Differences determination between the latero-lateral slices is carried out with the Wilcoxon Ranges test for related samples and they are shown in Table IV. Average normality distribution can be observed in Table III. Central distribution values, dispersion and position of lateral-lateral and superior-inferior slices measurements are found in Tables I and II. Shrinkage percentage determination, the mean and the values of their confidence interval were transformed into percentage and their result was subtracted from 100:Ĭentral tendency data and dispersion obtained from the lateral-lateral slices measurement before plastination process, as well as in after dehydration and after impregnation are shown in Table I. To establish the difference in means of shrinkage, the student's t-test was used for related samples, in the case of data that follow a normal distribution and Wilcoxon range test for related samples, in the case of data that follow a non-normal distribution. The normal distribution of the data was established through Shapiro-Wilk test. In relation to the statistical analysis, data collection was recorded in a Microsoft Office Excel spreadsheet, a descriptive analysis of the data was performed: mean, median, variance, minimum, maximum, standard error of the mean, standard deviation and coefficient of variation.
The slices showed great differentiation between gray and white matter. Measurements of the slices were made on millimeter sheets at three moments of the protocol: before starting the plastination process, after dehydration and after forced impregnation. Once the curing chambers were assembled, they were placed under UV light to accelerate the polymerization of the polyester and to finish the plastination process. Once the forced impregnation was finished, the curing stage was carried out, which in the first place consisted of the assembly of the curing chambers within which the slices were located, filling the chambers with polyester resin. Once the sheets were dehydrated, they were placed in Biodur® P40 polyester resin and the forced impregnation was carried out in a vacuum chamber at room temperature (20 ☌). Immediately the brain cuts were placed in dehydration in 100 % acetone, at 25 ° C, for 7 days the first acetone bath, and for another 3 more days, for the second acetone bath. Once the washing was finished, it was sectioned with a precision saw band machine, with stainless steel blade, obtaining 30 thin slices of 3 mm thickness. This brain was subsequently washed in running water for two weeks.
The sample used consisted of a human brain, fixed and preserved with 10% formalin for 6 months. The aim of this communication was to analyze and establish the shrinkage of brain sections preserved by a classic protocol of sheet plastination with polyester resin Biodur® P40 in 3 mm thick human brain slices ( Guerrero et al., 2019).
In relation to this disadvantage of the technique, it is necessary to establish statistically the shrinkage percentages. But in relation to sheet plastination with epoxy resin, polyester technique causes marked shrinkage of the tissues. Likewise, this technique can be applied to any body region (Ottone et al., 2014 Ottone et al., 2018a,b Prieto et al., 2019). In particular, sheet plastination with polyester resin was initially created for the preservation of brain slices, for the identification of gray and white matters (von Hagens, 1987). Plastination is an anatomical cadaveric conservation technique created in 1977 by Gunther von Hagens, in Heidelberg, Germany ( Ottone 2013, 2018), and which replaces biological and/or fixation fluids with an intermediate solvent (acetone), to then impregnate the samples with different polymers, depending on the technique of plastination chosen, to finally carry out the polymerization of the components incorporated into the samples, to obtain dry and totally durable biological samples (Ottone et al., 2015 Ottone et al., 2016 Vargas et al., 2019).
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