BACKGROUND OF THE INVENTION In dentistry, the reasons for illuminating a person's mouth include the curing of tight activated resins, transillumination of teeth, assistance in visualizing target areas and for the purposes of general examination.

Non-specific tight sources such as operating lights provide general illumination in the mouth but do not provide the concentrated focus that is sometimes required for specific purposes.

Light curing systems are well known in the dental industry and are used to initiate setting of tight activated resins used in fillings and restorations. These tight curing systems have a tight source, usually in the form of a hand held device, which connects to a tight curing tip commonly containing glass fiber optic tubes in fused or loose bundles. The tips are expensive and prone to permanent malfunction if damaged as a result of even minor accidents. The tips must also be produced in a range of sizes and shapes to allow application of tight to different locations in the mouth and for different indications. The tips are typically of relatively short length so that the light source when attached and in use is in close proximity to a patient's face.

Some instruments such as dental drills contain their own light channelling devices that are commonly composed of glass fiber optic components. These components also suffer from the disadvantages of comparative fragility and are prone to damage.

Because of their expense, the tight curing tips are used repetitively and therefore must be sterilisable by the processes of gas sterilisation, autoclaving or other suitable process. Particular precautions are required to guard against the spread of HIV Virus, Hepatitis or Tuberculosis.

The prior art lacks a versatile dental light guide that can be used in different locations in the mouth and for a variety of purposes such as tight curing of resins, general illumination and transillumination of teeth. There would be clear advantages in such a device, particularly if it was readily resterilisable or of such a relatively tow cost that it could be considered disposable. A further advantage would result from having a lighting system that removed the light source from proximity to the patient.

OBJECT OF THE INVENTION It is an object of this invention to provide a versatile dental light guide.

It is a further object of this invention to provide a flexible tight guide for use in the mouth.

It is yet a further object of the present invention to provide a dental tight guide that overcomes one or more of the above identified problems or, at least, offers a useful alternative to existing means of oral illumination.

DISCLOSURE OF THE INVENTION In one form, although it need not be the only or indeed the broadest form, the invention resides in a tight guide for dental use comprising an optical tip formed from thermoset plastics material allowing transmission of visible and invisible tight from a tight source to a dental region, wherein the tight guide is flexibly adaptable to different configurations.

Preferably, the optical tip is resiliently deformable.

Suitably, the light guide has a tight-receiving end and a light-emitting end. The surface area of the light-emitting end may be less than the surface

area of the light-receiving end.

Preferably, at least one of the ends of the tight guide is polished.

Suitably, the tight guide is connected to a multispectral light source.

Multispectral means the tight source can produce tight of different wavelengths, typically from more than one of the infra-red, visible or ultra violet regions of the spectrum. Alternatively, the tight guide may be connected to a tight source that produces tight of a specific wavelength or selectable range of wavelengths.

In a further aspect, the invention resides in a dental lighting system comprising : a tight source ; a flexible elongate optical fibre for light-receiving connection to the tight source ; and a tight guide in removable light-receiving connection with the elongate optical tight guide ; wherein the light guide is resiliently deformable.

In a further aspect, the invention resides in a method of applying light for curing light activated resin in teeth including the steps of : bending a light guide formed from thermoset plastics material into a configuration for directing light onto said resin ; activating a light source associated with the light guide for a period necessary to cure the resin ; directing light from said light source into a receiving end of the light guide ; positioning the light guide so as to direct light emitted from said dental light guide onto the resin ; and illuminating the resin for a period necessary to cure it.

In yet a further aspect, the invention resides in a method of transillumination of teeth, including the steps of :

bending a tight guide formed from thermoset plastics material into a configuration for channelling tight from behind a tooth ; activating a light source associated with the tight guide ; directing tight from said tight source into a receiving end of the tight guide ; positioning the tight guide so as to direct tight from a tight emitting end through the tooth ; and examining the tooth for defects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of a dental tight guide and tight curing hand piece ; FIG. 2 is a schematic representation of a dental lighting system ; and FIG. 3 is a schematic representation of a dental light guide of the invention in association with a dental drill.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 displays a dental light guide 1, located in a light curing hand piece 2. The light curing hand piece 2 typically provides narrow spectrum light in the range of 400 to 500 nanometres, which is suitable for curing light activated resins commonly used in dentistry for reconstructions and fillings.

The configuration of the dental light guide 1 as shown is suitable only for areas of direct access in the mouth, for example, on the labial surface of the incisors.

One of the great advantages of the dental light guide is the ability for the optical tip to be adjusted into different shapes, as required. Two such shapes are shown in phantom as a downward deflection 3 or an upward reverse orientation 4. The upward reverse orientation 4 displays one advantage of the invention in that it can be used to direct emitted light from

inside the mouth towards a location outside the mouth. Adjustment into appropriate shape also facilitates access to the back of the mouth or to locations that are awkward to illuminate. The dental light guide 1 is releasably received by a fitting 5 of the light curing hand piece 2 to enable easy application or removal of the dental light guide 1. The dental light guide 1 is removable to make it easily repetitively sterilisable.

The dental light guide 1 is composed of a thermoset polymer. An example of such a polymer is a substance comprising 60-90% allyl diglycol carbonate (CR39), 0. 1 % to 10% solution of 150 propylpercarbonate (IPP) and the balance methyl methacrylate. The monomer solution is polymerised in a hot liquid bath for a period of 2-36 hours. A person skilled in the art will readily understand that the concentration of the above components can be varied as required. Alternatively, different formulations may be required for different embodiments.

The components of the thermoset polymer may be varied so as to give different degrees of flexibility. These different components will result in differing amounts of effort required to shape the dental light guide 1 to a desired configuration and also the period for which the dental light guide 1 will retain that shape. For example, the thermoset polymer may be mixed to give a positional retention time of ten seconds. If desired, the thermoset polymer may be composed of components that give a positional retention time of sixty seconds. The range of ten to sixty seconds is for example only and the positional retention time may be varied outside this range, if required.

It is also possible to produce a thermoset polymer which is fully flexible and requires support to maintain any specific configuration, and which in use, produces a loose, flexible dental guide. Alternatively, components and production of a constituent thermoset polymer may be altered to give a range of resistance to bending, from easy to difficult.

The properties of thermoset polymers may be such that if the end of the light tip is damaged, the end may simply be severed and the remaining

segment of the dental light guide will still effectively allow the transmission of required tight.

The invention also has the added advantage of being relatively cheap when compared to the prior art light guides. Therefore, if the dental light guide is damaged, it may be readily replaced. A further advantage of the invention is that the relatively low cost of the dental light guides enables them to be treated as disposable in situations of risk such as when treating a patient with an infectious pathology such as Hepatitis, Tuberculosis or HIV Virus.

Thermoset polymers are preferred to thermoplastic polymers because the former do not melt until temperatures are above 150°C and they also resist oxidisation. They are therefore suited to hot sterilization techniques such as autoclaving.

FIG. 2 is a schematic representation of an embodiment of a dental lighting system 6. The dental lighting system 6 comprises an elongate optical fibre 7 of fibre optic thermoplastic resin that is connected at one end by a collar 8 to a dental light guide 9. The elongate optical fibre 7 and dental light guide 9 may be formed of similar material. The dental light guide 9 is adjustable to a desired configuration as shown in phantom 10. The other end 11 of the elongate optical fibre 7 is connected to a fitting 12 on a light source 13 so that light from the light source 13 is transmitted through the elongate optical fibre 7. The light source 13 is further connected to a power source 14 and a foot operated control switch 15.

The dental light guide 9 has a light-emitting end 16 and light-receiving end 17. Both ends are polished to enhance tight transmission. Light- emitting end 16 has a smaller surface area than tight receiving end 17, which leads to a concentration of emitted tight.

The ends 18, 19 of elongate optical fibre 7 may also be polished, however polishing is not essential. If a polished end of the dental light guide 9 is damaged, it is possible to sever the damaged end. Although there will be a decrease in transmission of tight through the dental light guide 9, the

device will still perform substantially as required.

The elongate optical fibre 7 can be any convenient length but is typically of the order of two metres and is flexible. There are numerous advantages to the dental lighting system. As can be seen from FIG. 1, the tight curing hand piece 2 or tight source is in close proximity to the patient.

Typically such a tight source will generate noise from a cooling fan during operation. Noise from the light source can add to the level of discomfort felt by a patient undergoing dental treatment. Relocation of the tight source away from the patient removes this inconvenience.

As the tight source is powered by electricity, its removal to a distance from the patient further isolates the patient from potential hazards thereby contributing to safety.

The tight source is unlikely to be contaminated by biological matter because of its remoteness from the patient. The prior art tight curing hand piece 2 of FIG. 1 is used in close proximity to a patient's mouth and is therefore susceptible to contamination from a patient's oral discharges or aerosols formed during treatment.

The embodiment shown in FIG. 2 has the added advantage that it removes the weight of the tight curing hand piece 2 from a dental operator's hands, allowing better controlled manipulation of the dental light guide.

The tight source 13 may be a multi wavelength tight source that can be used to produce light with a wide range of wavelengths. Alternatively, the light source 13 may be dedicated to producing a single wavelength or restricted range of wavelengths of light.

FIG. 3 shows a dental light guide 20 used in connection with a dental drill 21. The dental light guide 20 is attached to the dental drill 21 by snap clips 22. The end 23 of dental light guide 20 is directed so as to illuminate the working area for drill bit 24.

Clearly, the embodiment shown in FIG. 3 can be attached to other dental equipment such as mirrors or vacuum tubes.

Throughout the specification, the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features.