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Objetivo: Testar a hipótese nula de que a orientação das ranhuras superficiais não influencia na vida em fadiga de fios de níquel-titânio (NiTi). Material e Métodos: Segmentos de fio de NiTi (Moreli, Sorocaba/SP, Brasil) medindo 30mm e com diâmetro de 0,40mm fo- ram utilizados. As ranhuras foram criadas em relação à direção longitudinal, em 45 e 90 graus. O fio foi analisado sob microscopia eletrônica de varredura e a rugosidade, quantificada por interferometria. O número de ciclos para a fratura (NCF) foi determinado pelo teste de flexão rotativa. Resultados: A rugosidade entre os grupos de 45 e 90 graus apresentou diferenças estatisticamente significativas (p more...

The objective was to analyze the influence of dentary and orthopedic forces under static and dynamic loads in temporary screw stability. Self-drilling titanium (Ti6Al4V) screws (6 × 1.5 mm) were inserted and removed from pig ribs. Screws were loaded by static loads of 2 N and 5 N for 5 weeks. Dynamic force was applied during 56,000 cycles for simulations of a patient’s opening–closing mouth movements. Dynamic applied loads ranged from 2 to 5 N and from 5 to 7 N under a frequency of 1 Hz. Torque peak values at placement and removal were measured before and after static and dynamic cycles. Similarities in torque peaks (p = 0.3139) were identified at placement (12.54 Ncm) and removal (11.2 Ncm) of screws after a static load of 2 N. Statistical comparisons showed significant stability loss after dynamic cycles under loads of 2 N (64.82% at p = 0.0005) and 5 N (64.63% at p = 0.0026). Limited stability loss occurred in temporary screws submitted to 2 N static forces (p = 0.3139). The detrimental effects of dynamic cycles in temporary screws stability was attested after the simulation of dentary and skeletal forces, being intermittent forces more relevant in the loss of mechanical stability. Refereed/Peer-reviewed more...