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.

Cyclic fatigue using severely curved canals and torsional resistance of thermally treated reciprocating instruments.

OBJECTIVES: To evaluate the cyclic fatigue using severely curved canals and torsional resistance of ProDesign R (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil), Reciproc Blue (VDW, Munich, Germany), and WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland) reciprocating instruments MATERIALS AND METHODS: Twenty instruments of the ProDesign R (25/0.06) system, 20 instruments of the Reciproc Blue (25/0.08v) system, and 20 instrument of the WaveOne Gold (25/0.07v) system were used. Cyclic fatigue resistance was tested measuring the time to fracture and the number of cycles to fracture in an artificial stainless steel severely curved canal with 80° angle and a 3-mm radius of curvature (n = 10). Torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. The fracture surfaces of all fragments were examined with a scanning electron microscope. Results were statistically analyzed using one-way ANOVA and Tukey's test at a significance level of p < 0.05. RESULTS: ProDesign R instruments showed a significantly longer cyclic fatigue life than the other tested instruments (p < 0.05). Reciproc Blue showed longer cyclic life than WaveOne Gold (p < 0.05). Reciproc Blue showed the higher torsional strength, followed by WaveOne Gold and ProDesign R instruments (p < 0.05). Moreover, Reciproc Blue showed significantly higher angular rotation to fracture than ProDesign R (p < 0.05). WaveOne Gold showed intermediary results regarding angular rotation to fracture with no differences when compared to Reciproc Blue or ProDesign R instruments (p < 0.05). CONCLUSIONS: ProDesign R presented the highest cyclic fatigue resistance in severely curved canals when compared with Reciproc Blue and WaveOne Gold. However, Reciproc Blue showed the higher torsional strength overall and higher angular rotation to fracture when compared to ProDesign R. CLINICAL RELEVANCE: Despite the numerous advantages of reciprocating instruments, these instruments still have some risk of fracture during its use, especially in severely curved canals. The present study evaluated the cyclic fatigue and torsional resistance of thermally treated reciprocating instruments.

Marginal gaps and voids of three root-end filling materials: A microcomputed tomographic study.

A root-end filling material is required to fill the root-end cavity without gaps or voids, to prevent root canal reinfection and to provide periapical healing. Thus, this study evaluated the volume of marginal gaps and voids of three root-end filling materials using microcomputed tomography (micro-CT). Thirty maxillary incisors were prepared and filled with gutta-percha and endodontic sealer. The specimens were scanned using micro-CT and distributed into three groups (n = 10): White MTA, MTA Repair HP, and Bio-C Repair. The root tips were resected at 90° to the longitudinal axis and the cavity (3 mm depth) was prepared with an ultrasonic tip. The materials were handled, and the cavities were filled. The specimens were rescanned and the percentual volume of gaps and voids were analyzed. The data were analyzed using Kruskal-Wallis and Dunn tests (p < .05). No statistical difference was found in the percentage of gaps among the tested materials (p > .05). White MTA presented less voids than Bio-C and MTA Repair HP (p < .05). The materials presented a similar percentual volume of gaps and White MTA presented less voids than other tested materials.

Influence of surgical decompression on the expression of inflammatory and tissue repair biomarkers in periapical cysts.

OBJECTIVE: The biologic effects of surgical decompression on the epithelium and connective tissues of periapical cysts are not fully understood. The aim of this study was to evaluate the expression of tissue repair and inflammatory biomarkers in periapical cysts before and after surgical decompression. STUDY DESIGN: Nine specimens of periapical cysts treated with decompression before undergoing complete enucleation were immunohistochemically analyzed to investigate the expression of interleukin-1ß, tumor necrosis factor-α, transforming growth factor-ß1, matrix metalloproteinase-9, Ki-67, and epidermal growth factor receptor. Expression of the biomarkers was classified as positive, focal, or negative. Ki-67 immunoexpression was calculated as a cell proliferation index. The expression of the biomarkers was compared in the specimens from decompression and from the final surgical procedure. RESULTS: Computed tomography demonstrated that volume was reduced in all cysts after decompression. There were no differences in the immunoexpression of the proinflammatory and tissue repair biomarkers when comparing the specimens obtained before and after the decompression. CONCLUSIONS: Surgical decompression was efficient in reducing the volume of periapical cysts before complete enucleation. When comparing the specimens obtained from surgical decompression and from complete surgical removal, the immunohistochemical analysis did not show a decrease in proinflammatory biomarkers; neither did it show an increase in tissue repair biomarkers.