Thermal conduction of three rotary gutta-percha cones using a two-dimensional axisymmetric transient heat conduction simulation: An in vitro study

Abstract Introduction: System B is a widely used endodontic heat source for warm vertical condensation (WVC) during root canal obturation. As gutta-percha (GP) remains the most commonly used obturation material, this study evaluated the thermal conduction characteristics of three rotary GP cones with different tapers using both experimental measurements and thermal modeling. Materials and Methods: Root canal treatment was performed on eight extracted, single-rooted maxillary central incisors. The thermal conductivity and diffusivity of ProTaper NEXT, WaveOne Gold (W1G), and ProTaper Universal (PTU) GP cones were measured using a modified transient plane source technique. Temperature changes were recorded at 0.5 mm, 2.5 mm, and 10.5 mm along the cone using K-type thermocouples and the System B heat source. A two-dimensional axisymmetric transient heat conduction simulation was performed to validate experimental results. The output temperature of the System B tip was also evaluated for consistency and accuracy. Data were statistically analyzed. Results: PTU exhibited the highest thermal conductivity (1.07 W/m·K) and diffusivity (6.0 × 10 -7 m²/s), while W1G showed the greatest mean maximum temperature and temperature rise at 0.5 mm and 2.5 mm ( P < 0.05). Thermal simulation showed that up to 0.9 mm of the GP cone reached the softening temperature (≥65 °C). Taper size significantly influenced both the extent and direction of heat conduction. Conclusions: GP cone composition and taper significantly influence thermal conduction during WVC. Cones with low zinc oxide content showed superior heat transmission, and greater taper enhanced apical heat flow.