## 3 Results
### Results of Individual Studies  
According to six of the included studies, the XP-Endo Finisher instrument (XPF) showed a greater root canal cleaning efficacy than the passive ultrasonic irrigation technique (PUI) [5; 15; 16; 17; 18; 19]. On the contrary, seven articles stated that the passive ultrasonic irrigation technique and XP-Endo Finisher showed no significant differences among them in removing root filling material from canal root, and that both protocols have a greater efficacy than conventional needle irrigation procedure (CNI) [10; 12; 20; 21; 22; 23; 24]. [PERSON] et al. demonstrated in his studies [4; 25] that PUI and laser-activated irrigation (LAI) were more efficient than XPF and CanalBrush (CB). All of the included researches recorded a lower cleaning performance of the standard needle procedure than the other irrigation methods (Table 3). The root filling material mean reduction (bacteria, AHTD, and organic tissues) obtained with XPF was equal to 63.84% [5; 10; 19; 20; 23; 26]. Conventional needle irrigation and PUI guaranteed a mean reduction of 44.82% [10; 19; 23] and 64.12% [5; 10; 19; 20; 23], respectively. [PERSON] et al. [26] stated that the mean bacterial reduction in apical third (at 150 \(\upmu\)m) was 70% using Er:YAG laser, 47% using EndoActivator, and 23% using XP-Endo Finisher, demonstrating that the irrigation protocol with the aid of erbium:yttrium-aluminium-garnet (Er:YAG) laser had the greatest disinfection efficacy at higher depths. However, the same study recorded a greater efficacy of XP-Endo Finisher in killing apical third bacteria at 50 \(\upmu\)m depth than the EndoActivator instrument and Er:YAG laser. Five of the included studies [4; 12; 22; 24; 25] used the scoring system by [PERSON] et al. and [PERSON] et al. [27; 28] in order to determine the amount of remaining debris in canal root systems (Figure 2). Out of 168 teeth that were irrigated with the aid of XPF (84 teeth) and PUI (84 teeth), 52.3% and 51.1% received a score of 2 (44/84 and 43/84), and 23.8% and 10.7% received a score of 3 (20/84 and 9/84), respectively. Empty grooves (score 0) were found in 12 teeth (14.2%) and in 15 teeth (17.8%), while in 8 teeth (9.5%) and 17 teeth (20.2%), respectively, calcium hydroxide was present in less than half of the grooves (score 1). Most of the teeth (39 out of 54) that were treated with CNI presented grooves still completely filled with calcium hydroxide (Score 3), and no teeth had empty grooves (Score 0) [12; 22; 24]. According to [PERSON] et al. [24], [PERSON] et al. [12], and [PERSON] et al. [22], XPF and PUI may ensure better results than CNI, although there are no significant differences among them. [PERSON] et al. [4; 25] claimed in their articles that no significant differences were found between PUI and laser-activated irrigation (LAI), and that these procedures eliminated root canal debris better than XPF, CanalBrush (CB), Vibringe, and CNI. Moreover, [PERSON] et al. demonstrated that the XPF system showed similar results to those of CNI. One of the included articles [29] used a five-score scale to evaluate the remaining root filling material, highlighting that XPF and EndoActivator (EA) methods were more efficient than CNI, and that there were no significant differences between XPF and EA. In conclusion, almost all of the studies stated that none of the tested procedures were able to completely remove all root canal debris from all three root parts.  
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