WO1999037239A1

WO1999037239A1 - Device for hardening composite materials used in the dental field

Info

Publication number: WO1999037239A1
Application number: PCT/EP1999/000499
Authority: WO
Inventors: François Duret; Hervé NOUI
Original assignee: Dmds Ltd.
Priority date: 1998-01-27
Filing date: 1999-01-27
Publication date: 1999-07-29
Also published as: FR2773986B1; AU2719599A; FR2773986A1

Abstract

Device for hardening composite materials used in the dental field, of the type including a central control unit (2), a light source (11) connected to said central control unit (2), a light wave guide (4) to apply the light energy to the area to be treated and optical means (5) for filtering the light emitted between said light source (11) and said guide (4). The central control unit (2) comprises electronic means (20, 21, 22) for defining and/or memorising an energy profile according to the colour of the composite material (3) to be treated and/or which the composite contains, and electronic means (23) for controlling the light intensity of the light source (11) and possibility of the filtering means (5) so as to vary the characteristics of said filtering.

Description

DEVICE FOR HARDENING COMPOSITE MATERIALS USED IN THE DENTAL FIELD.

The present invention concerns a device for hardening composite materials used in the dental field. The composite materials used in dental applications are generally comprised of a photopolymerizable resin whose molecular structure transforms under the effect of a radiation of a wavelength determined according to the absorption capacity of said composite materials. The photopolymerization of the composite material is effected with the aid of a source emitting a radiation of a wavelength activating the photocatalyzers of the material during a calculated exposure time according to the energy of the radiation so as to avoid any excessive heating of the tissues surrounding the treatment area. The wavelength, radiation intensity and exposure time parameters are also determined according to the color of the material by adjusting a higher intensity for a darker or more loaded colored composite. However, the increase of the intensity of the emitted radiation results in risks excessively heating the surrounding tissues.

There are devices for hardening soft composite materials which use mercury vapor lamps, but these emit within the ultraviolet spectrum which is dangerous for the eyes and the buccal mucous membrane of the patient.

Other devices use halogen lamps which have the drawback of having a low lumen/watt ratio and a high thermic dissipation with respect to the light energy produced.

Certain devices are equipped with lasers, but the light beam they generate is a monochromatic light which, owing to its narrow wavelengths, is only able to polymerise a limited number of composites. In addition, the laser is a costly device expensive to use and maintain.

Other devices use a light source generated by two spaced electrodes subjected to electric potential differences able to produce an electric arc through which a gas passes, said gas being partly ionized at a high 2

temperature, and a system for filtering the light emitted and comprising an infrared filter placed immediately in front of the source and making it possible to obtain a light emission spectrum of between 400 and 800 n and a low pass filter placed behind said infrared filter and making it possible to fix the high cut-off frequency of the filter to about 515 nm.

The document FR-A-261132 describes a device for cutting or treating hard or soft materials, especially living tissues, via the production of an ionized gas current whose emitted light can be used to activate the photopolymerization of substances, especially certain resins, by using filters placed in front of the source.

However, the filtering system of these devices does not permit to safely increase the luminous power of the source as the light energy absorbed by the biological tissues can result in them being destroyed if there is a high rise of temperature. In addition, the energy profile, which represents the variations of the light intensity over a period of time, cannot be adjusted as a function of the application, especially to be adapted to composite materials having different colors.

The aim of the present invention is to remedy these various drawbacks of known devices by proposing a device for treating composite materials so as to harden them by using a radiation whose energy profile can be modified dynamically according to the application so as to carry out a gradual photopolymerization able to reach the various layers of the composite, irrespective of its color, and which is in addition able to significantly reduce the time for treating said material.

The treatment device of the present invention is of the type including a central control unit, a light source connected to said central unit, a light wave guide to apply the light energy to the area to be treated, and between said light source and said guide means for filtering the light emitted, this device being mainly characterised in that the 3

filtering means is selected so that the light coming out of the light wave guide has a spectrum ranging from 450 to 500 nm and in that the central control unit comprises firstly electronic means able to define and/or memorise an energy profile according to the colour of the composite to be treated and/or the type of photocatalyzers the composite contains, and secondly electronic means for controlling the luminous power of the light source and possibly the filtering means to vary the characteristics of said filtering.

According to an additional feature of the device of the invention, the filtering means include, placed successively from the source towards the light guide inlet, a first infrared filter and then two low-pass and high-pass filters placed in this order.

According to another additional feature of the invention, at least one of the low-pass and high-pass filters is an electrochemical filter electrically connected to the central unit and whose transmission characteristics can be modified by said central unit according to the energy profile corresponding to the composite material to be treated.

In a first embodiment of the invention, the central unit comprises in its memory a table of energy profiles, each corresponding to a composite with a specific color or to a composite whose photocatalyzers react to another wavelength of the radiation able to be selected by using keys disposed on the box containing said central unit.

In another embodiment, the energy profile of a composite having a given color is automatically calculated with the aid of a spectro-colormeter whose measuring signal representative of the color of the material to be hardened is treated by the central unit so as to determine an energy profile, possibly stored. The advantages and characteristics of the present invention shall appear more clearly from a reading of the following non-restrictive description with reference 4 to the accompanying drawing given by way of mere illustration.

In the annexed drawing :

- figure 1 represents the synoptic diagram of the device of the invention.

- figure 2 represents the spectrum of the source and the frequency band at the outlet of the filter of the device, compared with the frequency band of the filters of existing devices. - figure 3 represents the block diagram of the central unit of the device. figure 4 represents a front view of the filtering device in a particular embodiment.

If reference is made to figure 1, this figure shows a device according to the invention, which includes a box 1 housing a light generator 10 comprising a lamp 11 controlled by an electronic central unit 2 for managing control of the light generator according to the parameters of a composite material 3 to be hardened by being exposed it to the light radiation emitted by the lamp 11. The light radiation is directed onto the material to be treated with the aid of an optical fiber 4 connected by one of its ends to the outlet of a filtering device 5 placed in front of the light source 11 and by its other end to a curved joining piece 40.

The box 1 is fitted with a keyboard 12 comprising thirteen tactile keys 13 and control indicator lights 14 enabling an operator to communicate with the device . Amongst the thirteen tactile keys 13, eight keys

130 enable the user to adjust the application time, three keys 131 are used to adjust the power level of the lamp 11, and two keys 132 make it possible to select an operational mode for the device. Tests have shown that the light spectrum coming out of the light wave guide needs to be preferably situated inside a wavelength band ranging from 450 to 500nm and that 5

the light intensity measured at the outlet of the wave guide, that is at the location where the effective light intensity is available for photopolymerization of the composite 3 to be hardened, needs to be at least about lW/cm^ and preferably 1.3 /cm^.

It shall also be observed that the length of the optical fiber 4 needs to be determined so as to avoid a significant attenuation of the amplitude of the light radiation and thus of its efficiency, and that it preferably ought to be about 1.8 metres.

The coating of the optical fiber 4 and of the joining piece 40 ought to be a material resistant to currently used disinfection products, such as silicon which is fully acceptable in the medical field. The optical fiber 4 is preferably a liquid fiber allowing for improved transmission of the light inside the selected spectral range and resistant to high energies, whereas the joining piece 40 is made up of a multifilament polymer. The insertion of the optical fiber 4 into the light generator 10 is of the push-pull type and the curved joining piece 40 is magnetically rendered integral to the fiber 4 so as to favor its rotation.

The light generator 10 preferably includes a discharge lamp 11 delivering a power of about 300W fed by an alternating current source 15 and fitted with a focusing optics device 16. The light spectrum of the lamp 11, identical to that of discharge lamps used in current devices, is extremely wide and is between 400 and 800 nm. From the lamp 11, the filtering device 5 includes a first infrared filter 50 stopping the infrared radiations harmful to the behaviour of the optical fiber 4 and having no useful purpose in the present application, followed by a second filter 51 of the low-pass type cutting the high frequencies above 500nm, and finally a third filter 52 of the high-pass type eliminating frequencies below 450nm. 6

The combination of the three filters 50, 51 and 52 allows a frequency band 61 to pass transmitting a fraction of the emission spectrum 62 of the lamp, as shown on figure 2. The high-pass filter 52 is an electrochemical filter electrically connected to the central unit 2 whose molecular structure can be modified via the sending of an electric signal or by any other electrical or optical means changing its light transmission characteristics and thus the value of its low cut-off frequency 520.

The low-pass filter 51 can also be controlled from the central unit 2 so as to also modify its high cutoff frequency 510.

It shall also be observed that it is also possible to have several telecontrolled filters or filters remote-controlled, via a Hertzian channel or an infrared beam, by the central unit 2, selectively or automatically or with the aid of electronic "smart" cards able to be inserted in the box 1. It is also possible to modify the light transmission by using filters sensitive to certain wavelengths. The method then consists of placing a filter photosensitive to a wavelength differing from the one used for photopolymerization, as shown on figure 4. In this particular embodiment of the filtering device 5, the intermediate filter is a photosensitive filter 57 and the device comprises a plasma source 55 for photopolymerization and a source 56 for the photosensitivation of the filter 57. Thus, according to the desired intensity, the efficiency of the sensitive filter 57 is more or less increased, thus making it possible to adjust the intensity transmitted into the optical fiber 4.

Figure 2 also shows a horizontal line 53 which represents the value of the power of a current lamp. It is known that the absorption capacity of light by a composite material 3 is proportional to the total energy of the spectrum lines represented diagrammatically by the curve 62 7

situated under the line 53 inside the frequency band of the light transmission and that it becomes more significant when the power is increased which has the effect of heating the tissues surrounding the area to be treated if the exposure time is retained.

The filtering device of the device of the invention makes it possible to avoid this heating by installing a more powerful light source 11 whilst significantly reducing the exposure time and the spectral zone. In fact, as shown on figure 2, the filters 50,51 and 52 make it possible to use a lamp with a power 54 superior to that, 53, of current lamps and to significantly reduce the exposure time whilst retaining the same absorption capacity of the materials exposed to the radiation via a reduction of the width of the frequency band 60 of the light transmitted by the optical filters of current devices, which is situated between 360 and 530nm, whilst the frequency band 61 is situated between 450 and 500nm.

The low-pass filter 51 shall preferably be slanted so as to avoid the retransmission of reflections onto the lamp 11.

Given the geometry of the retained lamp 11, two thermic dissipators (not shown) supported by a shim made of an insulating material observing the dielectric characteristics required for starting the lamp 11 and fitted with connection blocks shall be fixed to the anode and cathode of the lamp 11, that of the anode further including a bore for housing the optical filters 50, 51 and 52.

Figure 3 shows the central unit 2 comprising a microprocessor 20, ROM 21 and RAM 22, an electric circuit 23 for controlling the power of the lamp fed from the alternating current source 15 and connected to the microprocessor 20 which is also connected electrically to the keys 13 of the keyboard 12 and to the electroluminescent diodes 14.

The microprocessor 20 is electrically connected to the electrochemical filter 51 and controls the latter and 8

the control circuit 23 according to an energy profile stored in the RAM 22 corresponding to a cycle for treating a composite material having a given color and able to be photopolymerized by the radiation emitted by the light source 10.

In a first embodiment of the device of the invention, the energy profiles can firstly be stored by the manufacturer in the ROM 21 according to the color composites currently used, the user only having to select one of the thirteen keys 13 of the keyboard 12 of the box 1. In a second embodiment of the invention, the energy profiles can be defined and stored with the aid of a measuring instrument able to determine the optical characteristics of the composite material by sending to the microprocessor a signal representative of these characteristics and which is processed by using a processing program integrated in the ROM 21 so as to define the energy profile to be applied to the composite material by controlling the control circuit and possibly the filter 51, said energy profile also being stored in the RAM 22.

In this embodiment, the color of the material can be measured either by means of spectro-colormetry or with the aid of the optical fiber 4 which shall direct a measuring radiation whose return will be analyzed by the microprocessor so as to deduce from it the energy profile, or from an independent measuring device connected to the box 1. This embodiment enables the user to realize automatically and instantly a configuration to the type of composite material to be treated, regardless of its color and composition, according to the indications of a digital screen which would be integrated in the box 1.

The microprocessor 20 is also connected to a remote control device (not shown), such as a pedal, by means of a dry contact fitted with an anti-resilience mechanism (hardware or software) enabling the user to launch the previously selected photopolymerization cycle.

The device of the invention is able to gradually 9

photopolymerize the composite material to be treated so as to reach the various layers of the latter in an extremely short period of time by virtue of the variation of the power of the light source 10 with the aid of the control circuit controlled by the microprocessor 20 according to a selected energy profile and fully adapted to the composite. It also makes it possible to avoid any excess heating of the tissues surrounding the treatment area by varying the frequency band of the filtering device 5 by modifying the transmission characteristics of the filter 51, 52 or 57 under the effect of a signal emitted by the microprocessor 20 and determined according to the parameters of the selected energy profile.

It is to be noted that the modification of the color of the liquid of the optical filter 4 may also make it possible to modify the light energy of the radiation it carries .

Claims

10CLAIMS

1. Device for hardening composite materials used in the dental field, including : a. a box containing a light source ; b. a central control unit for controlling said light source ; c. a light wave guide coupled to said box at one end ; d. a treatment wand adapted to be connected to the other end of said light wave guide ; and e. optical filter means adapted to be interposed in the light path between said light source and said treatment wan ; whereby said filter means provide at said treatment wand a light beam having a spectral band ranging from 250 to 750nm.

2. Device according to claim 1 including a central control unit (2), a light source (11) connected to said central control unit (2), a light wave guide (4) for applying the light energy into the zone to be treated and, between said light source (11) and said guide (4), optical means (5) for filtering the light emitted, characterized in that the optical filtering means (5) are selected so that the light leaving the light wave guide has a wavelength spectrum ranging from 430 to 500 nm and in that the central control unit (2) comprises electronic means (20,21,22) able to define and/or store an energy profile according to the color of the composite material (3) to be treated and/or which the composite contains, and electronic means (23) for controlling the light intensity of the light source (11) and possibly the optical filtering means (5) so as to vary the characteristics of said filtering.

3. Device according to claim 2, characterized in that the filtering means (5) include, disposed successively from the source towards the inlet of the light guide, a first infrared filter (50) and two low-pass (51, 57) and high-pass (52) filters placed in this order. 11

4. Device according to claim 3, characterized in that at least one of the low-pass (51, 57) or high-pass (52) filters is an electrochemical or photosensitive filter whose transmission characteristics are able to be modified by said central unit (2) according to the energy profile corresponding to the composit (3) to be photopolymerized.

5. Device according to any one of claims 2 to 4, characterized in that the central unit (2) comprises in its memory a table of energy profiles, each profile corresponding to a composite having a specific color or to a composite whose photocatalysts react to another wavelength of the radiation and able to be selected by using keys (13) accessible on the box (1).

6. Device according to any one of claims 2 to 4, characterized in that the energy profile of a composite having a given color is automatically calculated by a spectro-colormeter whose measuring signal, representative of the color of the composite material to be hardened, is processed by the central unit (2) so as to restore to it an energy profile, possibly stored (22).

7. Device according to any one of claims 2 to 6, characterized in that the optical guide (4, 40) is an optical fiber (4) ended at its free end by a curved joining piece (40) .

8. Device according to claim 7, characterized in that the optical fiber (4) is a liquid fiber and in that the joining piece (40) is made up of a multifilament polymer.

9. Device according to claim 7 or 8, characterized in that the joining piece (40) is magnetically rendered integral with the fiber (4) so as to favor its rotation.

10. Device according to claim 8 or 9, characterized in that the light energy is selected according to the selected fiber, with or without any coloring agent.