ISO/DIS 23401-2:2026(en)

ISO/TC 106/SC 2

Secretariat: ANSI

Date: 2025-12-01

Dentistry— Denture lining materials — Part 2: Soft type materials for short-term use

© ISO 2026

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 Classification 2

4.1 Types 2

4.2 Classes 2

5 Requirements 2

5.1 Shore A0 hardness 2

5.1.1 Shore A0 hardness at 2 h 2

5.1.2 Shore A0 hardness at 7 d 3

5.2 Consistency 3

5.3 Detail reproduction 3

6 Sampling 3

7 Test methods 3

7.1 Ambient conditions for testing 3

7.2 Shore A0 hardness 3

7.2.1 Apparatus 3

7.2.2 Procedure 4

7.3 Consistency test 5

7.3.1 Test conditions 5

7.3.2 Apparatus 5

7.3.3 Test procedure 5

7.4 Detail reproduction test 6

7.4.1 General 6

7.4.2 Apparatus and materials 6

7.4.3 Procedure 6

8 Requirement for packaging, marking and instructions supplied by the manufacturer 8

8.1 Packaging 8

8.2 Marking and manufacturer's instructions for use 8

Bibliography 10

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).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

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This document was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 2, Prosthodontic materials, 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 first edition of ISO 23401-2 cancels and replaces ISO 10139-1:2018 which has been technically revised.

The main changes compared to the previous edition are as follows:

—  a new standard number has been given.

—  in the Introduction, an explanation of the purpose of the grouping work has been added.

— a correction of position of indenter points and key in Figure 1

A list of all parts in the ISO 23401 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

ISO 23401 consists of the following parts, under the general title Dentistry – Denture lining materials.

— ISO 23401-1

— ISO 23401-2: former ISO 10139-1

— ISO 23401-3: former ISO 10139-2

The purpose of denture lining materials is to improve the fit of dentures to the oral mucosa. The materials can reline the denture the same day. Thus, they can be a useful material for the general denture patients and especially for bedridden patients who may have no access to dental surgery.

Denture lining materials are classified in hard type and soft type depending on the hardness of the material. The hard type materials are mainly used when the denture in use no longer fits the morphology of the oral mucosa, while the soft type materials are used for patients who are particularly susceptible to pain in the oral mucosa, and there are two types of materials: short-term materials and long-term materials, depending on the period of use in the mouth.

Clinically, soft type denture lining materials for short-term use are used commonly as tissue conditioners and as temporary soft lining materials. Furthermore, some materials are also indicated for use in functional impression taking. Therefore, the tests are designed to cover the more common usages.

It is recognized that the short-term material, when used as a tissue conditioner, is commonly changed every few days with the aim of returning the mucosa to a healthy condition as quickly as possible. As a temporary soft lining, the material is commonly placed in immediate dentures and in dentures that need to be modified as part of implant treatment. Therefore, the specification has been so designed to necessitate that a material exhibit the required properties over a 7 d period. It is of course recognized that there are a number of clinical situations where it is appropriate to retain the soft lining in the denture for periods longer than 7 d. It is also recognized that manufacturers may wish to provide more than one set of times, temperatures, proportions and procedures to mix or prepare the material properly in order that the material can satisfy the requirements of more than one type or class. In addition, as the functional impression, the detail reproduction, hardness, and consistency also necessary for this type of materials.

On the other hand, denture lining materials intended for chairside use are widely used in clinical practice. Therefore, ISO 23401-1:2023 was developed and published, which specifies requirements and test methods for chairside denture lining materials for hard type.

Subsequent discussions on the need to develop standards for chairside denture lining materials for soft type resulted in a confirmation and agreement that no new standards would be developed, as these are covered by ISO 10139-1:2018 and ISO 10139-2:2016. Based on this resolution, it was decided to review the title of the standard. Additionally, the possibility of integrating standards for denture lining materials including ISO 10139-1:2018 and ISO 10139-2:2016 will be considered.

Specific qualitative and quantitative requirements for freedom from biological hazard are not included in this document, but it is recommended that, in assessing possible biological or toxicological hazards, reference be made to ISO 10993-1 and ISO 7405.

Dentistry — Denture lining materials — Part 2: Soft type materials for short-term use

This document specifies requirements for soft type denture lining materials suitable for short-term use, including functional impression taking using existing removable prosthesis, and the test methods to determine compliance with these requirements. This document also specifies requirements for packaging, product marking, and manufacturer instructions for use.

This document is not applicable to hard type denture lining materials or soft type denture lining materials for long-term use.

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 1942, Dentistry — Vocabulary

ISO 3696:1987, Water for analytical laboratory use — Specification and test methods

ISO 48‑4, Rubber, vulcanized or thermoplastic — Determination of hardness — Part 4: Indentation hardness by durometer method (Shore hardness)

ISO 8601‑1, Date and time — Representations for information interchange — Part 1: Basic rules

ISO 20795‑1, Dentistry — Base polymers — Part 1: Denture base polymers

For the purposes of this document, the terms and definitions given in ISO 1942, ISO 20795-1 and the following apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

denture lining material

denture base lining material

dental material designed to be used on the intaglio surface of a denture base to modify its adaptation to soft tissues

[SOURCE: ISO 1942:2020, 3.3.5.1, modified — A preferred term has been added.]

3.2

soft type denture lining material

denture lining material (3.1) bonded to the intaglio surface of a denture base to reduce trauma to the supporting tissues

Note 1 to entry: A cured soft type denture lining material is softer than a cured denture base material.

Note 2 to entry: A soft type denture lining material for short-term use (3.3) can be used as a tissue-conditioning material when placed in the intaglio surface of a denture base and intended to be in contact with the denture-supporting mucosa, commonly for a period of up to 7 d, with the aim of assisting its return to a healthy condition.

3.3

short-term use

use normally for a continuous period of between 60 minutes and 30 days

3.4

functional impression taking

use of a soft type denture lining material (3.2) to take a functional impression using existing removable prosthesis

Soft type denture lining materials for short-term use shall be classified into the following types in accordance with Shore A0 hardness test at 2 h (5.1.1) as determined in accordance with 7.2.

— Type A: soft materials;

— Type B: extra soft materials.

The materials shall be further subdivided into classes in accordance with consistency (5.2) as determined in accordance with 7.3:

— Class 1: medium flow materials;

— Class 2: high flow materials.

When 2 h old test specimens are subjected to the Shore A0 hardness test in accordance with 7.2, the individual mean Shore A0-value for three specimens of the material shall conform to the requirements in Table 1. If only two or fewer specimens meet the requirement, the material shall be deemed not to conform to this document.

Table 1 — Shore A0 hardness

The individual mean Shore A0 hardness at 7 d shall be no higher than 60. If only two or fewer specimens meet this requirement the material shall be deemed not to conform to this document.

When specimens are subjected to the consistency test in accordance with 7.3, at least three of the four specimens of the material shall conform to the requirement for the relevant type as shown in Table 2. If only one or two specimens meet the requirement, the material shall be deemed not to conform to this document.

Table 2 — Flow measured by the consistency method

This requirement applies only to materials which are claimed also for functional impression taking. When tested in accordance with 7.4, the detail of reproduction shall be at least 75 µm, line c in Figure 2.

The test sample shall consist of a retail package, or packages, from the same batch and containing enough material to carry out the specified tests, plus an allowance for any repeat tests, if necessary.

Conduct all tests at (23 ± 2) °C and relative humidity of 30 % to 70 % unless otherwise stated.

7.2.1.1 Timer device, accurate to 0,1 s.

7.2.1.2 Mould, suitable for producing test specimens of 50 mm to 55 mm diameter and (8 ± 0,5) mm thickness, made of smooth metal or using a polymer disc as a template.

NOTE A mould release agent, e.g. Polytetrafluoroethylene (PTFE) spray, can be used to avoid the adherence of material to the mould.

7.2.1.3 Water bath, capable of being maintained at (37 ± 1) °C, with water in accordance with grade 2 of ISO 3696:1987.

7.2.1.4 Stand, capable of supporting the durometer pressure-foot surface parallel to the test piece support table.

7.2.1.5 Shore A0 hardness equipment, in accordance with ISO 48-4.

7.2.1.6 Ruler, with subdivision of accuracy 0,5 mm.

Preparation of test specimens

Prepare each test specimen in the mould cavity in accordance with the manufacturer’s instructions. Fifteen minutes ±30 seconds from start of mixing, as timed using a timer device (7.2.1.1), immerse the specimens with the mould (7.2.1.2) into the water bath (7.2.1.3) at (37 ± 1) °C for 2 h. Prepare three test specimens.

NOTE A non-stick foil can be helpful to generate a flat surface.

Key

1 specimen, diameter 50 mm to 55 mm

2 indenter points, ≧15 mm from the edge and ≧6 mm apart

Figure 1 — Shore A0 hardness specimen and testing points

Shore A0 hardness test, 2 h specimen

After (120 ± 5) min immersion, remove the test specimen from the mould and measure the Shore A0 hardness as described below within 3 min after having removed the specimen from the water bath. Place the specimen on a flat and solid base. Using the stand (7.2.1.4), lower the Shore A0 hardness tester (7.2.1.5) slowly onto the surface of the specimen, ensuring that the specimen surface is coplanar with the surface of the hardness tester, until the indenter foot just touches the specimen surface. Record the values 5 s after loading, using a timer device (7.2.1.1). Repeat the test using four more loading points ensuring that no measurement is made closer than 6 mm to a previous one, as determined by a ruler (7.2.1.6). All the loading points shall be at least 15 mm inside from the edge of the specimen. Each loading point shall be 90° from another loading point and the 5th point shall be on the centre of the specimen (see Figure 1).

Return the specimens to the water bath at (37 ± 1) °C and maintain them for an additional 7 d ± 5 h.

Carry out the test on all three specimens, and calculate the mean of the five Shore A0 values for each specimen.

Shore A0 hardness test, 7 d specimen

Remove the specimen from the water bath 7 d ± 5 h after the first testing, and measure the Shore A0 hardness as described in 7.2.2.2 on the opposite side of the 2 h measurement within 3 min ±1 s after having removed the specimen from the water bath.

Carry out the test on all three specimens, and calculate the mean of the five Shore A0 values for each specimen.

An outer package may be used to present the containers as a single unit.

Allow the test apparatus (“upper” glass plate and weight) to reach equilibrium in the environment of (37 ± 1) °C for at least 30 min before testing.

7.3.2.1 Unplasticized polymer sheets (polyester, polyethylene, or polypropylene), 100 mm by 100 mm and (50 ± 25) μm thickness.

7.3.2.2 Delivery tube or syringe, for example, glass or polytetrafluoroethylene (PTFE), capable of dispensing a volume in excess of sample size [i.e. in excess of (2 ± 0,1) ml].

7.3.2.3 Two glass plates of size 100 mm by 100 mm, one of which (the “upper” plate) has a mass of (100 ± 1) g and a thickness of not less than 2 mm.

7.3.2.4 Timer device, accurate to 0,1 s.

7.3.2.5 Weight, (1 000 ± 5) g.

7.3.2.6 Ruler, with subdivision of accuracy 0,5 mm.

Cover the bottom of the sample with an unplasticized sheet (7.3.2.1).

Prepare a sample using the manufacturer’s recommended technique. Where a range of mixing times is given, use the mean time. Using the syringe (7.3.2.2), dispense a sample of (2,0 ± 0,1) ml onto the middle of the unplasticized polymer sheet (7.3.2.1) on the glass plate (7.3.2.3) at (30 ± 1) s after the end of mixing, as timed using a timer device (7.3.2.4).

At the time for insertion in the mouth as given by the manufacturer, transfer the plate (7.3.2.3) and the sample immediately to the environment maintained at (37 ± 1) °C and cover the upside of the sample with a unplasticized polymer sheet and the “upper” glass plate (7.3.2.3), and compress by vertically applying the weight (7.3.2.5) so that the total load becomes (1 100 ± 6) g. In case that the time for insertion is not given by the manufacturer, it shall be (120 ± 5) s. Maintain this load for (300 ± 1) s and then remove the weight and glass plate.

Measure the maximum and minimum diameters of the disc to an accuracy of ±0,5 mm using the ruler (7.3.2.6) and calculate the average of the two measurements.

Repeat the test three more times.

Perform the detail reproduction test only on materials which the manufacturer claims may be used for functional impression taking.

7.4.2.1 Test block and ring mould accessory (Figure 2 and Figure 3), cleaning the test block ultrasonically using ultrasonic bath (7.4.2.2) before each use.

NOTE A mould release agent, e.g. Polytetrafluoroethylene (PTFE) spray, can be used to avoid the adherence of material to the mould.

7.4.2.2 Ultrasonic bath.

7.4.2.3 Water bath, capable of being maintained at (37 ± 1) °C, with water in accordance with grade 2 of ISO 3696:1987.

7.4.2.4 Flat glass or metal plate, approximately 50 mm by 50 mm and at least 3 mm thickness.

7.4.2.5 Unplasticized polymer sheets (polyester, polyethylene, or polypropylene), 50 mm by 50 mm and (50 ± 25) μm thickness.

7.4.2.6 Water, grade 2 of ISO 3696:1987.

7.4.2.7 Microscope or magnifying glasses, equipped for x4 to x12 magnification and low angle illumination.

Preparation of test samples

Before mixing the material for each of the three specimens, place the test block and ring mould (7.4.2.1) in the water bath (7.4.2.3) or oven at (37 ± 1) °C for conditioning for at least 15 min.

Cover the underside of the glass or metal plate (7.4.2.4) with an unplasticized polymer sheet (7.4.2.5).

Accomplish the following steps within (60 ± 2) s after completion of mixing:

— remove the test block and ring mould from water bath or oven;

— seat the ring mould on the test block to form the specimen forming cavity;

— introduce an increment of the mixed material (enough to slightly overfill the cavity) along one side of the cavity such that it can be directed to first enter the scribed lines a, b, and c on one side of the test block, and then be gradually forced, via application of pressure applied by the glass or metal plate, to flow into the lines to their opposite ends;

— press the plate covered by unplasticized polymer sheet down against the top of the ring mould so as to expel the excess material;

— at 60 ± 2 s after completion of mixing, place this specimen-forming assembly in the water bath being maintained at (37 ± 1) °C for (48 ± 1)h.

After completion of the water bath treatment, separate the relining material specimen in the ring mould from the specimen forming assembly and flush the specimen surface with distilled or deionized water (7.4.2.6). Then use a gentle stream of clean air to blow away moisture. The lines on the specimens will be positive copies (raised lines) of the lines scribed in the test block surface.

Test procedure

Immediately after blowing moisture from specimen, use the microscope or magnifying glasses (7.4.2.7) to examine the specimen for compliance with the related line width. The line reproduction shall be considered satisfactory if the required line c is continuous between lines d₁ and d₂.

Key

1 line a

2 line b

3 line c

4 line d₁

5 line d₂

^a Has the same width as line c.

NOTE 1 Unless otherwise specified, dimensions are in millimetres.

NOTE 2 Unless otherwise specified, tolerances are ±0,1 mm; surface roughness is 3,2 µm max. and material is cast or wrought austenitic stainless steel.

Figure 2 — Test block for detail reproduction

Key

1 cut-out approximately 1 mm deep

^a Made of polymer, brass or stainless steel.

Figure 3 — Ring mould accessory^a

The components shall be supplied in sealed containers made of materials that shall neither contaminate, nor permit contamination, of the contents. The immediate containers shall be packaged so as to prevent damage or leakage during transit and storage.

An outer package may also be used to present the containers as a single unit.

The outer packages and the immediate containers or wrappings of the components shall be clearly marked with the information given in Table 3.

In those cases where the size of the immediate container or package is too small to fit in all the details, reference shall be made on the outer package to a leaflet inside where the additional information shall be provided.

Instructions for use shall accompany each package and, shall at a minimum include the information given in Table 3.

Table 3 — Requirements for labelling and manufacturer’s instruction

Bibliography

[1] ISO 7405, Dentistry — Evaluation of biocompatibility of medical devices used in dentistry

[2] ISO 10993‑1, Biological evaluation of medical devices — Part 1: Requirements and general principles for the evaluation of biological safety within a risk management process