Dr. Wm. Ben Johnson
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There was a great deal of interest in the WaveOne Reciprocating File at the DENTSPLY Tulsa Dental Specialties booth during the recent American Association of Endodontists (AAE) annual session. It was the product’s first official preview in the U.S. Judging from the attention, it’s safe to say it was a successful launch.
For a product just being introduced, the WaveOne concept has a long history. It was first conceived in the late ’90s as a mechanized form of “balanced forces technique” to compete with rotary NiTi. Few clinicians — other than Gianluca Gambarini, Pierre Machtou, and myself — gave the idea much consideration. There were two major reasons: Rotary NiTi files skyrocketed to popularity and maintained that status; and, DENTSPLY owned the patent for the movement and reportedly had more than 90% of the market at the time they were introduced.
With such success, there was little motivation to introduce a new concept. However, in 2008 Ghassan Yared published an article that kindled renewed interest that led to action. In his article, Yared described this alternating clockwise/counter-clockwise motion that has a greater degree of rotation in the cutting direction than the relieving direction, which with repeated movements results in the file making slow revolutions. Yared demonstrated the ability to prepare almost any small canal from orifice to apex using a single instrument.
Ultimately, DENTSPLY put together a team of endodontists to work with design engineers at DENTSPLY’s Maillefer division to optimize the movements of the motor and design the best instrument for use with this motion.
Many files work in this reciprocating mode to some degree. The real challenge for the team was grasping a greater understanding of file attributes in a reciprocal motion.
Evaluation of a series of prototypes led to the realization that the optimal design should cut aggressively in one direction (the cutting stroke) and be passive in the other (the relieving movement).
After determining the cross-sectional shape, adjustments were made to rake angle, helical angle, and pitch to accommodate the additional stresses put on the shaft due to the cross-sectional shape and reciprocating action. It truly is possible to choose from one of the three sizes (21/.06, 25/.08, or 40/.06) and progress from orifice to apex without changing instruments.
Goals of instrumentation
Achieving efficiency and efficacy were certainly among the goals for this new product/technique. Several studies have been conducted aimed at substantiating those goals. The objective of developing convenience with instrumentation is to create a tapering preparation from orifice to apex without transportation of the canal at the apex.
Studies performed at Nova Southeastern University using Micro CT reconstruction demonstrated perfect centering of the preparation without apical transportation, and in most cases the use of only one instrument per tooth. Research also demonstrated less instrument separation, which is owed to the unique reciprocating movement that prevents or delays the instrument’s advancing from plastic deformation to its elastic limit.
The elimination of procedural errors (i.e., broken instruments, transportation, perforation, and decreased working time), were demonstrated by studies at Nova, the University of British Columbia, and the University of Tlaxcala in Mexico. Little or no apical debris was found in studies conducted at Nova and Tlaxcala.
Studies have been conducted in a short time confirming the attributes of this technique even prior to reaching the market place.
Its only perceived drawback is that it requires a special motor. However, this motor also performs normal rotary movements and is preprogrammed for use with all DENTSPLY instrumentation systems.
“Quality is everything; time is money” was my charge to students over the years. WaveOne delivers.
Dr. Wm. Ben Johnson serves as a clinical professor at several universities and is known worldwide for his lectures on endodontics, and as the inventor of Thermafil obturators and ProFile hand/rotary instruments. He has been instrumental in developing many others. Reach him at [email protected].