Issue 28

A. Brotzu et alii, Frattura ed Integrità Strutturale, 28 (2014) 19-31; DOI: 10.3221/IGF-ESIS.28.03 23 I NSTRUMENTSCHARACTERIZATION he EDS analysis of the HERO 642 instruments gives the following results: Ni 54,9% w (49.9 % a ) , Ti 45,32% w (50.1% a ) as a Ni-Ti superelastic alloy (NiTiNol). The SEM observations of the instruments - as provided by the manufacturer - show that the surfaces of all instruments are covered for the entire length by parallel signs (quite perpendicular to the file, Fig. 4) andby a high quantity ofmicro-cavities (Fig. 5). Figure 4 : SEMmicrographof as received instruments surfaces. Figure 5 : SEMmicrographof as received instruments surfaces. G EL C HARACTERIZATION ompared to theEDTA based lubricant, the aqueous gel shows a remarkable stability to the temperature change in the temperature range of use. Fig. 6 shows, in fact, between 25 and 45 ° C the viscosity of the aqueous gel remains constant while that of the EDTA based emulsion decreases considerably. Such behavior is probably due to solid- liquid components separation: it can be also noted that the viscosity of the emulsion initially is substantially higher than that of the aqueous gel, whichdefinitely involves a lower lubricating effect. Figure 6 : Comparisonof viscosity betweenEDTA emulsion andTool SaverGel vs. Temperature. Tab. 2 shows that at any temperature the thermal capacity of the aqueous gel is greater than that of the emulsion. This implies that, during theworkwithin the canal, the heat generated by the friction causes a lubricant temperature increase in T C