Temperature Variations on the External Root Surface During Warm Injectable Gutta-Percha Obturation at Different Thermo-Plasticization Settings: An In Vitro Study

Background and Objectives: Warm injectable gutta-percha techniques may improve three-dimensional filling of complex canal anatomy, but heat transfer to the external root surface may threaten periodontal tissues when the 47 °C threshold is exceeded. This in vitro study quantified external root-surface temperature changes during obturation with the Woodpecker FI-G/FI-P system and compared manufacturer preset temperatures with actual device output. Materials and Methods: Twenty extracted single-rooted human teeth standardized to 18 mm were prepared and assigned to obturation at 180 °C (Group A, n = 10) or 230 °C (Group B, n = 10). Infrared thermography recorded coronal, middle, and apical root-surface temperatures. A second device-based experiment measured FI-G and FI-P output at preset temperatures of 150 °C, 180 °C, 200 °C, and 230 °C. Results: The 230 °C setting produced significantly higher middle-third temperatures than the 180 °C setting (41.84 ± 5.52 °C vs. 36.99 ± 3.21 °C; p = 0.027; Cohen’s d = 1.07), whereas coronal and apical differences were not significant. The highest external root-surface value was 49.6 °C, and 3/10 specimens obturated at 230 °C exceeded 47 °C in the middle third. A significant coronal-to-middle gradient reversal was observed at 230 °C (p = 0.045). Device measurements showed strong attenuation between preset and output temperatures: at 230 °C, the FI-G tip base reached 150.0 °C but the tip apex reached 51.3 °C, while FI-P plugger tips reached 120.0 °C. Conclusions: The 180 °C setting produced a more predictable thermal profile, whereas 230 °C increased localized middle-third overheating risk. These in vitro findings support cautious temperature selection, especially in teeth with reduced dentin thickness or compromised root anatomy.