations of PVA hydrogel in course of time; different specifications PVA dry gel was soaked in SBF so as to see the effects of its size and shape to its water-absorbing rate; to test the gel absorbent swelling under certain pressure by placing the dry gel sample in the container, in which weights of different quality were given so to create some external pressure; fully soaked PVA hydrogel glue was put into100ml PBS buffer containing10'u/l lysozyme in37℃swelling of the oscillation, and by measuring the degradation rates at1,2,4,8w respectively to observe the swelling properties of PVA gel dry at room temperature preservation.3. Primary cultures of fetal rat calvarial osteoblasts were selected to test the toxicity of the PVA gel on osteoblasts by MTT assay.[Results]1. The moisture content of the different molecular weight of the hydrogel changes in different groups (high molecular weight group>medium molecular weight group>low molecular weight group),while taking the water content of PVA hydrogel rate as the evaluation indicators in the same conditions as other factors, which indicates there was significant difference (P<0.05); in one time refrigeration cycle contains the lowest moisture content of the PVA hydrogel, while in the refrigeration cycles three times, five times, seven times between the two groups there were no significant difference (P>0.05); in different concentrations of the hydrogels moisture content test results (10wt%group>15wt%group>20wt%group>25wt%group) the difference was significant.2. PVA hydrogel samples in SBF of37℃within72hours while being soaked the initial volume increased three more times in size with fastest water absorption to the PVA gel of25%, the slowest to15%PVA gel absorbent. After being soaked8d, all the samples increased more than95%maximally in size with10d stable and60d no significant dissolved evidence. Flake-shaped PVA hydrogel is found a lot of suction within a few days, while the cube of PVA hydrogel being found the slowest rate of water uptake, indicating there was no significant difference in the rectangular and cylindrical gel swelling rate. Under the pressure, the gel with the increase of pressure lowered the absorption rate, but there was no significant reduce to the volume swelling ratio. PVA hydrogel initial under the ormal temperature declined faster in quality, but gradually stabilized after10days being placed10d and the gel re-swelling in the volume swelling was low;1,2,4,8w PVA gel for the determination of the degradation rate of1.43%,2.56%,3.57%,3.93%, indicating no significant difference.3.To osteoblasts in direct contact with PVA hydrogel in1to2day, the relative growth rate was close to99%with toxicity grading for1. On the fifth day the relative growth rate was close to more than99%with toxicity rating of0level,8and10d relative growth rating in more than90%, and toxicity graded as1. The statistical analysis results showed that there was no significant difference to the absorbance value of the PVA hydrogel group and negative control group (P>0.05), while there was significant difference to the absorbance values of the PVA hydrogel group and the blank control group or positive control group (P<0.01).[Conclusion]1. It is indicated that under our experimental conditions the higher the molecular weight the higher the moisture content of the PVA hydrogel is while the higher the PVA concentration, the lower the PVA hydrogel moisture content and the refrigeration cycle PVA hydrogel with refrigeration cycle for3-7times has a high moisture content.2. PVA gel initial swells faster in37℃SBF and10d of the inner volume swelling ratio goes up to five times to reach the equilibrium faster than the surface area of the PVA hydrogel.5kp within the pressure of PVA gel the swells properly with lower swelling ratio of PVA gel at the normal temperature and low degradation rate of the PVA gel.3. The results of high molecular weight PVA hydrogel with osteoblast cell toxicity test0or1, suggest that the gel has good biocompatibility. |
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