Study On Three-dimensional Structure And In Vitro Degradation Rate Of Demineralized Dentin Matrix

[Objective]Using physical and chemical methods for preparing demineralized dentin matrix particles observed in vitro demineralized dentin matrix surface ultrastructure and three-dimensional structure, calculated pore size, surface area and mesoporous test distribution, while in vitro studies degradation rate of demineralized dentin matrix, to provide theoretical support emineralized dentin matrix as a bone graft material.[Methods]Part one:Preparation for DDM particles. Collecting teeth, using dental handpiece to remove the attached soft tissue,cutting the apical about3mm, removing enamel, cementum and pulp. The dentin crushed with a grinder, sub-sieve to filter out particles200～800μm, using chloroform/methanol liquid skim, gradient dehydrated in ethanol; Then placed the particles in0.6mol/L Hcl for demineralization treatment under2℃, incubated in a neutral phosphate buffer, which was added thiol protease to inhibit enzyme BMP for protecting BMP from damage,then the particles were ultrasonic vibration washed three times with distilled water, gradient dehydrated in ethanol, dried and stored at4℃using sealed ampoules after internal ethylene oxide sterilization.Part two:Study on the three-dimensional structure and In vitro degradation rate of DDM. The Bio-Oss (L), Bio-Oss (S) were divided into group A, group B as a positive control;"the Bone regeneration"--ommercialization DDM and the homemade DDM in part one divided into group A, group B were divided into group C, group D as the experimental groups. The four materials spraying coating material, after drying, the ultrastructure was observedl under a scanning electron microscope to calculate the respective aperture by computer image processing system. Taking A, B, C, D for each set of sample0.1g, static volumetric method using nitrogen adsorption to test specific surface area and pore size distribution. There are9samples of each group (0.1g/sample), placed aa of them in O.lmol/LPBS degradation solution at37℃water bath and incubated for degradation and weighed in2,4,6,8,10,12weeks after vacuum drying. Calculated degradation rate of four materials, plotted the degradation rate curve and measured buffer PH.[Results]Part one:Preparation of200～800μm diameter of demineralized dentin matrix, general observation of visible particles uniform, irregular shape, chalk-colored particles.Part two:l.The ultrastructural observations under scanning electron microscopy, Group A (large particles Bio-Oss) scanning electron microscope like spongy and porous loose hole mutual traffic, the average pore size was360.70±82.11μm, reflected under high magnification rough surface, and a amount of mesoporous and micro-hole; Group B (small particles Bio-Oss) has no such macroporous structure like group A, showing only some of the incomplete section of the hole, there is no sponge-like structure, but can be seen under high magnification many pore structure,and the pore sizes with an average of32.70±21.25μm; Demineralized dentin matrix,the different sections of either homemade DDM or commercialization DDM in the electron microscope were rough and porous surface, hole irregular shape, pore size due to different sections.Homemade DDM aperture average of3.38±0.53μm, commercialization DDM average of24.13±23.70μm. Large hole diameter of groupA, B, C, D using ANOVA LSD pairwise comparison of group,the difference of the aperture of A and B, C, D group was statistically significant compared (p<0.05), the aperture of A group of materials significantly larger than the other three materials; The aperture of B, C, D groups pairwise comparisons showed no significant difference (P>0.05).2. Detection of the four groups by nitrogen adsorption material static volumetric method, their adsorption-desorption isotherms are type Ⅳ isotherm, indicating the four groups exhibited the adsorption behavior of mesoporous solids materials. Although all belong to mesoporous materials, there are different forms holes. The specific surface area of large particles Bio-Oss is89.96m2/g, the small one81.96m2/g, the specific surface area of the commercialized DDM10.20m2/g,the homemade DDM14.10m2/g.The surface area of group A, group B (Bio-oss particles) is similar and significantly higher than group C, D group (DDM)3. The degradation rateof four materias with two-factor analysis of variance between groups p>0.05, the difference was not statistically significant, indicating that in group A, B, C, D, the degradation rate was no significant difference; within group p<0.05, the difference was statistically significance, indicating that the amount of degradation with time gradually increased.[Conclusions]1. Scanning electron microscope observations,the pore size of commercialized DDM and homemade is much smaller than that the large particles Bio-Oss,but DDM still have a lot of uniformly distributed pores.2. DDM and Bio-Oss are both mesoporous materials, homemade DDM pore size distribution and the average of pore size is less uneven, and its preparation method may need further improvement.The specific surface area of Bio-Oss is closest to human cancellous bone, the specific surface area of demineralized bone matrix and the DDM is approach.3.DDM has the desired degradation as a bone substitute material.