ABSTRACT
INTRODUCTION: Determination of the glide path is recommended before using rotary instruments. This study aimed to evaluate the dynamic cyclic fatigue resistance of new and used glider rotary instruments in up to 6 root canals. METHODS: Seventy-two TruNatomy Glider files were used for the preparation of root canals of extracted lower molars, which were then submitted to the dynamic cyclic fatigue test carried out in a curved metallic artificial canal. The instruments were divided into 4 groups (n = 18): Control group, new instruments without any use in the root canal; Group 2U, instruments used in 2 mesial canals; Group 4U, instruments used in 4 mesial canals; Group 6U, instruments used in 6 mesial canals. The time to failure (TF) of the instrument was recorded, and the number of cycles to failure (NCF) was calculated. The data were submitted to 1-way analysis of variance and to the Games-Howell test for multiple comparisons, adopting a significance level of 5%. RESULTS: TF and NCF were significantly affected by the number of file uses. The Games-Howell test revealed that TF and NCF were significantly greater in the control group than in Group 4U. In Group 2U, TF and NCF were intermediate and not significantly different from the control group. Group 6U had significantly lower TF and NCF than all other groups. CONCLUSION: The TruNatomy Glider can be used as a glide path for up to 2 mesial canals of mandibular molars, whereas its use on 4 or 6 root canals is not suggested.
Subject(s)
Equipment Failure , Root Canal Preparation , Root Canal Preparation/instrumentation , Root Canal Preparation/methods , Humans , Dental Instruments , Equipment Design , In Vitro Techniques , Molar , Dental Stress Analysis , Dental Pulp Cavity , Materials TestingABSTRACT
Objetivo: avaliar a influência de diferentes modos de polimerização sobre a resistência à flexão de três pontos de duas resinas compostas. Métodos: foram confeccionadas 88 amostras, sendo divididas em dois grupos, conforme a resina composta utilizada: Filtek Z350 XT e Forma. Os grupos foram subdivididos, de acordo com diferentes modos de polimerização, em: G1- Z350 por 20s a 1.000 mw/cm²; G2- Forma por 20s a 1.000 mw/cm²; G3- Z350 por 20s a 1.000 mw/cm² e micro-ondas por 3 minutos em 450w; G4- Forma por 20s a 1.000 mw/cm² e micro-ondas por 3 minutos em 450w; G5- Z350 por 2 vezes de 3s a 3.200 mw/cm²; G6- Forma por 2 vezes de 3s a 3.200 mw/cm²; G7- Z350 por 2 vezes de 3s a 3.200 mw/cm² e micro-ondas por 3 minutos em 450w; G8- Forma por 2 vezes de 3s a 3.200 mw/cm² e micro-ondas por 3 minutos em 450w. As amostras foram submetidas ao teste de resistência à flexão de 3 pontos, sob taxa de carregamento de 50 N/min, até a falha completa. Os dados foram analisados estatisticamente por análise de variância com dois fatores (two-way ANOVA) e teste de Tukey. Resultados: não houve diferenças estatísticas entre as resinas compostas e os modos de polimerização utilizados. Conclusão: de acordo com os resultados do estudo, e dentre suas limitações, os modos de polimerização não influenciaram a resistência à flexão, independentemente da resina composta testada. (AU)
Objective: to evaluate the influence of different polymerization modes on the three-point flexural strength of two composite resins. Methods: 88 samples were produced and divided into two groups according to the composite resin used: Filtek Z350 XT and Forma. The groups were subdivided according to different polymerization modes into: G1- Z350 for 20 s at 1000 mw/cm²; G2- Forma for 20 s at 1000 mw/cm²; G3- Z350 for 20 s at 1000 mw/cm² and microwave for 3 min at 450w; G4- Forma for 20 s at 1000 mw/cm² and microwave for 3 min at 450w; G5- Z350 2x for 3 s at 3200 mw/cm²; G6- Forma 2x for 3 s at 3200 mw/cm²; G7- Z350 2x for 3 s at 3200 mw/cm² and microwave for 3 min at 450w; and G8- Forma 2x for 3 s at 3200 mw/cm² and microwave for 3 min at 450w. The samples were subjected to the three-point flexural strength test under a 50 N/min loading rate until complete failure. The data were statistically analyzed using two-way analysis of variance (two-way ANOVA) and Tukey's test. Results: there were no statistical differences between the composite resins and the polymerization modes used. Conclusion: according to the study results and within its limitations, the polymerization modes did not affect flexural strength, regardless of the composite resin tested. (AU)
