This indention relates to a liner for prosthetics impression holders, particularly, but not exclusively for dental impression trays. At present, dental impression trays require the application of an adhesive substance (by means of a spray or brush and bottle) onto the fitting surface of a D or U-shaped trough for location on said surface of an impression material and after use, when the impressed material has been removed, the tray has to be cleaned and any remnant of the impression material removed. A disadvantage of this procedure is that cleaning . and removal of material can be time consuming and often results in discolouration of the tray. Further, a discoloured tray can often be repellant to a patient.

An object of this invention is to obviate or mitigate the aforesaid disadvantage.

Once the dental impression has been taken, the tray, with the impressed material sti ll on it, is often located in a sealed bag in order to prevent moisture loss from the impressed material. In so doing the handle at the front end of the tray by which the dentist holds the tray whi le making the dental i pression, is also enclosed in the bag and the tray cannot therefore be-hung from a peg via a slot provided in the handle for that purpose.

Another object of this invention is to obviate or mitigate this further disadvan age.

According to one aspect of the present invention -here is provided a liner for prosthet cs impression holders, said liner having areas on each side for securing location of the liner to the fitting surface of the holder and for securing location on an impression material on the liner. According to another aspect of the present invention there is provided a liner for prosthetics impression

holders, said L ner ha ing areas on each side for securing location of the liner to the fitting surface of the holder and for securing Location on an i pression material on the liner and having means for enclosing the impressed material in a substantially a r ght manner while st ll on the holder.

Preferably, the area of the liner on at Least the face for location to the fitting surface of the shoulder is coated w th an adhesi e, and preferably, such adhesive is a tack peelable adhesive

Preferably also, the area of the liner on the face for securing the impression material has means to secure the impression mater al by icro mechanical bonding and/or chemical inter-reaction. Preferably also, a surface which provides for micro mechanical bonding is a fabric.

Preferably also, said means for encLos ng the impresse material comprises at least one flap portion wh ch, after the material has been impressed, is foldable over the material to form a closure within which the material is contained .

Preferably, at least one flap portion has an adhesive area for securing the l ner in the enclosed condition.

Alternatively, said enclosure means is a bag member which s attached to or incorporates the areas for attach¬ ment to the holder and for recei ing the mpressed material said bag member be ng closeable over the impressed material.

Preferably said bag when closed can contain there n a quantity of fluid adapted to treat the impressed material. The adhes e coating to -secure the liner to the holder pref rably incorporates or is treated with a medium which enables the liner as it is being applied to the holder to be slidably ad usted into correct position thereon before the adhes e properties prevent further movement. Said medium may be an organic solvent such as

turpentine and may be applied during manufacture or prior to application of the liner to the holder.

Embodiments of the present invention wi ll now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a plan view of a liner for a prosthetics impression holder according to the invention in the form of a dental impression tray:

Fig. 2 is a plan view of an upper dental impression tray with a folded liner therein to a different scale; Fig. 3 is a side elevation of Fig. 2; Fig. 4 is a plan view of a lower dental impression tray with a liner therein;

Fig. 5 is a plan iew of a liner in the form of a reversible bag; and

Fig. 6 i-s a plan view. of a basic liner i llustrating modified securing means.

Referring firstly to Figs. 1 to 4 the impression holder, in the form of an upper dental impression tray 10 shown in Fig. 2 comprises a fitting surface formed by a base 11 having a U-shaped trough portion 12, a central raised 'pallet' portion 13 and a rim 14 defining the outer edge of the trough; also a handle 15 at the base of the U;shaped rim, i .e. at the front end of the tray by which the dentist holds the tray when making the dental impressio A second tray 16 shown in Fig. 4 is a lower dental impression tray in which the fitting surface is a trough 19 which is U-shaped and has outer and inner rims 17. The tr 16 has an inner open area 20 to accommodate the patient's tongue during use, and a handle 21.

Referring to Figs. 1 to 3, the Liner 25 of this embodiment comprises a piece of non-stretch or pre-stretche material, e.g. polythene sheeting approximately 9" wide by 7" long. It has an area 26 on its underside as viewed in Fig. 1 ⁽ and shown in chain lines) by which the Liner can

be secured to the fitting surface 11 to 14 of the ho Ide ^r and an area 27 on its upper side, overlying the lower area by w ich a supply of impression material can be secured to the l ner. The impression material may be a rubber or rubber based material or an alginate. The lower securing area 26 is, in this embodiment substantially D-shaped as shown in F g. 1 to engage the fitting surface of the tray including the nner s des of the rim, but it may be substantially U-shaped to engage only the sides 14 and trough portion 12. The upper securing area 27 in this embodiment is also substant ally D-shaped to engage the impression material which fills the fitting surface of the tray.

The securing areas 26, 27 of the l ner 25 are, n this embodiment, coated with adhesive such as a ^" tack- peelable adhesive and the ^' lower area 26 s covered, prior to use, by a peelable cover 26' .

The upper area 27 may also be s milarly covered. However, it has been found that, while a rubber or rubber based mpression mater al adheres to an adhesive surface, alginates do not read ly do so. Therefore, the upper adhesive coating 27 is covered by a fabric material 27' which keys ^' the impression material to the l ner by a micro-mechanical bonding solely o r in addition to a chemical interaction with the adhesi e coating or with the material of the fabric. The fabric may be of natural or man made f bres or a plast cs material. One suitable fabric is a polyamide fabric such as is produced in the manufacture of stockings and tights. Preparatory to use, the liner 25 is positioned on -the tray 10 such that a large portion 25A extends forwards over and beyond the handle end of the tray; afterwards that portion is folded over the tray as hereinafter described and shown in Fig. 2. Side portions 25B of the l ner extend beyond the sides of the tray. A portion of the

Liner may extend be ond the back of the tray, but is preferably in line therewith and narrow strip of adhesive 28 extends along the front edge of the liner on the upper face thereof, covered by peel-off cover strip. Preferably, adhesive strips 28A are also provided on the upper side edges and at least one edge strip 28B on the lower side for the purpose referred to hereinafter.

A tab 29 is attached to the underside of the liner 25 on the portion 25A which is intended to fold over the impressed material.

Before the liner is secured to the tray the patient's detai ls are recorded on the tab 29 and those detai ls wi ll then remain attached to the closure containing the impressed material, thus eliminating possible errors in identification.

Once the lower adhesive cover 26' has been peeled off the liner is fi rmly adhered to the fitting surface of the tray (by finger pressure) with overlapping portions at the sides, front and rear. To allow for adjustabi lity when fitting the liner 25 to the tray, the surface of the tray or. the exposed adhesive portion 26 is brushed with a solvent, such as turpentine. This has the effect of allowing the liner to slide on the surface for about 30 seconds after which the spirit evaporates and the adhesive properties securely hold the liner in position. Alternatively and preferably, the adhesive portion is treated during manufacture before it is covered by its cover portion with a solvent which wi ll remain effective for a sufficient period of ti e between manufacture and use. Such a solvent may be a heavy derivative of petrol _^ , e.g. turpentine 'or paraffin.

The upper adhesive cover (if provided) is then peeled off and the impression material 30 placed on the adhesive or fabric surface to cover the fitting surface of the tray up to the Level of the rim.

With the overlapping portions of the Liner tucked

under the bottom of the tray, the dentist then inserts the tray rearwards into the patient's mouth and makes the dental impression; when the tray has been removed from the patient's mouth, the i-mpressed material is covered to prevent loss of moisture. This is done by peeling off the cover strip from the marginal adhesive strip 28, then folding the front portion of the liner over the impressed material, tucking the edge under the rear end of the tray and securing the tucked edge by its adhesive strip 28. The side edges of the folded liner are also secured together by the r adhes ve strips 28A (if provided). The side flaps formed by the folded side portions are then also tucked under the tray and if the outer tuck has an adhesive strip 28B the folded l ner is securely closed thereby. Alternatively, a piece of adhesi e tape can be used to secure the folded liner.

Alternatively, the overlapping portions of the liner may be gathered under the underside of the tray and secured by, for example, an adhesive str p on one of the portions.

The liner used with the Lower impression tray 16 of Fig. 4 is modified to take account of the open area 20 between the U-shaped trough 19; this can be done by cutting out of portion of the liner at 31 before or after it has been secured to the trough of the tray, or simply cutting a slot 32 so that the patient's tongue can push the liner as de when the tray is inserted (upside down) into the patient's mouth. Thus, the impressed mater al 30 is enclosed in a substantially airtight closure while the handle 15, 21 is outside the enclosure and can be used for hanging the f lled tray pending further processing, e.g. dipping and casting. During the casting process the liner prevents adherence of casting material to the edges of

t h e t r a y .

After a cast has been made, the liner, together with the impressed material, can be peeled off the tray and cleaned or steri lized before re-use. However, in many instances the casts are made remote from the premises where the impression was taken; in which cases, empty trays are subsequently returned, but these are often simply the same number of trays as received and not necessari ly the actual trays that were dispatched; often too less trays are returned than dispatched. Therefore the dentist 's name and address can be provided on the liner so that the tray, complete with its liner and impressed material, can be returned to the correct address. The peel-off cover over the or each adhesive portion

26, 27 may be perforated for selective removal of all or a portion of the covers according to the size of the dental tray; thus one standard size of liner could be produced for use with the various sizes of impression trays. Liners having adhesive areas on both sides may be packaged in layers such that removal of the upper Liner effectively removes the peelable cover from the under¬ side of the removed liner. This can be achieved by using one cover portion for the adjacent adhesive portions of adjacent liners, the peelable strength of the upper adhesiv being less than that of the Lower adhesive so that the cover remains on the lower liner.

A second embodiment wi ll now be described with reference to Fig. 5 which is a plan view of a liner in the form of a flat reversible bag 39.

The bag has two flat walls 40, 41, is open at one end and may be of a-ny—s-u-i-t ab I e shape-. In this embodiment it has a substantially key-hole shape with the opening at the end towards which the sides 42 diverge. At the closed end 43 of the bag, but spaced a short distance of e.g. 1 inch, from the edge is a D - or C -

shaped adhesive portion 44, 45 on both sides of one wall. As in the previous embodiment each adhesive portion may be covered by a peel off protecti e cover, but preferably one portion 44 is covered by a peel off cover 46 while the other portion 45 is covered by a fabric mater al 47.

These portions 44, 45 curve towards the open end of the bag. In use,,the trough 48 of the tray 49 is adhered to one side of wall 40 and the impression material is adhered to the other side. In 'a preferred arrangement the outer cover 46 is removed and the outer adhesive port on 44 secured by finger pressure to the tray 49 the tray being disposed w th its heel or back 50 spaced 1 inch from the closed end of the bag. The front of the tray or handle 51 extends towards the open end of the bag.

With one hand inside the bag to press -the bag wall against the trough 48, the bag is then drawn inside out so that the fabric covered portion 45, 47 is exposed. The impression material (not shown) is then placed in the trough and adhered to the (previously inner) fabric portion 45, 47.

With the material of the bag gathered about the handle 51 the dental impress-ion can be made, after which the bag is drawn back to its original mode, thus locating the mpressed material w thin the bag but with the handle 51 outside the bag. At this stage a ster lizing or other l quid can be introduced nto the bag either directly or in a sponge or other reta ning means and open end can then be sealed- e.g. by adhesive strip of plast c bead closure A Label 52 is attached to the outer face of the bag liner to carry details of the pa ient and the dental surgeon. These deta ls are written on the label before use of the liner.

In an alternative arrangement, not shown .the tray is firstly located inside the bag and the trough adhered to

the inside adhesive portion whi ch in this arrangement is covered by a peel off cover but this wi ll requi re easy removal of the inner peeL off cover and prevention of the inner faces of the bag sticking together. Once the tray has been adhered to the inside of the bag, the outer cover, if provided can be peeled ^' off and the impression m-a erial can be located in the liner trough. Preferably, however, the outer adhes e portion in this arrangement is covered by a fabric material. On complet on of the impression, the bag is then folded inside out to draw the open end over the tray and after adding steri lizing fluid if desi red, the opening can be sealed so that the impressed material is within the closed bag but the handle is outside. Prior to further processing the tray of either above arrangement can be hung up vi_§ a slot 53 in the handle 51. When the cast is to be made, the bag is unsealed and t h.e impressed material uncovered. However, as the tray is sti ll covered by the liner it is protected against contam- ination from the material from which the cast s made. ^• An alternative liner for the modified arrangement described above comprises the bag liner in the form of a pouch, i .e. with one wall shortened for example to line X - X of Fig. 5. This allows easy removal of the peel off cover 46 within the pouch and location of the tray therein with subsequent location of the impression material on the outside face of the pouch. On completion of the impression, the longer wall of the pouch can be folded over the impressed material and secured. As an alternative to coating a Liner of Figs. 1 to 5 with adhesive on both sides and covering one side with a fabric, the Liner, e.g. liner 25 may have one or more cut out portions ⁽ 26 ⁾ so that during manufacture a self adhesive backed fabric (27) can be secured to one side of the liner with adhesive portions over the or each cut

out portion (26. These portions can then be treated w th a solvent if desired and/or covered by a peel-off cover 26 ' .

In a third embodiment. Fig. 6 a liner 60 is provided simply to provide a barrier between the tray and the impression material.

The liner is for example formed of a fabric such as a polya ide fabric coated on one side with an adhesive 61 such as a tack-peelab le adhesive which is covered by a peelable cover 62 prior to use. Preferably a tab portion 63 is provided to extend beyond the tray when the liner is secured thereto for easy removal of the liner after use. The tab 63 may be for example at the handle end of the liner, as illustrated in Fig. 6. The adhesive coating 61 may be over the whole area which engages the surface- of the tray or it may be on selected areas only. For example, as illustrated in Fig. 6 in order to prevent the adhesive surface prematurely adhering to the r m of the dental impression tray, in this instance, an upper tray, the D shaped adhesive portion 61 is smaller than the dimensions of the fitting surface which n this embodiment correspond with the dimensions of the liner. Separate arcuate strips 61' are spaced from the D-shaped portion 61 so that, once the D-shaped portion 61 has been correctly positioned, the arcuate strips 51 ' can be secured to the rim of the tray.

This arrangement s an alternative to the use of a solvent to allow the liner to be momentarily slid into the correct position. Fabric surface 64 secures the material 30.

As an alternative to coating the fabric with an adhesive, the liner may be manufactured from an adhesive coated fabric 64 and a backing 60 which has cut out portions 61, 61 ' equivalent to the coated area or areas. The fabric can then be adhered to a backing so that the

adhesive surface is covered by the cut out portions and these can be covered by a peelable cover.

A liner as described with reference to Fig. 6, i .e. one ha ing no means for enclosing the impressed material may be enclosed in a known bag or ^' it may be attached to a sheet or bag in which it can be enclosed after the impression has been made. However, the main purpose of this liner is to protect the tray from the impression material by for ing a barrier between the two and it has the following advantages:

1 ) Connects impression more firmly to tray than other methods,

2) Is quick and clean to use. 3) Avoids the use of messy spray on or brush on glues,

4) Old stock trays can now be used pleasantly and hygienically - (expensive disposables no longer requi red) .

5) Trays cleaned off rapidly like new.

The liners as hereinbefore described with reference to Figs. 1 to 5 have these and additional advantages, namely :

6) Protects impression from moisture loss,

7) Tray can be prepared ready for impression before session starts with name, moisture sealant and adhesive,

8) Provides a further barrier between patient's body fluids and dentist giving complete protection for technicians.

9) Facilitates impression identifications, 10) Handle remains exposed allowing easy storage awaiting collection or processing.

11 ) Tray remains identified up to point of return (no more lost trays) ..

The Liner, described with reference to dental trays, can be adapted for use with other holders when the aforesaid advantages accrue, e.g. impression holders for aki ng opti ca L impressions for the production of contact Lenses, and in production of artificial limbs and joints.