ISO/DIS 3843:2026(en)

ISO TC 106/SC 2

Secretariat: ANSI

Date: 2025-12-23

Dentistry — Dental attachments — Measurement of placement and removal forces

© ISO 2026

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 Test methods 3

4.1 Mechanical testing machine 3

4.2 Test chamber 4

4.3 Materials 4

4.4 Loading geometry 4

4.5 Fixation of the test specimens 4

4.6 Test environment 4

4.7 Loading frequency 4

4.8 Required number of cycles 4

4.9 Sampling 5

4.10 Preparation of specimens 5

4.10.1 Upper structure of specimen 5

4.10.2 Lower structure of specimen 5

4.11 Test procedure 5

5 Lifetime 7

6 Test report 7

Bibliography 9

Foreword

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This document was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 2 Prosthodontic materials.

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Introduction

Removable prostheses, dentures and overdentures on natural teeth, root post copings and implant abutments, are used widely in dentistry. To increase their retention (and patient’s comfort) attachment systems may be used. However, the most common problem associated with their use is the loss or decrease of retention over time, caused by wear, deformation, and fracture of the components of the attachment system. This loss is related to repeated placement and removal of the prosthesis. The period of time over which the retentive force of a dental attachment system is effective is of clinical significance. This document describes a test procedure for measuring the placement and removal forces of dental attachment systems during their repeated simulated functional assembly and disassembly.

Dentistry — Dental attachments — Measurement of placement and removal forces

This document specifies a test method for measuring the forces needed for the placement and removal of dental attachments (frictional retention elements of ball head-, snap-on, prefabricated telescopic and bar systems used for the attachment, support and stabilization of crowns and bridges, single attachments, removable partial dentures, complete dentures, and other superstructures on dental implant systems (including monopart implants) and, if not other justified, on natural teeth and root post copings).

If not otherwise justified, this document can also be used for tests on custom-made or patient matched devices (e.g. laboratory manufactured).

This test method is not applicable to retention devices for which normal placement and removal requires any off-axis rotation for the path of least resistance.

This test method is not applicable to dental magnetic attachments, these are specified in ISO 13017.

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 14233, Dentistry — Polymer-based die materials

ISO 16443, Dentistry — Vocabulary for dental implants systems and related procedure

For the purposes of this document, the terms and definitions given in ISO 1942, ISO 16443 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

attachment

prosthetic attachment

part of a dental prosthesis that provides anchorage by engagement of a matrix (3.2) and a patrix (3.3) component

Note 1 to entry: See Figure 1.

[SOURCE: ISO 1942:2020, 3.3.1.8— modified, Note 1 to entry and Figure 1 added]

Key

1 matrix component

2 patrix component

Figure 1 — Examples of attachment designs

3.2

patrix

extension of a dental attachment system that fits into the matrix

Note 1 to entry: The screw section is used for the direct anchoring on the implant body and consists of a retention part; in case of an implant of a component with a transmucosal cuff and a screw section.

Note 2 to entry: See Figure 2.

[SOURCE: ISO 1942:2020, 3.3.1.41, modified — Note 1 to entry, Note 2 to entry and Figure 2 added.]

Key

1 retention part (patrix)

2 connecting part (transmucosal cuff)

3 screw section or connecting part

Figure 2 — Example of use of a patrix for an implant

3.3

matrix

part of an attachment system that receives the patrix (3.2) and consists of a housing and a resilient retention element and is usually incorporated in the removable prosthesis

Note 1 to entry: See Figure 3.

[SOURCE: ISO 1942:2020, 3.3.1.35, modified — Further clarification, Note 1 to entry and Figure 3 added.]

Key

1 housing

2 retention element

3 matrix component

Figure 3 — Example of a matrix component

3.4

abutment

structure that serves to support or retain a dental prosthesis

[SOURCE: ISO 1942:2020, 3.3.1.1]

3.5

retention element

holding element for removable prostheses

3.6

retention force

minimum force required to separate the matrix (3.3) and the patrix (3.2) along the design axis for assembly and dis-assembly

3.7

insertion force

minimum force required to connect the matrix (3.3) and the patrix (3.2) along the design axis for assembly and dis-assembly

3.8

telescopic system

crown in crown system with a primary permanently fixed crown and a secondary removable telescopic crown

3.9

bar system

prefabricated bar between two or more crown-shaped abutments on implants, or if not other justified on natural teeth or root post copings as primary retaining element and one or more secondary snap-on elements in the removable prosthesis

Note 1 to entry: The prefabricated bar can additionally be attached as a free attachment to a terminal abutment.

The mechanical testing machine shall:

— be able to apply uniaxial displacement;

— having an accuracy of ±1 N or better;

— be equipped with an adapter suitable for fixing and aligning the test specimens;

— be able to apply the loading at the specified frequency;

— be equipped with measuring instruments so that the peak values of the force when separating and pushing back the retention element and the loading frequency can be monitored and the failure of the test specimen determined;

— be able to register the number of loading cycles during the test.

The chamber shall be made to be filled with a solution described in 4.6 and placed on the mechanical testing machine (4.1). The volume of the chamber is enough to include both upper structure specimens (matrix) and lower structure specimens (patrix) and grip.

Self-curing acrylic resin for embedding the screw section or the connecting part of the patrix and the housing in the specimen mount or clamping device with properties in accordance with ISO 14233.

If an embedding material is used, its modulus of elasticity shall be at least 1 GPa.

The longitudinal axis of the retention portion of the specimen shall be the same as the loading direction of the test machine.

The part of the test specimen which would be anchored in the implant and the part of the test specimen anchored in the prosthesis shall be fixed in a rigid clamping device.

The clamping device can be fixed to the mechanical testing machine (4.1). The materials for the holding device shall have corrosion and wear resistance (e.g. alloy, acrylic resin) and appropriate strength for fixing specimen during cyclic dislodgement (placement and removal).

The geometry of the clamping device shall be such that the test geometry specified in 4.4 is achieved. The clamping device shall be so designed such that the specimen is not deformed.

The test shall be performed in physiological saline, synthetic saliva solution or in an alternative physiologic medium. The fluid and test specimen shall be kept at (37 ± 2) °C during the test. The testing environment shall be justified and reported.

Testing shall be carried out under uniaxial loading along the axis A-B (Figure 5). The loading frequency shall be not more than 20 cycles/min.

2 000 cycles or the number of cycles until a failure of the specimen is observed.

NOTE On the assumption of 5 cycles per day (one per each meal + two others during day time), the number of 2 000 cycles is considered equivalent to usage for a year.

Test specimens shall be selected as a batch of 5.

The test shall be performed on specimen representative of the finished product (i.e. components that have undergone the same manufacturing process and sterilization as the product to be marketed). If the dental attachment is to be sterilized by the dentist prior to surgical application, the sterilization as described in the Instructions for Use shall be performed before testing. If it is proven that the specified sterilization procedure does not have a significant influence on the properties of all materials of the specimen to be tested, sterilization prior to testing is not necessary.

Holding device for matrix component and matrix component of attachment shall be combined at least 50 N of bond strength with auto polymerized acrylic resin and/or adhesive. Prepare 5 specimens.

In accordance with the manufacturer’s recommended instructions, connect the implant abutment having patrix portion to the dental implant body, or connect the patrix component of attachment to the holding device. Holding device for patrix component of attachment shall be combined at least 50 N of bond strength with auto polymerized acrylic resin and/or adhesive. Prepare 5 specimens.

The upper structure of the specimens shall be fixed to the upper member of the mechanical testing machine (4.1). The lower structure of the specimens shall be attached to the test chamber (4.2) and seated on the lower member of the mechanical testing machine. The test chamber was filled with physiological saline or in an alternative physiologic medium. Attachment parts of upper structure of specimens shall be completely immersed into the fluid. Fluid and specimens shall be kept at (37 ± 2) °C during testing.

The test specimen is subjected to a displacement-controlled tension in the mechanical testing machine (4.1) so that the housing with the retention insert separates completely from the patrix component. The matrix component is then pushed back onto the patrix component (see Figure 4).

Key

Y displacement

1 cycle 1

2 cycle 2

3 cycle 3

T cycle

Figure 4 — Displacement curve

The measured values for the tensile (retention) and compressive (insertion) force are determined for each cycle with an accuracy of ±1 N or better. This procedure is repeated for each specimen until the required number of cycles is reached or the retention insert fails, e.g. by separating from the metal housing.

Calculate the mean force at the start (10 cycles), at the end (10 cycles), and determine the maximum force, in each direction, for each device. Illustrate clear graphical plots of the measured force against number of cycles (see Figure 5).

Key

1 upper table

2 specimen (matrix part)

3 specimen (patrix part)

4 lower table

5 test medium

^a Connected to the part of universal testing machine which performs a vertical pushing and pulling movement.

^b Connected to the table of the universal testing machine.

AB direction of movement

Figure 5 — Mechanical testing set‐up

Figure 6 — Example of a force‐cycles diagram (upper line corresponds to insertion force;
lower line corresponds to the retention force).

If the retentive force of the attachment falls below 85 % of the value indicated in the manufacturer’s Instructions for Use of the device, then it shall be designated as having reached the end of its functional life.

A test report shall be prepared. The following minimum information shall be given in the test report:

— a reference to this International Standard;

— identification of the institute, person;

— date of the test;

— the identity of the test specimens, including size, material, type, manufacturer, packaging, sterilization method, batch and lot number;

— a description of the test machine, type of system used for generating motion, range of motion, type of system used for measuring motion and force, arrangement for mounting specimen (see Figure 4), arrangement for test environment (fluid), arrangement for temperature control, test temperature, test time, loading frequency (Hz) and crosshead speed;

— clear graphical plots of the measured force against number of cycles (see Figure 5);

— a statement of results including:

— the total number of cycles applied;

— mean forces at start, mean forces at end, maximum forces;

— the reason for terminating the test if less than the required number of cycles has been applied.