# In Vitro Evaluation of Root Surface Temperature Using Different Endodontic Filling Techniques
## 2 Materials and Methods  
Research for this laboratory study was in compliance with the ethical principles set out in the World Medical Association Declaration of Helsinki, version 7 (2013) and was approved by the local ethics committee (reference number EK 24-202). None of the teeth used were extracted for research purposes; individual indications were present in the context of dental care, and the teeth were made available after the patients had provided informed consent. The samples were supplied by dentists who were not involved in the study. The study included seventy-five extracted single-rooted teeth, which were stored in isotonic sodium solution with additional sodium azide (0.9% NaCl, 0.001% NaN\({}_{3}\)). The roots of the teeth were undamaged and exhibited complete root growth. Only single-rooted teeth with straight roots were selected in order to achieve standardization and comparability of the results. Furthermore, the application of the method for multi-rooted teeth, especially with curvatures, is not yet fully developed and is linked to more difficult evaluation. The samples were previously sorted by tooth type. Various single-rooted teeth were included, and considerable root length deviations were observed. After cleaning the root surfaces, the teeth were shortened to a length of 11 mm using a saw (cut-grinder Primus diamond cutting device; Walter Messner GmbH, Oststeinbek, Germany) in order to provide standardized specimens, which consist of root dentin and cement but no enamel to guarantee intra-experimental comparability. The samples were then divided into preliminary groups based on their dentin thickness and randomized into individual study groups by the study director according to computer software to ensure diversity in each test group. Root canal preparation was carried out up to 1 mm to patency using initially manual K-Files up to ISO size 25/.02 (VDW GmbH, Munich, Germany), followed by F1 up to F4 Protaper Gold(r), ISO size 40/.06 (Dentsply Sirona Inc., Charlotte, NC, USA) as a master file. The preparation was carried out with irrigation using sodium hypochlorite (NaOCI) 2.5% and ethylenediaminetetraacetic acid (EDTA) 17% at 2 mL/canal plus a 1-min exposure time, and for the second disinfection, NaOCI 2.5% at 5 mL/canal, in accordance with the Aachen endodontics irrigation protocol [19]. The samples were coated with molten wax (Dippy Light; Yeti Dentalprodukte GmbH, Engen, Germany and BEGO(r) Bremer Goldschlagerei Wilh. Herbst GmbH & Co., Bremen, Germany) so that a layer 0.2 mm thick was formed. The teeth were subsequently sealed in a thermoforming sheet (DURAN(r), diameter 0.5 \(\times\) 125 mm; Scheu Dental Technology, Iserlohn, Germany). The wax layer was removed, and the root was repositioned in the thermoforming sheet and fixed coronally with composite (Ivoclar Vivadent, Schaan, Liechtenstein), with a gap of <1 mm now created, simulating the periodontal space. Two inflow cannulas (capillary tips 0.48 mm; Ultradent products GmbH, Cologne, Germany) were attached to the thermoforming sheet 3 mm coronal to the apex at an angle of 45\({}^{\circ}\) using Tetric EvoFlow (Ivoclar Vivadent, Schaan, Liechtenstein). A simulated periodontal blood flow (tap water was used for the purpose) was able to circulate through the cannulas and thus the simulated periodontal space. Subsequently, the apex was also sealed with Tetric EvoFlow to prevent liquid leakage from the apex into the canal under pressure. The samples were then connected to the tube system of a hose pump (ISMATEC(r), Wertheim, Germany) and placed approximately 3.5 cm in front of the thermal imaging camera (VarioCAM HD; InfraTec GmbH Infrarotsensorik und Messtechnik, Dresden, Germany). As in the studies by [PERSON] and [PERSON] et al., the following fluid circulation rates were selected: 0 mL/min, 2.6 mL/min, and 6 mL/min [20; 21]. These represent no blood supply at all (0 mL/min), low blood supply (2.6 mL/min), and intensive blood supply on a root surface (6 mL/min).