WO2007025636A1 - Illumination device for a dental handpiece, use thereof and method for selective removal of a tooth colored intra-coronal restoration - Google Patents

Abstract

An illumination device suitable for temporary attachment to a tubular neck (34) of a dental handpiece (36) comprises a body (2) holding a light source (42) with an emission maximum at a wavelength in the range from 360 nm to 480 nm. Body (2) is provided with releasable attachment means comprising a neck engaging recess (32) and at least one retaining element (16, 18) cooperating therewith. Light source (42) is oriented towards the treatment area (T) of the handpiece (36) when the illumination device is attached thereto.

Description

Illumination device for a dental handpiece, use thereof and method for selective removal of a tooth colored intra-coronal restoration

Technical Field of the Invention The present invention relates to an illumination device for a dental handpiece, to a use thereof and to a method for selective removal of a tooth colored intra- coronal restoration.

Background of the Invention Prior to replacement of a compromised restoration, the dentist needs to completely remove the old restoration. Therefore, he must differentiate between the restorative material, which has to be removed, and the dental hard tissue, which is to be conserved.

Tooth colored restorations are being used increasingly in industrial countries whereas the use of amalgam restorations is decreasing for esthetical, psychological and environmental reasons. In the next decades the need for replacement of tooth colored restorations will increase due to material related problems (restoration fracture or loss, marginal or total discoloration) or due to dental hard tis- sue related problems (caries, secondary caries, tooth fractures).

However, tooth colored intracoronal resin composite and ceramic restorations are difficult to remove because due to their good optical and physical adaptation to dental hard tissue they are not readily distinguishable from it. This leads to

« either (i) an extensive removal of sound dental hard tissue in order to ensure that all the composite has been removed, or (ii) to remainders of unrecognized composite at the cavities' finishing line. The latter prevents adhesion of the renewed restoration to dental hard tissue and may result in an accelerated need for replacement due to discolorations or fractures because the dental hard tissue in this case is not stabilized by the adhesive restoration. The currently available methods for distinguishing between tooth colored intra- coronal restorations and sound dental hard tissue are time consuming and inaccurate.

Visual distinction under normal illumination fails because of the good optical adaptation. Even the use of a dental handpiece provided with a small light bulb, e.g. a contra-angle handpiece as the ones disclosed in US 4,680,011 and US 5,908,295 will not be sufficient due to the simple fact that the color and general appearance of modern tooth colored intra-coronal restorations are very similar to those of dental hard tissue.

Differences in hardness are not clearly detectable because ceramic inlays provide similar hardness as human enamel and modern (fine-) hybrid composites provide similar hardness as human dentin.

If the tooth and the restoration are isolated with rubber dam and completely air- dried, a probe will produce thin black scratches on most composite surfaces and the restoration can thus be identified. Unfortunately, the drying procedures are time consuming and the effect of the probe is only visible on the very surface and is over glossed immediately by the water spray coolant.

A method for the distinction of a dental material applied to a substrate from natural teeth, false teeth or parts thereof is disclosed in EP 431 452 A. According to that method, 0.00001 to 1% by wt. of a fluorescent substance having an absorp- tion maximum in the wave length range of 360 to 480 nm and a fluorescence maximum in the wave length range of 480 to 600 nm is incorporated in the dental material. The dental material is applied to the substrate and irradiated with a light source emitting light of a wavelength in the region of 360 to 480 nm and is then viewed through a light filter filtering out at least partially the light of a wave length in the region of 360 to 480 nm. EP 431 452 A does not teach how to work when removing a dental material other than those specifically disclosed therein. Summary of the Invention

It is the principal object of the present invention to provide a simple and reliable device for distinguishing between tooth colored intracoronal restorations and sound dental hard tissue.

According to a first aspect of this invention, there is provided an illumination device suitable for temporary attachment to a tubular neck of a dental handpiece, said illumination device comprising a body holding a light source with an emission maximum at a wavelength in the range from 360 nm to 480 nm, said body being provided with releasable attachment means comprising a neck engaging recess and at least one retaining element cooperating therewith, said light source being oriented towards the treatment area of the handpiece when the illumination device is attached thereto.

The illumination device is easily attached to and removed from a dental handpiece, most notably a contra-angle handpiece. Energy can be supplied to the light source by a stabilized battery or from the dental unit. A dentist will need one or more illumination devices depending on the workflow and intensity of his practice, and he can use most if not all of his existing contra-angle handpieces with the same illumination device. If is not needed, the dentist can unclip the illumination device from his handpiece and work with the latter as usual. The attachment or removal of the device is carried out within a few seconds.

By means of this simple device the dentist is able to accurately identify and re- move compromised tooth-colored intracoronal restorations and to identify and preserve sound dental hard tissue. The illumination device may be used equally well with high-speed contra-angle handpieces and air turbines, which may be equipped with water-spray cooling, and with low speed contra-angle handpieces without water-spray cooling. In particular, the dentist does not need to repeatedly air-dry the tooth during restoration removal and will therefore save a lot of time. Because the releasable attachment means fit to most If not all the commonly used handpieces, the investment for adopting the method for distinguishing between tooth colored intracoronal restorations and sound dental hard tissue is low. The dentist can keep his handpieces and only needs to buy one or perhaps a few more illumination devices depending on the workflow in his practice.

Especially in the regions of finish line and margins, where restorative removal and hard tissue prevention are crucial, the illumination device turns out to be extremely helpful.

Advantageous embodiments are defined in the dependent claims.

In principle, the light source may comprise a bulb, a laser, a fiber-optic or any other light emitting or conducting means. Advantageously, the light source has an emission maximum at a wavelength of approximately 400 nm, which is in the blue-violet part of the visible spectrum, at its lower wavelength end. Preferably, the light source is a light emitting diode (LED), which has the advantage of small size and low energy consumption. Moreover, the light source may be equipped with means for collimating and or focussing the light emitted by the light source.

In a particularly advantageous embodiment, the attachment means comprise first and second legs extending from the body. Each one of said legs includes an inner side adjacent the inner side of the other leg. At least one of said legs is elas- tically deformable relative to the body. A neck engaging recess and retaining element of the illumination device is formed by cooperation of the inner sides of the first and second legs, which preferably are made of stainless steel.

While the illumination device could be built as an autonomous unit comprising a suitable power supply, it is preferable to use a power supply that is not located near the tip of the dental handpiece. Accordingly, the illumination device preferably comprises a power cable for connecting the light source to an external power supply. Moreover, the illumination device may further comprise a clip for temporarily securing the power cable to the neck or sleeve of the dental handpiece on which the device is being used.

According to another aspect, the invention comprises using the illumination device for identifying tooth colored intra-coronal restorations during treatment thereof by means of a handpiece.

According to a further aspect, the invention comprises a method for selective removal of a tooth colored intra-coronal restoration arranged within dental hard tissue of a tooth, the method comprising the steps of:

a) attaching an illumination device according to this invention to a tubular neck of a dental handpiece;

b) turning on the light source;

c) selectively removing portions of said restoration by means of the handpiece while using a difference in fluorescent behavior to distinguish between said dental hard tissue and either said restoration or a luting compound present between said restoration and said dental hard tissue.

The above method works particularly well if the commonly used surgical spotlights are dimmed off or tilted away from the treatment area.

Brief description of the drawings

The above mentioned and other features and objects of this invention and the manner of achieving them will become more apparent and this invention itself will be better understood by reference to the following description of various em- bodiments of this invention taken in conjunction with the accompanying drawings, wherein Fig. 1 shows an illumination device without light source, in a top view;

Fig. 2 shows the illumination device of Fig. 1 in a sectional view according to section U-Il of Fig. 1 ;

Fig. 3 shows the illumination device of Fig. 2 with an inserted light source and attached to a dental handpiece;

Fig. 4 shows, under normal light illumination, a photograph of a tooth- colored material used for intra-coronal restoration arranged between two human teeth;

Fig. 5 shows a photograph of an illumination device, three contra-angle dental handpieces and a securing clip;

Fig. 6 shows a photograph of the illumination device and securing clip of Fig. 5 and a power supply unit;

Fig. 7 shows the illumination device and securing clip of Fig. 5 mounted onto the neck portion of a contra-angle handpiece;

Fig. 8 shows, under UV illumination, a tooth with a tooth-colored intra- coronal restoration made of a fluorescent material;

Fig. 9 shows, under UV illumination, a tooth with a tooth-colored intra- coronal restoration made of a non-fluorescent material featuring a marginal contact zone comprising a fluorescent luting compound.

Detailed description of the invention The exemplifications set out herein are not to be construed as limiting the scope of this disclosure or the scope of this invention in any manner. The illumination device shown in Figs. 1 to 3 comprises a body 2 having a substantially planar top side 4 and a substantially planar bottom side 6 that are substantially parallel to each other, a substantially planar front side 8 that is substantially perpendicular to said top and bottom sides, and a pair of lateral sides 10 and 12 that are substantially parallel to each other and substantially perpendicular to said front, top and bottom sides. Moreover, body 2 has a concave rear side 14 that is formed substantially symmetrical with respect to a longitudinal axis Z of body 2. Advantageously, body 2 is made of aluminum or stainless steel.

As particularly shown in Fig. 1, the illumination device further comprises a pair of legs 16 and 18, preferably made of stainless steel, that project in rearward direction. First leg 16 is attached at its proximal end 20 to the first lateral side 10 by means of a first screw 22 whereas second leg 18 is attached at its proximal end 24 to the second lateral side 12 by means of second screw 26. Each one of said legs has a substantially straight section at its respective proximal end so as to abut against the associated lateral side of body 2. Moreover, each one of said legs has a curved section with an S-type shape towards its distal end. As shown in Fig. 1 , first leg 16 includes an inner side 28 and second leg 18 includes an inner side 30, each one of said inner sides being adjacent to the inner side of the other leg. The two inner sides 28 and 30 and the rear side 14 of body 2 define an approximately circular neck engaging recess 32 therebetween, having a diameter D. Moreover, the S-type shape defines a distal entry portion at which the distance E between the two legs 16 and 18 has a local minimum. In particular, E is smaller than D.

The two legs 16 and 18 are elastically deformable relative to the body 2 in a deformation direction that is substantially perpendicular to the bisector A of the two legs and substantially within a plane formed by the two legs and said bisector. In this way, the two legs 16 and 18 act as retaining elements cooperating with the neck engaging recess 32. As shown in Fig. 3, the illumination device is suitable for temporary attachment to a tubular neck 34 of a dental handpiece 36, shown here schematically as a con- tra-angle handpiece with a bur 38 that is oriented roughly perpendicularly to a longitudinal axis H of said tubular neck. It will be understood that the two elasti- cally deformable legs 16 and 18 and the rear side 14 function as releasable attachment means. For this purpose, the diameter D of recess 32 is chosen so as to be substantially equal to the outer diameter of neck portion 34. Therefore, the illumination device can be snapped onto the tubular neck by temporarily driving apart the two legs 16 and 18; thereafter, the illumination device is retained in its operational position by the elastic force of the two legs.

Body 2 further comprises a cylindrical borehole 40 located near the front side 8; as shown in the figures, the borehole goes all the way through the body 2 and has a longitudinal axis L oriented at an inclination angle α with respect to the bi- sector axis A and substantially parallel to the lateral sides 10 and 12. In the example shown, the inclination angle is roughly 45°. Borehole 40 holds a light source 42 (shown in Fig. 3, only) with an emission maximum at a wavelength in the range from 360 nm to 480 nm. As seen in Fig. 3, light source 42, for example a light emitting diode (LED), is plugged into borehole 40 and oriented towards the treatment area of the handpiece, i.e. a region T located near the tip of bur 38, when the illumination device is attached to the handpiece 36. As further seen from Fig. 3, the light source has a pair of electrically insulated wires 44 for connection to a suitable electrical power supply not shown in this figure. In the example shown, the light source generates a cone-like light bundle with a full aper- ture angle of approximately 35°. If required, a narrower illumination code can be achieved by collimating the light emitted from the LED, e.g. by arranging the LED in a retracted position within borehole 40, or by providing a focussing optic in front of the LED.

It will be appreciated that the specific geometric shape of various parts of the illumination device - particularly the inclination angle α, which essentially defines the angle between illumination direction and a relevant orientation of the neck engaging recess - are to be chosen according to the type of handpiece for which the device shall be used. Apart from the widely used contra-angle handpieces, another kind of handpiece is the so-called straight type, wherein the bur axis is roughly parallel to the neck axis H. For such handpieces the inclination angle α will have to be roughly 90°. Furthermore, the shape of the two legs 16 and 18 and of the rear side 14 may have to be adapted to specific shapes of the neck portion of the handpiece, such as e.g. a pair of lateral planar sections as shown in Fig. 7 or a curvature of the neck portion in the region against which the rear side 14 is to abut. In particular, it may be appropriate to have the two legs 16 and 18 to lie in a plane that is somewhat tilted with respect to a principal symmetry plane of the body 2.

Fig. 4 shows the good color adaptation of modern composite resins for intra- coronal restorations. Depending on the initial quality and the patient's care for maintenance of the restoration, restoration lifetimes from less than two to more than ten years can be expected. The main reasons for failure of such restorations are secondary caries, restoration fractures or dental hard tissue fractures. Virtually in all failure cases, most of the restoration will still be in place and needs to be removed with rotating diamond burs. In an initial phase, usually a highspeed contra-angle handpiece is used. In the latter phase, two or three water- spray valves are integrated into the drill head for cooling the bur, the restoration to be removed and the dental hard tissue to prevent the latter from thermal damages. In some contra-angle handpieces, a light source emitting visible light is integrated to illuminate the operative field.

Because of its good color adaptation, the restoration or its remainder is hard to identify during restoration removal especially if water-spray is used for cooling. If old composite resin is still present in marginal areas of the cavity, it is impossible to lute a new composite to the cavity in this area with standard procedures. This may result in reduced restoration lifetime for the new restoration. To prevent this problem, it is customary to remove an excessive amount of sound dental hard tissue, thus resulting in larger cavity sizes. This, however, may reduce the life expectancy of the tooth.

Fig. 5 shows a photograph of the illumination device and three contra-angle handpieces that are used in every dental office for every kind of tooth preparation. The photograph shows, in particular, the attachment means (D), the light source consisting of a 3UV400-30 LED (E) and a clip for the power supplying cable (F). Moreover, (A) is a low speed handpiece (A) with a drill head for con- ventional burs (KaVo, Gentle Power LUX 7LP), whereas (B) is a high-speed contra-angle handpiece (KaVo, Gentle Power LUX 25LP) and (C) is another highspeed contra-angle handpiece (Sirona Sirius), both of which have drill heads for friction grip burs. All these contra-angle handpieces are connected to micromotors and transmit the speed of the latter to the bur. The illumination device can readily be attached to the contra-angle handpieces shown here and to most other commonly used handpieces. Moreover, because the customarily used handpieces all have the same diameter in the portion near the attachment to the micro-motor unit, a universal spring ring (F) can be used to secure the electric cable thereto. As shown in Fig. 6, electrical power may be provided to the LED light source by a stabilized battery contained in a housing (E) with a socket on the lower left side into which is plugged the electrical cable. Alternatively, electricity for the LED may be taken directly from the dental unit.

Fig. 7 is a photograph of an illumination device mounted to a high-speed contra- angle handpiece with a cylindrical friction grip diamond bur. The light from the LED is directed towards the tip of the bur, which is the expected working area where visual distinction between various materials is required. The illumination device is snapped onto the contra-angle handpiece only when this is needed for the treatment, i.e. when an intracoronal restoration has to be removed for any reason. The device can be mounted onto the handpiece in a few seconds. After having carefully removed any remainders of old dental restorative material, the illumination device can be un-mounted and the handpiece can be used in its customary way. It should be noted that a built-in conventional light source as it is present in some commercial handpieces does not need to be switched off or covered up during use of the LED. This, again, saves time.

Fig. 8 shows the effect of illumination by a 3UV400-30 LED whereby the restorative material (A) is easily discriminated from dental hard tissue (B) because of fluorescent particles that are integrated within most modem composites and in some dental ceramics for optical and esthetical reasons. This contrast is also visible when the water-spray integrated within the handpiece is used for cooling.

Fig. 9 shows illumination of an older ceramic material - in this case it is Cerec MKII - that does not contain fluorescent particles for brightening effects. However, all intra-coronal ceramic restorations must be luted with composite resin. Therefore, in the critical marginal contact zone, ceramic, luting composite (A) and dental hard tissue (B) can easily be discriminated (A). If a non-fluorescent ceramic inlay needs to be removed, unnecessary removal of sound dental hard tissue can be prevented because of the fluorescence of the luting composite. This is evidenced in Fig. 9, where the thin, fluorescent luting composite is clearly visible at the interface between a well fitting non-fluorescent ceramic inlay and the dental hard tissue. Because virtually all intra-coronal ceramic restorations need luting to dental hard tissue by means of a composite, even non-fluorescent ceramics can be removed with this technique.

Claims

Claims

1. An illumination device suitable for temporary attachment to a tubular neck (34) of a dental handpiece (36), said illumination device comprising a body (2) holding a light source (42) with an emission maximum at a wavelength in the range from 360 nm to 480 nm, said body being provided with releas- able attachment means comprising a neck engaging recess (32) and at least one retaining element (16, 18) cooperating therewith, said light source being oriented towards the treatment area (T) of the handpiece when the H- lumination device is attached thereto.

2. The illumination device of claim 1 , wherein the light source (42) has an emission maximum at a wavelength of approximately 400 nm.

3. The illumination device of claim 1 , wherein the light source (42) is a light emitting diode.

4. The illumination device of claim 1 , further comprising means for collimating and or focussing light emitted by the light source (42).

5. The illumination device of claim 1 , wherein said attachment means comprise first and second legs (16, 18) each extending from the body (2), each one of the first and second legs (16, 18) including an inner side (28, 30) adjacent the inner side (30, 28) of the other leg (18, 16), at least one of the first and second legs being elastically deformable relative to the body, said neck engaging recess (32) and said retaining element being formed by cooperation of the inner sides of the first and second legs.

6. The illumination device of claim 1 , wherein the first and second legs (16, 18) are made of stainless steel.

7. The illumination device of claim 1 , further comprising a power cable (44) for connecting the light source (42) to an external power supply.

8. The illumination device of claim 7, further comprising a clip for temporarily securing the power cable (44) to the neck or sleeve of a dental handpiece

(36).

9. Use of an illumination device according to any one of claims 1 to 8 for identifying tooth colored intra-coronal restorations during treatment thereof by means of a handpiece.

10. Method for selective removal of a tooth colored intra-coronal restoration arranged within dental hard tissue of a tooth, comprising the steps of:

a) attaching an illumination device according to any one of claims 1 to 8 to a tubular neck of a dental handpiece;

b) turning on the light source;

c) selectively removing portions of said restoration by means of the handpiece while using a difference in fluorescent behavior to distinguish between said dental hard tissue and either said restoration or a luting compound present between said restoration and said dental hard tissue.