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.

Efficacy of different rotary instruments for gutta-percha removal in root canal retreatment.

The purpose of this study was to evaluate the efficiency of FlexMaster, ProTaper, and RaCe rotary instruments compared with Hedström files for removal of gutta-percha during retreatment. Sixty mandibular premolars with one single straight canal were instrumented with K-type files and filled using cold lateral compaction and sealer. The teeth were randomly divided into four groups of 15 specimens each. After repreparation with Gates Glidden burs and the test instruments the specimens were cleared. The area of remaining gutta-percha/sealer on the root canal wall was measured from two directions. The RaCe group showed significantly less residual obturation material than FlexMaster and Hedström group (p < 0.05; closed test procedure). There was no difference between ProTaper and all other instruments (p > 0.05). ProTaper and RaCe instruments required significantly less time for retreatment than FlexMaster and Hedström files (p < 0.05). One RaCe file, two ProTaper, and two FlexMaster instruments separated. RaCe cleaned obturated canals more effectively than hand files and FlexMaster files.