Evaluation of the dimensional stability of different thermoplasticized gutta-percha fillings using simulated glass root canals

Percentage of Gutta-Percha-, Sealer-, and Void-Filled Areas in Oval-Shaped Root Canals Obturated with Different Filling Techniques: A Confocal Laser Scanning Microscopy Study

Objective  This study compared different obturation techniques, analyzing percentage of areas filled with gutta-percha, sealer, and voids (PGFA, PSFA, and PVFA, respectively) in oval-shaped root canals.

Materials and Methods  A total of 60 extracted human mandibular central incisors were decoronated, instrumented, and irrigated using the same protocol. After drying, the root canal was filled with AH Plus labeled with 0.1% rhodamine B dye using a Lentulo spiral. The filling procedure was performed by dividing the teeth into four groups according to the respective technique: G1, cold lateral condensation; G2, continuous wave of condensation; G3, modified cold lateral condensation using an F3 master cone; and G4, modified continuous wave of condensation using an ISO (International Organization for Standardization) sized 30 gutta-percha cone. Then, slices measuring 1.5 mm in thickness were obtained 3 and 6 mm from the apex and evaluated by confocal laser scanning microscopy to determine PGFA, PSFA, and PVFA.

Statistical Analysis  The data were analyzed statistically with analysis of variance and Games-Howell’s tests ( p = 0.05).

Results  The groups showed no significant differences in the apical third (3 mm from the apex). In the middle third (6 mm from the apex), G3 and G1 showed higher PGFA and PVFA, respectively. G3 showed lower PSFA than G2 and G4. Both cold techniques (G1 and G3) promoted lower PSFA than both warm techniques (G2 and G4).

Conclusions  Notwithstanding the limitations of this in vitro study, PGFA, PSFA, and PVFA ranged significantly only in the middle third, as observed by the different filling techniques. Higher PGFA and PVFA values were obtained for G3 and G1, respectively. Both cold techniques promoted lower PSFA than both warm techniques.

Shrinkage of backfill gutta-percha upon cooling

INTRODUCTION

The temperature and related shrinking kinetics of gutta-percha injected from heat guns are not known; therefore, we investigated them in this study.

METHODS

The temperatures of 3 different backfill gutta-percha brands extruded from 3 commercially available heat guns set to 200°C were studied. To validate the results, temperature development of 1 gutta-percha brand injected from a heat gun during a simulated backfilling procedure was assessed in single-rooted human teeth containing thermocouples in a water bath of 37°C. These values were compared with the counterparts obtained in a tabletop testing device for shrinkage at an ambient temperature of 37°C. Using this device, linear shrinkage upon cooling was assessed for all 3 gutta-percha brands under investigation. Results were compared by parametric statistics (alpha = .05).

RESULTS

The temperatures of extruded gutta-percha differed significantly (P < .05) between heat guns and gutta-percha brands. Mean temperatures ranging between 57.6° ± 4.5°C and 103.9° ± 7.8°C could be observed with different combinations. The temperature of extruded gutta-percha in tabletop experiments equaled that observed in the root canals. However, the cooling of gutta-percha was (P < .05) faster in the tabletop measuring device compared with the root canal environment. Within the controlled temperature drop from 75°C to 37°C, the total shrinkage differed significantly (P < .05) between the 3 gutta-percha brands under investigation and ranged between 0.96% ± 0.20% and 2.31% ± 0.26% after 10 minutes (P < .05). Shrinking kinetics showed different patterns between the gutta-percha brands.

CONCLUSIONS

Gutta-percha designed for thermoplastic application shrinks quickly and extensively upon cooling.

An in vitro investigation of Thermafil obturation at different temperatures

The apical leakage of lower premolars obturated with Thermafil at three different temperatures was investigated in vitro. The temperatures were determined after calibration of the Thermaprep oven. The root canals of 35 extracted teeth were prepared chemomechanically and divided into three groups of 10 each with a control group of five. The root canals of the experimental group were obturated using plastic Thermafil obturators at three different temperatures 144, 120 and 100 degrees C with the controls being obturated using laterally condensed gutta percha. The teeth were suspended in indian ink for 28 days prior to being cleared and the degree of apical leakage assessed. The results showed no significant difference (p > 0.05) in the apical leakage of the teeth obturated with Thermafil compared to laterally condensed gutta percha. There was a trend towards less leakage in the teeth obturated with Thermafil at the lower temperatures, this, however, was not significant (p > 0.05).