Master core apical movement during compaction: evaluation of two in vitro models

Interaction Between Sealers and Gutta-percha Cones

Clinical observations seem to indicate that some gutta-percha cones are softened by contact with sealers. The purpose of the study was to verify whether an interaction existed between some sealers and different brands of gutta-percha cones. Because previous studies have indicated that the differences between brands of gutta-percha are magnified by heat, thermatic compaction was used in conjunction with a model of a root-canal preparation with lateral canals. Three brands of cones (Kerr, UDM, Beldent) were tested with three types of endodontic sealers (AH 26, Apexit, Roth's). A group without sealer served as a control. The length of flow into the lateral canals was measured for each combination and analyzed by two-way ANOVA. A highly significant difference was found, confirming the hypothesis that an interaction between sealer and cones is present in some combinations. It was not possible to ascribe a trend of greater effect to a certain sealer, but Roth's 811 had the least effect on flow.

Warm vertical compaction sequences in relation to gutta-percha temperature

The aim of this study was to analyze warm vertical compaction sequences in relation to the temperature variations of gutta-percha. Twenty-four maxillary incisors were obturated according to two different instrumentation techniques: Compaction and heating were performed with either the monomanual classical or bimanual method. To evaluate gutta-percha temperature, thermocouples (TC) were introduced into channels bored through the dentin into the root canal system or fixed on the root surface at 8 (TC8), 4 (TC4), 2 (TC2), and 0 mm (TC0) from the apex. Maximal temperature was 118 degrees C for TC8, 52 degrees C for TC4, and 44 degrees C for TC2 and TC0. At TC0, the temperature remained above 42.9 degrees C for 10 +/- 5 s. These results show the importance of heating down to a distance of 7 mm to ensure a significant increase in apical gutta-percha temperature. They further indicate that the last compaction should last more than 15 s to avoid detrimental cooling and dimensional variations. The principal differences between the monomanual and bimanual methods were the compaction time (5.07 +/- 0.2 min vs 4.02 +/- 0.3 min) and the number of compactions (8 +/- 1 vs 12 +/- 2).

Apical enlargement: influence on overextensions during in vitro vertical compaction

This study evaluated the apical movement of gutta-percha master cones under in vitro vertical compaction. A split natural tooth model was used. The gutta-percha cones were first fitted at 0.5 and 1.0 mm short of the apical end of a canal instrumented up to a size 25 file and then condensed. Then the canal was cleaned of gutta-percha and reshaped up to a size 40 file, other cones fitted and obturated. Photographs were taken before and after compaction and measurements were made. The canals instrumented to a size 40 file had significantly more overextensions than those instrumented to a size 25 file.

Elongation and movement of the gutta-percha master cone during initial lateral condensation

This study evaluated gutta-percha master cone elongation and apical movement during initial lateral condensation. A split natural tooth model was used. Measurements on photographs taken before and after initial spreading were made. The results showed that both elongation and total cone displacement occur.