WO2003061514A1

WO2003061514A1 - Hand apparatus with predetermined light distribution

Info

Publication number: WO2003061514A1
Application number: PCT/GB2003/000242
Authority: WO
Inventors: Silk Graham; Michael John Colles
Original assignee: Carl Zeiss Meditec Ag
Priority date: 2002-01-22
Filing date: 2003-01-22
Publication date: 2003-07-31
Also published as: GB0418574D0; GB2401320A; GB2401320B; GB0201328D0

Abstract

A hand apparatus (10) comprises: a housing (20); and an optical carrier (30) extending from the housing (20) and having a substantially linear light emitter (40) at one end. The emitter (40) is adapted to allow a predetermined profile of light emission along the length of the emitter (40).

Description

Hand Apparatus with Predetermined Light Distribution

The present invention relates to an apparatus for delivery of a beam of light to an area of application. In particular, but not exclusively, the invention relates to a hand apparatus including an emitter that provides a predetermined distribution of laser light to an area of application during dental treatment.

Hand pieces are used in medicine, dentistry and other forms of treatment to apply light locally to an area being treated. The light may be generated at a base unit and transmitted along a cable to a fixed hand piece. Alternatively the base unit may include a power source, with electrical power transmitted along a cable to a hand piece to generate the light at the hand piece itself. The flexible cable connection allows the operator of the hand piece to move the hand piece easily to the required point of application. Traditionally, the treatment of caries of a tooth has involved removing the caries by reaming the tooth using a mechanical reamer and then applying a filling material to the cavity. This process can cause discomfort to a patient and two or three sessions, with temporary and then permanent fillings may often be required. An alternative approach is to use laser light to irradiate the tooth and then to fill the cavity with a resin. Such an approach causes less discomfort and can be carried out in one visit by the patient to the dental practitioner.

A typical tooth cavity has a depth of around 15 mm. Also, the root canal of a tooth is arcuate and so the applicator portion of the hand piece must be of sufficient flexibility to bend within the passage. However, typical emitters produce light radiation that is non-uniform along the length of the emitter. This entails a less controlled application where multiple passes are required. The typical diameter of the emitters is about 3 mm and this places a limitation on the flexibility of the applicators that can be achieved using conventional materials.

As the internal profile of the tooth cavity is so irregular, it is desirable to have emitters that emit different distributions of light along their length, such as cylindrical or conical radiation profiles.

According to a first aspect of the present invention there is provided a hand apparatus comprising: a housing; and an optical carrier extending from the housing and having a substantially linear light emitter at one end, wherein the emitter is adapted to allow a predetermined profile of light emission along the length of the emitter.

Preferably the optical carrier comprises at least one optical fibre. Preferably the optical carrier further comprises an elongate sleeve. Preferably the sleeve is resiliently flexible. Preferably the sleeve is made of a Polyethylene, PVC or PTFE material. Alternatively, the sleeve is plastically deformable.

Preferably the radial light emission is of uniform intensity over the length of the emitter. This may be termed a cylindrical profile of light emission. Alternatively the intensity of radial light emission varies linearly over the length of the emitter. This may be termed a conical profile of light emission.

Preferably the light emitter comprises a scattering medium that causes light to be emitted from the light emitter. Preferably the scattering medium is dispersed within a resin. Preferably the pattern of intensity of light emission is determined by the concentration of scattering medium per unit length of the emitter. Alternatively the light emitter comprises an optical fibre having a reflective cladding and light is selectively emitted by alteration of the cladding. Preferably the pattern of intensity of light emission is determined by the degree of alteration per unit length of the emitter. Preferably the alteration comprises perforations in the cladding. Alternatively the alteration comprises abrasions or microcracks in the cladding. Alternatively the alteration comprises thermal or chemical treatment of the cladding.

Preferably the light emitter is substantially cylindrical or conical. The light emitter may comprise both a cylindrical and a conical portion. Preferably the light emitter has a diameter of less than 2 mm. Preferably the light emitter has a diameter of between 0.2 mm and 0.8 mm, preferably about 0.5 mm. Preferably the light emitter has a length of between 8 mm and 30 mm, preferably about 15 mm.

According to a second aspect of the present invention there is provided a light delivery system comprising a light source and a hand apparatus, the hand apparatus comprising: a housing; and an optical carrier extending from the housing and having a substantially linear light emitter at one end, wherein the emitter is adapted to allow a predetermined profile of light emission along the length of the emitter. Preferably the light source is battery powered.

Preferably the optical carrier comprises at least one optical fibre. Preferably the optical carrier further comprises an elongate sleeve.

Preferably the profile of light emission is substantially cylindrical. Alternatively the profile of light emission may be substantially conical.

Preferably the light emitter comprises a^' scattering medium that causes light to be emitted from the light emitter. Preferably the scattering medium is dispersed within a resin. Preferably the profile of light emission is determined by the concentration of scattering medium per unit length of the emitter.

According to a third aspect of the present invention there is provided a method of delivering a beam of light to a point of application, the method comprising the steps of: providing a light source; providing a hand apparatus comprising a housing and an optical carrier extending from the housing; and providing a substantially linear emitter at one end of the optical carrier, wherein the emitter is adapted to allow a predetermined profile of light emission along the length of the emitter. Preferably the optical carrier comprises at least one optical fibre. Preferably the optical carrier further comprises an elongate sleeve.

Preferably the light emitter comprises a scattering medium that causes light to be emitted from the light emitter. Preferably the scattering medium is dispersed within a resin.

Preferably the step of providing the emitter comprises the steps of: preparing a mix of scattering medium and resin; cleaning the end of the or each optical fibre and inserting the or each optical fibre into the sleeve; immersing the fibre and sleeve in the mix; withdrawing the fibre from the sleeve by a specified distance causing the mix to be drawn into the sleeve; and curing the mix that has been drawn into the sleeve.

Preferably the resin is cured using light transmitted from the fibre.

Preferably the step of providing the emitter further comprises the step of trimming the mix and sleeve to a specified length.

Preferably the profile of light emission is substantially cylindrical. Alternatively the profile of light emission may be substantially conical .

Preferably the profile of light emission is determined by the concentration of scattering medium per unit length of the emitter. The profile may be determined by varying the concentration of scattering medium during withdrawal of the fibre from the sleeve. Preferably a conical profile is achieved by applying a tensile force to the sleeve and mix before curing of the resin, the force varying along the length of the sleeve and mix. Alternatively a conical profile is achieved by stratifying the concentration of scattering medium through the depth of the resin.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of a hand apparatus according to the first aspect of the present invention;

Fig. 2 is a perspective view of the hand apparatus of Fig. 1 with one component removed;

Fig. 3 is a sectional side view of a component of the hand apparatus of Fig. 1 within a tooth; Fig. 4 is a longitudinal view of a component of the hand apparatus of Fig. 1 within a root canal of a tooth;

Fig. 5 is a sectional longitudinal view of a component of the hand apparatus of Fig . 1 ;

Fig. 6 is another sectional longitudinal view of a component of the hand apparatus of Fig. 1; and

Fig. 7 is a sectional perspective view of a component of the hand apparatus according to the third aspect of the present invention.

Referring to Figs. 1 and 2 there is shown a hand apparatus 10 comprising a housing 20 and an optical carrier 30 extending from the housing 20. The hand apparatus 10 may be of the type described in UK Patent Application Number 0107853.4.

The optical carrier 30 comprises an optical fibre 32 within a sleeve 34. As explained below, the optical carrier 30 is adapted to form an emitter 40 at its free end. The sleeve 34 is typically produced from a transparent or translucent polymer material such as Polyethylene. Alternatively, a PTFE or PVC material could be used.

The housing comprises two moulded plastic members 22, 24 which are assembled together. Fig. 2 shows the hand apparatus 10 with one of the members 24 removed. It can be seen in this figure that the optical fibre 32 continues within the housing 20 to an optical connector 50, 52. A female portion 52 of the connector is connected to a light source 60 by a further optical fibre within a sheathed cable 62. The light source 60 may be a light generator such as the type described in UK Patent Application Number 0118209.6. The optical connector 50, 52 allows removal of the main portion of the hand piece 10 for disposal and the replacement by a new hand piece 10.

The hand apparatus 10 also includes a disconnecting latch 70 and a gripping portion 72 for the user.

Fig. 3 shows the emitter 40 of the hand apparatus 10 inserted within a tooth 200. It can be seen that, to reach the furthermost regions 204 of the root canal 202, the length and diameter of the emitter 40 should be of suitable values. Also, the root canal 202 is arcuate and so the emitter 40 must be of sufficient flexibility to bend within the passage 202. The diameter of the emitter 40 is one factor that determines the flexibility of the emitter 40.

Fig. 4 shows a typical profile of an emitter 40 within an idealised representation of a root canal 202 according to an embodiment of the present invention. The overall length of the emitter 40 is typically 15 mm. At this distance ^• from the open end of the root canal 202, represented by location ^λA' , the diameter of the root canal 202 is typically 1.4 mm. At a location of 3.3 mm from the free end, represented by location ^λB', the diameter of the root canal 202 has typically reduced to 0.5 mm. At a location proximate to the base of the root canal 202, represented by location 'C, the diameter has typically reduced to 0.25 mm.

Also shown in Fig. 4 is a root canal 202 with a larger diameter at the open end. It is clear from Fig. 4 that it is advantageous to be able to provide an emitter 40 having a diameter of around 0.5 mm. It is also advantageous to be able to predetermine the profile of light distribution from the emitter 40 to suit the geometry of the root canal 202 to be treated. Although a smaller diameter emitter 40 has the advantage of being able to be used in narrow dental passages, it is to be understood that the principles of the invention may be applied to larger diameter emitters.

Fig. 5 shows a sectional view of the construction of the free end of the optical carrier 30. The end of the optical fibre 32 does not extend to the end of the sleeve 34. Typically the distance between the two ends is 15 mm.

An optical fibre typically consists of the glass core 36, a cladding 37 and a buffer coating 38. Light beams 220, typically laser light, are passed along the glass core 36. If the beam 220 is not parallel to the longitudinal axis of the core 36, or the core bends to any degree, the beam 220 will strike the cladding 37. Providing that the beam 220 strikes the cladding 37 at an angle relative to a line normal to the surface of the cladding 37 (angle of incidence) that is greater than a critical angle, then the beam 220 will be reflected back into the core 36 at an angle 222 (angle of reflection) equal to the angle of incidence . The critical angle is dependent on the ratio of the refractive indices of the two materials.

A buffer coating 38 surrounds the cladding 37 to protect the fibre 32 from surface damage and the ingress of moisture and to provide a greater structural strength.

Between the ends of the optical fibre 32 and the sleeve 34 there is provided a scattering medium 80. The medium 80 consists of a resin to which is added a quantity of reflective particles 82. The resin is typically a standard dental resin such as 1/1 BisGMA/THFMA. Typically, the reflective particles 82 are made from Titanium Dioxide.

Light beams 220 exiting the optical fibre 32 enter the scattering medium 80. The beam 220 travels through the medium 80 until it strikes a reflective particle 82. The beam 220 is then reflected at an angle dependent on the orientation of the surface of the particle 82 that is struck. In many cases, the beam will be reflected towards the sleeve 34 and will strike the surface of the sleeve 34 at an acute angle 224 relative to a line normal to the surface of the sleeve 34. In these cases, as the angle 224 is less than the respective critical angle, the beam 220 is refracted through the sleeve. Light will then be emitted from the sleeve at the same angle 224.

Fig. 6 shows the free end of the optical carrier 30 having a substantially uniform and a substantially non-uniform distribution of reflective particles 82 along the length of the emitter 40. The probability of a light beam 220 striking a particle 82 is proportional to the concentration of particles 82 at any given region of the emitter 40. Therefore, a substantially uniform distribution of particles 82 leads to a substantially uniform intensity 230 of light emission along the length of the emitter 40. Similarly, a linearly decreasing distribution of particles 82 leads to a linearly decreasing intensity 230 of light emission along the length of the emitter 40.

In practice, a substantially uniform concentration of particles 82 will lead to a slightly conical profile of light emission along the length of the emitter 40 (linearly decreasing from the end of the optical fibre 32) . This is because the proportion of all the available light that has been emitted from the optical fibre 32, and not already scattered, decreases over the length of the emitter 40. It should be appreciated that the resulting profile is generally advantageous, given the geometry of the root canal as shown in Fig. 4. However, in Fig. 6, the profile of light emission has been idealised as cylindrical. Fig. 7 shows how scattering medium can be introduced to the end of the optical carrier 30. The optical fibre 32 is inserted into the sleeve 34 until the end of the fibre 32 extends a distance, typically between 2 to 5 mm, beyond the end of the sleeve 34. The end of the optical carrier 30 is then immersed in a reservoir 84 of the scattering medium 80. The scattering medium 80 is in a liquid state at an ambient temperature.

The optical fibre 32 is then retracted in the direction shown as *D' until there is a typical distance of just greater than 15 mm between the end of the fibre 32 and the end of the sleeve 34. This retraction draws the scattering medium 80 into the sleeve. The optical carrier 30 is rapidly removed from the reservoir 84 and light 220 is passed down the optical fibre 32. The light 220 refracting through the scattering medium 80, or reflecting from the particles 82, generates heat that cures or partially cures the resin of the scattering medium 80. However, the medium remains in a viscous state. The scattering medium 80 that coated the end of the optical fibre 32 prior to retraction provides adhesion between the fibre 32 and the sleeve 34. The end of the sleeve 34 can be trimmed to obtain an emitter 40 with the correct length and having a clean tip.

The scattering medium 80 shown in Fig. 7 has a substantially uniform concentration of reflective particles 82 throughout the depth of the reservoir 84. Alternatively, the medium 80 may be stratified so that the concentration of reflective particles 82 varies throughout the depth of the reservoir 84. This would produce a non-uniform concentration along the length of the emitter 40. It has been explained above how a uniform concentration of particles 82 will lead to a slightly conical profile of light emission along the length of the emitter 40. If a more cylindrical profile is desired, this can be achieved by increasing the concentration of particles 82 in the scattering medium 80 during the retracting of the optical fibre 32. This will lead to an emitter 40 with an increasing concentration of particles 82 towards the free end of the emitter 40.

The viscous nature of the resin may also be utilised to produce an emitter 40 with a varying concentration of reflective particles 82 along the length of the emitter 40. A transient tensile force can be applied to the emitter before curing of the resin, the magnitude of the force varying along the length of the emitter 40. The medium 80 will deflect, with the degree of deflection being proportional to the magnitude of the force, and the average distance between neighbouring particles 82 will increase proportionally. When the force is removed, the medium will remain in its deflected state. Any resilience of the medium 80, or the sleeve 34, can be resisted once the resin is cured. In this case, the sleeve must be produced from a plastic or viscoelastic material. Variations and modifications can be made to the embodiments herein described without departing from the scope of the invention. In particular the shape of the emitter is not limited to the shapes illustrated in the drawings or described above. It is to be understood that the term optical fibre includes in its scope optical carriers comprising two or more optical fibres bundled together.

Claims

1. A hand apparatus comprising: a housing; and an optical carrier extending from the housing and having a substantially linear light emitter at one end, wherein the emitter is adapted to allow a predetermined profile of light emission along the length of the emitter.

2. A hand apparatus as claimed in Claim 1, wherein the optical carrier comprises at least one optical fibre.

3. A hand apparatus as claimed in Claim 1 or 2 , wherein the optical carrier further comprises an elongate sleeve, the sleeve being resiliently flexible.

4. A hand apparatus as claimed in any preceding claim, wherein the radial light emission is of uniform intensity over the length of the emitter.

5. A hand apparatus as claimed in any of Claims 1 to 3 , wherein the intensity of radial light emission varies linearly over the length of the emitter.

6. A hand apparatus as claimed in any preceding claim, wherein the light emitter comprises a scattering medium that causes light to be emitted from the light emitter.

7. A hand apparatus as claimed in Claim 6, wherein the pattern of intensity of light emission is determined by the concentration of scattering medium per unit length of the emitter.

8. A hand apparatus as claimed in any of Claims 1 to 5 , wherein the light emitter comprises an optical fibre having a reflective cladding and light is selectively emitted by alteration of the cladding.

9. A hand apparatus as claimed in any preceding claim, wherein the light emitter is substantially cylindrical or conical.

10. A hand apparatus as claimed in any preceding claim, wherein the light emitter includes a first portion having a diameter of less than 2 mm.

11. A hand apparatus as claimed in any preceding claim, wherein the light emitter has a length of between 8 mm and 30 mm.

12. A light delivery system comprising a light source and a hand apparatus, the hand apparatus comprising: a housing; and an optical carrier extending from the housing and having a substantially linear light emitter at one end, wherein the emitter is adapted to allow a predetermined profile of light emission along the length of the emitter.

13. A method of delivering a beam of light to a point of application, the method comprising the steps of : providing a light source; providing a hand apparatus comprising a housing and an optical carrier extending from the housing; and providing a substantially linear emitter at one end of the optical carrier, wherein the emitter is adapted to allow a predetermined profile of light emission along the length of the emitter.

14. A method of delivering a beam of light as claimed in Claim 13, wherein the light emitter comprises a scattering medium that causes light to be emitted from the light emitter.

15. A method of delivering a beam of light as claimed in Claim 14, wherein the step of providing the emitter comprises the steps of: preparing a mix of scattering medium and resin; cleaning the end of the or each optical fibre and inserting the or each optical fibre into the sleeve; immersing the fibre and sleeve in the mix; withdrawing the fibre from the sleeve by a specified distance causing the mix to be drawn into the sleeve; and curing the mix that has been drawn into the sleeve.

16. A method of delivering a beam of light as claimed in Claim 15, the resin is cured using light transmitted from the fibre.

17. A method of delivering a beam of light as claimed in any of Claims 14 to 15, wherein the profile of light emission is determined by the concentration of scattering medium per unit length of the emitter.