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Why geometry matters most

Dr L. Stephen Buchanan
Dr L. Stephen Buchanan, USA

Dr L. Stephen Buchanan, USA

Thu. 16. April 2009

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Shortly after the excitement of the rotary file revolution wore off, the next frontier in shaping technology became the search for faster cutting efficiencies. This is very understandable and similar to our continuing search for faster and faster computers.

However, experienced clinicians started seeing overfills from transportation, shortened canals, apical ripped canal termini, over-shaped coronal regions and cyclic fatigue failures that hadn’t occurred with their safer, slower files. The first-order question in file selection became, 'safe or fast?' Landed-blade instruments with radiused-tip geometry were much safer in terms of avoidance of transportation, but non-landed blades with aggressive cutting tips were faster cutting.

The advent of GTX Files with M-Wire has eliminated that difficult decision — they are the first rotary shaping instruments that deliver speed of cutting with safety from transportation and breakage.

M-Wire, a new rhombohedral-phase nickel titanium metal used in GTX Files, has radically improved their resistance to cyclic fatigue. However, Dentsply/Tulsa is not the only company with R-phase NiTi (the sweet spot between austenite-phase and martensite-phase NiTi). While R-phase NiTi will become the new industry standard for addressing cyclic fatigue, it will never solve the problem of dangerous file geometries.

The radial lands on GTX Files have been optimized by varying the width of those lands along the length of the file. This geometrical change vastly improves cutting efficiency without derangement of the canal path, a claim that no file set without lands can make. Furthermore, the decreased flute angle has significantly increased GTX File’s flexibility over other landed instruments, simultaneously doubling the chip space between the flutes for longer cutting time before clogging.

Another important, yet underappreciated, design feature of GTX Files is their limited maximum flute diameter. Keeping the cutting flute diameters limited to 1 mm controls the amount of coronal enlargement during the shaping procedure — critical to the maintenance of the structural integrity of roots and to the avoidance of strip perforation.

All of these innovations in design geometry have resulted in a file set that typically cuts ideal shape in most canals with one to three instruments, and in as little time as 30–45 seconds. That is why geometry matters.

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