Introduction: This study evaluated the propagation of dentinal microcracks and the Root Canal volume increase after being prepared with two endodontic instruments: ProTaper Next (PTN) and WaveOne Gold (WOG) by micro-computed tomography analysis. Methods and Materials: We selected 48 maxillary molars randomly distributed in two groups: PTN and WOG. The samples were scanned before and after instrumentation, and then the image analysis was performed to detect the propagation of pre-existing dentinal micro-cracks and calculate the pre-and post-instrumentation volume. The statistical analysis was performed using Student’ s t-test, Fisher's exact test, and ANCOVA (P<0. 05). Results: Dentinal microcracks were observed in 95. 8% of the samples, both PTN and WOG instruments propagated microcracks after instrumentation, but there was no significant difference between the instruments (P=0. 538). In relation to the Root Canal volume there was no statistic difference between PTN and WOG systems for the mesiobuccal (P=0. 426) and distobuccal Root Canals (P=0. 523). Conclusion: We can conclude that both ProTaper Next and WOG systems propagate dentinal microcracks after Root Canal Preparation in this in vitro study, without statistical significance. The Root Canal volume prepared also showed no statistically significant difference between the two groups. This in vitro study requires further studies for more concrete conclusions.

Objective: This study investigated the effect of glide path Preparation and different instruments in creating dentinal cracks during Root Canal instrumentation. Methods: Eighty maxillary molars were divided into four groups (n=20). The mesiobuccal Root Canals were prepared using two rotary systems (Group 1: Hyflex EDM and Group 2: ProTaper Gold) and two reciprocating systems (Group 3: WaveOne Gold and Group 4: Reciproc Blue R25). In each group, ten specimens were prepared using the designated glide path files. Methylene blue dye was injected into the Root Canals to highlight dentinal cracks. The samples were then sectioned and examined under a microscope to count the number of dentinal cracks at the apical, middle, and coronal thirds. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests (P<0.05). Results: When glide path files were not used, the number of cracks was comparable across the groups in coronal, middle and apical sections (P>0.05). Among the samples prepared with glide path files, those instrumented with WaveOne Gold showed a significantly higher number of dentinal cracks in the coronal section compared to ProTaper Gold (P<0.05), and in the middle section compared to both HyFlex EDM and ProTaper Gold (P<0.05). In the apical section, no significant difference in the number of cracks was observed among the groups (P=0.627). Conclusions: Glide path Preparation with rotary systems (ProTaper Gold and HyFlex EDM) resulted in fewer dentinal cracks in the mesiobuccal Root Canals of maxillary molars compared to a reciprocating system (WaveOne Gold).

Introduction: Root fracture is not an instant phenomenon but a result of gradual development of tiny craze lines in tooth structure. Recent studies have shown that Canal instrumentation has the potential to cause dentinal cracks. The purpose of this study was to evaluate and compare the formation of dentinal cracks caused by ProTaper rotary system to hand instrumentation.Materials and Methods: This in vitro study was carried out using 57 mandible incisor teeth. The teeth were decoronated. The Roots were then examined to exclude cracked samples. A standard model for PDL simulation was used. The teeth were randomly divided into two experimental and one control group (n=19). The teeth in the experimental groups were prepared using hand or ProTaper Universal rotary instrumentation. The teeth in the control group were left unprepared. The teeth were then sectioned horizontally 3 and 6 mm from the apex, and the number of various dentinal defects was recorded using a dental operating microscope. The differences between groups were analyzed with Fisher’s exact test.Results: The hand group demonstrated significantly more defects than the control group (P=0.001). However, there was no significant difference between the rotary compared to the control and hand groups (P>0.05). There was no significant difference between groups with regards to fracture (P>0.05). Other defects including internal, external and surface cracks were more frequent in the hand than in the control or rotary groups (P=0.02), but the difference was not significant between the rotary and control groups (P>0.05).Conclusion: Canal Preparation, whether hand or rotary, produces structural defects in dentin. The ProTaper rotary system when used according to the manufacturer’s instructions, tends to produce fewer cracks and can be considered a safe Preparation technique.

Background: This study aimed to investigate the extent of apical transportation following instrumentation with EdgeEvolve rotary instruments applying single‑, length and crown‑, down techniques. Materials and Methods: In this experimental in‑, vitro study, 60 mandibular molars with mesiobuccal curvatures of 20°, –, 40°,were selected, and digital radiographic images were taken. Teeth were randomly assigned into two groups of single‑, length and crown‑, down Preparation techniques. In both mentioned groups, EdgeEvolve rotary system was used. After Preparation, the same as the previous ones, digital radiographic images were taken from the Canals. The data were analyzed using Student’, s t‑, test and ShapiroWilk normality test (P = 0. 05). Results: The mean standard deviation (SD) for apical transportation in the single‑, length and the crown‑, down group was 4. 42 (2. 9) and 7. 48 (3. 9) degrees, respectively (P < 0. 05). The mean SD of the Preparation time in the single‑, length and crown‑, down group was 135. 07 (30. 8) and 109. 07 (20. 8), respectively (P < 0. 05). The apical transportation and the time of Preparation between the two groups were significant. Conclusion: Using EdgeEvolve rotary instruments Canal Preparation with both single‑, length and crown‑, down techniques led to some degrees of apical transportation.