![\"pasted-image-133\"](\"https:\/\/www.zerodonto.com\/en\/wp-content\/uploads\/2015\/06\/pasted-image-133.jpg\")
<\/a>Fig. 1 – Adapted from Paqu\u00e8 et Al<\/p><\/div>\n
<\/a>Fig. 2 – Adapted from DeDeus et Al.<\/p><\/div>\n
The search for more effective instruments has consequently led to\u00a0 the manufacturing of files with increasingly\u00a0 “active\u201d cutting edges,\u00a0 resulting in greater amounts of treatment debris, as well as\u00a0 greater\u00a0 stress in the dentin, which may cause\u00a0 “micro-cracks” within roots . These are likely to provoke actual root cracks at first , and possible vertical fractures thereafter [6,7,8,9].The\u00a0 introduction\u00a0 of the SAF\u00ae (Self Adjusting File, Redent Nova, Israel), in 2010,\u00a0 marked \u00a0 a new definition of the concept of 3D shaping, cleaning and maintenance of\u00a0 endodontium anatomy, thanks to an approach which is\u00a0 completely different from the past.Nowadays,\u00a0 the assertion\u00a0 that\u00a0 endodontic treatment is safer and less\u00a0 invasive\u00a0 than in the past, can be confirmed by over 50 studies published in leading international scientific journals, and by a\u00a0 growing number of clinical applications.<\/p>\n
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The SAF System<\/h2>\n
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1.THE FILE<\/h3>\n
The SAF is the first endodontic file with a hollow tube and not characterized by a solid metal core. As a matter of fact, it consists of a hollow cylinder with two parallel longitudinal beams held together by a Nickel- Titanium lattice; the manufacturing process is not performed using carving techniques, but sand-blasting induced roughening.The working part has no flutes, but only a rough surface that ensures a gentle and effective action of grinding and smoothing the root. (Fig 3).<\/p>\n
The\u00a0 hollow core, letting \u00a0 liquid flow within,\u00a0 facilitates debris\u00a0 removal with\u00a0 continuous irrigation flow. This takes place thanks to the\u00a0 small connector,\u00a0 placed on the shaft of the instrument and attached to an endodontic motor (Fig.4), equipped with a peristaltic pump (Endostation \u00ae, Redent Nova, Israel) that provides\u00a0 continuous and pre- calibrated(4ml \/ min)\u00a0 flow of irrigant solution [10,11,12].<\/p>\n
<\/a>Fig. 3<\/p><\/div>\n
<\/a>Fig. 3<\/p><\/div>\n
<\/a>Fig. 4<\/p><\/div>\n
A\u00a0 peculiar hollow design, gives\u00a0 the SAF specific features, such as compressibility along root canals. In fact, the diameter size of a\u00a0 standard instrument is 1,5mm, but if fully compressed, it is reduced to the size of a 0.20\u00a0 manual K-file. If instead,\u00a0 it is inserted into a oval-shaped canal with mesio-distal diameter of 0.2mm,, the SAF stretches\u00a0 bucco-lingually to an extent of\u00a0 2.4 mm, thus succeeding in coming in\u00a0 contact\u00a0 with a large portion of the inner surface of the canal. This happens regardless of the operator being aware of the oval canal , since\u00a0 the file itself adjust to it (hence the name of Self-Adjusting -File) [10].<\/p>\n
Its\u00a0 particularly flexible structure, makes the SAF a very safe and reliable instruments with\u00a0 regard to fractures.<\/p>\n
In fact, its hollow Ni-Ti lattice\u00a0 enables it to twist , but even if\u00a0 detachment\u00a0 from the grip occurs, the instrument does not get locked in the canal, but can be easily removed used a simple Headstrom file, since it has no blades. This, however, is a rather rare occurrence; it is more likely\u00a0 that, when mechanically damaged while being used, small pieces\u00a0 may come off the net\u00a0 (fig.5) , flow directly into the liquid leaking from the canal, and then into the aspirator.<\/p>\n
The file is assembled on a RTD3 headpiece (Fig.6) which performs a dual function: it turns the rotation motion of the motor into an up-and-down motion of the\u00a0 instrument shaft with\u00a0 0.4 mm amplitude, and also generates a rotation in absence of torque, when the file is free from the canal [10,11,13].<\/p>\n
From a clinical perspective,\u00a0 this makes it possible for the SAF to performed in-out movements, changing its circular position each time, thus exerting a dentinal smoothing action, which affects nearly 80% of the canal surface (compared to 50%\u00a0 with normal rotary or reciprocating instrumentation\u00a0 ) [13,14].<\/p>\n