Efeito da instrumentação endodôntica, do tipo de retentor intrarradicular e da ciclagem mecânica na resistência à fratura de raízes

Abstract

The aim of this study was to evaluate the effect of root preparation strategy, the type of post and mechanical cycling on root fracture resistance. Eighty single-rooted human teeth were divided into 8 groups (n=10): G1 and G2 - hand file, glass fiber post, without and with mechanical cycling (MC) respectively; G3 and G4 - hand file, cast post and core, without and with MC respectively; G5 and G6 rotary file, glass fiber post, without and with MC respectively; G7 and G8 rotary file, cast post and core, without and with MC respectively. Obturation was performed by the lateral condensation technique. Root canals were prepared to a length of 10mm, using a #2 preparation bur of a tapered fiber glass post system. The following protocol was used for the cycling: 45o angle, 37°C, 88N, 4Hz, 2 million cycles. All groups were submitted to fracture resistance test in a device in 45°, at 0.05cm/min. The 3-way ANOVA showed the instrumentation strategy (p<0.03) and the post type (p<0.0001) had significant effects, however, mechanical cycling had not (p<0.29). The type of instrumentation caused effect on the fracture strength, only when the roots were restored with fiber glass post and cycled, with disadvantage for hand instrumentation. The cast post and core promoted higher fracture resistance, although showed more irreparable failures than roots restored with glass fiber post.