What do Dr. Herbert Schilder and Dr. Zvi Fudim have in common?
Fifty years apart, in two different dental disciplines, one architectural idea keeps recurring: work from the larger instrument at the coronal surface toward the smaller instrument at the working depth. This is the historical arc, in Dr. Zvi Fudim's own words \u2014 and where it lands now in implant surgery.
The editorial · by Dr. Zvi Fudim
Crown Down in dentistry.
Not too much, but one thing is for sure: the term “Crown Down.”
For many years, endodontists used the traditional Step-Back technique, preparing canals from the apex backward, using small instruments first and gradually enlarging the preparation. This was the standard way of thinking for decades.
In the late seventies, Dr. Herbert Schilder introduced the crown-down concept, which inverted the order of the instruments. Instead of starting with the smallest instrument, the preparation began coronally with the biggest one. Dr. Herbert Schilder helped establish this new philosophy in endodontics. Later, with the introduction of NiTi rotary files, crown-down root canal preparation became practical and eventually replaced the old Step-Back mentality.
The entire Crown Down revolution took approximately 15 years, from a new idea to a widely accepted clinical standard. Today, many dentists barely think about the old Step-Back method — it became history.
Implantology is now facing a similar moment.
For about 40 to 60 years, implantologists have been using the pilot-to-final ascending drilling sequence: starting with a small pilot drill, then increasing the drill diameter step by step until the final osteotomy is reached.
But normal does not always mean good.
Dr. Zvi Fudim applies a different logic to implant drilling. Instead of forcing the smallest drill to begin the entire preparation, Implant Crown Down addresses the hardest part first: the cortical bone. Once the cortical resistance is cleared, the trabecular bone can be prepared more safely and efficiently.
This change is especially important because Crown Down for implant drilling introduces solid tungsten carbide drills into implant osteotomy preparation. Just as NiTi helped crown-down endodontics become clinically practical, tungsten carbide allows a new drilling logic: sharper, harder, more wear-resistant, and designed for a different sequence.
The Step-Back technique lasted for years before crown-down became the new standard. Implantologists may also need time to move away from the pilot-to-final ascending method. However, today we have the internet, social media, clinical videos, webinars, digital publications, and instant communication between dentists around the world. What took dentists who practice endodontics 15 years will hopefully take implant dentists much less time.
So what do Crown Down, Dr. Herbert Schilder, and Dr. Zvi Fudim have in common?
They remind us that progress in dentistry often begins with one simple question:
Why are we still doing it the wrong way?
— End of editorial. Extended historical and material-science context follows below.
Extended context: the Schilder paper and what came before.
Before Schilder’s crown-down concept, endodontic instrumentation followed a step-back logic. The clinician negotiated the canal with a small stainless steel hand file to the working length, established a master apical file diameter, and then worked back coronally in progressively larger steps, finishing with the widest instrument at the coronal orifice. The apical portion was prepared first; the coronal flare came later. It was the industry-standard approach.
Dr. Herbert Schilder, then Professor and Chair of Endodontics at Boston University’s Henry M. Goldman School of Dental Medicine, argued in a 1974 Dental Clinics of North America paper for the opposite direction. Open the coronal third with a larger instrument first, then step down progressively with smaller instruments toward the apex. In the years that followed, Schilder refined the crown-down concept into a clinically taught technique — the version that would take hold in the late 1970s and 1980s and, ultimately, replace step-back.
The rationale was not novelty for its own sake. Working coronal-first accomplished three things a step-back sequence struggled with: it removed coronal interferences before the file was already at the apex (which reduces procedural errors like ledging and transportation), it limited apical debris extrusion (because the coronal space for irrigant and debris egress was created before apical cutting began), and it preserved the natural constriction near the apex. Schilder also defined the biological objectives of root canal preparation in the same paper — continuously tapering funnel form, apical constriction preserved, minimum enlargement, no procedural errors — and those objectives, together with the Crown Down direction, became the foundation of modern endodontic instrumentation.
The NiTi transition: when the material caught up to the technique.
Schilder’s Crown Down technique was correct immediately. It was also, immediately, hard. Stainless steel hand files could implement it, but only in the hands of a specialist willing to spend the chair time to pre-flare coronal segments manually, one file at a time, in each canal. In general-practice endodontics through the 1970s and 1980s, the technique was aspirational more than routine.
The change came from a material. In 1988, Harmeet Walia, William Brantley, and Harold Gerstein published an initial investigation of the bending and torsional properties of Nitinol root canal files in the Journal of Endodontics. Nickel-titanium (NiTi) was already known to metallurgy for its superelasticity; Walia and colleagues demonstrated it could take the shape of a canal file. The next few years established what NiTi made possible clinically: instruments that could negotiate curved canals without permanent deformation, and that could be driven rotationally rather than manually.
Dentsply commercialized the first widely-adopted NiTi rotary system (ProFile) in the early 1990s. Every major NiTi rotary system that followed — ProTaper, K3, WaveOne, Reciproc, TruNatomy, and dozens of others — implemented some version of Schilder’s Crown Down direction, because the direction is the biology, not a marketing distinction. What changed was the ergonomics: with NiTi rotary, a general practitioner could deliver a technique that had been mostly specialist territory for two decades.
This is the pattern that governs the whole argument. The technique and the material are separate things. Crown Down as an architecture existed in the late 1970s, long before NiTi was a canal file. But it became clinically routine only when the material substrate arrived. The gap between Schilder’s concept and general-practice adoption was roughly 15 years — the same 15 years the editorial above marks as the endodontic Crown Down “revolution.”
Implant osteotomy in 2026: the same argument, one field over.
Modern implant surgical kits use an ascending-diameter drill sequence: a small pilot drill to the working depth first, then progressively wider drills through the same osteotomy to the final diameter. Every major implant system — Nobel Biocare, Straumann, Zimmer Biomet / ZimVie, Astra Tech, BioHorizons, and every other — implements a variant of this ascending sequence. The pilot cuts through the dense cortex first at the smallest diameter, then wider drills widen the same site up to the final osteotomy.
This is analogous to the pre-Schilder step-back logic in endodontics. It works. It has been the standard for four decades. But it inverts the ideal mechanical loading of the drill: the smallest drill does the hardest work (dense cortical bone at the pilot stage), and each subsequent drill widens material that is progressively easier to cut. The consequence is measurable in clinical data: heat concentration at the cortex, drill wear concentrated at the smaller diameters, and the familiar cadence of steel drill replacement every 20 to 50 osteotomies.
The Crown Down implant osteotomy protocol takes the same architectural inversion Schilder made in the 1970s. The first drill is larger and matched to the implant diameter — it clears the cortical plate at the full working diameter, before any smaller instrument engages the site. The second drill is smaller and used only for the trabecular portion of the osteotomy, with the cortex already relieved. Two drills per site instead of four to six. The final diameter Nobel or Straumann or Astra Tech specifies for a given implant is reached by two passes, not five.
Endodontics: pre-Schilder Step-Back
- Small apical file first (working length)
- Wider files step-back coronally
- Coronal orifice opened last
- Apical debris extrusion elevated
Foundation of endodontics through the mid-1970s.
Endodontics: Schilder Crown Down (late 1970s → now)
- Coronal orifice opened first (larger instrument)
- Progressively smaller files apically
- Apical constriction preserved
- Debris extrusion reduced
Standard of care in every major NiTi rotary system.
Implantology: conventional ascending sequence
- Pilot drill first, smallest diameter
- Widening drills to the final diameter
- Cortex cut at every diameter step
- Steel drills, 4 to 6 changes per site
Foundation of every major implant surgical kit today.
Implantology: Crown Down 2-drill protocol
- Cortical drill first, matched to final diameter
- Trabecular drill second, smaller diameter
- Cortex crossed once at the final diameter
- Tungsten carbide, 2 drills per site
The direction is Schilder’s, one discipline over.
Why the material had to change first.
A conventional stainless steel implant drill would not survive a Crown Down osteotomy sequence for long. Once the cortex is opened at the full implant diameter with the first drill, the smaller-diameter trabecular drill is exposed to unsafe torsional stress if it hits residual cortical resistance or dense trabecular interference. Steel yields; small-diameter steel drills deform and eventually fail. The architecture only becomes clinically reproducible when the smaller drill is made of a material with fundamentally different mechanical properties.
Solid tungsten carbide is the answer. Its Vickers hardness sits roughly five times that of surgical stainless steel, its fracture toughness under torsional load is orders of magnitude higher than steel at the same drill diameter, and its thermal conductivity is enough that osteotomy heat conducts away from the cutting edge without depending on saline reaching the site — the same thermal property that makes tungsten carbide the natural material for guided-surgery osteotomies where saline through the sleeve is restricted.
The role tungsten carbide plays in the Crown Down implant protocol is the role NiTi played in the NiTi rotary transition of endodontics: the material that closes the gap between a correct technique and a technique that a general practitioner can perform reproducibly. In both cases, the technique existed before the material was widely available; in both cases, the material was what made the technique go from specialist territory to broadly clinical.
In the endodontic case, the gap between Schilder’s concept and the ProFile launch was roughly a decade and a half. In the implant case, the material was already there in the form of industrial tungsten carbide (WIDIA hard-metal, patented by Krupp in 1926 for metal-cutting applications), and it already existed in dental hardware for other purposes (finishing burs, restorative burs, laboratory milling). What did not exist was a drilling architecture designed around carbide’s specific mechanical properties. That’s where the Crown Down 2-drill protocol lives — the architecture built to make the material clinically safe.
Why the implant transition should be faster than the endodontic one.
The editorial makes a point worth taking seriously: the endodontic Crown Down transition took roughly 15 years because the diffusion mechanisms of the 1970s and 1980s were journals, dental-school lecture halls, hands-on courses at annual meetings, and word-of-mouth between clinicians. Technique change moved at print-cycle speed.
The 2020s carry the same technique-change dynamic across an entirely different diffusion substrate. Clinical procedure videos are on YouTube within hours of the case. Webinars pull thousands of live participants across time zones. Peer-reviewed journals publish online-first within weeks of acceptance. Dentist-to-dentist communication is instant across specialties and continents. Case-report threads on LinkedIn and Instagram have replaced conference poster sessions as the first line of clinical exchange.
The endodontic Crown Down transition took 15 years partly because the material took a decade to arrive and partly because the information architecture of dentistry was slower than it is now. The material for implant Crown Down is already available. The diffusion mechanisms are already in place. What’s left is the practice habit — and habit is the fastest of the three variables to change once the technique reaches a practitioner.
Related on the Crown Down site
The clinical protocol lives on the 2-Drill Protocol page. The material-science argument, with peer-reviewed citations, lives on Wear-Proof Implant Drills. The step-by-step surgical description lives on the Crown Down Drilling Technique page.
Frequently asked questions
Quick answers to questions clinicians ask most about this topic.
References
- 1.Schilder H. Cleaning and shaping the root canal. Dental Clinics of North America. 1974;18(2):269-296. The foundational paper introducing the Crown Down technique in endodontics.
- 2.Walia HM, Brantley WA, Gerstein H. An initial investigation of the bending and torsional properties of Nitinol root canal files. Journal of Endodontics. 1988;14(7):346-351. The seminal paper describing NiTi as an endodontic instrument material. doi:10.1016/S0099-2399(88)80196-1
- 3.Peters OA. Current challenges and concepts in the preparation of root canal systems: a review. Journal of Endodontics. 2004;30(8):559-567. Documents the transition from stainless steel hand files to NiTi rotary systems in clinical practice. doi:10.1097/01.DON.0000129039.59003.9D
- 4.Eriksson AR, Albrektsson T. Temperature threshold levels for heat-induced bone tissue injury: a vital-microscopic study in the rabbit. Journal of Prosthetic Dentistry. 1983;50(1):101-107. The 47°C thermal-necrosis threshold that governs implant osteotomy design. doi:10.1016/0022-3913(83)90174-9
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