Temperature evolution of preheated irrigant injected into a root canal ex vivo

Objectives: The aim of this study is to test the influence of the temperature of the surrounding medium, flow rate, duration of irrigation, and apical patency on the evolution of the temperature of irrigants injected in a root canal. Materials and methods: Thermocouples were inserted into an incisor at different positions to monitor irrigant temperature during and after injection at 21, 45, or 60 °C. The tooth was immersed in a water bath at 21 and 37 °C. Results: Preheated syringes were used for up to 2.5 min before being cooled down from 60 to below 45 °C. The irrigant temperature was higher apically than at coronal levels (P ≤ 0.028). The duration of irrigation had no influence on the average temperatures during delivery (P ≥ 0.337), but the apical patency lowered the intracanal temperature (P = 0.004). The highest temperature measured on the outside of the tooth was 39 °C. Conclusions: Preheating the irrigant at 60 °C resulted in temperatures higher than 45 °C throughout the root canal, during irrigant delivery. After completion, the temperature dropped rapidly. Clinical relevance: These results contribute to a better understanding of the optimum irrigant delivery time at given temperature, the cooling rate of irrigant in the syringe, and the influence of heated irrigant temperature in the periodontium, which should guide the preheated syringe turnover.