title: Temperature-dependent rheological property changes of thermoplastic gutta-percha root filling materials.
abstract: OBJECTIVE
  To compare the penetration resistance (PR) of six thermoplastic gutta-percha (GP) materials against needle penetration at different temperatures.
  
  
  METHODS
  The PR of the following materials based on warm gutta-percha techniques, Beefill GP Cartridge (Beefill), GP Obturator-Hard/Medium/Soft (Dia-H, Dia-M, Dia-S), Obtura (Obtura) and Tactendo Gutta (Tactendo), was measured as a function of temperature change (from 30 °C to 200 °C). The PR was measured using a force gauge, mounted on a motor-driven micrometre stage, which pushed the penetration needle against GP in a glass cylinder at the designated temperatures. Data were analysed using Kruskal-Wallis anova and Duncan's multiple range tests at 5% significance.
  
  
  RESULTS
  The mean PR values for all assessed materials ranged from 15.55 MPa to 26.02 MPa at 30 °C, decreased to 0.18-1.61 MPa at 60 °C, and finally reached 0.02-0.12 MPa at 200 °C. The Obtura had the highest PR values at most of the measured temperatures. At 40-60 °C, Obtura had the highest PR value (P < 0.05), and Tactendo had the lowest amongst the tested materials. At 70-200 °C, both the mean PR values and melt flow temperature (MFR) of Obtura, Dia-H and Dia-M were significantly higher than those of other materials (P < 0.05).
  
  
  CONCLUSIONS
  The PR values were changed by both the heating temperature and the brand or type of GP materials tested. Each material was associated with drastic decreases before reaching 60 °C in different degrees, and Obtura had the highest PR at most of the measured temperatures.
authors: Department of Dental Materials and Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea.
authors: H J
authors: HJ
authors: Moon
authors: Department of Dental Materials and Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea.
authors: J H
authors: JH
authors: Lee
authors: Department of Dental Materials and Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea.
authors: J H
authors: JH
authors: Ahn
authors: Department of Dental Materials and Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea.
authors: H J
authors: HJ
authors: Song
authors: Department of Dental Materials and Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea.
authors: Y J
authors: YJ
authors: Park
mesh_terms: D006171:Gutta-Percha / Q000737:chemistry*; D008422:Materials Testing; D012212:Rheology; D012387:Root Canal Filling Materials / Q000737:chemistry*; D013696:Temperature
chemical_list: D012387:Root Canal Filling Materials; C113130:obtura II; D006171:Gutta-Percha
keywords: endodontic obturation; penetration resistance; rheological property; thermoplastic gutta-percha