IE51907B1 - A method of forming an impression of the inside of an ear - Google Patents

Description

This invention relates to a method of forming an impression of the inside of an ear, e.g. a human ear, to be used in the subsequent manufacture of ear inserts or earmolds, e.g. for hearing aids, as plugs for swimmers or noise abatement use, or to assist stammerers or tinnitus sufferers.

Previously impressions of the inside of an ear have been formed by inserting impression material into the external acoustic meatus of the ear using a syringe., by .. pouring or by employing the most widely used finger-pressing method, allowing the impression material to harden and finally removing the finished impression from the inside of the ear. However it has been found that impressions which do not accurately reproduce the inside of the ear are prod15 uced by this known method since the inside of the ear is often distorted by the act of inserting the impression material into the inside of the ear and pressing the inserted impression material to conform to the shape of the inside of the ear. in many applications such inaccurate impressions, although undesirable, are tolerated. However in the manufacture of hearing aids for very deaf people, where high powered hearing aids instead of ordinary hearing aids are employed to enable the deaf people to hear, it is essential for accurate ear inserts or earmolds to be produced so that the high powered hearing aids can be used at maximum volume without feedback problems. With the known method of forming an impression of the inside of an ear it has proved difficult to obtain easily the desired accuracy of repro30 duction of the inside of an ear to enable earmolds of sufficient quality to be produced for such high powered hearing aids. Consequently the earmold has to be subsequently modified to obtain the desired quality or the hearing aid has to 8190? be operated at less than full volume.

The present invention seeks to provide an improved method of forming an accurate impression of the inside of an ear.

According to the present invention a method of forming an impression of the inside of an ear comprises providing a coating of a hardenable impression material on a former having a base and a projecting portion extending therefrom, the former having a through passage therein which passes from the base of the former, through the projecting portion of the former to emerge at or adjacent the tip of the projecting portion, the coating of hardenable impression material not blocking said through passage, inserting the coated former into the inside of the ear with the coated base positioned in the outer ear and the coated projecting portion positioned in the external acoustic meatus, allowing the coated impression material to harden and removing the hardened impression from the inside of the ear.

The provision of the through passage in the coated former allows air to escape from behind the coated former as it is inserted into the inside of the ear. Thus the air pressure on either side of the coated former is equalised as the coated former is positioned so as to be fully seated inside the ear.

It may be necessary on inspection of the hardened impression to repeat the method one or more times, the former being constituted by the hardened impression which is removed from the inside of the ear.

Preferably, in a particularly advantageous embodiment of the invention, the former is initially formed by inserting hardenable impression material to fill the inside of the ear, allowing the impression material of the former to harden to form the former with its said base and projecting portion but without the said through passage, remov51907 ing the former from the ear, and providing the said through passage in the former. Conveniently, a canal plug, e.g. a small piece of cotton wool or sponge material attached to a length of thread, is inserted into the external acoustic meatus prior to inserting the hardenable impression material of the former in the inside of the ear. Such a canal plug is also preferably employed during any subsequent insertions of the coated former into the inside of the ear.

The hardenable impression material employed for forming 10 the former may be a putty-like material or a mixture of one or more putty-like materials and/or one or more gels suitably admixed with an activator. Suitably the coating impression material comprises a gel mixed with an activator.

The through passage formed in the former may comprise 15 tubing, e.g. a metal tube or plastics, such as polyethylene, tube, fitted into a pre-drilled or otherwise formed hole.

The invention will now be described, by way of example, with reference to the following non-limitative example.

Example The inside of a patient’s ear was examined to ensure chat there was no infection, no excessive build up of wax, no collapsed canals or no abnormal growths. The ear was then syringed and cleaned and all hairs removed therefrom. A small piece of cotton wool (or sponge) was then tied to a piece of nylon thread and inserted into the external acoustic meatus of the patient. This cotton and string (i.e. the so-called canal stop) serves to plug the external acoustic meatus and protect the ear drum so that impression material to be used subsequently for forming an ear impression does not flow into the ear drum.

A quantity of hardenable impression material was then prepared according to the manufacturer's instructions. Al61907 though many types of hardenable impression materials may be used, in the present example 17 - 20 g of putty-like material, e.g. Eden putty was mixed with 3 - 20 g of an activator or hardener, e.g. Eden gel, the Eden putty and Eden gel both being obtainable from Edenvale Laboratories of 10, Balcarres Road, Musselburgh, EH21 7SD.

The mixed impression material was then pressed into the inside of the patient’s ear whilst the material was still in a workable state by the well-known finger-pressing method. After approximately 2 minutes when the impression material had set hard, the impression was withdrawn from the patient's ear and a hole of varying diameter was cut in the impression to extend from a base of the impression to a free end of a meatus projecting portion extending from the base. A polyethylene tube (having an internal diameter of' from 1 mm to 3 mm, typically 2,5 mm) was then fitted in the hole.

Further impression material comprising 2 g of gel material mixed with J g of activator was then thoroughly mixed and applied by brush or with the aid of a spatula over the impreseion taking care not to cover the ends of the tube so ensuring that the tube was not blocked. The coated impression was then gently replaced in the ear and the coating material was allowed to set. The impression was then removed from the ear and inspected to see if there were any defective areas. If a defective area is found, a further coating of hardenable impression material is provided on the coated impression and the impression once again inserted into the ear and the coating allowed to set. Thus the coating step is continually repeated until a perfect impression is obtained.

Iv was found that the provision of the polyethylene tube in the impression allowed air to escape from behind the impression as it was inserted into the ear, thus ensuring that the ear was not excessively distorted during the formation of the impression. If air is not allowed to escape, air pressure on the ear drum prevents the impression from being fully reseated in the ear and the resulting impression has areas of air voids. A high-powered hearing aid was fitted to the finished impression at this stage to ensure that there was no feedback with the impression when the latter was inserted in the patient’s ear. If there is any feedback this can be easily rectified by coating the impression with further hardenable gel material and re-inserting the impression into the patient’s ear until a final impression is obtained giving no feedback even at maximum volume of the hearing aid.

The finished impression was then employed to manufacture an earmold by pressure deforming, e.g. vacuum drawing, a sheet of pressure deformable material over the impression to conform the sheet to the shape of the impression, separating the impression from the sheet of material without permanently disturbing the shape into which the sheet has been deformed to leave the mould cavity in the sheet material, and introducing moulding material into the mould cavity to form an earmold. Such a method of forming an earmold is described and claimed in the ccxrplete Specification of British Patent Specification No. 1596369.

As a preferred optional step, after cleaning and stopping the patient's ear and prior to pressing the hardenable impression material into the inside of the patient’s ear to form the initial impression during making of the former, hardenable liquid silicone material (e.g. Eden silicone spray available from Edenvale Laboratories) is applied, e.g. sprayed into the inside of the patient’s ear. Conveniently the silicone spray is applied to the inside of the ear out to the pinna by spraying two or three times in a circular motion.

As an alternative to the step of coating the impression with further impression material by applying the latter with a brush or spatula, the impression may be coated by dipping it into a thin solution of gel material containing an activator or by spraying it with sprayable hardenable silicone 81807 impression material to provide the impression with a uniform coating of further impression material.

Furthermore for children or adults with sensitive ears or ears having severe undercuts or thin pinnas, the initial impression of the ear can advantageously be formed without the use of the putty-like material. In this case, hardenable, inert gel material (e.g. Eden gel) may be poured into the patient's ear so as to flow inside the ear to reproduce any undercuts. The gel material being inert does not generate any heat of reaction and will not affect the patient's ear.

The main advantage of the present invention is the employment of the through passage in the impression which enables air to be removed from the ear as the set hard impression is fully seated inside the ear. If the through passage was not provided, the seating of such set hard impression in the ear would be accompanied by extreme pain and/or would possibly cause damage to the ear drum. By subsequently coating the set hard impression with further hardenable impression material and reseating the coated impression in the ear, it is possible to provide an extremely accurate reproduction of the inside of the ear, even enabling severe undercuts in the ear to be reproduced.

Thus it is possible, from such an impression, to form an earmold of such quality as to be usable in a high powered hearing aid with no feedback when the hearing aid is used at maximum volume.

In other embodiments of the invention, a pre-formed former having a passage therethrough may be provided in30 stead of having to form a first impression and then subsequently cut a hole in the latter and fit a tube therein. However, it is preferable to form the first impression as previously described. Furthermore, the impression obtained by the method according to the invention may be employed to make earmolds other than by the method described and claimed in the afore-menticned British Patent Spedficaticn No. 1596369.

Claims (18)

1. A method of forming an impression of the inside of an ear comprising: (a) providing a coating of a hardenable impression material on a former having a base and a projecting portion 5 extending therefrom, the former having a through passage therein which passes from the base of the former, through the projecting portion of the former to emerge at or adjacent the tip of the projecting .portion, the coating of hardenable impression material not blocking said through lo passage, (b) inserting the coated former into the inside of the ear with the coated base positioned in the outer ear and the coated projecting portion positioned in the external acoustic meatus, 15 (c) allowing the coated impression material to harden, and (d) removing the hardened impression from the inside of the ear.

2. A method according to claim 1, in which steps (a) 20 to (d) are repeated in sequence at least one further.time, the former in the or each repeated sequence of method steps (a) -co (d) being constituted by the hardened impression formed at step (d) of the immediately preceding sequence of method steps (a) to (d). 25

3. A method according to claim 1 or 2, in whioh the former is initially formed by introducing hardenable impression material into the inside of the ear, allowing the impression material of the former to harden to define the former with its said base and projecting portion but without the 30 said through passage, removing the former from the ear, and providing the said through passage in the former. B1907

4. A method according to any of the preceding claims, in which a removable canal plug is inserted into the external acoustic meatus prior to performing method step (a).

5. · A method according to any of claims 1 to 3, in which, prior to performing method step (a), a removable canal plug is inserted into the external acoustic meatus and a thin layer of hardenable liquid silicone material is applied inside the ear and allowed to harden.

6. A method according to claim 5, in which the hardenable liquid silicone material is sprayed inside the ear.

7. A method according to claim 3 or any of claims 4 to 6 when dependent upon claim 3, in which the hardenable impression material employed for forming the former comprises a putty-like material or a mixture of one or more putty-like materials and/or one or more gels suitably admixed with an activator.

8. A method according to claim 3 or any of claims 4 to 6 when dependent upon claim 3, in which the hardenable im-. pression material employed for forming the former comprises a hardenable liquid silicone, material introduced into the inside of the ear.

9. A method according to claim 8, in which the formerforming hardenable liquid silicone material is introduced into the inside of the ear by means of a syringe.

10. A method according to any of the preceding claims, in which the said coating impression material comprises either a gel mixed with an activator or a hardenable liquid silicone material.

11. A method according to any of the preceding claims, in which the through passage formed in the former comprises tubing fitted in a pre-drilled or otherwise pre-formed hole. 519 07

12. A method according to claim 11, in which the said tubing has a bore of from 1mm to 3mm in diameter.

13. A method of forming an impression of the inside of an ear substantially as carried out in the foregoing 5 Example.

14. A method of improving the fit of an impression of the inside of an ear comprising: (a) introducing first hardenable impression material into the inside of the ear, 2_ 0 (b) allowing the first hardenable impression material to harden to define a former having a portion projecting into the external acoustic meatus, (c) removing the former from the ear, (d) providing a through passage in the former which 25 passage passes through the projecting portion to emerge at or adjacent the tip of the projecting portion, (e) applying a layer of a second hardenable impression material to the projecting portion so as not to block the said through passage the second hardenable impression 20 material being the same material as, or different material from, the first hardenable impression material, (f) reinserting the former into the ear until it is fully seated therein, the coating on the former being shaped by the inside of the ear, to improve the fit of the 25 former within the ear, under conditions in which the air pressure on either side of the coated former is equalised via said through passage, tg) allowing the layer of second hardenable impression material to harden within the ear, and 30 (h) removing the hardened impression from the ear.

15. An impression formed by the method claimed in any of claims 1 to 14·

16. An improved impression of the inside of an ear comprising a former of a first hardenable impression material 5 with a through passage therein and at least one coating of a second hardenable impression materia], which coating(s) improves (improve) the fit of the former within the ear and has (have) been shaped by the inside of the ear under conditions in which the air pressure on either side of the coated former is 10 equalised via said through passage.

17. An impression according to claim 16, in which said first hardenable impression material is the same material as said second hardenable impression material.

18. An earmold manufactured from an impression according to any of claims 15 to 17.