Shrinkage of backfill gutta-percha upon cooling.
BACKGROUND
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.
Department of Preventive Dentistry, Periodontology and Cariology, University of Zurich, Center of Dental Medicine, Zurich, Switzerland.
Silvio
S
Lottanti
Department of Preventive Dentistry, Periodontology and Cariology, University of Zurich, Center of Dental Medicine, Zurich, Switzerland.
Tobias T
TT
Tauböck
Department of Preventive Dentistry, Periodontology and Cariology, University of Zurich, Center of Dental Medicine, Zurich, Switzerland. Electronic address: matthias.zehnder@zzm.uzh.ch.
Matthias
M
Zehnder
D003786:Dental Pulp Cavity / Q000033:anatomy & histology; D006171:Gutta-Percha / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012389:Root Canal Obturation / Q000295:instrumentation; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
D012387:Root Canal Filling Materials; D006171:Gutta-Percha
Gutta-percha; shrinkage; temperature