# In Vitro Evaluation of Root Surface Temperature Using Different Endodontic Filling Techniques
## 1 Introduction  
Inflammation of the dental pulp has various causes, such as trauma, caries, or tooth wear [1, 2]. The bacteria descend to the apex and trigger inflammation of the periapical tissue, which becomes visible radiologically as an apical translucency--an apical lesion [3]. Root canal treatment is carried out to prevent the inflammation from spreading. The treatment should conclude with tight sealing of the canal system. The prerequisite for obturation of the canal is complete preparation and disinfection of the root canals. When these requirements are met, the chances of healing are 74-98% [4]. For root canal treatment, conclusive three-dimensional filling of the root has to be achieved. According to [PERSON], this can be accomplished using warm obturation methods [5]. [PERSON] has reported that all obturation methods achieve better results when a sealer is used in addition to the core material. This helps compensate for canal unevenness and fills the gaps between the core material and any voids [6]. Gutta-percha (GP) is recognized as the gold standard for obturation materials [7]. The naturally occurring variety of gutta-percha is the \(\alpha\)-form, which becomes thermoplastic at 65 \({}^{\circ}\)C. If rapid cooling occurs over a short time, the \(\beta\)-form, used in industry, develops. In contrast to the \(\alpha\)-phase, it becomes thermoplastic at 56 \({}^{\circ}\)C [8]. The \(\beta\)-phase is also used in dentistry as gutta-percha points for cold lateral condensation or warm vertical compaction, whereas the \(\alpha\)-phase is used for backfill methods using injectable gutta-percha [9]. Commonly used techniques were also applied in the present study, such as the continuous wave technique, squirting technique (injection technique), a gutta-percha-coated rigid carrier technique, and the Schlider technique [10]. There has been wide discussion in the literature on whether cold or warm obturation methods lead to better results in endodontic treatment [11]. The cold lateral condensation technique is regarded as the one most commonly used [12]. A common criticism of warm obturation is that it introduces heat into the root canal, with a temperature increase in the periapical region potentially leading to damage to the periodontal ligament. Reports in the literature have highlighted the importance of temperature increases, especially in mandibular incisors undergoing warm obturation methods [13; 14]. Notably, an animal study conducted by [PERSON] and [PERSON] showed that a temperature increase of up to 47 \({}^{\circ}\)C leads to heat-induced damage to the alveolar bone, while a rise of up to 56 \({}^{\circ}\)C even damages alkaline phosphatase [15; 16]. It is also discussed whether heat-induced damage to cementoblasts results in less mRNA expression of mineralized tissue-associated proteins, which may have an effect on apical healing [17]. Interestingly, none of these studies have taken into consideration the physiological effects of periodontal blood flow as a potential cooling factor. To better evaluate the risks associated with warm obturation methods, it is essential to consider the influence of periodontal blood flow during obturation. However, the literature includes only a few studies that address this phenomenon. One finite element analysis (FEA) study explored the impact of periodontal blood flow on temperature increases during obturation, reporting lower temperature rises with simulated periodontal blood flow [18]. Here, it must be taken into account that FEA is only an approximation method and cannot be completely transferred to real situations. There is a notable lack of published studies directly investigating the effect of periodontal blood flow without using finite element analysis software. The aim of the present study was, therefore, to analyze the effects of the periodontal blood flow on the periapical and periadicular region during the application of warm obturation techniques.