# In Vitro Evaluation of Root Surface Temperature Using Different Endodontic Filling Techniques
## 4 Discussion
used thermocouples to measure the temperature differences, the present study used a thermal imaging camera. The disadvantage of thermocouples is that temperature changes can only be observed in very specific areas of the root. The thermal imaging camera has the advantage of being able to measure temperature changes on the entire surface. For a better assessment, three points (P1-P3) were selected in the present study and connected using L1 in order to observe the average heating. A study by [PERSON] et al. investigating the cold single-cone technique noted a small increase in temperature. This was likely due to a flame-heated instrument that was used to separate the gutta-percha [27]. There was a larger increase in temperature when flame-heated instruments were used in the canals compared to systems for warm obturation, such as System B. It should be mentioned here that the BeeFill 2 in1 unit (VDW GmbH, Munich, Germany) was set at 200 \({}^{\circ}\)C for the plugger, whereas the flame-heated instrument only reached a mean temperature of 126.23 \({}^{\circ}\)C. While [PERSON] et al. obtained a significantly larger temperature increase using the flame-heated instrument, which could lead to damage to the periodontal ligament, this was not the case in the present study when the cold single-cone technique was used, with a median of 1.11 \({}^{\circ}\)C for a fluid circulation rate of 6 mL/min [27]. When interpreting the results, it is important to note that different obturation techniques require different amounts of time, which can lead to inaccuracies. While the continuous wave and Schilder techniques are more complex, the GuttaFusion technique (VDW GmbH, Munich, Germany) has a longer cooling time than the 10 s required by the other techniques. At flow rates of 2.6 mL/min or 6 mL/min, a constant temperature of approximately 37 \({}^{\circ}\)C was maintained, in contrast to a flow rate of 0 mL/min where the specimen reached 37 \({}^{\circ}\)C before measurements began. Efforts were made to keep the temperature stable during obturation techniques, but due to the temperature gradient, cooling to room temperature was expected. T\({}_{\text{max}}\) is therefore often equal to T\({}_{0}\) as the starting temperature. Another factor requiring consideration is the thickness of the dentin and enamel. This was addressed in the present study by randomizing the samples beforehand with computer software by the study director to ensure diversity in each test section and to obtain a mean representation of dentin thickness. Previous work by [PERSON] et al. shows that the thickness and porosity of the dentin can have a significant influence on its conductivity. An increase in porosity corresponds to a decrease in conductivity [30]. Low conductivity leads to greater thermal insulation. This indicates that teeth with lower conductivity should have a smaller increase in temperature during warm obturation; the thicker the dentin is, the less heat is transferred to the surface of the root [31]. It is important to recognize that the thickness of the dentin varies within the tooth. The coronal third of the root, in particular, showed the largest changes in temperature in comparison with other segments. The heated instruments were inserted into different depths in the canal, and for the apical third, gutta-percha remained as an insulator for a length of 5 mm [32]. This study utilized randomly selected single-rooted teeth with varying dentin thicknesses. As such, results across the different teeth are expected to differ slightly due to variations in the dentin thickness of each tooth. [PERSON] reported an increase in temperature of more than 10 \({}^{\circ}\)C during the application of warm obturation techniques, particularly in the mandibular central incisors [14]. However, periodontal blood flow was not taken into account. To avoid the risk of damage to the periodontal tissue, it has been suggested that the application time for a heat-plugger,as well as the thermoplasticized gutta-percha injected, should be minimized [33].