This study aimed to evaluate and compare the dynamic cyclic fatigue, torsional and bending resistance of two novel RACE EVO (FKG Dentaire SA, La Chaux de Fonds, Switzerland) and R-Motion (FKG) nickel–titanium instruments with traditional RaCe (FKG) instruments. RACE EVO, R-Motion and RaCe instruments with a size of 25 and taper of 0.06 were used. A dynamic cyclic fatigue test was used to assess the time to fracture. The fractured surfaces were further analyzed using scanning electron microscopy at ×350 and ×3000 magnifications. A torsional resistance test was performed to measure the maximum torsional strength and angle of rotation. Phase transformations with temperature were evaluated using differential scanning calorimetry. The results were statistically analyzed with a Kruskal–Wallis test at a 5% significance level. R-Motion had the highest time to fracture and the lowest torsional and bending resistance, whereas RaCe had the lowest time to fracture and the highest torsional and bending resistance (p < 0.05). In relation to the angle of rotation, RACE EVO instruments had the highest deformation capacity followed by R-Motion and RaCe instruments (p < 0.05). The greater cyclic fatigue resistance and lower torsional and bending resistance results indicate that the novel R-Motion and RACE EVO instruments are less rigid and more flexible than RaCe instruments.

Objectives: This study aims to evaluate the effectiveness of current conventional and advanced irrigation techniques after minimally invasive instrumentation in necrotic oval root canals by histological analysis. Methods: Seventy extracted necrotic lower premolars with single oval canals classified utilizing bidirectional radiographs (mesiodistal diameter 2.5 times larger than buccolingual) were prepared up to 20.04 v. The samples were assigned to five experimental groups (n = 14) using the complementary irrigation technique: needle (control), passive ultrasonic, and shockwave-enhanced emission photo-acoustic streaming activation using Er:YAG laser (SWEEPS), Er,Cr:YSGG laser (Waterlase iPlus), and multisonic ultracleaning technology (GentleWave). After irrigation protocols, the roots were demineralized and the apical 5 mm was multi-sliced and processed for histologic examination. The residual necrotic tissue and debris percentage was calculated via image analysis software. One-way ANOVA and Tukey’s test were used to verify the variables influencing debridement (p < 0.05). Results: The mean value of the GentleWave group was the record low at 1.54 ± 1.46, and the utmost was needle irrigation with 15.64 ± 7.23. The main effect of techniques on the debridement was statistically significant (p < 0.001). The course of debridement effectiveness, according to the levels of significance between the groups, was as follows: Multisonic ultracleaning > Er:YAG > Er,Cr:YSGG > Passive ultrasonic irrigation > Needle irrigation (p <0.05). Conclusions: In necrotic oval-shaped canals after minimally invasive instrumentation, multisonic ultracleaning with updated software was considerably more effective in removing remnants in the apical level. Er:YAG and Er,Cr:YSGG lasers were highly promising, with results close to multisonic ultracleaning. It should be considered that needle irrigation and passive ultrasonic activation may not be able to provide competent debridement in treating such types of root canals.

Objectives: The aim of this study is to compare the effects of intracanal treatments with calcium hydroxide (CH) or triple antibiotic paste (TAP) on bond strength of a calcium silicate-based sealer (MTA Fillapex) and an epoxy resin- based sealer (MM Seal). Materials and Methods: Sixty extracted maxillary central incisors were prepared with a rotary system to size 40. The specimens were randomly divided into two groups, which received either intracanal CH or TAP. After rinsing, the teeth in each group were further divided into two additional groups, which were obturated with gutta percha and either the MTA Fillapex or MM Seal root canal sealer. Then, slices were obtained from three sections of the canal (coronal, middle, and apical). A push-out test was performed to measure the bond strength between the root canal dentin and the sealer. Results: The push-out bond strengths of the root canal sealers were significantly affected by the type of intracanal medicament. Both the sealers showed bond strengths that were nearly two-fold higher after TAP application than after CH application, and these results were independent of the position along the canal. Conclusions: The use of TAP rather than CH improves the bond strength of calcium silicate- and epoxy resin-based sealers throughout the root canal.

This study aimed to evaluate the effectiveness of energy-intensive irrigation activation systems for removing residual pulp tissue in completely uninstrumented oval root canals with different access cavity designs, using histological analysis. Seventy extracted human mandibular premolars with oval root canal morphology and organic tissue remnants were randomly assigned to five irrigation protocols: syringe-needle irrigation (control), Er: YAG laser (SWEEPS, Fotona), Er, Cr: YSGG laser (Waterlase iPlus, Biolase), multisonic high-speed irrigation (GentleWave G4 with ProControl, SonEndo, 5-min protocol), and an extended multisonic protocol (9-min). Each group was further divided according to access cavity design into ultra-conservative and traditional cavities (n = 7). Following irrigation with sodium hypochlorite and EDTA, serial histological sections from the apical third were prepared, and the percentage of residual pulp tissue was quantified using ImageJ software. Data were analyzed using two-way ANOVA with Bonferroni multiple comparisons (p < 0.05). The irrigation activation system significantly affected residual tissue percentages (p < 0.001; η²=0.736), whereas access cavity design showed no significant effect (p = 0.965). Syringe-needle irrigation demonstrated the highest residual tissue values (≈ 20%). Both laser activation systems significantly reduced residual tissue compared with needle irrigation but showed comparable performance (≈ 4–6%). Multisonic high-speed irrigation further improved canal cleanliness, with the 5-min protocol showing lower residual tissue values (≈ 2%), and the extended 9-min protocol achieving the lowest percentages (< 1%), approaching near-complete debridement. Within the limitations of this in vitro histological study, energy-intensive irrigation systems significantly improved the removal of residual pulp tissue in uninstrumented oval root canals. The extended multisonic irrigation protocol demonstrated the highest debridement efficiency under the tested conditions. These findings may inform future minimally invasive endodontic strategies; however, they should not be interpreted as supporting the clinical replacement of mechanical instrumentation.