Cavit-LC - Produktdossier

3M ESPE Elipar FreeLight

Cordless LED Curing Light

Table of contents

1. Introduction......

2. Technical design......

3.Indications......

4.Technical properties......

5.Instructions for use......

6. Frequently Asked Questions...... 21

7. Summary...... 23

8. References...... 24

9. Technical data...... 26

Scientific Affairs 73/2001

1. Introduction

The long-term success of clinical composite restorations depends, apart from optimal materials and a suitable dentine bonding system, upon complete and appropriate polymeriszation.

Until quite recently, the efficiency of curing lights was often specified by the physical quantity ofexpressed in terms of radiation flux density, also called light intensity (mW/cm2). High light intensities were regarded as a basic requirement for complete polymeriszation, especially for deep cavities. Incomplete polymerizationpolymerisation of a composite can lead tomay well result in the deterioration of its mechanical and physical properties. It also , in makes it more susceptible towardsan increased tendency towards discolouration and causesin increased water absorption byof the material.

Only a very small segmentpart of the spectral range can be utilized tois effective for initiateingpolymerizationpolymerisation,consequentlyso that, besides light intensity, the emission spectrum is alsoafurther qualitative factor governing aof curing light's quality. Halogen lamps, the most frequently used dental polymerizationpolymerisation devices, emit a continuous spectrum of which only a small part can be ustilized for the initiation of polymerizationpolymerisation. A large proportion of the emitted light is of an ineffective wavelengthicient and must be filtered out via a filter system. Although the remaining wavelengths illuminate reach the cavity, this light is either not at all, or only partly, effective in the promoting polymerizationpolymerisation. It can , process and also leads to cause an an unwanted undesirable rise in temperature.

Unlike halogen lamps, LEDs (Light Emitting Diodes) produce blue light via a combination of different semiconductors. One particular advantage of this kind of technology is that a narrow emission spectrum can be generated which is ideally suited to the polymerizationpolymerisation of dental composites. As a consequence, the light emitted by LED lamps is much more efficient and there are no high light intensities with their inherent drawbacks.

Overview

It has been known since the 1970s that blue light can be used to light cure dental composites. Halogen lamps are the most frequently used sources of light for this purpose. Blue light with wavelengths between 410 and 500 nm is of central importance since camphorquinone, which is the usual photo initiator for dental materials, has its absorption maximum in this range (465 nm). When compohorquinone is exposed Exposure to lighto light t in the presence of Together with co-initiators, e.g. amines, radicals are leads toa light induced reaction produces the formedation of radicals s which, in turn, initiate polymerizationpolymerisation.

Currently, there are four different technologies for light curing of materials used in dental practice:

1. Halogen lamps
2. Plasma arc lamps
3. LED lamps
4. Lasers

As there are major variations in the respective modes of blue light production, the different technologies as well as their benefits and drawbacks are presented below.

Halogen lamps

Presently, halogen lamps are the most frequently used light sources for polymerizationpolymerisation of dental materials. Their light is produced by an electric current flowing through an extremely thin tungsten filament. This filament functions as a resistor and is so strongly heated by the current that it emits electromagnetic radiation in the form of visible light.

The physical basis of this phenomenon is the fact that heated objects emit electromagnetic radiation. For example, a filament which is heated up to approx. 100 °C gives off heat energy in the form of infrared radiation. When the temperature is increased to between 2000 and 3000 °C, a significant portion of the radiation is emitted in the visible light spectrum. Each rise in the temperature also increases the intensity proportion of the short-wave, i.e. blue light. Therefore, with further heating a red-hot object becomes incandescent. This colour shift due to rising temperatures is described by the Wien’s law. To provide blue light for photopolymerizationpolymerisation, halogen lamps must be heated up to very high temperatures. Selective blue light production is not possible with this kind of technology. The benefits and drawbacks of halogen lamps are summarized in Table 1.

Halogen lamps emit a wide range of wavelengths covering a large part of the spectrum (eg Planck radiator). This results and resulting in white light. In order to produce light of a specific colour, the unwanted portions of the spectrum must be filtered out. The greatest part of the radiativeon power can therefore not be utilized.

Table 1: Benefits and drawbacks of halogen lamps

The most important drawback of halogen curing lights for dental use is the required cooling of the lamps. As the fan cooling air current has to enter and exit through slots in the framecasing, disinfection of the handpiece is necessarily incomplete.

Plasma arc lamps

In the past few years, alternative methods of light curing have been developed, for example, the so-called plasma arc curing lamps. Manufacturers of these expensive devices claim that although curing times are significantly reduced whilst maintaining equivalentthe mechanical properties of the cured materials are comparable to those curedin comparison with conventional lamps.However, scientific studies have demonstrated that these shorter curing times have a negative impact on the mechanical properties of the polymeriszed materials.

Unlike halogen devices, the light of plasma curing lamps is not produced by heating a tungsten filament. In plasma lamps, two electrodes are placed very close to each other. When high voltage is applied, a light arc appears between the two electrodes. However, even with plasma curing lamps Planck’s radiation law also remains validholds true for plasma curing lamps, i.e. a continuous spectrum is emitted, and the higher the operating temperature rises in proportion to the amount ofthe more blue light is produced.

Table 2: Benefits and drawbacks of plasma arc technology

LED lamps (3M ESPE ELIPAR FREELIGHTElipar FreeLight Cordless LED curing light)

In contrast to halogen lamps, light emitting diodes (LEDs) do not produce visible light by the heating of metal filaments, but by quantum-mechanical effects. In simple termsBasically LEDs are a combination of two different semiconductors i.e. the ‘n-doped’ and ‘p-doped’ semiconductors. N-doped semiconductors have an excess of electrons and p-doped semiconductors have a lack of electrons or ‘holes’. When both types of semiconductor are combined and a voltage is applied, electrons from the n-doped and holes from the p-doped elements connect. As a result a characteristic light with a specific wavelength range is emitted.

Figure 1: Structure of an LED (from Scientific American, 2, 63-67 (2001))

The colour of an LED light, which is its most important characteristic, is determined by the chemical composition of the semiconductor combination. Semiconductors are characteriszed by a so-called band gap. In LEDs this band gap is directly utilized for light production. When electrons in the semiconductor combination relax from a higher to a lower energy level, the exact energy difference of the band gap is set free in the form of a photon.

In comparison with conventional lamps, the light produced in by LEDs has a narrow spectral distribution. This is the main difference between the light produced by LEDs and halogen lamps. When LEDs with a suitable band gap energy are used, they produce only the desired wavelength range. Consequently, this innovative method of light production is a much more efficient way of converting an electric current into light.

Tabelle 3: Benefits and drawbacks of LED technology

Motivation for the development of an LED curing light

Today LEDs are another promising alternative in light polymerizationpolymerisation of dental materials. The use of LEDs in dentistry has been discussed ever since the development of blue diodes in the 1990s. Important research in this field was carried out by the study group around Jandt. Several investigations by these authors demonstrated that the polymerizationpolymerisation capacity of LED lamps is at least equivalent to that of halogen lamps applied with the same light intensity. At a respective light intensity of 100 mW/cm2, curing depth and monomer conversion rate of the composite was significantly improved with an LED as compared with a halogen lamp.

In the meantimeState-of-the-art LED, new LED curing lights described in literature are reported to achievehave a light intensitiesy of 350 mW/cm2. However, commerciallyConventional available halogen devices achieve two to threefold times higher light intensities.; however In, a study comparing a 350 mW/cm2 LED curing light and a 755 mW/cm2 halogen lamp there wererevealed no statistically significant differences within respect ofto flexural strength and modulus of elasticity of the polymeriszed materials. In respect ofRegarding the depth of polymerizationpolymerisationofwithin the materials, the LED device achieved slightly lower values than the halogen curing light.

The above mentioned studies demonstrate that the quality of light polymerizationpolymerisation is not exclusively due to the light intensity: the narrow absorption peak of. A further significant fact is that the initiator system must also be taken into accountused in the photocured material only absorbs a certain wavelength range. This makeserefore the emitted spectrum is an important qualitative parameter determinant of a curing light's performance. The absorption curve of camphorquinone extends between 360 and 520 nm, the respective absorptionwith itsa maximum is found at 465 nm. The optimal emission spectrum of a curing light source is therefore between 440 and 480 nm.

In conventional curing devices, 95 % of the light is emitted in wavelengths between 400 and 510 nm. Thus a major portion of the photons are emitted outside the optimal spectrum range for light curing. These photons cannot, or only with reduced probability, be absorbed by camphorquinone. In contrast, 95 % of the emission spectrum of blue LEDs is situated between 440 and 500 nm. The emission maximum of a blue LED is 465 nm, which is identical with the maximum of camphorquinone. The probability of a photon emitted by an LED curing lamp beingabsorbed by camphorquinone is therefore much higher than with halogen lamps.

The following conclusion may be drawn from the above considerations: LED lamps have a lower light intensity than halogen lamps, but their emitted blue light can be utilized more efficiently to start the polymerizationpolymerisation reaction.

2. Technical design

In theELIPAR FREELIGHT3M ESPE Elipar FreeLight cordless LED curing light curing unit, light is produced by means of 19 LEDs which are aligned on three consecutive planes. The distances between the planes, the angles of emission of the light cones and the angles at which the LEDs are placed are chosen to allow the light rays to enter the end face of the light guide as directly as possible. The rays of the first and second planes are hardly shadowed at all by the LEDs installed in front of them. Therefore a narrow angle of emission is needed for the LEDs situated at a greater distance from the light guide. The prismatic panel diffuser does not affect the optical path as the rays of the first two LED planes pass through the diffuser’s planar area.

LEDs with a relatively wide angle of emission have an even greater light intensity than LEDs with narrower angles. Wide angle LEDs were chosen for the third plane because the largest portion of the rays emitted by these LEDs is utiliszable due to their short distance from the light guide. However some of the outer rays would, if unhindered, by-pass the light guide due to the wide angle of emission. A prismatic panel diffuser prevents this from happening since its geometrical design directs these rays back into the optical fibre. The rays primarily directed into the light guide pass through the planar area of the prismatic panel diffuser, like the rays of the first and second planes, and are therefore collected without hindrance.

Another favourable property of the prismatic panel diffuser is that it protects the LED array from contamination. To further enhance light power, and in order to minimisze loss of light intensity due to reflection, the diffuser is coated on both sides.

The LED array described above has the benefit that the optical properties of the LEDs themselves (i. e. their angles of emission) are utiliszed for light concentration. A complex arrangement ofComplex optical components for light collectorsion (lens systems, reflectors, focussed optical fibres, etc.) are is therefore not needed. This is of advantage, since these complex optical systems can As only collect a reduced light portion perfraction of each LED's emissions, can be collected with these complex optical systems they leading to a significant loss of light intensity. Furthermore, they are more difficult and expensive to manufacture and needrequire more space than the array described above.

3.Indications

The ELIPAR FREELIGHT3M ESPE Elipar FreeLight cordless LED curing light is a universal light polymerizationpolymerisation device for composites, compomeres, adhesives and light-cured glass ionomer materials. In order to be safely cured by the ELIPAR FREELIGHTElipar FreeLight,these materials must contain camphorquinone as a photo intitiator. Dental materials with differing photo initiator systems which have an absorption spectrum outside the 440-480 nm range are not compatible with the ELIPAR FREELIGHTElipar FreeLight. Table 1 shows a list of all tested materials tested, stating their capacity to be photopolymerized for compatibility with ELIPAR FREELIGHTElipar FreeLight. The curing times of the listed materials when polymeriszed with ELIPAR FREELIGHTElipar FreeLight are not different from those of conventional halogen curing lights.

Table 4: List of materials and their compatibility with ELIPAR FREELIGHTElipar FreeLight

4.Technical properties

The ELIPAR FREELIGHT3M ESPE Elipar FreeLight cordless LED curing light produces blue light in a completely innovative way by using LED technology. Therefore, technological investigations have concentrated focused on comparisons with conventional polymerizationpolymerisation units. Halogen lamps represent the generally accepted standardstate-of-the-art in the field of light polymerizationpolymerisation. Consequently,it was the object of the respective following studies' objective was to prove that, in spite of its lower total light intensity, the ELIPAR FREELIGHTElipar FreeLight allows a polymerizationpolymerisation quality equivalent to that of halogen curing lights.

The properties of different restorative and luting materials were evaluated in internal tests. Additionally, external investigations into the following topics were carried out by acknowledged experts:

1)Emission spectra of the ELIPAR FREELIGHTElipar FreeLight and halogen lamps and their respective compatibility with camphorquinone

2)Depth of polymerizationpolymerisation and conversion rate of different composites when cured with ELIPAR FREELIGHTElipar FreeLight or halogen lamps, respectively

3)Temperature development associated with theduring use of ELIPAR FREELIGHTElipar FreeLight and halogen lamps

4)Mechanical properties of materials light- cured with ELIPAR FREELIGHTElipar FreeLight or halogen curing lamps

5)Adhesive strength of restorative materials bonded with Prompt L-Pop and photopolymeriszed with the ELIPAR FREELIGHTElipar FreeLight or a halogen curing lamp, respectively

Internal measurements

Mechanical properties of materials polymeriszed with the ELIPAR FREELIGHTElipar FreeLight

The measurements were made in the clinical research laboratory of 3M ESPE Dental, Germany, according in accordance with to ISO 4049 (resin-based filling materials) or ISO 9917-2 (dental water-based cements) or DIN 53456 (indentation hardness test), respectively. All tests were carried out with the “softstart” polymerizationpolymerisation mode, curing times corresponded to the manufacturers’ instructions. Table 4 summariszes the compressive and flexural strengths and the depths of polymerizationpolymerisation of the tested materials as measured for the ELIPAR FREELIGHTElipar FreeLight and the 3M ESPE Elipar TriLight curing lightELIPAR TRILIGHT, respectively. 3M ESPE PertacERTAC II composite and 3M ESPE Compolute Aplicap luting compositeOMPOLUTEAplicap were evaluated according to ISO 4049, 3M ESPE Photac-FilHOTAC Fil Quick glass-ionomer filling material according to ISO 9917-2.