Barry Musikant

1. No one system is good for all cases. This has then been morphed into the limitations of a cookie-cutter approach, implying that the SafeSiders can produce only one result that does not fit all cases, reinforcing the idea that the SafeSiders are a cookie-cutter system.
2. A reamer-based system will distort the canals apically when a curve exists.
3. A Peeso-like reamer is too dangerous to use, often leading to ledging and strip perforations.
4. The canal shapes produced by SafeSiders do not have the continuous taper that rotary NiTi produces.
5. While the SafeSiders approach does not separate instruments, the concern for separated rotary NiTi instruments is overrated.
6. The SafeSiders represent a simplistic approach that does not recognize the subtleties of endodontic anatomy.
7. If the SafeSiders are so good, why aren’t all endodontists using them, and why are they not being taught in the dental schools?

Let’s see how well we can answer some of these concerns:

1. No one system is good for all cases.
    To a large extent, if a system is designed right, it should have the adaptability, versatility, and flexibility to be used in the vast majority of cases.  Techniques that have a very narrow range of use are the ones that are poorly designed.  The versatility of the SafeSiders is apparent in the mix of both stainless steel and NiTi reamers, the fact that they can be used prebent or straight, manually driven or engine driven, in any combination that is deemed most efficient and effective.  The 30-degree reciprocating engine creates a small envelope of motion that allows precurved instruments to be driven through a highly curved canal without distorting it.  For even the most highly curved canals, a prebent SafeSiders reamer can be manually placed with the correct orientation to the initiation of the curve and then driven the rest of the way to the apex via the reciprocating handpiece.  This type of versatility is not available with any rotary NiTi system.
    What is gained is not just the ability to shape most curved canals without distortion, but the virtual elimination of the torsional stress and cyclic fatigue that lead to rotary NiTi separation.  In this way, the SafeSiders permit both safe and effective canal shaping.

2. A reamer-based system will distort the canals when a curve exists.
    This concern has been partially answered by the first response.  However, a more detailed response demonstrates why distortion is far less a concern with relieved K-reamers than non-relieved files.  The amount of resistance that an instrument encounters on its way to the apex is a function of the amount of contact along the length of the instrument with the canal walls as well as the efficiency with which the flutes cut the dentin.  The greater the amount of resistance along the length of the instrument, the less the tactile perception of what the instrument is encountering apically.  A relieved reamer has about one-third the contact along the length of the root compared with a non-relieved K-file.  This increased contact is due to the greater number of flutes that a file has within its 16 mm of working length.  A file has about 30 flutes, while a reamer has about 16.  Since both reamer and file are fabricated from a square wire, the file has about 120 contact points (30 x 4 contact points) while the non-relieved reamer has 64 contact points (16 x 4 contact points).  The relieved reamer has 48 contact points (64 minus an entire column of contact points or 16 contact points).  The flutes on a file are far more vertically oriented because there are so many more crammed into the 16 mm of working length.  The greater the number of flutes, the more horizontally they must be oriented.  The more horizontally oriented, the less efficient they are at cutting the dentin along the walls of the canal if the motion is either rotation or reciprocation (short rotation).
    The combination of fewer contact points and the more vertical orientation of the flutes allows the relieved reamers to produce a far more exquisite tactile perception of what is encountered at the apex.  That increased apical tactile awareness gives the dentist the ability to distinguish between a tight straight canal and one with a sharp curve that requires prebending the instruments to negotiate around it.  Again, the use of the reciprocating handpiece—with its small envelope of motion connected to the reamer after it has negotiated to the start of the curve—prevents distortion as the reamer negotiates the rest of the way to the apex.  This is obviously not the case with non-relieved K-files, which have a long history of causing distortions and perforations in curved canals.
    The negative aspects of reamers emerged when they were used with abandon in a rotary fashion (often manually) in curved canals.  When used in the prescribed way, their less-engaging design becomes a major advantage over K-files.  The key is the increased apical tactile perception that relieved reamers give the dentist.

3. A Peeso-like reamer is too dangerous to use.
    The first thing to appreciate about all Peesos and Peeso-like reamers is that they are designed not to cut at the tip. They should be used in a pecking motion, never lingering at the most apical placement of the tip.  They are lateral cutting instruments that for endodontic purposes are used to straighten coronal curves. The Pleezer®, a tapered Peeso, deepens the apical preparation and straightens the coronal curve more efficicently than non-tapered Peesos.  Encountering less resistance, the Pleezer pushes less debris apically while minimizing any bottling that might go along with the deepening process.  The tapered Peeso is also quite efficient when used to extend preparations to the buccal and lingual when the canal configurations call for it.
    The tapered Peeso used with a firm pecking motion without apical lingering minimizes impacting of apical debris.  Always directing the lateral cutting blades to the outer walls of the canal prevents the strip perforation that can occur when Peesos are used incorrectly.  Using a tapered Peeso correctly takes a minimal amount of training, and the instrument can then be used with safety in practically all situations.

4.  The canal shapes produced by SafeSiders do not have the continuous taper that rotary NiTi produces.
    This is one of the great misconceptions fostered by rotary NiTi advocates.  We are accustomed to a limited view of canal shapes after rotary NiTi instrumentation: a mesio-distal one.  However, the data comparing the mesio-distal dimensions of canals with the bucco-lingual dimensions clearly demonstrate that the average bucco-lingual widths in the most apical 2 mm of the canal are approximately twice as wide as the mesio-distal dimensions.  Furthermore, at 5 mm from the apex the average bucco-lingual widths are often several times as wide as the mesio-distal dimensions.  The image of a continuous consistent taper is at best limited to the mesio-distal plane.  Problematic is the fact that rotary NiTi instruments tend to stay centered, producing these mesio-distal continuous tapers even when they don’t reflect the initial shape of the canal, potentially leaving significant amounts of debris in the buccal and lingual extensions of the canal.  The final canal shape at its best mirrors a wider version of the natural anatomy before shaping.  The shaping should do away with as many undercuts as possible while maintaining as much as possible the original canal configuration. The SafeSiders clearly demonstrate that they can maintain the shape in the mesio-distal plane at least as well as rotary NiTi.  However, in the bucco-lingual plane they prove themselves to be far superior to rotary NiTi in accomodating themselves to the far wider dimensions that often exist is this plane.  The tapered Peesos used within 6 mm of the apex have the ability to selectively cut to the buccal and lingual, removing debris that may be hidden in these recesses.  Rotary NiTi’s so-called advantage of staying centered in the mesio-distal plane fails to account for these greater bucco-lingual diameters because they do stay centered.
    A well-thought-out system must account for the non-uniformity between the bucco-lingual planes and the mesio-distal planes.  The SafeSiders are better designed to handle this asymmetry than rotary NiTi.

5. While the SafeSiders approach does not separate instruments, the concern for separated rotary NiTi instruments is overrated.
    Whether rotary NiTi instrument separation is a legitimate concern is dependent upon whom you speak to.  It is enough of a concern that more than 1,000 articles have been written about it.  There are endless articles telling dentists what they must do to avoid separations.  Ironically, rotary NiTi instruments are not to be used where the canals are so curved that a glide path cannot be predictablly created, an absolute essential for their safe usage.  Yet, these are the canals where these instruments are most needed, because these are the situations in which conventional endodontics using K-files produces the most distortions, ledges, and perforations.  Rotary NiTi produces torsional stress and cyclic fatigue, the two factors most responsible for instrument separation.  Substitute 30-degree reciprocation for rotary, and virtually all torsional stress and cyclic fatigue is eliminated.
    From our own experience, most dentists take our courses as well as switch to the SafeSiders because they want to rid themselves of the stress they have, never knowing when the next rotary NiTi instrument will break.

6. The SafeSiders represent a simplistic approach that does not recognize the subtleties of endodontic anatomy.
    On the contrary, as stated above, the SafeSiders represent a single system that can be used in many ways.  When used manually in a straight canal, they can be freely rotated.  When used in a mildly curved canal, the relieved reamer design takes this curve with minimal distortion.  As the curves become more pronounced, all the stainless steel instruments can be prebent and introduced into a canal of any curvature to the start of the curve and then driven the rest of the way with the 30-degree reciprocating handpiece. The 30 degrees of rotation represent a very small envelope of motion, preventing the distortions that would occur in a curved canal if the arc were greater.  Dr. Schilder described the benefits of a small envelope of motion more than 35 years ago.
    The SafeSiders’ flexibility, versatility, and adaptability allow a single system to address so many endodontic challenges.  The SafeSiders instruments adjust to the endodontic situation no matter what it is. Rotary NiTi instruments are useful only when the case falls within their metallurgical limitations, of which there are many.  Hence, the myriad of articles written about how they should be used most safely.
    It is rather astonishing that articles rationalizing rotary NiTi separations have been written.  In all the years I have been an endodontist, I never saw an article that diminished the problems of separated instruments until rotary NiTi was introduced and started to have these problems.

7. If the SafeSiders are so good, why aren’t all endodontists using them, and why are they not being taught in the dental schools?
    When I hear this question, I just shake my head and smile.  Rotary NiTi is a product marketed by multi-billion-dollar companies.  When it was first introduced, the concerns about separation were not understood or appreciated as they are now.  Furthermore, rotary NiTi has significant advantages over the traditional use of K-files that made rotary NiTi an attractive comparison.  Again, ironically, despite the limitations of K-files, they are required to gain the glide path necessary to use the rotary NiTi.  Even those who have graduated from inefficient traditional techniques are still tied to them.
    Given the advantages of rotary NiTi over traditional techniques, the multi-billion-dollar dental companies that manufacture these products brought all the essential components of a multi-media marketing campaign together to sell rotary NiTi as the new endodontic paradigm of the ages.  Their place in the universities and their advocacy by leading endodontists is financially supported in ways that only huge companies can undertake.  Because the cost of these instruments is so much higher than the cost of conventional endodontics, the companies can support this self-perpetuating marketing model.
    The question every dentist who does endodontics should ask himself is this: if there is a system that can allow him to shape canals as well as rotary NiTi, virtually eliminates separations, can be used without reservation on all types of cases, and costs about 90 percent less, wouldn’t it be to his or her benefit to learn what this system is all about?
    In the next issue of Endo-Mail I’ll discuss some of the devil’s advocate questions that have occurred on Dentaltown regarding the EZ-Fill® obturation technique.