ISO/DIS 3630-1:2026(en)
ISO TC 106/SC 4/WG 9
Secretariat: DIN
Date: 2025-12-27
Dentistry — Endodontic instruments — Part 1: General requirements
Médecine bucco-dentaire — Instruments d'endodontie — Partie 1: Exigences générales
© ISO 2026
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Contents
5.4.4 Tip ………...........................................................................................................................................
8.3 Packaging ...................................................................................................................................................
Figures and Tables
Figure 1 — Dimensions and locations for Class 1 instrument (standard instrument: taper=02)
Figure 2 — Dimensions and locations for Class 2 instrument (taper instrument: taper other than 02)
Figure 3 — Dimensions and locations for Class 3 instrument (non-taper instrument: zero taper)
Figure 4 — Dimensions and locations for Class 4 instrument (Non-uniform taper instrument: more than one taper)
Figure 5 — Dimensions and locations for Class 5 instrument (Shape instrument: arc shape)
Figure 6 — Shank dimensions
Figure 7 — Apparatus for torque test
Figure 8 — Details of test chuck
Figure 9 — Apparatus for bending test
Figure 10 – Schematic of test device
Figure 11 – Test device design
Figure 12 – Dimensions for the R5 test device
Figure 13 – Dimensions for the R7.5 test device
Figure 14 - Plan view of test device
Figure 15 - Instrument positioning
Figure 16 - Three measuring points selection and rmin determination
Figure 17 -Marking (symbols) for endodontic instruments
Table 1 — Symbols to be used
Table 2 — Dimensions, size designation, and colour designation for Class 1 (standard instrument)
Table 3 — Shank tolerances
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 4, Dental instruments, Working group WG 9, Endodontic instruments in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 55, Dentistry, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 3630-1:2019), which has been technically revised.
The main changes compared to the previous edition are as follows:
— clarification of vocabulary and symbols to make it harmonize with the other parts of the 3630 standards.
A list of all parts in the ISO 3630 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.
Introduction
This document specifies general requirements and test methods for endodontic instruments. Other parts of the ISO 3630 series provide the specific requirements and test methods for specific endodontic instruments (enlargers, compactors, auxiliary instruments, shaping and cleaning instruments, and ultrasonic inserts). It also provides test methods for accuracy of electronic apex locators.
With the current use of nickel-titanium alloys for the manufacture of endodontic instruments, a need for adequate expertise in their safe use is recommended. Cyclic fatigue and subsequent breakage of engine-driven -titanium endodontic instruments remain an issue when practicing endodontic treatment. A test method is provided to evaluate the fatigue resistance of such instruments using a custom-made device.
This document provides guidance and information for the proper use of these instruments.
The sizes of the endodontic obturating points (cones) specified in ISO 6877 Dentistry — Endodontic obturating materials should coordinate with the corresponding sizes for the endodontic instruments which are specified in all parts of the ISO 3630 series.
Dentistry — Endodontic instruments — Part 1: General requirements
1.0 Scope
This document specifies general requirements and test methods for endodontic instruments used for specific purposes, e.g., enlargers, compactors, auxiliary instruments, shaping and cleaning instruments, and ultrasonic inserts. In addition, it covers general size designations, colour-coding,, identification symbols, and product information including marking, labeling, packaging, and instructions for use.
2.0 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 554, Standard atmospheres for conditioning and/or testing — Specifications
ISO 1797, Dentistry — Shanks for rotary and oscillating instruments
ISO 1942, Dentistry — Vocabulary
ISO 3630‑2, Dentistry — Endodontic instruments — Part 2: Enlargers
ISO 3630‑3, Dentistry — Endodontic instruments — Part 3: Compactors
ISO 3630‑4, Dentistry — Endodontic instruments — Part 4: Auxiliary instruments
ISO 3630‑5, Dentistry — Endodontic instruments — Part 5: Shaping and cleaning instruments
ISO 3630‑7, Dentistry — Endodontic instruments — Part 7: Ultra sonic inserts
ISO 3630‑8, Dentistry — Endodontic instruments — Part 8: Accuracy of electronic apex locators
ISO 8601‑1, Date and time — Representations for information interchange — Part 1: Basic rules
ISO 15223‑1:2016, Medical devices — Symbols to be used with medical device labels, labelling and information to be supplied — Part 1: General requirements
ISO 17664‑1, Processing of health care products — Information to be provided by the medical device manufacturer for the processing of medical devices — Part 1: Critical and semi-critical medical devices
ISO 20417:2021, Medical devices — Information to be supplied by the manufacturer
ISO 13402:2025, Surgical and dental hand instruments — Determination of resistance against autoclaving, corrosion and thermal exposure
3.0 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1942 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
endodontic instrument
dental device designed to explore, shape, clean and help obturate the root canal system
3.2
nominal size
general designation of an endodontic instrument (3.1) using the value of the extended diameters at the tip of the working part (3.11) or working surface (3.12) in hundredths of a millimetre and for shape instrument, the maximum diameter.
3.3
taper
variation of the outer diameter of the working part of an endodontic instrument, expressed in hundredths of a millimetre per millimetre of length (3.10)
3.4
standard instrument
endodontic instrument (3.1) having a uniform taper of 0,02 mm per millimetre of length of the working part (3.11) or working surface (3.12) throughout the range of available sizes
Note 1 to entry: The nominal sizes of Class 1 endodontic instruments are listed in Table 1.
Note 2 to entry: Some manufacturers may designate taper as a 2-digit number, e.g., ‘02’ or as a percentage, e.g., ‘2 %’.
3.5
non-standard instrument
endodontic instrument (3.1) which has either a tip diameter or shape, or both, other than that of an endodontic standard instrument (3.4)
3.6
taper instrument
endodontic instrument (3.1) which the sizes are determined by the tip sizes and have uniform tapers of the working part (3.11) or working surface (3.12) other than 0,02 mm per millimetre of length
3.7
non-taper instrument
endodontic instrument (3.1) having a cylindrical shape, i.e., zero taper, along the working part
3.8
non-uniform taper instrument
endodontic instrument (3.1) having more than one taper along the working part
3.9
shape instrument
endodontic instrument (3.1) having a contoured working part with continuously varying profile
3.10
tip
part of an endodontic instrument (3.1) which is intended as a tapered or rounded point or flat surface
3.11
working part
part of an endodontic instrument (3.1) which has a cutting surface
3.12
working surface
part of an endodontic instrument (3.1) that contacts obturation material
Note 1 to entry: This definition is used in ISO 3630-3.
3.13
operative part
part of an endodontic instrument (3.1) from the tip to the handle or shank
3.14
shaft
part of an endodontic instrument (3.1) between the handle or shank and the working part (3.11) or working surface (3.12)
3.15
handle
part of an endodontic instrument (3.1) which is held by the user’s fingers for manipulation of the instrument in the root canal system
3.16
shank
part of a rotary, oscillating or reciprocating endodontic instrument (3.1) which is designed to fit into the chuck of a dental handpiece
4.0 Classification and Symbols
4.1 Classification
For the purposes of this document, endodontic instruments are classified as follows:
Standard instrument
— Class 1: standard instrument (taper = 02);
NOTE: Some manufacturers can designate taper as a percentage, e.g., ‘2 %’.
Non-standard instrument
— Class 2: taper instrument (taper other than 02);
— Class 3: non-taper instrument (zero taper);
— Class 4: non-uniform taper instrument (more than one taper); and
— Class 5: shape instrument (arc shape).
4.1.1 Symbols
Table 1 — Symbols to be used
D | diameter of the projection of the working surface (3.12) at the tip. In hundredths of millimetre) |
dn | diameter of the endodontic instrument (3.1) at n mm from the tip |
ds | diameter of the shank (3.16) |
dw | diameter of the working part (3.11) |
ln | length of the endodontic instrument (3.1) at n mm from the tip |
lw | length of the working part (3.11) or working surface (3.12) |
lop | length of the operative part (3.13) |
lmin | Minimum length of the tip (5.2.4.2) |
5.0 Requirements
5.1 General
Specific endodontic instrument classes, such as enlargers, compactors, and auxiliary instruments, have unique shapes, which are not included in this document. These instruments are covered in separate parts of the ISO 3630 series.
5.1.1 Class 1: Standard instrument
5.1.2 Length
The length of the working part or working surface, lw,, shall be a minimum of 16 mm unless otherwise specified by the manufacturer (see Figure 1).
The length of the operative part, lop, shall be specified by the manufacturer, and shall be within ±0,5 mm of the specified length.
Test in accordance with 7.3.
Key
1 handle (X) (see 5.8.3.1)
2 shank (Xa) (see 5.8.3.2)
Figure 1 — Dimensions and locations for Class 1 instrument (standard instrument: taper=02)
5.1.3 Size designation and diameters
Table 1 gives the nominal sizes and dimensions for the working part or working surface of Class 1 (standard) instrument.
Figure 1 shows the measurement dimensions and locations for a Class 1 (standard) instrument. The nominal sizes of all endodontic instruments shall correspond to the values of D.
5.1.4 Colour designation
The colour marking on the handle or shank of a Class 1 instrument shall be in accordance with the requirements of Table 1.
NOTE: The colour marking on the handle or shank of instrument sizes not included in Table 1 is at the discretion of the manufacturer.
5.1.5 Tip shape
The shape of the tip is at the discretion of the manufacturer. The minimum length is 0,25 of D.
Table 2 — Dimensions, size designation, and colour designation for Class 1 (standard instruments)
Dimensions in millimetres
Nominal size | D | d3 | d3 Tolerance | d16 | d16 Tolerance | Colour designation |
06 | 0,06 | 0,12 | ±0,02 | 0,38 | ±0,02 | pink |
08 | 0,08 | 0,14 | 0,40 | grey | ||
10 | 0,10 | 0,16 | 0,42 | purple | ||
15 | 0,15 | 0,21 | 0,47 | white | ||
20 | 0,20 | 0,26 | 0,52 | yellow | ||
25 | 0,25 | 0,31 | 0,57 | red | ||
30 | 0,30 | 0,36 | 0,62 | blue | ||
35 | 0,35 | 0,41 | 0,67 | green | ||
40 | 0,40 | 0,46 | 0,72 | black | ||
45 | 0,45 | 0,51 | 0,77 | white | ||
50 | 0,50 | 0,56 | 0,82 | yellow | ||
55 | 0,55 | 0,61 | 0,87 | red | ||
60 | 0,60 | 0,66 | 0,92 | blue | ||
70 | 0,70 | 0,76 | ±0,04 | 1,02 | ±0,04 | green |
80 | 0,80 | 0,86 | 1,12 | black | ||
90 | 0,90 | 0,96 | 1,22 | white | ||
100 | 1,00 | 1,06 | 1,32 | yellow | ||
110 | 1,10 | 1,16 | 1,42 | red | ||
120 | 1,20 | 1,26 | 1,52 | blue | ||
130 | 1,30 | 1,36 | 1,62 | green | ||
140 | 1,40 | 1,46 | 1,72 | black |
5.2 Class 2: Taper instrument
5.2.1 Length
The lengths of the working part or working surface and of the operative part shall be specified by the manufacturer, and shall be within ±0,5 mm of the specified lengths.
Test in accordance with 7.3.
5.2.2 Tip shape
The shape of the tip is at the discretion of the manufacturer. The minimum length is 0,25 of D.
5.2.3 Size designation
The nominal size of the instrument shall be designated with the first two digits (three) for diameter identification and the second two digits (three) for taper identification.
5.2.4 Designation and diameters
Figure 2 shows the measurement dimensions and locations for Class 2 instrument.
The nominal sizes of Class 2 endodontic instrument shall correspond to the values of D (Table 1).
NOTE: The diameter and the tolerances are left at the discretion of the manufacturer.
NOTE: Nominal sizes other than those listed in Table 1 are permitted.
Key
1 handle (X) [see 5.8.3.1]
2 shank (Xa)[see 5.8.3.2]
Figure 2 — Dimensions and locations for Class 2 instrument (taper instrument: taper other than 02)
5.2.5 Taper designation
The taper designation for a Class 2 instrument shall be in number form (e.g., 04) [5.3.3.]
NOTE: Some manufacturers may designate taper as a percentage.
EXAMPLE The taper 04 designates 0,04 mm per millimetre of length or 4 %, and 12 designates 0,12 mm per millimetre of length or 12 %.
5.2.6 Diameter colour identification
The colour marking on the handle or shank of Class 2 instrument shall be in accordance with the requirements of Table 1.
NOTE: The colour marking on the handle or shank of instrument sizes not included in Table 1 is at the discretion of the manufacturer.
5.3 Class 3: Non-taper instrument
5.3.1 Length
The lengths of the working part or working surface and of the operative part shall be specified by the manufacturer and shall be within ±0,5 mm of the specified lengths.
For tip specifications refer to 5.3.2. Test in accordance with 7.3.
5.3.2 Size designation and diameters
Size designation and diameters shall follow the pattern of Table 1 but are not restricted to the sizes shown.
NOTE: Since the working part or working surface is cylindrical in shape, the D tip diameter is the diameter of the working part or working surface. The zero taper shape shown in Figure 3 is an example of a non-tapered diameter.
Key
1 handle (X)[see 5.8.3.1]
2 shank (Xa)[see 5.8.3.2]
Figure 3 — Dimensions and locations for Class 3 instrument
(non-taper instrument: zero taper)
5.3.3 Colour designation
The colour of the handle or shank marking of a Class 3 instrument shall be in accordance with the requirements of Table 1.
NOTE: The handle or shank colours of instrument sizes not included in Table 1 are at the discretion of the manufacturer.
5.3.4 Tip
The shape of the tip is at the discretion of the manufacturer. The minimum length is 0,25 of D.
5.4 Class 4: Non-uniform taper instrument
5.4.1 Length
The lengths of the working part and of the operative part shall be specified by the manufacturer, and shall be within ±0,5 mm of the specified lengths.
If the manufacturer specifies the total instrument length, it shall be within ±1,0 mm of the specified length. Test in accordance with 7.3.
5.4.2 Size designation
The instrument size shall be designated as in 5.3.4 and taper identification as in 5.3.5.
5.4.3 Diameter designation and diameters
The diameter and length for Class 4 instruments shall be identified by the manufacturer (see Figure 4)
Key
1 handle (X)[see 5.8.3.1]
2 shank (Xa)[see 5.8.3.2]
Figure 4 — Dimensions and locations for Class 4 instrument
(Non-uniform taper instrument: more than one taper)
5.4.4 Diameter colour identification
When colour-coding is used for diameter sizes, the colour sequence shall be white, yellow, red, blue, green, and black. This sequence shall be repeated for an endodontic instrument with more than six sizes.
NOTE: For taper sizes less than 01, one digit may be omitted. The third space is for a letter to indicate a non-uniform taper.
5.4.5 Tip shape
The shape of the tip is at the discretion of the manufacturer. The minimum length is 0,25 of D.
5.5 Class 5: Shape instrument (Arc shape)
5.5.1 Length
The lengths of the working part and of the operative part shall be specified by the manufacturer, and shall be within ±0,5 mm of the specified lengths.
If the manufacturer specifies the total length, it shall be within ±1,0 mm of the specified length.
NOTE: Shape instruments are defined in ISO 3630-2.
Test in accordance with 7.3.
5.5.2 Size designation and diameters
The size designation shall be in accordance with dimension D in Table 1, such that D is the maximum diameter of the working part. This requirement shall not preclude other sizes.
NOTE 1: The Class 5 instrument shown in Figure 5 is an example of the maximum diameter D. NOTE 2: The shape of the working part is at the discretion of the manufacturer.
Key
1 shank (see 5.8.3.2)
Figure 5 — Dimensions and locations for Class 5 instrument (Shape instrument: arc shape)
5.5.3 Colour designation
The colour of the handle or shank of Class 5 instrument shall be in accordance with the requirements of ISO 3630-2 clause 5.2
NOTE: The handle or shank colours of instrument sizes not included in Table 1 are at the discretion of the manufacturer.
5.6 Material
The operative part and the handle or shank, if one piece, shall be made of stainless steel or shape memory alloys which allows the instrument to meet the requirements of this document.
The material of the handle or the shank shall be made of any material at the discretion of the manufacturer which allows the instrument to meet the requirements of this document.
If the requirements of 5.9 are fulfilled, the endodontic instrument are considered to be also in accordance with the requirements of 5.7.
5.6.1 Dimensions
5.6.2 General
The dimensions are given in millimetres.
The dimensions designated D, dn, ds, and l shall be in accordance with the requirements of the specific instrument's respective Tables and Figures. Variations in shape and design are permitted.
Test in accordance with 7.1, 7.2, and 7.3.
5.6.3 Length
The length of the tip (3.10), working part (3.11) or working surface (3.12) and the operative part (3.13) of the instrument shall be in accordance with the requirements of the specific instrument clauses.
Test in accordance with 7.1, 7.2, and 7.3.
5.6.4 Handle and shank
Handle
The diameter of the handle is at the discretion of the manufacturer.
Shank
The shank shall be in accordance with ISO 1797 and the dimensions shown in Figure 6 and Table 3.
NOTE: The length and the tolerance of the diameter ds are based on the maximum revolutions per minute of the instrument and the material of the shank. This clause differs from ISO 1797. The minimum length ls of the shank is shown in Table 2.
Plastics shank
After reprocessing there will be no signs of deterioration of shank or shaft shall show no deformation, heat effects, nor colour change.
Dimensions in millimetres
Figure 6 — Shank dimensions
Table 3 — Shank tolerances
Material | Manufacturer’s recommended speed r/min | Shank diameter ds | Length ls (minimum) |
Metal | >1 000 | 2,35 + 0/−0,016 | 12,5 |
Metal | ≤1 000 | 2,35 + 0/−0,03 | 9,5 |
Plastics | ≤1 000 | 2,35 + 0/−0,05 | 11 |
5.7 Mechanical requirements
5.7.1 Resistance to fracture by twisting and angular deflection
The endodontic instrument shall meet the requirements specified in ISO 3630-2 to ISO 3630-5. Test in accordance with 7.4.
5.7.2 Stiffness (Resistance to bending)
The stiffness (resistance to bending) shall be in accordance with the requirements specified in ISO 3630-2 to ISO 3630-5.
Test in accordance with 7.5.
5.7.3 Handle and shank security
If the handle or shank and the operative part are not in one piece, the handle or shank shall be securely affixed to the shaft. The shaft shall have no axial movement greater than 0,02 mm from the handle or shank after an axial force of 20 N is applied. The shaft shall not twist within the handle or shank when a torque of 35 mN·m is applied.
Test in accordance with 7.6.
5.7.4 Resistance to fracture by cyclic fatigue
The number of cycles to fracture, Cf, shall be greater than the minimum value, Cmin. where
Cmin | is the required minimum number of cycles before fracture, but at a minimum of 200 cycles. |
Cf | is the measured number of cycles at fracture Test in accordance with 7.7. |
6.0 Sampling
Test 10 instruments of each size. If all 10 samples pass, the product passes. If eight or fewer samples pass, the product fails. If nine samples pass, test 10 additional samples. When 10 additional samples are required to be tested, all 10 shall pass for the product to comply. If a different sample size is tested, it shall be justified.
Note: In some case if more sample sizes are required, for example during product development validation where 30 samples may be required.
7.0 Measurement and test methods
7.1 Visual inspection
Carry out visual inspection at normal visual acuity without magnification, unless otherwise specified.
7.1.1 Test conditions
Condition the apparatus and the endodontic instruments to be tested, in accordance with ISO 554 at (23 ± 2) °C for a period of at least 1 h prior to testing. Maintain these conditions during testing.
NOTE: The resistance to fracture by twisting and angular deflection, stiffness and cyclic fatigue tests might be realized at a different set temperature (+/-2 °C) if duly justified.
7.1.2 Measurement of dimensions
7.1.3 Principle
The measurement of dimensions of endodontic instrument includes diameters, tapers, lengths, and angles.
7.1.4 Measuring device
For the operative part, use a device with an accuracy of ±0,001 mm such as an optical comparator, shadowgraph, measuring microscope, dial gauge, or other suitable device. For the shank or shaft, use a device that has an accuracy of ±0,002.
7.1.5 Procedure
Insert the endodontic instrument to be measured into the measuring device. Measure the length lw and the diameters D and dn. If the working part or working surface length lw is less than 16 mm measure the second diameter at 1 mm from the end of the working part or surface.
NOTE: As an alternative to measuring the D diameter the d3 diameter can be measured at a location 3,0 mm from the tip.
Calculate the tip dimension (diameter) from the projection of the taper of the working part or surface onto a plane at the tip of the instrument (datum line), which is perpendicular to the long axis (centre-line) of the instrument.
7.1.6 Taper calculation
Calculate the taper by subtracting the diameter d3 from the diameter d16 and dividing by 13.
endodontic
EXAMPLE: For a standard instrument size 10 (see Table 1), d3 = 0,16 mm, d16 = 0,42 mm, taper = (0,42 − 0,16) / 13 = 0,02.
NOTE: Taper tolerance is controlled solely by the tolerance of the specified diameters.
7.2 Resistance to fracture by twisting and angular deflection
7.2.1 Principle
The test of resistance to fracture of an endodontic instrument is performed by measuring the maximum torque and angular deflection for each size. [7.5.2]
7.2.2 Material
The test applies to endodontic instruments, which are specified in ISO 3630-5, of size equal to or less than a diameter of 0.564 mm at 3 mm from the tip.
7.2.3 Apparatus
7.4.3.1 Apparatus for torque test, such as shown in Figure 7 or other suitable device, consisting of the following parts:
7.4.3.1.1 Low-speed reversible geared motor capable of revolving the test piece at 2 r/min.
7.4.3.1.2 Torque-measuring device fixed on two linear ball bearings mounted on the shaft of the device.
7.4.3.2 Chuck with jaws made from metallic materials used to clamp the test piece 3,0 mm from the tip and coaxial with the torque axis (see Figure 8).
7.4.3.3 Separate amplifier for controlling the operation of the motor.
7.4.3.4 Digital display or strip chart recorder for recording the torque and angular deflection.
7.4.3.5 Wire cutter, suitable for cutting an endodontic instrument.
Dimensions in millimetres
Key
1 reversible gear motor
2 chuck with hardened steel jaws
3 chuck with metallic jaws
4 torque measuring device
5 linear ball-bearing
6 instrument (test piece)
Figure 7 — Apparatus for torque test
7.2.4 Procedure
If necessary, remove the handle or shank with a suitable wire cutter at the point at which it is attached to the shaft of the endodontic instrument (test piece). Calibrate the torque-measuring device for the torque range of the sample to be tested. Set the test piece into the chuck of the geared motor end leaving a maximum of 1 mm from the working part or working surface of the test piece. Tighten the chuck and slowly slide the torque- measuring device along the linear bearing until the tip of the test piece enters 3 mm into the jaws of the chuck. Check to ensure that the test piece is straight and centered into the jaws (see Figure 8). Tighten the chuck, ensuring that the test piece has not been distorted or damaged.
Activate the geared motor in steps until the torque digital display or the strip chart recorder shows a zero reading.
NOTE: This is necessary as clamping may induce a pre-stress in the test piece from the handle or shank.
Ensure that the geared motor is set for the same rotation direction as instrument normal operating, viewed from the test piece shank end, activate the device. Record the maximum torque and angular deflection at failure for each test piece.
NOTE: The device shown is designed to stop the operation when the test piece fails.
Dimensions in millimetres
Key
A chuck with hardened steel jaws
B chuck with metallic jaws
C instrument (test piece)
Figure 8 — Details of test chuck
7.2.5 Expression of results
Express the maximum torque in millinewton metre (mN·m) and the angular deflection in degrees.
7.3 Stiffness (resistance to bending)
7.3.1 Principle
The determination of stiffness is performed by bending the endodontic instrument through 45 degrees.
7.3.2 Material
The test applies to an endodontic instrument, which are specified in ISO 3630-5, of size equal to or less than a diameter of 0,564 mm at 3 mm from the tip.
7.3.3 Apparatus
7.5.3.1 Apparatus as described in 7.4.3, with the modification of the clamping jaws and the bending device or catch pin as shown in Figure 9.
7.5.3.2 Separate amplifier for controlling the operation of the motor.
7.5.3.3 Digital display or strip chart recorder for recording the torque.
7.5.3.4 Wire cutter, suitable for cutting an endodontic instrument.
7.3.4 Procedure
Remove the handle or shank from the endodontic instrument with a wire cutter at the point at which the handle or shank is attached to the operative part of the endodontic instrument.
Set the amplifier (7.5.2.2) to stop at a pre-selected angular deflection of 45°.
Set the chuck onto the shaft of the torque-measuring device. Set the tip of the test piece into the jaws of the chuck perpendicular to the axis of the motor to a depth of 3 mm. Tighten the chuck. Mount the catch pin onto the motor shaft. Slide the torque-measuring device along the linear ball bearing until the test piece is located above the rotating pin. Rotate the motor in the correct direction in stages until the catch pin is lightly touching the test piece. Ensure that the display shows zero. Activate the torque-measuring device.
Record the applied torque for each instrument tested.
Dimensions in millimetres
Key
1 reversible gear motor
2 stop
3 torque measuring device
4 catch pin
Figure 9 — Apparatus for bending test
7.3.5 Expression of results
Express the stiffness in millinewton metre (mN·m).
7.4 Handle or shank security
7.4.1 Principle
The determination of the handle or shank security includes tests of the axial movement or twist strength.
7.4.2 Apparatus
7.6.2.1 Apparatus as described in 7.4.3 or another suitable normal laboratory device.
7.6.2.2 Torquemeter
7.4.3 Preparation of test sample
Select ten instruments of each class and size and test for axial movement.
Select a further ten instruments of each class and size and test for twist strength.
7.4.4 Procedure
Axial movement
Measure and record the length of the operative part. Grasp the operative part within 1 mm of the handle or shank. Support the handle or shank to prevent axial movement without applying any restriction to the operative part. Apply the force axially for 30 seconds. Measure the length of the operative part to determine evidence of axial movement.
NOTE: Excluded from this test are paste carriers with a spiral between the working part and the shank, which are designed to fracture at this point if safe torque limit is exceeded.
Twist strength
Mount the handle or shank into the chuck of a torquemeter. Grip the handle or shank along a part behind the extension of the operative part. Insert the shaft of the operative part of the instrument. Twist the instrument in a clockwise motion when looking down from the tip to the handle or shank end.
Rotate the torque meter until the operative part slips within the handle or shank or until the minimum torque is obtained.
NOTE: For wire diameters up to 0,60 mm, the shaft can twist before slippage within the handle or shank. Excluded from this test are compactors, designed to compact obturation materials in the root canal system manually used in an apical/lateral direction.
Expression of results
For axial movement, record the change of length of the operative part in mm. For twist strength, record the torque in millinewton metres (mN·m).
7.5 Resistance to fracture by cyclic fatigue
7.5.1 Principle
The test method is based on the free rotation of an endodontic instrument with a specific curvature until fracture.
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a) locking device open | b) locking device closed |
Figure 10 — Schematic of test device
7.5.2 Material
The test applies only to engine driven nickel titanium endodontic instruments of size equal to or less than a diameter of 0,65 mm at 3 mm from the tip.
7.5.3 Apparatus
Test device
A schematic diagram of the test device is shown in Figure 10 a), test device with the locking feature open; Figure 10 b), test device with the locking feature closed.
Two test devices are used, one with a radius of 5 mm [Figure 11 a), R5 device] and one with a radius of 7,5 mm [Figure11 b), R7,5 device].
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a) Radius of 5 mm | b) Radius of 7,5 mm |
Figure 11 — Test device design
Figure 12 shows the dimensions of the test device with a radius of 5 mm.
Figure 12 — Dimensions for the R5 test device
Figure 13 — Dimensions for the R7,5 test device
A plan view of the test device is shown in Figure 13.
Figure 14 — Plan view of test device
Locking device
A cover locks the instrument into the jig [Figure 10 b)].
Driving system
The instrument is driven by an electric motor.
Cooling device
Since the cyclic fatigue test is exothermic, a cooling device is required to maintain a constant temperature.
NOTE: compressed air at 200 kPa is suitable.
Ruler, protractor, and thermometer
A ruler with a precision of 0,1 mm, a protractor with a precision of 1° and a thermometer with a precision of 1 °C.
7.5.4 Preparation of test samples
Select at random 10 nickel titanium endodontic instruments from the product validation manufacturing lot. Test each size (diameter) of that lot.
7.5.5 Procedure
Select the appropriate test device based upon the test diameter (d3) of the instrument to be evaluated. For instruments with d3 ≤ 0,50 mm use the R5 test device, and for instruments with d3 >0,50 mm and ≤0,65 mm, use the R7,5 test device.
Place the instrument such that the tip projects approximately 1 mm from the guiding groove (Figure 15). Ensure that the instrument rotates freely and is not blocked or gripped within the groove.
Figure 15 — Instrument positioning
Determine the minimum radius of the instrument (rmin), accomplished by means of a template or a microscope, by selecting three points along the central axis of the instrument, the first one at 30° from the base horizontal line of the jig, the second one at 45° and the last one at 60° (Figure16).
Figure 16 — Three measuring points selection and rmin determination
Record the ambient temperature (Tt), preferably 23 °C with a range ±2 °C, which shall be maintained during the test.
Record if the temperature deviates outside the range ±2 °C during the test.
Direct the compressed air stream (clause 7.7.3.4) onto the test device, rotate the instrument with the motor at the speed specified by the manufacturer, and record the number of cycles at fracture (Cf).
Measure the diameter of the instrument at the point of breakage, dbreak. Calculate the deformation of the instrument, | ε, according to the formula.
alternative formula 
expressed in %
Verify that the deformation, ε, is >2 % and <8 %. If the deformation is outside these limits, discontinue testing.
NOTE: The test is only valid for instruments within the above defined range of deformation. If the instrument is outside the above deformation limits, then the test is invalid.
For deformation, ε, lower than 2 %, or very fine instruments, those instruments will last for a very long time. Testing such an instrument doesn’t t bring more safety to the clinical usage. For deformation larger 8 %, or big size instrument shall be used in curved canal
Determine the austenite transformation finish temperature, Af, of the instrument, either as given by the raw material supplier, or based on either the free recovery method (ASTM 2082) or the DSC test method (ASTM F2004-17). Apply a correction coefficient, CT, using either method:
a) Free recovery method
if 
if 
+ 30 °C
b) Differential Scanning Calorimetry method
if 
- 20 °C
if
+10 °CCalculate the required minimum number of cycles to fracture, Cmin, using the formula:
Where:
Cmin is the required minimum cycles to fracture
CT is the correction coefficient for the austenite transformation temperature
ε is the deformation of the instruments expressed in %
7.5.6 Results
Report the required minimum number of cycles to fracture (Cmin) and the measured number of cycles to fracture (Cf ).
If the deformation (ε ) of any instrument was calculated to be <2 % or >8 %, report the size of the instrument, the calculated deformation value, and assign ‘Not applicable’ to the result of the cyclic fatigue test.
7.6 Resistance to processing/reprocessing
Endodontic instruments may be reusable or single use.
7.6.1 Principle
The content and detail of the information to be provided to the user for processing (sterilization)/ reprocessing (cleaning, sterilization and sterile storage) of an endodontic instrument (3.1) used intraorally shall be based on risk analysis for potential transmission of infectious microorganisms including blood-borne pathogens. This includes processing a non-sterile endodontic instrument (3.1) from its packaging.
Classification information on processing of an endodontic instrument (3.1) to be provided by the manufacturer shall be in accordance with ISO 17664-1 .
7.6.2 Procedures
Carry out the number of reprocessing cycles permitted in the manufacturer’s instructions. If the manufacturer makes no indication of the number of reprocessing cycles permitted, carry out 10 cycles according to ISO 13402:2025.
8.0 Product information
8.1 Marking (symbols)
Marking a symbol, if used on a handle or shank, on the packaging, or in manufacturer’s literature, shall be in accordance with Figure 17.
Figure 17 — Marking (symbols) for endodontic instruments
8.1.1 Labeling
Each package of endodontic instruments shall be labeled with at least the following information:
a) name of manufacturer or distributor;
b) type of instrument(s), product identification;
c) length of operative part;
d) for Class 1 instruments only, the length of the working part or working surface if less than 16 mm;
e) nominal diameter and taper designation of Class 2 instruments, in accordance with 5.3.3;
f) lot number;
g) if the instruments are not visible, the number of instruments in the unit package;
h) material of the operative part;
i) whether the instruments are intended for single-use;
j) when the package is sterile, marked with the symbol for "Sterile" in accordance with ISO 15223-1;
k) "Do not use if package is damaged" (Use ISO 15223-1:2016, Table 1, Symbol 5.2.8,);
l) when the package is marked sterile, the expiry date expressed as year and month according to ISO 8601; and
m) a unique device identifier (UDI), if necessary.
8.1.2 Packaging
Endodontic instruments shall be packaged in unit packs of sets of instruments or as single instruments that protect the contents from damage and, where sterility is claimed, maintain sterility during handling.
8.1.3 Instructions for use
Instructions for use (ISO 20417:2021, 3.11) shall include at least the following information:
a) name and address of manufacturer or distributor;
b) type of endodontic instrument;
c) recommended method of use of rotary instrument, including rotational speed;
d) if the package is not sterile, the recommended method(s) for sterilization/disinfection; and
e) if reprocessing is claimed, the recommended reprocessing instructions, as required by ISO 17664-1.
Bibliography
[1] ISO 3274, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Nominal characteristics of contact (stylus) instruments
[2] ISO 6876, Dentistry — Endodontic sealing materials
[3] ISO 6877, Dentistry — Endodontic obturating materials
[4] ISO 13402, Surgical and dental hand instruments — Determination of resistance against autoclaving, corrosion and thermal exposure
[5] ISO/TR 3630‑6, Dentistry — Endodontic instruments — Part 6: Numeric coding system
