Temperature-dependent rheological property changes of thermoplastic gutta-percha root filling materials

Aim: To compare the penetration resistance (PR) of six thermoplastic gutta-percha (GP) materials against needle penetration at different temperatures.

Methodology: 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.