Multimethod analysis of large- and low-tapered single file reciprocating instruments: Design, metallurgy, mechanical performance, and irrigation flow.

AIM: To compare eight large- and low-tapered heat-treated reciprocating instruments regarding their design, metallurgy, mechanical properties, and irrigation flow through an in silico model. METHODOLOGY: A total of 472 new 25-mm E-Flex Rex (25/.04 and 25/.06), Excalibur (25/.05), Procodile (25/.06), Reciproc Blue R25 (25/.08v), WaveOne Gold Primary (25/.07v), and Univy Sense (25/.04 and 25/.06) instruments were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy (energy-dispersive X-ray spectroscopy and differential scanning calorimetry), and mechanical performance (cyclic fatigue, torsional resistance, cutting ability, bending and buckling resistance). Computational fluid dynamics assessment was also conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparations. Kruskal-Wallis and one-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Instruments presented variations in blade numbers, helical angles, and tip designs, with all featuring non-active tips, symmetrical blades, and equiatomic nickel-titanium ratios. Cross-sectional designs exhibited an S-shaped geometry, except for WaveOne Gold. Univy 25/.04 and Reciproc Blue displayed the smallest and largest core diameters at D3. Univy 25/.04 and E-Flex Rec 25/.04 demonstrated the longest time to fracture (p < .05). Reciproc Blue and Univy 25/.04 exhibited the highest and lowest torque to fracture, respectively (p < .05). Univy 25/.04 and Reciproc Blue had the highest rotation angles, whilst E-Flex Rec 25/.06 showed the lowest angle (p < .05). The better cutting ability was observed with E-Flex Rec 25/.06, Procodile, Excalibur, and Reciproc Blue (p > .05). Reciproc R25 and E-Flex Rec showed the highest buckling resistance values (p < .05), with WaveOne Gold being the least flexible instrument. The impact of instruments' size and taper on wall shear stress and apical pressure did not follow a distinct pattern, although Univy 25/.04 and E-Flex Rec 25/.06 yielded the highest and lowest values for both parameters, respectively. CONCLUSIONS: Low-tapered reciprocating instruments exhibit increased flexibility, higher time to fracture, and greater angles of rotation, coupled with reduced maximum bending loads and buckling strength compared to large-tapered instruments. Nevertheless, low-tapered systems also exhibit lower maximum torque to fracture and inferior cutting ability, contributing to a narrower apical canal enlargement that may compromise the penetration of irrigants in that region.

Multimethod analysis of three rotary instruments produced by electric discharge machining technology.

AIM: This study aimed to compare three rotary instruments produced by the EDM process with the heat-treated ProTaper Gold system regarding design, metallurgy, mechanical properties and shaping ability. METHODOLOGY: HyFlex EDM (25/~), Neoniti (25/.06), EDMax (25/.06) and ProTaper Gold (25/.08v) instruments (n = 58 per group) were compared regarding design, metallurgy and mechanical performance. Unprepared canal areas were calculated for each system after preparation of mesiobuccal, mesiolingual and distal canals of mandibular molars (15 canals per group) using micro-CT technology. Statistical analyses were performed using One-way anova post-hoc Tukey and Kruskal-Wallis post-hoc Dunn's tests (α = 5%). RESULTS: All instruments had asymmetrical blades, no radial lands, no major defects and almost equiatomic nickel/titanium ratios, but different cross-section designs, tip geometries and surface appearances. Although instruments had distinct transformation temperature curves, they showed crystallographic martensitic arrangement at 21°C and mixed austenite plus R-phase at body temperature. Neoniti and HyFlex EDM showed similar results in all mechanical tests (p > .05), while EDMax and ProTaper Gold had similar time to fracture (p = .841), maximum bending load (p = .729), and cutting ability (p = .985). ProTaper Gold showed the highest torque to failure (p < .001) and HyFlex EDM had the lowest buckling resistance (p < .001). Mean percentages of unprepared canal areas ranged from 20.4% to 25.7% in the mesial canals, and from 20.8% to 26.2% in the distal canal, with no statistical differences among systems (p > .05). CONCLUSIONS: Instruments' geometry and phase transformation temperatures influenced the results of the mechanical tests, but not their shaping ability.

Design, metallurgy, mechanical properties, and shaping ability of 3 heat-treated reciprocating systems: a multimethod investigation.

OBJECTIVE: This study aimed to compare 3 reciprocating systems regarding design, metallurgy, mechanical properties, and shaping ability. MATERIALS AND METHODS: New Reciproc Blue R25, WaveOne Gold Primary, and REX 25 instruments (n=41 per group) were analyzed regarding design, metallurgy, and mechanical performance, while shaping ability (untouched canal walls, volume of removed dentin, and hard tissue debris) was tested in 36 anatomically matched root canals of mandibular molars. Results were compared using one-way ANOVA post hoc Tukey and Kruskal-Wallis tests with a significant level set at 5%. RESULTS: All instruments showed symmetrical cross sections with asymmetrical blades, no radial lands, no major defects, and an almost equiatomic nickel and titanium ratio. The highest R-phase start temperatures were observed with WaveOne Gold (46.1°C) and REX (44.8°C), while Reciproc Blue had the lowest R-phase start (34.5°C) and finish (20°C) temperatures. WaveOne Gold had the lowest time to fracture (169 s) and the highest maximum load (301.6 gf) (P <0.05). The maximum torque of Reciproc Blue (2.2 N.cm) and WaveOne Gold (2.1 N.cm) were similar (P >0.05), but lower than REX (2.6 N.cm) (P <0.05). No statistical differences were observed among instruments in the angle of rotation (P >0.05) and in the shaping ability in both mesial and distal canals (P >0.05). CONCLUSION: Although the overall design, temperature transition phases and mechanical behavior parameters were different among tested instruments, they were similar in terms of shaping ability. CLINICAL RELEVANCE: All tested heat-treated NiTi reciprocating systems showed similar shaping ability, without clinically significant errors.

A Multimethod Assessment of a New Customized Heat-Treated Nickel-Titanium Rotary File System.

This study aimed to compare three endodontic rotary systems. The new Genius Proflex (25/0.04), Vortex Blue (25/0.04), and TruNatomy (26/0.04v) instruments (n = 41 per group) were analyzed regarding design, metallurgy, and mechanical performance, while shaping ability (untouched canal walls, volume of removed dentin and hard tissue debris) was tested in 36 anatomically matched root canals of mandibular molars. The results were compared using one-way ANOVA, post hoc Tukey, and Kruskal−Wallis tests, with a significance level set at 5%. All instruments showed symmetrical cross-sections, with asymmetrical blades, no radial lands, no major defects, and almost equiatomic nickel−titanium ratios. Differences were noted in the number of blades, helical angles, cross-sectional design, and tip geometry. The Genius Proflex and the TruNatomy instruments had the highest and lowest R-phase start and finish temperatures, as well as the highest and lowest time and cycles to fracture (p < 0.05), respectively. The TruNatomy had the highest flexibility (p < 0.05), while no differences were observed between the Genius Proflex and the Vortex Blue (p > 0.05). No differences among tested systems were observed regarding the maximum torque, angle of rotation prior to fracture, and shaping ability (p > 0.05). The instruments showed similarities and differences in their design, metallurgy, and mechanical properties. However, their shaping ability was similar, without any clinically significant errors. Understanding these characteristics may help clinicians to make decisions regarding which instrument to choose for a particular clinical situation.

Ten years of minimally invasive access cavities in Endodontics: a bibliometric analysis of the 25 most-cited studies.

OBJECTIVES: This study aimed to analyze the main features of the 25 most-cited articles in minimally invasive access cavities. MATERIALS AND METHODS: An electronic search was conducted on the Clarivate Analytics' Web of Science 'All Databases' to identify the most-cited articles related to this topic. Citation counts were cross-matched with data from Elsevier's Scopus and Google Scholar. Information about authors, contributing institutions and countries, year and journal of publication, study design and topic, access cavity, and keywords were analyzed. RESULTS: The top 25 most-cited articles received a total of 572 (Web of Science), 1,160 (Google Scholar) and 631 (Scopus) citations. It was observed a positive significant association between the number of citations and age of publication (r = 0.6907, p < 0.0001); however, there was no significant association regarding citation density and age of publication (r = -0.2631, p = 0.2038). The Journal of Endodontics made the highest contribution (n = 15, 60%). The United States had the largest number of publications (n = 7) followed by Brazil (n = 4), with the most contributions from the University of Tennessee and Grande Rio University (n = 3), respectively. The highest number of most-cited articles were ex vivo studies (n = 16), and 'fracture resistance' was the major topic studied (n = 10). CONCLUSIONS: This study revealed a growing interest for researchers in the field of minimally invasive access cavities. Future trends are focused on the expansion of collaborative networks and the conduction of laboratory studies on under-investigated parameters.

Immunoexpression of interleukin 17 in apical periodontitis lesions.

INTRODUCTION: Interleukin (IL)-17 expression has been detected in apical periodontitis lesions, but its role in the disease process remains unclear. The present study compared the expression of IL-17 in periradicular cysts and granulomas and evaluated the association of this cytokine with clinical and radiographic findings. METHODS: Apical periodontitis lesions (18 cysts and 20 granulomas) were obtained from 38 patients subjected to periradicular surgery. Some clinical, radiographic, and cone-beam computed tomographic features were recorded. Silanized slides containing paraffin sections were used for the immunohistochemical reactions using anti-IL-17 antibody. Image analysis was performed using an optical microscope, and each sample was divided into 5 high-power fields, which were evaluated for the expression of IL-17 in the epithelium and connective tissues. Results were evaluated for correlations with the lesion size and the occurrence of symptoms and sinus tract. RESULTS: Expression of IL-17 was significantly higher in cysts than in granulomas (P = .02). Among the periradicular cysts, a thin epithelium showed significantly increased labeling for IL-17 when compared with a hyperplastic epithelium (P = .003). IL-17 expression was usually associated with focal accumulations of polymorphonuclear leukocytes. No association of IL-17 expression with symptoms, sinus tract, or lesion size was observed (P > .05). CONCLUSIONS: The present study reinforces the notion that IL-17 may take part in the pathogenesis of apical periodontitis lesions. A role in the exacerbation of chronic inflammation and cyst formation is suspected. Further studies are required to shed light on the specific functions of IL-17 in periradicular inflammatory processes.

Glide path preparation in S-shaped canals with rotary pathfinding nickel-titanium instruments.

INTRODUCTION: This study compared the incidence of deviation along S-shaped (double-curved) canals after glide path preparation with 2 nickel-titanium (NiTi) rotary pathfinding instruments and hand K-files. METHODS: S-shaped canals from 60 training blocks were filled with ink, and preinstrumentation images were obtained by using a stereomicroscope. Glide path preparation was performed by an endodontist who used hand stainless steel K-files (up to size 20), rotary NiTi PathFile instruments (up to size 19), or rotary NiTi Scout RaCe instruments (up to size 20). Postinstrumentation images were taken by using exactly the same conditions as for the preinstrumentation images, and both pictures were superimposed. Differences along the S-shaped canal for the mesial and distal aspects were measured to evaluate the occurrence of deviation. RESULTS: Intragroup analysis showed that all instruments promoted some deviation in virtually all levels. Overall, regardless of the group, deviations were observed in the mesial wall at the canal terminus and at levels 4, 5, 6 and 7 mm and in the distal wall at levels 1, 2, and 3 mm. These levels corresponded to the inner walls of each curvature. Both rotary NiTi instruments performed significantly better than hand K-files at all levels (P < .05), except for PathFiles at the 0-mm level. ScoutRaCe instruments showed significantly better results than PathFiles at levels 0, 2, 3, 5, and 6 mm (P < .05). CONCLUSIONS: Findings suggest that rotary NiTi instruments are suitable for adequate glide path preparation because they promoted less deviation from the original canal anatomy when compared with hand-operated instruments. Of the 2 rotary pathfinding instruments, Scout RaCe showed an overall significantly better performance.

Avaliação antimicrobiana dos vapores de para monoclorofenol e tricresol formalina utilizando uma nova metodologia / Antimicrobial evaluation of vapors of paramonochlorophenol and tricresol formalin using a new methodology

O objetivo do presente estudo foi avaliar o efeito antimicrobiano do Paramonoclorofenol Canforado (PMCFC) e do Tricresol Formalina (TF) frente ao Enterococcus faecalis utilizando uma nova metodologia para simular a volatilização dos compostos. Enterococcus faecalis foram inoculados em placas de Petri com BHI, na qual foram fincados escalpes contendo algodão embebido em PMCFC e TF. Bolinhas de algodão sem medicação foram utilizadas como controle negativo. Após 48 horas de cultivo, foi avaliada a formação de halos de inibição de crescimento bacteriano. Pode-se constatar que o grupo com TF produziu halos de inibição em 100% dos escalpes, enquanto o PMCFC e o controle negativo não produziram halo de inibição. Conclui-se que somente o TF apresentou atividade antimicrobiana por volatilização.

The aim of the present study was to evaluate the antimicrobial effects of paramonochlorophenol and tricresol formalin using a new methodology to simulate the volatilization of these substances. Enterococcus faecalis were inoculated em petri dishes with BHI and mm scalps containing cotton balls soaked with the tested substances were stucked in the petri dishes. Cotton balls without medication were used as negative control. After 48 hours the inhibition halo formation was evaluated. The results showed that tricresol formalin group presented inhinition zones in 100% of scalps, while paramochlorophenol and control group produced no inhibition zone. The results suggested that the vapor of formalin tricresol has antibacterial activity; however paramonochlorophenol was unable to exert antibacterial activity from the volatilization of its gases.