Page 29 - The Beauty and Sorrow in Endodontics (WL and C/S)

#10, its ISO definition mean its cross-sectional diameter at D1 is 0.10mm (#15 is 0.15mm,

and so on). Therefore, even if #10 can reach RT without trouble, it might not be the case
with a #15 file. This is because the tip diameter of #15 is 50% larger than a #10 [(0.15-
0.10)/0.10]. The ISO design requires the D1 diameter to increase by 0.05mm every
increase in file size (from #10-60), therefore, the rate of increase varies with each size up.
The rate of increase is the highest from #10-15 (50%), with gradual decrease in the rate

as the file sizes get larger, eg. #30-35 (16.7%) [(0.35-0.30)/0.30], and #55-60 (9.09%)
[(0.60-0.55)/0.55]. Since the commonly used files at the initial cleaning and shaping steps
have a large rate of increase in diameter, this often causes headaches for many dentists at

the beginning of treatment. As a result, manufacturers have developed the so-called
“golden mediums”, which adds a #12 file between #10 and #15. But if you think about it,
knowing the basic concepts of the ISO system with 0.02 taper designs, cutting 1mm off
the tip of a #10 file would give you a #12 file; cut another 1mm off and you’ll get a #14
file, and so on. Similarly, take a #15 file and remove 1mm off the tip and you will have

made yourself a #17 file without having to spend money to buy those golden mediums.
One thing to note though, is if you do decide to modify your own files, remember to
adjust the sharp transition angle on the files as well to avoid perforating or damaging the

canal walls.

Dr. Schilder’s Patented Concept on Series 29

To combat this design flaw within the ISO system, Dr. Schilder had put forward an

idea to improvement the design concept, which suggests a constant rate of increase in the
tip diameter of each subsequent file. The Profile Series 29 is the product of this concept,
fixing the increase ratio at 29.17% for every subsequent file. This “fixed ratio” concept

has been patented, even if the manufacturer decides to use a ratio that is not 29.17%.
Based on the most commonly used ISO traditional stainless-steel files #10-60, the
first file in Series 29 has a tip diameter equivalent to ISO #10 (0.10mm), and the last file
to that of #60 (0.60mm). In the standard ISO system, enlarging the canals from #10 to
#60 requires 11 files, versus 8 in Series 29. It should be noted that 6 of these files are

frequently used for more delicate canals [ISO #10-35; Series 29 #1 (0.10) - #6(0.36)].
From then on, only two files (#7, #8) are needed to replace the five files in ISO #40-60
(Fig B7).

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