GB2329337A - Dental root canal instrument - Google Patents

Abstract

The instrument, which may be used to spread and compact gutta-percha filler within a root canal space, comprises a flexible working portion 12 which tapers towards a smooth, parallel-sided tip portion 14. The working portion may be helically fluted and may have a shank portion 10 adjacent thereto. An engagement portion 9, provided with a fitting designed to mate with the shank 20 of a dental handpiece, may also be included. The instrument may be coated with gutta-percha for root canal filling by use of a vertically sectioned, metal mould (Figs.1-3) having a mould cavity of generally tapering form. The mould is heated, the gutta-percha and carrier instrument placed therein and the two halves of the mould compressed together, heated and then slowly cooled.

Description

Apparatus and Method for Applying Gutta Percha.

Background of the Invention This invention relates to the field of endodontics and particularly to the obturation of a prepared root canal.

The aim of endodontics is to clean, shape and fill the entire root canal system Known methods of obturating the root canal involve packing a thermo-plastic material such as gutta-percha into the root canal and therefore due to the ffow of the material produce a three-dimensional filling. A thiehtnensional filing is required to prevent leakage within the root canal which would in turn lead to failure of the root filling.

Several methods have been developed to apply warm gutta percha to the root canal system.

One method involves injecting heated gutta-percha via a needle into the root canal system. Control of the extent of the root canal filling material is unpredictable, and may be too short, producing a risk of contamination and leakage of the root filling .Over extension of the root filling material may produce pain and inflammation of the bone and tissues surrounding the apex of the toot.

Another method involves heating gutta-percha that has been placed on a grooved carrier and then applying it to the root canal. Again this method provides no control of the extent of the filling material.

Also the carrier which is designed to be left within the root canal system is a potential source of leakage within the root filling which could lead to failure of the root filling. Furthermore removal of the root filling material is difficult due to the presence of the carrier.

Another technique involves the placement of cold gutta-percha strips within the root canal system these are then heated with a hot probe and forced into a three < iirnensional shape within the root canal . This technique also has the disadvantage of being susceptible to over heating the gutta-percha and thus risking the over-extension of the gutta-percha. Also it requires a larger preparation of the root system than other systems to enable placement of the heated probe. Over preparation of the root-canal is not recommended because it weakens the root of the tooth. This technique is sensitive to the ability of an operator to use the equipment clinically and may be time consuming.

Another technique involves the application, via a syringe, of warm gutta-percha to a carrier instrument designed to force the warm gutta-percha into the root canal. Again this technique provides no control of the apical extent of the root filling and is therefore technique sensitive. Also controlling the amount of gutta-percha placed on the carrier instrument is dependent on several variables such as temperature, viscosity, size of the applicator instrument and time taken to apply the gutta-percha to the instrument.

It is the object of the present invention to provide an improved apparatus and method for heating gutta-percha pre-coated to a special carrier instrument and subsequent introduction into the root canal system.

From one aspect the present invention provides, as an altemative to the afore described prior art methods, a method involving the heating of gutta-percha at two different temperatures prior to its introduction into the root canal system.

From another aspect ,the present inventions provides an apparatus and method which manufactures the customized gutta-percha coated carrier instruments.

From yet another aspect, the present invention provides a carrier instrument which allows for application of the gutta-percha at two different temperatures to be applied to the root canal system.

An advantage of the present invention is that the method of use is effective and predictable in clinical operation.

More particularly, the invention is embodied in an apparatus and method for coating a carrier instrument with gutta-percha and a further apparatus for heating it to two different temperatures prior to insertion of the gutta-percha into the root canal system with the carrier instrument which is finally removed leaving a homogeneous mass of gutta-percha within the root canal. The preferred apparatus for coasting the carrier instrument includes a mold prepared in metal and sectioned vertically to expose two halves of the mold cavity designed to shape the gutta-percha to a suitable form for introduction into the root canal system. The metal mold is heated and gutta-percha placed with the carrier instrument into the mold. The two halves of the metal mold are then compressed together.

Once processed the mold is split open and the carrier removed with guttaperclk formed in a shape of the original mold, the shape of the mold being gently tapering with the widest dimension at the surface of the blockwhew the instrument carrier protrudes from the mold. The carrier having been coated with gutta-percha is then heated by the apparatus embodying the present invention.

More particularly the carrier instrument coated with the pre-fonned gutta-percha is inserted into the heating apparatus which is designed to preferentially heat the gutta-percha nearer the handle of the instrument, whilst maintaining the gutta-percha at the tip of the instrument at a cooler temperature.

The method of the invention includes the use of an instrument designed to carry the gutta-percha coating at two different temperatures into the root canal system and unload, at the same time, the gutta-percha at two different teratures such that the cool gutta-percha in a solid state, will locate and seal the root system at the precise location while at the same time condense the warm gutta-mba against this solid plug of gutta-percha, thereby compressing the gubasercha in a three-dimensional manner.

A more complete understanding of the present invention may be had by z*eece to the specification and accompanying drawings, wherein like numerals refer to like parts throughout and in which: Fig 1 is a perspective view of a metal molding block for forming the gutt~acins onto the carrier instrument; Fig 2. is a perspective view of the mold, opened to allow placement of the gutta-percha and the carrier instrument; Fig 3. shows the detail of the molding and the design cut into the mold to provide fins for heat absorption; Fig. 4. shows the mold packed with gutta-percha and the carrier instrument, protruding from the metal mold; Fig. 5 is a perspective view of a carrier instrument according to the present invention; Fig 6. shows the carrier instrument of Fig. 5 coated with gutta-percha; Figs.7a,b,c, show diagrammatically the process of obturating a prepared canal with preferentially heated gutta-percha loaded onto the special carrier instrument shown in Fig. 5; and Fig 8 is a diagram of the heater designed to preferentially heat the gutta-percha.

There is illustrated in Fig. 1 an exemplary device 1 for pre-forming the gutta-percha onto a carrier instrument. The device is made of metal or any other material that can be heated and so soften and mold the gutta-percha within the mold sections 2 and 3. The two halves 2,3 of the mold 1 are formed with matching depressions 6 and the mold halves are compressed together to avoid over-extension of the gutta-percha between the two halves of the mold. With reference to Fig. 2 and Fig.3. it is apparent that the mold can be varied, to provide gutta-percha coatings of a variety of dimensions and a variety of taper throughout the length of the mold. Usually the tip deepest within the mold will vary between 0.25mm and l.Omm and taper at rate of between 0.04-0.08 mm/mm to the aperture of the mold which may have dimensions of between O.9.mm to 2.5.mm.

It is also visible from Fig.3 that the tip 7 of the mold depression is smooth to a level ranging between 1.5.mm-3mm. The remaining inner circumference of the mold has a rifled grooving 9. This is designed to give the molded gutta-percha a rifled, finned form on the surface. This is designed to act as a more efficient surface absorbing heat and also to aid compressing the warm gutta-percha into the root canal system.

Fig.4 represents the mold in use with gutta-percha and carriers ss placed to a precise position within the gutta-percha with an engagement portion 9 at one end extending from the mold. The mold is heated to approximately 90"C under pressure for one hour and then slowly cooled. The mold is opened and the carriers removed with gutta-percha completely encasing the caniers as shown in Fig. 6.

Fig. 5 shows an exemplary carrier 8 for spreading and compacting filler material such as gutta-percha, within a root canal space. The instrument, 8 is made of Ni,Ti alloy and includes the engageable portion 9, a shank portion 10 which is plane and cylindrical, a working portion 12, extending along a substantial portion of the length of the carrier and terminating with a smooth parallel tip portion 14 whose length varies for different instruments and clinical requirements but is 1typically 1 to 3 mm in length. At least the working portion 12 is flexible in order that the carrier can follow the prepared root canal; in use.

During an obturating process the gutta-percha 15 is molded over the working and tip portions 12,14 as shown in Fig. 6, is compacted within the root canal space by the carrier 8 loaded with gutta-percha being inserted into the root canal space and rotated at slow speed. To this end, the engagement portion 9 located above the working portion 12, is provided with a fitting which is designed to mate with the shank 20, of a dental handpiece, for powering the rotation of the instruent Alternately the portion 9 may be mated to a T-handle (not shown) to facilitate rotation and manipulation of the instrument carrier 8 by hand.

The working portion 12, ofthe carriermay be in variety forms; the illustrated working portion includes a helical flute 13 extending along the length of the working portion so as to provide a downwardly-directed screw along the length of the working portion towards the smooth parallel tip 14.

Figs. 7a,b,c, are diagrammatic representations of the process of obtuyrrting a root canal using the carrier as shown in Fig. 6. Fig. 7a shows a view of a tooth 21 of a prepared root canal 21a terminating in a patent hole 21b. Fig. 7b shows the coated instrument 8 being placed to length. The tip of the carrier is coated with cool, relatively solid gutta-percha 8a. The cone of gutta-percha precisely fits the shape of the apex or tip of the root canal and efficiently seals the tip 1-3mm from the prepared apex. The working portion of the carrier carries the molten gutta-percha.

Fig. 7c shows the rotation of the instrument carrier. As the carrier is rotated the molten gutta-percha flows towards the smooth apical 1-3mm of the carrier and forces the solid apical portion of gutta-percha to be released therefrom. The warm gutta-percha is compacted into the root canal by the rotation of the instrument carrier and forces gutta-percha into the intricacies of the root canal Thereafter, rotation of the carrier in the appropriate direction allows the carrier to be removed leaving only gutta-percha in the root canal.

With reference to Fig.8 there is illustrated an embodiment of an apparatus that can be used to preferentially heat the gutta-percha coated to the carrier. The two steps involved with this process involve placing a coated instrument onto a collar support 22, which may be a varied dimension depending on the length and design of the carrier. Having located the instrument in the collar it will be seen that the tip of the carrier is located within a heat sink 23, and surrounded by a heat shield 24. Heating occurs when heating elements 25 are activated by a switch mechanism 26 for a pre-set time interval. In this way, the tip of the coated carrier is cool relative to the majority of the length of the carrier which is molten. The instrument is then removed from the heating apparatus and is ready for insertion into a prepared root canal as described previously.

It will be understood that numerous modifications and substitutions can be made to the aforedescribed embodiments. Therefore, the described embodiments are intended for the use of illustration and not as limitation.

Claims (7)

Claims:

1. A dental instrument designed to be inserted into the root canal of a tooth, comprising a working portion which tapers towards a smooth parallel sided tip portion, wherein at least the working portion is flexible.

2. An instrument according to claim 1, wherein the working portion includes a helical flute extending along its length.

3. An instrument according to claim 1 or 2, further comprising an engageable portion located at an end away from the tip, the engageable portion being provided with a fitting which is designed to mate, in use, with a fiuther component.

4. An instrument according to any preceding claim, furrier comprising a shank portion located adjacent to the working portion.

5. An instrument according to any preceding claim, wherein at least a plait Of the instrument is made of NiTi alloy.

6. An instrument according to any preceding claim, wherein the tip portion is between lmm and 3mm in length.

7. A dental instrument substantially as hereinbefore described with reference to the accompanying drawings.