Shaping Curved Canals With Stainless Steel Reamers

?From the perspective of rotary NiTi, shaping curved canals with stainless steel reamers is fraught with the greater possibility of canal transportations to the outer walls as well as an increased incidence of ledging. Rotary NiTi advocates note the greater stiffness of comparably sized stainless steel instruments and assume that transportation is a predictable result. This concern is real if stainless steel instruments are used in rotation. However, confined to a 30o arc of motion, they faithfully follow the glidepath established by the initial thinner and far more flexible starting stainless steel reamers.?

?The best way to demonstrate the validity of non-distorted canal preparations using oscillating reamers confined to a 30o arc of motion is with the presentation of cases. All the cases presented here were done with stainless steel reamers generally combining their use first with the thinnest reamers negotiated to the apex manually and then shaped to completion, generally to preparations sized from a 30/02 to a 40/02 using the 30o handpiece oscillating at 3000-4000 cycles per minute. The short arc of motion within which these reamers are activated accomplish two main goals. One, as mentioned earlier they do not deviate from the original canal anatomy and two, the short arc of motion virtually guarantees their remaining intact regardless of the degree of canal curvature.?

?While following the canal anatomy accurately as they are widened is essential to any instrumentation system, the fact that they are virtually invulnerable to breakage allows them to be used effectively in what is often the wider bucco-lingual dimensions of the majority of teeth and the specific widening mesio-distally of the palatal roots of maxillary molars. With the frequency of oscillations at approximately 60 cycles per second the irrigants that should always be flooding the??canals are activated for increased effectiveness along with the accurate physical contact of the reamers being applied vigorously against all the canal walls.

?Applying instruments in three dimensions is only possible because of their invulnerability to breakage. Rotary with an increased tendency to separate are generally confined to the widest portion of the canals with only minor lateral movement to remove dentin that may be ensconced in narrow buccal and lingual exstensions. This limitation has been validated by research studies that note the inability of rotary systems to remove the pulp tissue and bacteria from oval canals.?

?Rotary advocates can rightfully state that despite these limitations, their use produces a high degree of success. Evidently, success depends upon a balance of the body’s defenses against the pathogenic potential of the remaining tissue. But, that same claim can be made for any instrumentation system and I prefer to employ one that virtually eliminates instrument separations, removes more tissue (it can’t hurt) in portions of the canal that are inaccessible to rotary systems and churn the irrigants with a high degree of sonic activation.

?The cases below cover at least two decades of using the oscillating reamers both unrelieved and relieved in the 30o oscillating handpiece. The concern of separation has never been an issue.

Case 1. Demonstrating a typical result in a maxillary molar using the stainless steel reamers both unrelieved through a 10/02 and shaping the canals to a 35/02.

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Case 2. Another example of a maxillary molar with curved mb canals. In all these cases, the reamers are strongly applied via the handpiiece against the buccal and lingual walls of the canals that have a high incidence of being significantly oval in cross-section.

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Case 3. I like this case not so much for the oscillating reamers’ ability to shape canals without distortion, but to show the apparent effectiveness of the oscillating reamers to churn the irrigants sufficiently to open up the lateral canals at the apical end of the roots.?

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Case 4. Is an example of the delicacy with which the oscillating reamers can be used. They are adaptable to all situations and reduce operator stress when the anatomy becomes more challenging.

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Case 5. This is another example of the apparently effective churning action of the oscillating reamers in opening up the lateral canal spaces that are often present in the apical third of canals. Activated NaOCl is particularly effective in digesting non-vital tissue in these accessory canals.

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Case 6. Here is another example of the delicacy oscillating reamers. While being used with vigor buccally and lingually, the subtle curves observed mesio-distally remain true to the original anatomy. I do not take ownership of #19.

Case 7. Finally, this case once again demonstrates the flexibility and adaptability of the reamers used in the oscillating handpiece to remain true to the original canal anatomy.

Rotary’s claim to fame is due to their greater flexibility that when used in rotation are far less likely to produce distortions than stainless steel?if they were also used in rotation.?30o oscillation removes the need to make that comparison as well as taking instrument separation off the table as a complicating and compromising issue.

Over the next few posts I will post cases that further support the safe use of the oscillating approach to instrumentation and their adaptability to any given situation.

Regards, Barry