## 4 Discussion  
This study evaluated the impact of two different reciprocating shaping systems on patients' postoperative QoL using systematic postoperative surveys. Patients' perspectives should be considered during the analysis of the endodontic clinical outcomes [3; 4; 26] and standardized assessment methods are extensively reported [27]. Postoperative pain can be influenced by occlusion, preoperative pain, periapical radiolucency, type of tooth, and previous emergency intervention [28]. However, the factors related to the chemo-mechanical root canal debridement are the main contributors to postoperative pain due to the extruded dentinal debris that could induce periadicular inflammation [15; 16]. This study considered only teeth with a diagnosis of pulp necrosis in order to achieve similar baseline characteristics [29]. Only multirooted teeth were selected, since it has been reported that molars experienced postoperative pain more frequently [28; 30]. A systematic balance between maxillary and mandibular molars was investigated and no significant differences were found between groups. During the clinical examination, the presence of periapical radiolucency was recorded, due to the correlation with the severity of the infection. A higher bacterial load increases the possibility of infected debris extrusion, with a subsequent inflammatory periapical reaction and worse postoperative trend [9]. Moreover, the preoperative pain at baseline could moderately influence postoperative pain [9]. Although some studies have reported no significant differences in terms of postoperative pain after root canal treatment completed by generalists or endodontics specialists, this study employed a single expert operator to perform all clinical cases [3; 31]. Previous studies reported that NiTi reciprocating single-file systems may be correlated to a stronger postoperative pain than rotary instruments [19; 22; 23]. Although they may be associated with a more conservative root canal preparation, reciprocating single-file systems may cause greater debris extrusion and, consequently, a higher degree of postoperative pain [17; 21]. It has been shown that the number of files used to reach the working length, the type of motion, and the instrument design can modulate the expression of neuropeptide in the periodontal ligament [29; 32]. In the present study, a core carrier obturation technique was performed for all clinical cases, with the aim of adopting a predictable method and avoiding bias linked to the root canal filling technique. The choice was supported by a systematic review and metanalysis, reporting that a core carrier obturation does not influence negatively postoperative symptoms, even if compared with cold lateral condensation [33]. However, thermafil technique has been associated to a more frequent incidence of overfilling, causing more intense postoperative symptoms [31]. In this observational study, for each clinical case the operator had to record in the relevant form (Appendix C) any complication, mistake, or difficulty. All the root canal treatments were performed by the same expert operator and  
Figure 4: Quality of life value. Statistical significance on day six after treatment (\(p=0.021\)). no overfilling was recorded. Nevertheless, to prevent this complication, the Thermafil core carrier size was chosen based on the diameter of the apical foramen and an X-ray confirmation was performed. Moreover, each Thermafil was adjusted in order to standardize a small amount of gutta-percha beyond the carrier. Apical patency was performed twice during each root canal treatment, in order to standardize the clinical protocol and to ensure the right detection of the working length. This procedure seems not to increase postoperative pain since it can promote the correct cleaning of the apical portion of the root canal walls, preventing the creation of blocks, ledges, perforations, or apical transportation.