Progressive Taper Technology: Rationale and Clinical Technique for the New ProTaper Universal System

ProTaper rotary technology (DENTSPLY Tulsa Dental) was launched in the United States in the spring of 2001. The required “waves of shaping” of these patented, endodontic, “progressively tapered” (hence the name ProTaper) Ni-Ti rotary files exactly mimic the techniques of the late master of endodontic cleaning and shaping, Professor Herbert Schilder of the Henry M. Goldman School of Dental Medicine, Boston, Mass. Dr. Schilder’s words for progressive shaping were “serial shaping and recapitulation.” Even today many clinicians interpret “recapitulation” to mean confirming apical foraminal patency. Nothing could be further from the truth.
Dr. Schilder originally stated that recapitulation refers to the “repeated reintroduction and reapplication of instruments previously used throughout the cleaning and shaping process in order to create a well-designed, smooth, unclogged, evenly tapered, unstepped root canal preparation.”¹ Using the “envelope of motion” and recapitulating with files and reamers enabled the clinician to remove restrictive dentin progressively and selectively. Dr. Schilder was teaching how to “connect the dots” from the apical foramen through the canal orifice and ultimately through the outline form of the access cavity. This smooth outline form achieved cleaning and shaping mechanical objective No. 1: “Make a continuously tapering cone throughout the radicular preparation.”²
The progressively tapering technology achieves this objective more accurately and more efficiently than the manual motions of “following,” “smoothing,” “balanced force,” and “envelope of motion.”³ The clinician knows exactly where cutting occurs in the preparation as the progressive file geometries provide intentional restrictive dentin removal. Further specific carving is easily accomplished using progressive geometries through the technique of “brushing” first introduced by Ruddle.⁴ Progressive taper prevents the dangerous taper lock, which is the grabbing of restrictive dentin, without warning, over an undetermined and undesirable length. This type of torsion loading is a major cause of Ni-Ti rotary failure and breakage.⁵ While every endodontic clinician is capable of breaking every endodontic rotary file, a progressively tapered file carves in predetermined locations along the canal walls. The instruments truly produce the desired “Schilderian” waves of shaping by carving the canal incrementally and not in one large and potentially dangerous “bite.”
The objective of this article is to discuss the rationale, design changes, and clinical technique of the newly developed ProTaper Universal file system so that clinicians will understand the clinical principles and proper use of this system. The article is divided into 3 parts: why? what? how?

WHY PROTAPER UNIVERSAL?

Even with the extremely high performance of progressively tapered rotary files, the marketplace had a “wish list” for a next generation. There has been a desire to have a wider apical diameter for wider original apices and also where the clinician wanted to “open an apex” to a size No. 40 or No. 50 in order to further ensure maximum cleaning of the foraminal constriction. Second, and justifiably so, there was a need for 31-mm length instruments for longer teeth such as canines. Third, some clinicians felt the F3 was too stiff, even though it was more flexible than other files of comparable size. Lastly, there were authors as well as conversation in the marketplace indicating that the ProTapers were aggressive. However, originally these authors failed to follow the ProTaper directions for use (DFU). They were naturally pushing and pressing, as their tactile muscle memory was created by having to push and press radial land-type rotary instruments in order for the inefficient blades to engage and cut dentin.

Figure 1. The original ProTaper “6-pack.”	Figure 2. Reconstruction of typical complex root canal system of actual molar. (Image courtesy of toothatlas.com.)
Figure 3. Clinical example demonstrating shapes that enable 3-D hydraulics of nature’s root canal system anatomy. (Image courtesy of Dr. Jason West.)	Figure 4. Subtle, yet profound, changes between ProTaper and ProTaper Universal.

ProTaper’s touchstones of tactile muscle skill memory are words like float, follow, brush, caress, gentle, soft, effortless, and supple. Their efficiency is the difference that makes the difference. Therefore, the changes that the marketplace desired were essentially additions to the existing ProTaper system while still minimizing the number of instruments and, therefore, keeping with the ProTaper Universal philosophy of “less is more.” The watchword is simplicity. At the Maillefer instrument plant in Ballaigues, Switzerland, a team of endodontists consisting of Clifford Ruddle, Pierre Machtou, and this author, in conjunction with Maillefer Swiss engineers, met last year as they have from the birth of ProTaper to fulfill these needs and desires.
And so it is that 5 years after ProTaper’s 2001 launch a new generation of “progressive taper” technology has been perfected and introduced (Figures 1 to 4). It is the intention of this article to examine each new feature and ask 3 questions: What is the thinking behind the feature? Exactly what is the change, if any? What is the clinical experience of each change, if any?

WHAT IS PROTAPER UNIVERSAL?

SX

Thinking. The Shaper SX’s exaggerated “Eiffel tower geometries” enable coronal shaping in short teeth, but, more importantly, they provide efficient brushing of coronal dentin away from furcal danger.6 Some colleagues have reported considerable desire to increase SX’s geometries even further. This change proved unnecessary, however, and caused a risk to inadvertently cut on the inside wall and therefore risk furcal danger. It became clear with just a few simple brushes of the original SX that orifi and the coronal portion of canals could easily be up-righted and coronal shaping could be finished.

Change. The SX remained the same, except that a rounded “safe” tip was added versus the previous “partially active tip.”

Clinical Experience. Unchanged, except safer.

S1 (Purple)

Thinking. S1 (Shaper No. 1) was designed to intentionally shape and clean the coronal one third of the canal. Many users call S1 and F1 (Finisher No. 1) their “money” instruments. These clinicians consider S1 and F1 indispensable, and when used creatively, ie, with brushing strokes, they could minimize the need for S2 as well as the other Finishers. Of course, precision would be lost, and whatever would have been saved in terms of less inventory cost would be lost in the cost of time and inexact results.

Change. S1 stayed the same with the exception of a “safe” tip addition. Keeping S1 the same comes as a big relief to ProTaper users.

Clinical Experience. Unchanged, except safer.

S2 (White)

Thinking. The thinking in the mid 1990s was to design a rotary file to shape the middle third of a canal with particular emphasis on the coronal third of the apical third.7 This area is often the beginning of an apical turn and is sometimes referred to as the “elbow.” The ProTaper DFU was to float, follow, withdraw, and then repeat until length was achieved. Several progressive passive passes were typically required. The S2 (Shaper No. 2) did exactly what it was engineered to do. “Brushing” with the S2 Shapers, however, has changed all this. With S1 brushing, S2 had less shaping to do. It had, if you will, less “work” to do. The waves of shaping were no longer evenly distributed.

Figure 5. ProTaper Universal including F4 and F5.

Change. The S2 progressive geometries have been slightly increased so that transition from Shaper to Finisher is seamless when brushing with Shapers. Now the F1 Finisher is a true Finisher and effortlessly “connects the dots” (Figures 4 and 5).

Clinical Experience. While the S2 change is subtle, it is conceptually and clinically profound because there is now a critical clinical distinction between “Shapers” and “Finishers.” This difference is, in itself, a unique feature of ProTaper and now ProTaper Universal. Brushing with the new ProTaper Universal S2 reduces the number of progressive passive passes required by Finisher F1. The “connecting the dots” seems to melt the shape together. A canal that previously required 4 progressive passes now may require one or perhaps 2. With less dentin volume to cut, the F1 has become even safer clinically.

F1 (Yellow)

Thinking. F1 (Finisher No. 1) is used in every canal that requires shaping. F1 has an ISO apical tip size of No. 20, and its first 3 mm (to level D3) have a 7% taper and then feature a decreasing rate of taper that produces excellent flexibility. The final radicular preparation shape of F1 provides superb “restrictive flow” hydraulics. With the Pro-Taper Universal change in S2, the F1 “workload” between S2 and F2 is perfectly distributed.

Change. Unchanged except the addition of the “safe” tip.

Clinical Experience. F1 now “drops” to length with greater ease and safety. The transition from “Shapers” to “Finishers” is smoother and feels seamless.

F2 (Red)

Thinking. F2 (Finisher No. 2) has always had the proper outline form, but the Ballaigues team was addressing the question, “Is F2 too efficient?” Should we “slow it down?” This characteristic was successfully tested with prototypes but required a change in motion from “follow” to having to press or push slightly to make the file cut. This disruption in flow was unsettling and made the clinician think, “Should I follow, or do I now need to push?” One of the critical distinctions of ProTaper and Pro-Taper Universal is that the “waves of shaping” with Finishers are natural, smooth, and effortless. When the concept of Schilder’s Five Mechanical Objectives  is understood and the dentist is vigilant about achieving them, then instrumentation occurs with grace and ease. It is a “flow” experience. It was determined that the answer was not to change the F2 but to change the thinking. Better education about the efficient performance was the answer.

Change. None except from a “modified guiding tip” to “rounded safe tip.”

Clinical Experience. F2 as it was originally designed is often the final finisher required. Evidence of carved apical dentin in its flutes means the canal is ready to pack with an F2 ProTaper gutta-percha cone or an F2  ProTaper obturator.

F3 (Blue)

Thinking. F3 (Finisher No. 3) has been one of those files that clinicians either loved or hated. In the past, this was the instrument that motivated some dentists to “hybridize.” Hybridization of files has always been a dilemma. This mixing and matching caused loss of rhythm because the dentist would have to stop, think, and ask, “What’s next, and how do I use this different instrument differently?” It also required increased instrument inventory. Dentists discovered that F3 success, as it was intended and designed, required extreme manual restraint. If the ProTaper F3 is “followed” in the same fashion as the F1 and F2, it could, in uneducated hands, follow further than desired. It was clear to the Ballaigues team that we wanted to “slow down F3 ever so slightly” in order to preserve the experience of doing the same thing with each of the Finishers. The bottom line was the F3’s “work” had already been done. F1 and F2 had literally paved the way. All F3 ever had to do was act like a true Finisher and, once again, “connect the dots.” What it boiled down to was that F3 was actually “over-qualified.”

Figure 6. Cross-sectional changes of F3 enable significantly increased flexibility.

Change. By changing the cross-sectional blades and other slight modifications, the engineers were able to give F3 a whole new feeling of increased safety and flexibility (Figure 6). As with all the new ProTaper Universal rotary and manual files, the file tip was changed from the “modified guiding tip” to the “rounded safe tip.”

Figure 7. Conservative, yet appropriate, shaping and obturation of simple anterior tooth.	Figure 8. ProTaper Universal rotary files enable successful following, shaping, cleaning, and 3-D obturation of the entire root canal system.

Clinical Experience. One dentist used to describe the F3 as “Mr. Stiffy.” That same dentist now calls F3 “Mr. Flexey.” The clinically significant benefit and the real value is that the F3 is now truly part of the ProTaper “6-pack family.” It now “feels” exactly like F1 and F2: safe, controllable, and still sufficiently efficient. When the set of Finishers are used properly, appropriate shapes for appropriate roots are routine (Figures 7 and 8).

New F4 and F5 (Black and Yellow Double Stripe)

Thinking. F4 and F5 (Finisher Nos. 4 and 5) did not originally fit into the ProTaper philosophy of “less is more.” ProTaper was not intended to be the instrument system for all seasons, but rather for one specific season, and that was to predictably, safely, simply, and efficiently carve a natural preparation shape in a canal that needed to be shaped, ie, where restrictive dentin was present. It did not matter if the canal was long or curved. If the walls are smooth, ProTaper can always follow to the terminus when the DFUs are observed. And we already had countless products that were attempting to provide a solution for every possible circumstance. Complexity and confusion was what the ProTaper philosophy was avoiding. To add instruments was clearly not part of the “thinking process.”
However, some colleagues suggest that the prepared apex needs to be a size No. 40 or 50 in order to successfully clean via better exchange of irrigants and make the foramen round. Consequently, one of the significant outcomes of the 2005 Ballaigues team was to produce Pro-Taper auxiliary files to meet the need. F4 and F5 are truly auxiliary instruments, however, and should be thought of in this way.

Figure 9. F4 for teeth with larger foramina or for intentional increase in foraminal diameter.	Figure 10. F5 for teeth with yet larger foramina or desired foramina.

Change. The F4 is an ISO 040 tip size, a 6% apical third taper, and then a progressively decreasing taper in the body, which produces excellent flexibility. F5 is an ISO 050 tip size, a 5% apical third taper, and then a progressively decreasing taper in the body, which, similar to the F4, provides the clinician with superior file flexibility. As with the entire ProTaper family, F4 and F5 are produced with a “rounded safe tip” (Figures 9 and 10).

Figure 11. ProTaper Universal is a concept from access to cleaning and shaping to drying to obturation. Note matching ProTaper gutta-percha and ProTaper obturators.

Clinical Experience. The F4 and F5 Finishers do what they are designed to do: increase the apical preparation size, or shape a canal that presents with an apical constriction of more than size 30. They are surprisingly flexible and have matching F4 and F5 ProTaper gutta-percha cones and matching F4 and F5 ProTaper obturators (Figure 11). This clinician finishes with F1 approximately 20% of the canals, F2 approximately 70% of the canals, and F3 approximately 10% of the canals. It is infrequent that the apices in clinical practice have been greater than a size No. 30, but when that patient presents, hybridization can now be avoided, and the same highly effective ProTaper efficiency can be enjoyed.

New 31-mm S1 to F5 Lengths

Thinking. Occasionally, a patient presents with root canal lengths greater than 25 mm. Longer ProTaper files were clearly needed to maintain ProTaper efficiency in longer canals and to minimize the inventory hybridization. The Ballaigues team found a need and filled it.

Change. None except increased shaft length for longer teeth with longer canals. The same ProTaper “preparation blades” have been preserved. ProTaper gutta-percha cones and ProTaper obturators will soon be available in these lengths.

Figure 12. ProTaper Universal is produced in 21-, 25-, and 31-mm lengths.	Figure 13. Maxillary canine shaped, cleaned, and obturated using ProTaper Universal technology.

Clinical Experience. Dentists can now make “ProTaper shapes” in longer teeth and have the same positive clinical experience (Figures 12 and 13).

ProTaper Retreatment Files

Thinking. A comprehensive solution for obturation removal really did not exist. Most clinicians simply used their dentin carving files for removal.

Figure 14. ProTaper Universal retreatment rotary files.

Change. Three ProTaper retreatment files have been designed for efficient obturation material removal. D1 has an apical taper of 9% followed by ProTaper reducing tapers, and is intended for coronal third obturation removal. It also has an effective cutting tip to remove gutta-percha or engage an obturation carrier. D2 has an 8% apical taper for middle canal third obturation removal. D3 has a 7% apical taper for apical obturation removal (Figure 14).

Clinical Experience. Pro-Taper retreatment technology allows retreatment in the spirit of the same ProTaper philosophy of safe, simple, and efficient.

Silicone Manual ProTaper Files

Thinking. There is a desire for clinicians to “feel like one” with delicate root canal system dentin when performing endodontics. Without the sense of “sight,” the sense of “touch” must be maximized in order to have optimal control over shaping canals.

Change. Silicone handles are installed on all manual ProTaper files.

Clinical Experience. With the addition of a silicone handle, dentists have reported, “I feel more like I am one with the file,” and “When using manual motions, my fingers do not become fatigued.” In a nutshell, the silicone handle makes the manual ProTaper files feel much more supple.

HOW PROTAPER UNIVERSAL?

How to incorporate ProTaper Universal is the best part. It is simple, and no thinking or planning is required. There is no change in clinical sequence, and new geometries will slide seamlessly into existing ProTaper inventories. There will be no sudden change in tactile sense, yet there will be a greater sense of smooth and effortless progression from Shapers through Finishers.

SUMMARY

ProTaper Universal has produced a comprehensive yet simple solution for dentists in search of a single, versatile system that solves major endodontic problems from access to obturation. The key in high-performance endodontics is to produce the most and the best while doing the least. We know this as leverage. Breakthrough safety and simplicity features, combined with optimum efficiency, are at the heart of ProTaper Universal. The net intentional result of these newest endodontic technologies is that the practitioner can predictably and consistently produce exceptional patient outcomes (Figures 15 to 20).

References

1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am. 1974;18:269-296.
2. West J. In: Cohen S, Burns RC, eds. Pathways of the Pulp. 7th ed. St Louis, Mo: Mosby-Year Book; 1998:203-257.
3. West JD. Introduction of a new rotary endodontic system: progressively tapering files. Dent Today. 2001;20:50-57.
4. Ruddle CJ. Shaping for success…everything old is new again. Dent Today. Apr 2006:25;120-127.
5. West J. Endodontic update 2006. J Esthet Restor Dent. 2006;18:280-300.
6. Ruddle C. The ProTaper Technique. Endodontic Topics. 2005;10:187-190.
7. West JD. Finishing: the essence of exceptional endodontics. Dent Today. Mar 2001;20:36-41.

As the founder and director of the Center for Endodontics, Dr. West continues to be recognized as one of the premier educators in clinical and interdisciplinary endodontics. He received his DDS in 1971 from the University of Washington, where he is affiliate associate professor. He received his MSD in endodontics  in 1975 at the Boston University Henry M. Goldman School of Dental Medicine, where he is a clinical instructor and was awarded the 1995 Distinguished Alumni Award. Dr. West has presented more than 400 days of continuing education in North America, South America, and Europe while maintaining a private practice in Tacoma, Wash. He coauthored “Obturation of the Radicular Space” with Dr. John Ingle in Ingle’s 1994 and 2002 editions of Endodontics and was senior author of “Cleaning and Shaping the Root Canal System” in Cohen and Burns’ 1994 and 1998 Pathways of the Pulp. Dr. West’s memberships include The American Academy of Esthetic Dentistry, The Northwest Network for Dental Excellence, and The International College of Dentistry. He is a Thought Leader for Kodak Digital Dental Systems and serves on the editorial advisory boards of the Journal of Advanced Esthetics and Interdisciplinary Dentistry, The Journal of Esthetic and Restorative Dentistry, Practical Procedures and Aesthetic Dentistry, and The Journal of Microscope Enhanced Dentistry.  He is the scientific endodontic editor for Boston University’s Communiqué and can be reached at (800) 900-7668 or johnwest@centerforendodontics.com.

Disclosure: Dr. West maintains a royalty position with ProTaper Rotary Files and Obturation Technology, DENTSPLY/Tulsa.