# In Vitro Evaluation of Root Surface Temperature Using Different Endodontic Filling Techniques
## 4 Discussion  
There has been considerable debate on whether the advantages of warm obturation techniques outweigh the disadvantages, such as overfilling or potential thermal damage to the surrounding tissue [22,23]. The phase 4 Toronto study similarly found that teeth obtutated using warm vertical condensation had a higher probability of healing than teeth filled using cold lateral condensation [24]. By contrast, another study found no significant difference in obturation quality, long-term outcome, or postoperative pain between cold and warm obturation methods [25]. With regard to the filling methods used in the present study, the squirting technique (injection technique), in particular, is associated with a risk of overfilling since a definite apical stop is not provided. Other methods, such as the continuous wave and Schilder techniques, use a master point to define the working length, which minimizes the risk of overfilling compared to the squirting technique [26]. The squirting technique offers a reduced chance of heat damage to periodontal tissue. Following the GuttaFusion technique (VDW GmbH, Munich, Germany), lower temperature changes were observed compared to the continuous wave or Schilder techniques. [PERSON] et al. reported an average temperature increase of 13.9 \({}^{\circ}\)C with the continuous wave technique [13]. The study did not include an artificial periodontal ligament or alveolar socket, nor did it take periodontal blood flow into account. The use of the continuous wave or Schilder technique leads to a higher increase in temperature since the gutta-percha is heated twice. The down-packing phase, therefore, leads to an increase in temperature after the separation phase, which is also reflected in the results of the present study [14]. While [PERSON] et al. observed the largest temperature change in the apical third, the present study identified a more substantial temperature change in the coronal and middle third of the root. This difference can be explained by the fact that the heat plugger was inserted up to about 5 mm short of the apex. Consequently, the heated plugger barely reached the apical third, given the total sample length of 11 mm, while the remaining gutta-percha up to 5 mm short of the apex limits heat conduction [27]. Irrespective of the flow rate, both studies identified the highest temperatures during the continuous wave technique. Even with the continuous wave technique, the temperatures reached in the present study did not pose any risk of damaging the periodontal ligament. This emphasizes the critical need to take periodontal blood flow into account and simulate it during in vitro studies. Alginate was used by [PERSON] et al. as an artificial periodontal ligament to represent water content similar to the tissue surrounding the teeth, and the maximum rise in temperature was up to 2.00 \({}^{\circ}\)C when the continuous wave technique was used 5 mm short of the apex [28]. These results are comparable to those of the present study, in which the highest temperature change was also observed with the continuous wave technique at L1 with a median of 3.76 \({}^{\circ}\)C, particularly in the coronal third with a median of 7.76 \({}^{\circ}\)C. The larger temperature rise compared to [PERSON] et al. is due to the fact that the present study included both the separation phase of the continuous wave technique as well as the backfilled phase with warm gutta-percha. This can be regarded as a second heat application that influences the coronal third due to filling up to the coronal end of the sample. Another reason for the temperature difference might be the use of different electric heat carrier systems for the obturation. [PERSON] et al. noted that the System B heating device did not reach the preset temperature of 200 \({}^{\circ}\)C, whereas the present study used the BeeFill 2 in1 unit (VDW GmbH, Munich, Germany), which heats up closest to the preset temperature [29]. While [PERSON] et al.