ISO/DIS 7260

ISO/TC 106/SC 6

Secretariat: DIN

Date: 2026-01-19

Dentistry — Protective filtering devices intended for use with powered polymerization activators

DIS stage

© ISO 2026

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester.

ISO copyright office

CP 401 • Ch. de Blandonnet 8

CH-1214 Vernier, Geneva

Phone: + 41 22 749 01 11

E-mail: copyright@iso.org

Website: www.iso.org

Published in Switzerland

Contents

Foreword

Introduction

Scope

Normative references

Terms and definitions

Requirements

Blue-light weighted transmittance

Construction of protective filtering eyewear

Construction of handheld protective filters

Construction of protective filters attached to powered polymerization activators

Processing

Sampling

Measurement and test methods

General

Test conditions

Transmittance and blue-light weighted transmittance measurements

Marking

Packaging

Packaging construction

Packaging information

Instructions for use

(informative) Rationale for blue-light weighted transmittance requirement

Bibliography

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.

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, Subcommitee SC 6, Dental Equipment, 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 is the first edition of this document.

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

Light emitted from powered polymerization activators may exceed limit values for photochemical retinal exposure to visible (blue) light under certain circumstances. Exposure limit values are specified in ICNIRP Guidelines on limits of exposure to incoherent visible and infrared radiation and applied in IEC 62471 [1].

The spectral emission of powered polymerization activators typically overlaps substantially with the blue-light hazard function for induction of retinal damage (peak interval between 435 nm and 440 nm). Most powered polymerization activators have emission spectra that match the absorbance spectrum of the photoinitiator camphorquinone, characterized by an absorption maximum of 468 nm. Some curing lights have more than one emission peak to match the absorption of other photoinitiators in the wavelength range approximately from 380 nm to 420 nm.

Powered polymerization activators have relatively small emission surfaces, typically 5 mm to 12 mm diameter, and high radiance values, up to 3000 times higher than that of LED sources for indoor lighting. The combination of the spectral emission, high power and small size of powered polymerization activators poses a risk of exceeding the limits specified for retinal blue light exposure.

Both patients and oral healthcare providers may be exposed to visible light from powered polymerization activators. Exposure may be either direct or indirect (i.e. reflected or scattered).

Protective filtering devices intended for use with powered polymerization activators can mitigate the retinal blue-light hazard exposure by attenuating the light in the wavelength range of concern. Such protective filtering devices can be in the form of protective filtering eyewear, handheld protective filters or protective filters attached to powered polymerization activators.

Dentistry — Protective filtering devices intended for use with powered polymerization activators

This document specifies requirements, test methods, and labeling for protective filtering devices intended for protection against retinal blue-light hazard exposure in the wavelength range from 380 nm to 550 nm from powered polymerization activators in the scope of ISO 10650, i.e. powered polymerization activators using quartz-tungsten halogen lamps or light emitting diodes (LED) to activate polymerization.

This document does not apply to protective filtering devices for lasers or plasma arc devices.

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 12609-1:2021, Eye and face protection against intense light sources used on humans and animals for cosmetic and medical applications — Part 1: Specification for products

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 17664-2, Processing of health care products — Information to be provided by the medical device manufacturer for the processing of medical devices — Part 2: Non-critical medical devices

ISO 18526-4, Eye and face protection — Test methods — Part 4: Headforms

ISO 21530, Dentistry — Materials used for dental equipment surfaces — Determination of resistance to chemical disinfectants

CIE S 017, ILV: International Lighting Vocabulary

ICNIRP Guidelines on limits of exposure to incoherent visible and infrared radiation, International Commission on Non‐Ionizing Radiation Protection, Health Physics 105(1):74‐96; 2013

International Commission on Non‐Ionizing Radiation Protection (ICNIRP), ICNIRP Guidelines on limits of exposure to incoherent visible and infrared radiation, Health Physics 105(1):74‐96; 2013

For the purposes of this document, the terms and definitions given in CIE S 017 and ISO 1942 as well as the following apply.

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

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

protective filtering device

optical element intended to protect the eye from incident radiation by attenuating that radiation, generally within a given wavelength range

[SOURCE: ISO 4007 [2], 3.10.1.1, modified ― "filter" replaced with "protective filtering device"; “lens” replaced with “optical element”; Notes to entry removed]

powered polymerization activator

device producing a light beam primarily in the 380 to 515 nm region, intended for chairside use in polymerizing polymer-based dental materials (e.g. filling, restorative and luting materials, cements, bonding agents, sealants, primers)

[SOURCE: ISO 10650:2018, 3.6, modified ― expanded the range of applicable materials]

exposure limit value

maximum level of exposure of optical radiation to the eye or skin that is not expected to result in adverse biological effects

[SOURCE: ISO 4007 [2], 3.4.14, modified - Note 1 to entry removed]

blue-light hazard

potential for a photochemically induced retinal injury resulting from optical radiation exposure in the wavelength range 300 nm to 700 nm

[SOURCE: ISO 4007 [2], 3.1.7]

spectral transmittance

τ(λ)

ratio of the spectral radiant flux or luminous flux transmitted by the material to the incident spectral radiant flux or luminous flux at any specified wavelength, λ, for a specified angle of incidence

[SOURCE: ISO 4007 [2], 3.10.1.22]

blue-light weighted transmittance

τB

normalized value of the spectral transmittance averaged between 380 nm and 550 nm, weighted by the blue-light hazard function

[SOURCE: ISO 4007 [2], 3.10.1.36, modified — added “weighted” to the term and replaced 500 nm with 550 nm to encompass the entire wavelength range over which the blue-light hazard weighting function has a value of > 0,01]

The blue-light weighted transmittance, τ_B, over the wavelength range from 380 nm to 550 nm of the protective filtering device shall not exceed 5,0 %.

Test in accordance with 6.3.

NOTE Further information about the rationale for the limit specified in this subclause is provided in Annex A.

If the protective filtering device is designed to be worn as eyewear (e.g. spectacles, goggles), then the requirements of ISO 12609-1:2021, Clause 5.3 shall apply.

ISO 12609-1:2021, 9.1 shall apply. Unless the manufacturer specifies the headform(s) (in accordance with ISO 18526-4) that is/are compatible with the protective filtering eyewear, the headform 1-M per ISO 18526-4 shall be used as the default.

Frames and lateral protection through which exposure to incident optical radiation could occur to the eyes shall provide at least the same level of protection as specified in 4.1 for the minimum area to be protected in accordance with 4.2.2.

Except for a marginal area 5 mm wide, protective filtering eyewear shall be free from defects likely to impair vision when in use (such as bubbles, scratches, inclusions, dull spots, pitting, mould marks, scouring, grains, pocking, scaling and undulation) when visually inspected.

ISO 12609-1:2021, 9.4 shall apply.

The minimum size of the transparent protective filter area of the device, excluding the handle, shall be no smaller than a circle having a diameter of 150 mm. The shape of the filter area is not restricted to being circular.

Except for a marginal area 5 mm wide, filters shall be free from significant defects likely to impair vision when in use (such as bubbles, scratches, inclusions, dull spots, pitting, mould marks, scouring, grains, pocking, scaling and undulation) when visually inspected.

Except for a marginal area 5 mm wide, filters shall be free from defects likely to impair vision when in use (such as bubbles, scratches, inclusions, dull spots, pitting, mould marks, scouring, grains, pocking, scaling and undulation) when visually inspected. This requirement does not apply if the protective filter attached to the powered polymerization activator is not intended to enable seeing the operating field through the filter.

Surfaces of the protective filtering device shall be suitable for processing using the protocol(s) recommended by the manufacturer without deterioration of surfaces or marking.

Test conformity of resistance against cleaning and disinfection in accordance with ISO 21530. In addition to evaluating compliance with the inspection and evaluation criteria specified in ISO 21530, evaluate compliance with the blue-light weighted transmittance requirement specified in 4.1 in accordance with 6.3 after completing the ISO 21530 test method.

One representative protective filtering device shall be evaluated for conformance with the requirements specified in this document.

All tests described in this document are type tests.

Tests shall be carried out under the following conditions:

1. ambient temperature of (23 ± 5)°C;
2. relative humidity of (50 ± 20)%.

This method verifies transmittance measurement accuracy with a control filter and measures blue-light weighted transmittance of the test specimen. Verification of transmittance measurement accuracy is performed using a neutral density filter with known spectral transmittance and is intended to ensure that certain sources of measurement uncertainty, such as possible misalignment of measurement apparatus components or misaligned mounting of the specimen, do not unacceptably affect measurements.

Verification of transmittance measurement accuracy may be omitted if both of the following conditions are met:

1. measurements are performed using a measurement system that has been calibrated for performing transmittance measurements over the wavelength range at least from 380 nm to 550 nm;
2. the relative uncertainty of transmittance measurements in that wavelength range has been demonstrated to be no greater than 10 % for a test specimen having a mean transmittance in the range from 2,0 % to 5,0 %.

EXAMPLE For a test specimen having a mean transmittance of 3,2 %, an uncertainty of 0,32 % or less is acceptable.

Measurement of blue-light weighted transmittance of the test specimen is performed by measuring spectral transmittance over the wavelength range at least from 380 nm to 550 nm and calculating blue-light weighted transmittance in accordance with ICNIRP Guidelines on limits of exposure to incoherent visible and infrared radiation (2013).

General

Either of the following can be used for the measurement apparatus:

1. an arrangement comprised of separate components, including a separate light source, integrating sphere and spectrometer;
2. a stationary spectrophotometer with integrated transmittance measurement capability.

Apparatus comprised of separate components

Light source

A broadband light source including emission in the wavelength range at least from 380 nm to 550 nm with a collimating lens (or lens system) shall be used to produce a collimated light beam.

Integrating sphere

An integrating sphere, also known as an Ulbricht sphere, that is compatible with the spectrometer (6.3.2.2.4) shall be used. The integrating sphere shall have at least two ports, a light entry port and an exit port to connect to the spectrometer (6.3.2.2.4). There shall be a baffle between the two ports to avoid direct measurement of light (see Figure 1).

Fiberoptic cable

A fiberoptic cable shall be used to connect the exit port of the integrating sphere to the spectrometer (6.3.2.2.4).

Spectrometer

A spectrometer with uniform spectral sensitivity over a wavelength range at least from 380 nm to 550 nm shall be used.

Arrangement of components

Arrange the light source with collimating lens, integrating sphere, and spectrometer as shown in Figure 1. Connect the spectrometer to the exit port of the integrating sphere with appropriate adapters and a fiberoptic cable.

The assembly can be mounted on an optical table to align and stabilize the measurement system.

Key

1 broadband light source

2 collimating lens

3 collimated light beam

4 test specimen (or control filter)

5 integrating sphere

6 light baffle

7 fiberoptic cable

8 spectrometer

9 computer

Figure 1

Schematic diagram of transmittance measurement apparatus comprised of separate components

Stationary spectrophotometer with integrated transmittance measurement capability

Alternatively, a stationary spectrophotometer with integrated transmittance measurement capability can be used (i.e. commercial, tabletop instrument with an integrated light source, integrating sphere and spectrometer configured as a stand-alone instrument). In this case, a separate light source, integrating sphere and spectrometer are not required.

A neutral density filter with mean transmittance in the range from 2,0 % to 5,0 % (optical density in the range from 1,7 to 1,3) and for which spectral transmittance data in 10 nm increments over at least the range of 380 nm to 550 nm shall be used as the control filter for verification of measurement accuracy. The optical density tolerance shall be no greater than ± 5,0 %.

The test specimen shall be a protective filtering device or portion thereof of sufficient size to fully cover the light entry port of the integrating sphere if using a measurement apparatus comprised of separate components or in accordance with the specifications of the manufacturer of the stationary spectrophotometer if using such an instrument.

Large or curved protective filtering devices may need to be disassembled or cut to produce a test specimen that fits properly in the measurement apparatus.

Measure the spectral transmittance of the control filter in accordance with 6.3.6.2 and 6.3.6.3. Calculate the transmittance of the control filter in accordance with 6.3.6.4. Repeat the spectral transmittance measurement two more times (three total measurements) and calculate the transmittance for each.

The measurement accuracy is acceptable if the mean transmittance from the three measurements deviates by no more than 10 % relative to the manufacturer’s specification for transmittance of the control filter over the range from 380 nm to 550 nm, i.e. 0,9∙τ_spec ≤ τ ≤ 1,1∙τ_spec, where τ_spec is the manufacturer’s specification for mean transmittance of the control filter and τ is the measured transmittance.

General

If the measurement accuracy fulfils the requirement specified in 6.3.5, measure the spectral transmittance of the test specimen in accordance with 6.3.6.2 and 6.3.6.3. Calculate the blue-light weighted transmittance of the test specimen according to 6.3.6.5. Repeat the spectral transmittance measurement two more times (three total measurements) and calculate the blue-light weighted transmittance for each. Compare the mean value of the three measurements to the requirement specified in 4.1 to determine whether the test specimen complies with the blue-light weighted transmittance requirement.

Spectral transmittance measurement procedure

If using the measurement system shown in Figure 1, perform the following steps:

1. If necessary, warm up the light source before making measurements to make sure that it is producing a stable energy output during the measurements.
2. Measure the spectral power of the broad band collimated light source with no test specimen over the wavelength range from 380 nm to 550 nm at wavelength intervals not exceeding 10 nm. Record the measurement as ϕ_source (λ).
3. Mount the test specimen or control filter over the light entry port of the integrating sphere. Care shall be taken when mounting curved test specimens to ensure that no stray light is allowed to pass around the test specimen.
4. Measure the spectral power of the broad band collimated light source with the test specimen or control filter covering the light entry port of the integrating sphere over the wavelength range from 380 nm to 550 nm at wavelength intervals not exceeding 10 nm. Record the measurement as ϕ_filtered (λ).

If using a stationary spectrophotometer with transmittance measurement capability, follow the manufacturer's instructions for performing a spectral transmittance measurement over the wavelength range from 380 nm to 550 nm at wavelength intervals not exceeding 10 nm using the test specimen or control filter. Care shall be taken when mounting curved test specimens to ensure that no stray light is allowed to pass around the test specimen.

Calculation of spectral transmittance

Spectral transmittance is calculated using the following equation:

(1)

where

τ (λ) is the spectral transmittance of the test specimen or control filter, unitless;

ϕ_filtered (λ) is the spectral power of broadband light source with test specimen or control filter in place, W;

ϕ_source (λ) is the spectral power of broadband light source with no test specimen or control filter in place, W;

λ is the wavelength, in nm.

Calculation of transmittance of control filter

Calculate the transmittance of the control filter from the spectral transmittance using the following equation:

(2)

where

τ is the transmittance of the control filter, unitless;

τ (λ) is the spectral transmittance of the control filter, unitless;

λ is the wavelength, in nm.

Calculation of blue-light weighted transmittance of test specimen

Calculate τ_B of the test specimen from the spectral transmittance using the following equation:

(3)

where

τ (λ) is the spectral transmittance of the test specimen, unitless;

B(λ) is the blue-light hazard weighting function per ICNIRP Guidelines on limits of exposure to incoherent visible and infrared radiation, unitless;

λ is the wavelength, in nm.

Protective filtering eyewear and handheld protective filters shall be marked (on the device) with at least the following information:

1. model number;
2. manufacturer’s identification;
3. standard(s) with which the product complies

NOTE The marking requirements of this document do not necessarily include all national or regional requirements applicable to protective filtering eyewear and handheld protective filters.

The protective filtering device shall be packaged for transportation in such a way that no damage can occur during anticipated transport conditions.

For protective filtering eyewear and handheld protective filters at least the following information shall be provided on the packaging or on a packaging insert:

1. name and address of the manufacturer or authorized representative or both, as applicable;
2. serial number, lot number or production date;
3. model number.

At least the following information shall be provided by the manufacturer in the instructions for use:

1. instructions for use and any routine maintenance of the protective filtering device;
2. processing instructions (e.g. cleaning, disinfection, sterilization) in accordance with ISO 17664-1 or ISO 17664-2, as applicable;
3. a statement informing the user that the protective filtering device is for protection against retinal blue-light exposure from powered polymerization activators and that it is not for protection against exposure to other blue light sources, lasers, or other types of radiation hazards;
4. nominal value of the blue-light weighted transmittance of the protective filtering device;
5. powered polymerization activator wavelength range over which the protective filtering device is intended to provide protection;
6. revision date or other version identifier of the instructions for use;
7. instructions on proper storage (e.g. store away from intense sunlight or other strong light sources).
8. 
   (informative)
   
   Rationale for blue-light weighted transmittance requirement
   1. Background

This informative annex provides information on the rationale for the blue-light weighted transmittance requirement specified in 4.1. The intent of the requirement is to establish a minimum performance requirement for the ability of protective filtering devices to mitigate retinal blue-light hazard exposure associated with powered polymerization activators in dentistry using international standards on photobiological hazards.

Light emitted from powered polymerization activators may under certain circumstances exceed the limit values for photochemical retinal exposure to blue light specified in ICNIRP Guidelines on limits of exposure to incoherent visible and infrared radiation (2013), referred to hereafter as ICNIRP Guidelines, and applied in IEC 62471 [1]. The spectral emission of powered polymerization activators typically overlaps substantially with the blue-light hazard function for induction of retinal damage (peak interval between 435 nm and 440 nm). Powered polymerization activators often have emission spectra that coincide with the absorbance spectrum of the photoinitiator camphorquinone, characterized by an absorption maximum of 468 nm. Some powered polymerization activators have one or more emission peaks to coincide with the absorption of other photoinitiators, typically in the range approximately from 380 nm to 420 nm.

Powered polymerization activators have relatively small emission surfaces, typically from 5 mm to 12 mm diameter, and high radiance values, up to 3 000 times higher than that of LED sources for indoor lighting. The combination of the spectral emission, high power and small size of powered polymerization activators poses a risk of exceeding the limits specified for retinal blue light exposure.

Conservative assumptions are made in evaluating the blue-light hazard exposure associated with identified exposure scenarios. Based on the calculated blue-light weighted radiance and assumed exposure duration for each scenario, the maximum blue-light weighted transmittance for the protective filtering device required to reduce the blue-light weighted radiance to a level that complies with ICNIRP Guidelines and IEC 62471 [1] is calculated.

• 1. Exposure scenarios
     1. General

Two exposure scenarios are considered:

1. Reflected light exposure: During normal use of a powered polymerization activator, light reflected from within the patient’s oral cavity can extend to the eyes of the oral healthcare provider(s), patient and any others in the dental treatment room who are near the powered polymerization activator while in use. Exposure will typically be greatest for the oral healthcare provider(s) due to their proximity to the oral cavity and the direct path of reflected light from the patient’s oral cavity to their eyes.
2. Direct exposure: While not an intended use of the powered polymerization activator, direct exposure to the center of the emitted beam at a distance of 200 mm (worst-case distance specified by the ICNIRP Guidelines and IEC 62471 [1]) is considered.
   • 1. Reflected light exposure analysis

Light from the powered polymerization activator is primarily incident on a patient’s tooth and the light-activated dental material. The relationship between reflected blue-light weighted radiance and incident blue-light weighted irradiance for a Lambertian reflective surface is given by:

(A.1)

where

L_{B, reflected} is the reflected blue-light weighted radiance, W/m²/sr;

R is the reflectance of the surface, unitless;

E_{B, incident} is the incident blue-light weighted irradiance, W/m².

Conservatively, the blue-light weighted irradiance incident on the oral tissue and light-activated dental material surface is assumed to be equal to the blue-light weighted exitance of the powered polymerization activator (i.e. blue-light weighted irradiance at the tip of the powered polymerization activator). The reflectance of the irradiated surfaces is assumed to be independent of wavelength over the applicable wavelength range and to have a value of 0,3, consistent with Reference ^[3].

Using the maximum radiant exitance of 40 000 W/m² for a powered polymerization activator allowed by ISO 10650 [4] (over the range from 380 nm to 515 nm) and assuming the emitted spectrum is substantially within the wavelength range for which the blue-light hazard function, B(λ), is approximately 1, E_{B, incident} is assumed to be 40 000 W/m². Applying these assumptions,

(A.2)

A further conservative assumption is that none of the reflected light is blocked by the tip of the powered polymerization activator.

The calculated value for L_{B, reflected} represents the “true” blue-light weighted radiance reflected by the surface. The blue-light hazard exposure limit values specified in the ICNIRP Guidelines and IEC 62471 [1] are based on a spatial average of radiance over an angle of acceptance (referred to as effective angular subtense, α_eff, in IEC 62471 [1]), which factors in eye movement over the expected exposure duration. Eye movement smears the image over a larger area on the retina. As exposure duration increases, larger acceptance angles are specified by the ICNIRP Guidelines and IEC 62471 [1]. If a light source is smaller than the field of view, the spatially averaged blue-light weighted radiance, referred to here as “effective” blue-light weighted radiance, is less than the “true” radiance. In the case where the light source is light reflected from a tooth, the following relationship applies (see Figure A.1):

(A.3)

where

L_{B, reflected, eff} is the “effective” reflected blue-light weighted radiance, W/m²/sr;

A_tooth is the irradiated area of the reflecting surface, mm²;

α_eff is the effective angular subtense, rad;

d is the distance from the reflecting surface to the viewer’s eye, mm.

A_tooth is assumed to be 1 cm² = 100 mm², following Reference ^[3], and d is assumed to be 200 mm, which corresponds to the worst-case distance per the ICNIRP Guidelines and IEC 62471 [1]. For this scenario, the daily exposure duration is assumed to be 10 000 s (approximately 2,8 h), which corresponds to the Exempt Group specified in IEC 62471 [1].

This conservatively long exposure duration assumption is consistent with the objective of ensuring that a protective filtering device is capable of effectively reducing retinal blue-light hazard exposure when the protective filtering device is used as intended. IEC 62471 [1] specifies setting α_eff equal to 0,1 radians for exposure times of 10 000 s (which is slightly more conservative than the value specified in the ICNIRP Guidelines: 0,110 radians).

Key

1 powered polymerization activator

2 tooth

3 viewer's eye

Figure A.1

Schematic diagram of reflected light exposure scenario

Applying the stated assumptions,

(A.4)

Per IEC 62471 [1] the maximum allowable blue-light weighted radiance for the Exempt Group (exposure duration = 10 000 s) is 100 W/m²/sr. To attenuate L_{B, reflected} to comply with this limit, the blue-light weighted transmittance for the protective filtering device needs to meet the following:

(A.5)

To allow for a margin of uncertainty, a slightly more stringent requirement of τ_B≤ 5,0 % is specified in 4.1.

• • 1. Direct exposure analysis

The worst-case viewing distance of 200 mm per ICNIRP Guidelines and IEC 62471 [1] is used in this analysis. An exposure duration of 10 s is assumed. This is a conservatively long exposure duration considering that powered polymerization activators are used by trained dental healthcare professionals and directing the beam from the powered polymerization activator directly into an eye is an obvious misuse of the device.

Additionally, bright light typically triggers an aversion response, such as blinking or directing the eyes or head in another direction, within about 0,25 s. For an exposure duration of 10 s, ICNIRP Guidelines and IEC 62471 [1] specify α_eff = 0,011 rad.

Using the method described in IEC 62471 [1]:2006, 5.2.2.2, the blue-light weighted radiance of a light source may be calculated based on the blue-light weighted irradiance, E_B, measured at the specified viewing distance (200 mm) with a circular field stop placed at the source, where the diameter of the field stop is given by:

(A.6)

where

F is the diameter of the field stop, mm;

α_eff is the effective angular subtense, rad;

r is the specified measurement distance, mm.

For α_eff = 0,011 rad and r = 200 mm, F = 2,2 mm. Powered polymerization activators typically have a larger emitting surface with a diameter in the range approximately from 5 mm to 12 mm. If the radiance varies over the emitting surface, which is the case for some powered polymerization activators, the worst-case measurement will result with the field stop positioned at the location of maximum radiance on the powered polymerization activator’s surface.

L_B is calculated as follows:

(A.7)

where

L_B is the blue-light weighted radiance of the source, W/m²/sr;

E_B is the blue-light weighted irradiance measured at the specified viewing distance with a field stop placed at the source, W/m².

In an evaluation of 13 representative powered polymerization activators conducted by the American Dental Association (ADA) and the Nordic Institute of Dental Materials (NIOM), which has not been published as of the date of this document, the maximum measured value of E_B at a distance of 200 mm was found to be 121 W/m² with no field stop to limit the field of view. Measurements with a field stop were not available. A worst-case assumption is that all of the measured irradiance measured at 200 mm from the powered polymerization activator emanated from within a circular area having a diameter of 2,2 mm, as if the field stop were in place. This assumption leads to an overestimate of E_B, which is discussed further below.

Applying the values indicated above,

(A.8)

For the assumed exposure duration of 10 s, ICNIRP Guidelines and IEC 62471 specify a maximum allowable blue-light weighted radiance of 100 000 W/m²/sr. To attenuate L_B to comply with this limit, the blue-light weighted transmittance for the protective filtering device needs to meet the following:

(A.9)

As noted above, the use of the irradiance measured without the field stop in place to limit the field of view to an angular subtense of α_eff = 0,011 rad leads to a calculated value of E_B that exceeds the actual value by an estimated factor of 4 or more. This means that the calculated requirement for blue-light weighted transmittance for the direct exposure scenario (i.e. τ_B ≤ 7,9 %) is overly stringent by an estimated factor of 4 or more.

• 1. Summary

The analysis here shows that the reflected light exposure scenario is the more critical scenario and supports specifying a blue-light weighted transmittance requirement of τ_B ≤ 5,0 % for protective filtering devices for use with powered polymerization activators. It may seem counter-intuitive that the reflected light exposure scenario is the more critical scenario due to the reduction in radiance that occurs when light reflects off a surface. However, the comparatively short duration to direct exposure allows a considerably greater radiance without resulting in a hazard.

Bibliography

[1] IEC 62471, Photobiological safety of lamps and lamp systems

[2] ISO 4007:2018, Personal protective equipment — Eye and face protection — Vocabulary

[3] Bruzell, Ellen M., et al. Evaluation of Eye Protection Filters for Use with Dental Curing and Bleaching Lamps. Journal of Occupational and Environmental Hygiene. Taylor & Francis. April 2007. 4(6), 432–439. Available at: https://doi.org/10.1080/15459620701354218

[4] ISO 10650, Dentistry — Powered polymerization activators