When using the Self-Adjusting Files, a preliminary reproducible glidepath should be established and/or verified. After glidepath preparation, it is important to verify its adequacy by manual insertion of an SAF to working length, before attaching it to the handpiece head, and optionally after dipping the file in EDTA lubricant paste.
With most other motorized instrumentation systems, the procedure ends when the final instrument reaches working length. With the SAF, best results are achieved when the SAF reaches working length at the beginning of the use of the file.
Note: The SAF is not a penetrating tool, and works best when compressed inside the root canal at working length, filing and scrubbing the canal walls laterally and circumferentially, all along its path.
The glidepath protocol should be chosen according to the degree of difficulty expected in a given canal. In all the following glidepath protocols, the final aim is first to establish a proper coronal access, then to establish an adequate glidepath:
A. Coronal access: first ensure an unobstructed straight access to the canal. Then, use the Pre-SAF OS (orifice shaper) to funnel the orifice of the canal if required . Operate it only in the coronal 2-4 mm part of the root canal, with slight lateral motions/pressure directed to the outer side of the curvature, in order to create and assure a straight-line access and operation of the SAF along the vertical axis of the root canal.
The following x-rays illustrate how the Pre-SAF OS should be used to ensure straight-line access to the canal according to the vertical axis (adapted from Kfir et al., Int Endod J, 2015):
B. Access to working length : Should allow the SAF to be manually inserted to working length . In cases of straight canals this may be done with a #20.02 hand-file, whereas in narrow and curved canals, an initial preparation of the canal with a Pre-SAF 2 rotary instrument (size #20/.04) is advised. Note that sometimes the curvature of the canal may not be obvious, such as canals with a bucco-lingual curvature, which is not apparent in clinical periapical radiographs. Therefore, such glidepath preparation should also be considered in any canal that has such tendency for curvature in the bucco-lingual plane. Such canals include mesial roots of mandibular molars, palatal roots of maxillary molars, etc., which may appear straight in periapical radiographs, which are taken from the buccal direction.
It is important to keep a minimally-invasive glidepath preparation, for the following reasons:
- To assure penetration of the SAF into buccal and/or lingual canal recesses: Preparation of a larger, more invasive glidepath, by either larger and/or bigger taper rotary instruments or large hand files, will create an excessively large round bore. This might lead the SAF to "recognize" the canal as a round canal and thus stay centralized within the large circular path which has been created. This in turn will diminish the chance for the file to be forced, as requited, into narrow buccal and/or lingual recesses, which are likely to already be packed by debris that was actively pushed there by the large initial rotary or reciprocating instrument that was used to create the wider initial preparation.
- To avoid negative side-effects of a larger initial preparation: Preparation of the canal with larger and/or more tapered rotary/reciprocating instruments (larger than #20/.04) or hand files has been shown to cause a number of side effects, including (a) packing of debris into narrow areas of the canal, (b) apical extrusion of debris, (c) canal transportation of curved canals, (d) excessive removal of sound dentin, and (f) creation of dentinal micro-cracks that may eventually lead to formation of vertical root fractures (VRFs). Most of these negative side-effects cannot be corrected by the subsequent use of the SAF.
Attempts to use the SAF only as a "finishing device" or as an irrigation device after a wider initial circular preparation will not allow the SAF to properly clean the recesses of canal and to shape it in a minimally-invasive way.
For these reasons, it is essential to keep the initial glidepath preparation to the minimum required for the insertion of the SAF and not go beyond #20/.04. This size was tested and proven not to create dentinal microcracks, yet allow the manual insertion of a 1.5 mm diameter SAF to working length (Kfir et al, Int Endod J, 2015)
The glidepath protocol is chosen according to the first hand instrument to bind (FITB) in the apical part of the canal. Each canal should be classified as a Difficult / Moderate / Easy / Wide canal, as described below:
Difficult Canals (FITB ≤ #10):
In difficult canals, with an initial size of #10 or less, the use of small-diameter path-establishment instruments is required.
Ensure coronal access, and then use an instrument that allows the establishment of the glidepath for the SAF:
- In canals with an initial size smaller than #10.02, use stainless steel or NiTi hand files to enlarge the canal to at least size #10.
In canals with an initial size #10 (but not yet #15), use the Pre-SAF 1 rotary instrument (size #15.02) or, alternatively, a #15.02 stainless steel or NiTi hand file.
Moderate Canals (FITB = #15) :
- In moderate difficulty cases, that only allow the insertion of a #15 file to working length, first ensure coronal access, and then use an instrument that allows the establishment of the glidepath for the SAF:
- In straight canals a minimum of #20.02 preparation is required. A #20 stainless steel or NiTi hand file may be sufficient, however the Pre-SAF 2 rotary instrument (see below) may be useful in such cases as well.
- In curved canals, or in canals in which a #20.02 glidepath is insufficient, use the Pre-SAF 2 rotary instrument (size #20.04) to establish the glidepath.
Note: the Pre-SAF 2 may and should be used only in canals in which a #15.02 hand file can freely reach working length, either as the FITB or after initial preparation of narrow canals up to this size (see above). Few small pecking motions will allow the Pre-SAF 2 file to reach working length.
Remove any gross pulp tissue, if present, and verify the glidepath by manually inserting an SAF 1.5 mm to working length (see the "Manual Verification" chapter below).
Note:
The SAF 1.5mm is equal in size to a #20 file when fully compressed. However, due to its three-dimensional structure, when it is inserted into curved canals it may be forced to slightly open, which means that a #20.04 glidepath preparation is required. The recommended instrument for such cases is the Pre-SAF 2 rotary instrument (sized #20/.04), that has been tested to enable the manual insertion of the SAF into curved canals, as well as to assure that it creates no dentinal micro-cracks and/or canal transportation.
Easy Canals (FITB = #20 – #30) :
In straight easy canals, usually no additional apical preparation is required. First, ensure coronal access and if necessary funnel the orifice using the Pre-SAF OS rotary instrument. Then use a #20 instrument to check that it can freely reach working length. Even though in easy curved canals, the SAF may be able to reach working length following a hand file size 20/.02 alone, it will be beneficial touse the Pre-SAF 2 instrument to create an easier and reliable glidepath.
Once established, verify the glidepath by manually inserting an SAF 1.5 mm to working length (see the "Manual Verification" chapter below).
Wide Canals (FITB ≥ #35) :
Ensure coronal access and make sure that a #35 hand file can freely reach working length and that the gross pulp tissue has been removed. Follow to verify the glidepath by manually inserting SAF 2.0 mm to working length, as detailed below.
Note that in canals that are ISO size #70 or more, the SAF 2.0 mm might not be sufficiently compressed inside the canals, and might rotate even when it is inside the canal, as it does not bind well enough with the walls of the wider canal. In such cases, make sure to limit the rotation speed of the SAF by pulling the irrigation tube, and perform regular visual inspections of the file during its operation, to rule out mechanical deformation. In those cases, only slight removal of dentin is expected, but this is usually beneficial, since preservation of sound dentin is a desirable goal in such cases.
Operation parameters for the Pre-SAF rotary instruments:
| Pre-SAF OS | Pre-SAF 1 | Pre-SAF 2 | |
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| Recommended speed (rpm): | 600 | 500-600 | 500-600 |
| Recommended torque limit (Ncm): | 1.5 | 1 | 1.5 |
| Special remarks: |
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