GB2379406A

GB2379406A - Dental tool

Info

Publication number: GB2379406A
Application number: GB0118778A
Authority: GB
Inventors: Sidney Grant
Original assignee: Medivance Instruments Ltd
Current assignee: Medivance Instruments Ltd
Priority date: 2001-08-01
Filing date: 2001-08-01
Publication date: 2003-03-12
Also published as: GB0118778D0; GB0126177D0

Abstract

A dental tool comprises a tool body (4) with a nozzle (1) for directing a gas stream towards the surface of a tooth. A liquid supply tube (2) has an outlet (7) positioned to the rear of the nozzle outlet (1) so that the liquid stream forms a wall of liquid about the gas stream moving towards the tooth surface. Alternatively, the tube may have a tapered leading end forming a nozzle, the tube arranged to supply pressurised gas to the nozzle and a cap, the cap being substantially the same shape and a nozzle with a diameter substantially the same size, and a liquid supply tube connected to the cap and having an outlet to the rear of the nozzle outlet.

Description

DENTAL TOOL The present invention relates to a tool for use in dentistry.

Air abrasive cutting is currently in regular use in dental practice and is an extremely useful technique in modem adhesive dentistry where resurfacing and filling materials adhere to the tooth rather than the material, such as amalgams that are keyed for retention. This means that decay can be removed by a process, such as air abrasion, which will remove the decay without the need to cut sound tooth material in order to achieve retention. The surface prepared with the gas abrasive technique leaves a surface ideal for the new materials to bond to.

Another advantage of the gas abrasive technique is low stress cutting of the tooth avoiding the stress fracturing found when using conventional rotary instruments.

The system also benefits from almost zero heat generation in the cutting process and reduces the need for injections. However the process is slow unless high pressure in the gas or lower pressure and high levels of abrasive media are used.

High pressure up to ten bar in some instruments means that the instruments can be difficult to control when cutting teeth, which by nature vary from patient to patient in hardness. There is a relationship between the pain factor and the pressure factor. The higher the pressure, the greater the sensitivity. Increasing the rate of abrasive to air to maintain high cutting rate means that one has a higher than desirable dust debris problem requiring very effective recovery equipment, like powerful aspirators and even external evacuation for airborne particles escaping the oral cavity. Many attachments have been developed in an attempt to eliminate this drawback of gas abrasion devices. These take the form of flexible plastic membrane mouldings that encompass the tip and create a

containment area against the tooth surface. These are often connected to aspiration tubes in an attempt to remove the cutting media from the mouth and the cutting face. The problem with these devices is that they encompass the area being cut or polished and observation for the operator is through the device or by lifting away for inspection of the area under treatment. These devices become quickly obscured by the very nature of the materials they are controlling. The invention is based on the realisation that the problem of dust control may be achieved by surrounding the gas stream with a curtain of liquid, conveniently water. Further, the invention is based on the realisation that by forming the curtain in a defined way many benefits result.

In one aspect the invention provides a fluid tool for use in dentistry, the tool comprising a body having at one end a nozzle for directing a stream of gas towards a tooth surface, and a liquid supply pipeline having an outlet which is located rearwardly of the nozzle so that the liquid emerging from the outlet is caused by the gas stream to form a wall of liquid about the gas stream moving towards the tooth surface.

In another aspect the invention provides a method of treating the surface of a tooth, the method comprising directing a stream of pressurised gas towards the tooth and drawing liquid to form a wall about the gas stream.

In yet another aspect there is provided a tool comprising a tube having a tapered leading end forming a nozzle of a predetermined diameter, the tube being arranged to supply pressurised gas to the nozzle, and a cap therefor, the cap having a body of substantially the same shape and a nozzle having a diameter of substantially

the same order, a liquid supply tube connected to the cap and having an outlet at a location rearward of the nozzle.

In the invention the liquid is unpressurised and is drawn by the flow of pressurised gas to form a wall about the gas stream. That wall acts as a shielding curtain and has several beneficial effects, as explained in better detail below.

While we do not wish the monopoly to be restricted in any way by the following theory, our investigations suggest that the drawn liquid is subjected to a Venturi effect to form the curtain.

Other features of the invention are set out in the subclaims.

One embodiment of the invention will now be described by way of example only with reference to the accompanying diagrammatic drawings, wherein: Figure 1 is a perspective view of one fluid abrasive tool of the invention ; Figure 2 is a longitudinal section of the head of the fluid abrasive tool of Figure 1; Figure 3 is a section taken on lines III-III on Figure 2 showing the formed gas/liquid stream.

As shown in Figure 1, the head portion of the fluid abrasive tool T comprises an air/abrasive nozzle 1 which is secured to the front end of a stainless steel gas/abrasive delivery tube 2. The nozzle has a tapered front portion 3, and the

outlet is of relatively small diameter. Preferably, the front portion is made of tungsten or the like. The air/abrasive delivery tube 2 is in the form of a swan neck to enable access of the cutting jet to the rear surfaces of a patient's teeth.

The tube 2 is connected to a tool body 4 having an inlet 5 which in turn, is connected to a reservoir of abrasive and of pressurised air, not shown. When air is passed along the body 4 and the tube 2 to the nozzle 1 a stream of flow gas emerges at a preselected gas pressure. (The stream may be made of gas or of gas and abrasive particles.) A cap 6 is mounted over the nozzle 1. The cap is made of plastics and has an external and internal tapered shape generally similar to that of the nozzle. The cap has a water inlet 7 which enters its main bore 8 rearwardly of the outlet of nozzle 1. The position of the inlet 7 is selected so that suction is generated by the Venturi effect of the flowing gas stream, i. e. there is a longitudinal distance L rearwardly of the outlet of the nozzle 1 and the inlet 7. The inlet 6 is connected to a water reservoir, not shown, containing unpressurised water or other liquid. It has been discovered according to the invention that the water is drawn by the Venturi effect in the bore of the cap 6 in advance of the nozzle outlet to form an outer flaring cylindrical curtain C of water adjacent the wall of the bore 8 and a somewhat similar cylindrical zone B of water, air and abrasive is formed at the interface with air/abrasive jet A. A cutting zone is defined by the boundary of zone at its interception with tooth surface E.

In use the water is drawn into nozzle 1 by the Venturi action of the gas stream or jet and flows around the tip 3 of nozzle and forms the curtain which captures the abrasive particles and prevents them from being dispersed in the patient's mouth

and airways. The pressure of the stream controls the volume of the liquid drawn to form the curtain. The pressure of the stream draws the liquid by the laminar flow of the outside surface of the stream of gas abrasive. The liquid is introduced such that it creates a complete curtain of liquid around the main jet drawn forward by Venturi effect without any tendency to affect its velocity. The tip of nozzle 1 is held about two to three millimetres from tooth surface E and the supply of water can be controlled by adjusting thumb pressure on a control lever 9. The velocity of the water stream automatically varies in accordance with the velocity of the air/abrasive stream. The water irrigates the abrasive in the cutting region so dramatically improving cutting performance. The slurry of abrasive particles in water formed at the tooth surface is easily removed by conventional aspiration equipment.

In a variant the water could be supplied to inlet 7 from a disposable one-use pack.

A dentally acceptable sterilising agent or other additive useful in dentistry could be added to the water, e. g. a drug or anaesthetic or flavour or surfactant. The abrasive particles can, for example, be of silica or sodium bicarbonate depending on the degree of abrasion required. In particular, relatively soft particulate material could be used in polishing applications.

The advantages of the invention are that a total curtain of liquid can surround the jet or stream of gas and abrasive to contain the gas and abrasive totally and continuously. The curtain of liquid is developed in such a way as to be totally intimate with and surrounding the gas powder stream such that they do not mix until they impact with the surface being treated.

The liquid and the gas powder stream are configured such that the surrounding liquid curtain is largely self-adjusting i. e. if the pressure of the gas powder stream is increased or decreased, the strength of the liquid curtain is increased or decreased. The curtain limits the divergence of the jet of gas and powder as it leaves the tip of the instrument keeping the gas powder stream concentrated and focused on the surface to be worked on which can increase the cutting effectiveness by up to almost 100%. The improvement in performance is a result of the combination of the dry stream and the irrigation effect of the liquid shield.

The slurry of liquid and debris can be removed simply by conventional evacuation techniques that the dentist uses when using a conventional rotary cutting instrument with its coolant.

The tool is compact and shaped such that it is pointed towards its working end so as to give good visibility of the cutting area externally of the tip during the cutting procedure. The tool can be disposable after every treatment at minimum cost.

The tip of the instrument can be used wet or dry by the simple expedient of a valve controlling the supply of liquid from the reservoir.

The invention is not limited to the embodiment shown. For example, a further valve can be incorporated to enable the instrument to supply an air stream only to the powder enabling drying and purging of the area with clean air. In addition, a valve may be present in the water pipeline to ensure that when the lever 9 is shut, water is removed from the nozzle and cap volume to avoid wetting of any residual powder.

Claims

1. A fluid tool for use in dentistry, the tool comprising a body having at one end a nozzle for directing a stream of gas towards a tooth surface and a liquid supply pipe having an outlet opening at a location which is rearwardly of the nozzle so that liquid stream emerging from the outlet is caused by the gas stream to form a wall of liquid about the gas stream moving towards the tooth surface.

2. A fluid tool according to Claim 1, wherein the cap is disposable.

3. A fluid tool according to Claim 1 or Claim 2, wherein the inlet for the liquid is formed in the outer wall of the cap.

4. A fluid tool according to any preceding Claim, wherein the liquid inlet for the liquid is generally transverse to the bore of the nozzle.

5. A fluid tool according to any preceding Claim, wherein the liquid inlet for the liquid communicates with an unpressurised supply of liquid.

6. A fluid tool according to Claim 5, wherein the supply of liquid is in the form of a disposable single-use pack.

7. A fluid tool according to Claim 6, wherein the single-use pack of liquid is integral with the cap.

8. A fluid tool according to any preceding Claim, wherein the liquid inlet communicates with a liquid supply via means for preventing reverse flow of the liquid.

9. A fluid tool according to any preceding Claim, including a supply of liquid containing a sterilising agent, anaesthetic, flavouring agent or surfactant.

10. A fluid tool according to any preceding Claim, which comprises an air abrasive delivery tube with a swan neck portion for enabling access to a rear tooth surface.

11. A fluid tool substantially as described hereinabove, with reference to Figures 1,2 and 3 of the accompanying drawings.

12. A method of treating the surface of a tooth, the method comprising directing a stream of pressurised gas towards the tooth and drawing a liquid to form a wall about the gas stream.

13. A method according to Claim 12, including adding particulate abrasive to the water.

14. A fluid tool comprising a tube having a tapered leading end forming a nozzle of a predetermined diameter, the tube being arranged to supply pressurised gas to the nozzle and a cap therefor, the cap having a body of substantially the same shape and a nozzle having a diameter of substantially the same

order, a liquid supply tube connected to the cap and having an outlet at a location rearward of the nozzle.

15. A tool according to Claim 13, wherein the nozzle is connected to the body of the tool by a swan neck portion.