Examples of Oscillating Reamers’ Ability To Prepare Canals Without Distortion

?I’ve written numerous posts over the years emphasizing the ability of 30o oscillating reamers’ abilities to shape and cleanse canals not only in three dimensions, but without any obvious distortions. I’ve explained the principles behind this approach that eliminates instrument separation while staying true to the original canal anatomy in both the bucco-lingual and mesio-distal planes. Short arcs of motion fall far short of exceeding the elastic limit of the stainless steel reamers preventing failure from excessive torsional stress and cyclic fatigue is eliminated as a factor in separation because the degree of rotation is reduced from repetitive 360o arcs to 30o arcs that never scribe a full circle. With instrument separation eliminated I am able to safely apply these instruments vigorously in three dimensions, something to be avoided when using rotary sytems.?

While negotiating to the apex in highly calcified curved canals is a challenge for any system, the initial use of extremely thin stainless steel reamers offer the best chances of negotiating through these spaces. The instruments can be used either manually or in the 30o handpiece oscillating at 3000-4000 cycles per minute, an engine-driven way that often makes apical negotiation faster and far less fatiguing. Given the limiting potential of the 30o arc of motion to produce damaging stresses to the instruments, they are used several times without the need to replace them because of the fear of breakage. That saves money and is mentally soothing.

The advantages of using a combination of unrelieved reamers up to a 10/02 and relieved with a flat along their entire working length from 15/02 to 40/02 over K-files has been covered in previous posts and is easily discerned by comparing the two under function. Anticipating a question from rotary advocates might include why rotary became so popular if oscillating reamers work so much more safely and effectively? The fact is that engine-driven oscillation when it first came out was used with K-files, instruments that are not compatible with the horizontal motion generated by the 30o handpiece and led to the apical impaction of dentinal debris undermining this approach from the beginning. That left manual usage of K-files as the traditional method, a form of instrumentation that entails a good deal of hand fatigue and still leads to the frequent blocking of canals via impacted debris.?

Against this background rotary NiTi was introduced that like the present version of oscillation uses reamers rather than K-files. The vertical blades on reamers efficiently shave dentin away from the canal walls when employing a horizontal arc of motion. That is what rotary and oscillation is all about, employing horizontal motions to shave dentin away from the canal walls with the added advantage of short arc horizontal motion in oscillation as opposed to full arcs of rotary motion eliminating the potential for instrument separation. However, rotary was introduced before the introduction of oscillating reamers both unrelieved and relieved so the dentists initially had no way to compare the two. Rotary proved to be far more efficient and convenient than the manual use of K-files and thus became the dominant way to shape and cleanse canals. Their superior flexibility compared to stainless steel K-files was used as a marketing tool to further increase the gap between the two techniques with rotary clearly being the more favored despite a higher incidence of instrument separation. In fact, instrument separation became an issue within the family of rotary NiTi as evidenced by competitive ads that recommended one system over another based on their greater resistance to separation.

?With the background of the various ways to shape canals discussed, from my perspective it all becomes a moot point given the results that I routinely attain using the 30o oscillating reamers. Below are cases that demonstrate the oscillating reamers’ abilities to shape canals without distortion. Unable to be observed in 2 dimensional x-rays is their vigorous function in the bucco-lingual plane that gives them a depth of cleansing that rotary cannot match.

Below are cases that demonstrate the consistent shaping of curved canal without distortion with the added benefit of knowing the instruments will remain intact.

Case 1. Maxillary second molar with significantly curved buccal canals. I will show in a case below the ability of the extruded epoxy resin cement to start binge digested by the macrophage within a few weeks of placement while allowing any areas to heal.

Case 2.??Here we see obturation of a mandibular second molar with excess cement extruded over the apex. Taken several weeks later, the cement is being digested. From viewing the digestion of cement over many years where areas were first present, the ability of the macrophage to digest the cement in no way compromises the apical seal as indicated by the healing of periapical areas that were originally present.

Case 3. The maxillary left second molar had an mb2 as curved as the mb, but was cleansed and filled without any distortions and again with no concern for instrument separation. It is that fact that allows us to treat the buccal and lingual extensions of oval canals with the same vigor we apply mesially and distally.

Case 4. 30o oscillation with relieved stainless steel reamers not only will cleanse curved canals without distortion. As this case shows, S-shaped canals are also treated routinely without any sign of distortions. Call it the magic of short arcs of motion, an extension of the balanced force technique that is applied via the oscillating handpiece eliminating hand fatigue in attaining these results.

Case 5. I like the subtlety of this case, an example of a curve in the apical third of the distal root. Give the original dimensions of the canals at least in the mesio-distal plane, it was likely that a thin mesio-distal preparation alone would be inadequate in removing all the tissue that might be present in the bucco-lingual plane. As stated above, the oscillating reamers are used vigorously in the bucco-lingual plane providing a better chance of three-dimensional cleansing as observed in an apical preparation that is not simply a thin white line to denote the instrumentation and obturation process. It is prepared to greater dimensions at this level because that was exactly what was called for.

The cases have infinite variations, but the approach that I employ is more than adaptable to all the situations. That adaptability rests on the basic principle that short arcs of stainless steel reamer motion, used at high frequency combines non-distorted three dimensional shaping, elimination of hand fatigue and relatively rapid canal preparation with total security of the instruments. It is that combination that makes this approach unique.?

Regards, Barry