Analysis of shrinkage of different gutta-percha types using optical measurement methods

The aim of this study was to compare the shrinkage of alpha- and beta-gutta-percha of the Multifill-system with commercial gutta-percha. Ten gutta-percha blocks of each of the three types were used. Speckle pattern shearing interferometry was used to prove that no trapped air and material defects were present in the specimens. The optical triangulation method was applied to assess shrinkage. The three gutta-percha types were examined after heating up to 90 degrees C and cooling down to 35 degrees C. Commercial gutta-percha showed less shrinkage (6.5%) than alpha- (7.2%) and beta-gutta-percha (7.3%; p=0.0051 for both comparisons; Wilcoxon's signed rank test). There was a significant difference between alpha- and beta-gutta-percha (p=0.0093; Wilcoxon's signed rank test). In the range of 45 degrees C to 40 degrees C, alpha- and beta-gutta-percha revealed the highest shrinkage (2.2%/5 degrees C and 2.1%/5 degrees C, respectively). Commercial gutta-percha showed the highest shrinkage (1.1%/5 degrees C) in the range of 55 degrees C to 40 degrees C. Overall, shrinkage of all types of gutta-percha was higher than could be assumed from former studies.