The adhesion between fiber posts and root canal walls: comparison between microtensile and push‐out bond strength measurements

TLDR

The study aimed to compare trimming and non‑trimming microtensile techniques with a micro push‑out test for accurately measuring fiber‑post bond strength in root canals. Fifteen endodontically treated teeth were cemented with Excite DSC/Variolink II (Group A) and fifteen roots with RelyX Unicem (Group B), and bond strength was evaluated in each group by trimming and non‑trimming microtensile tests and a push‑out test. Premature failures were frequent in the trimming microtensile test, non‑trimming yielded few usable sticks, whereas the push‑out test produced no premature failures, acceptable variability, and detectable regional differences, indicating it is the more reliable method for assessing fiber‑post bond strength.

Abstract

Aim of the study was to compare the trimming and non‐trimming variants of the microtensile technique with the ‘micro’ push‐out test in the ability to measure accurately the bond strength of fiber posts luted inside root canals. In 15 endodontically treated teeth (Group A), fiber posts were cemented with Excite DSC in combination with Variolink II (Ivoclar‐Vivadent). In 15 roots RelyX Unicem (3M‐ESPE) was used for fiber post luting (Group B). Within each group, the bond strength of cemented fiber posts was assessed with the trimming and non‐trimming microtensile technique, as well as with the push‐out test. The great number of premature failures (16.9% in Group A, 27.5% in Group B) and the finding of high standard deviation values make questionable the reliability of the trimming microtensile technique. With the non‐trimming microtensile technique, only five sticks were obtained from a total of six roots. The remaining specimens failed prematurely during the cutting phase. With the push‐out test no premature failure occurred, the variability of the data distribution was acceptable, and regional differences in bond strength among root levels could be assessed. Relatively low values of bond strength were, in general, recorded for luted fiber posts. In conclusion, when measuring the bond strength of luted fiber posts, the push‐out test appears to be more dependable than the microtensile technique.