IL41944A - Method and apparatus for the in-situ formation of denture - Google Patents

Abstract

1432664 Making dentures S SCHNEIDER and H S KATZ 3 April 1973 [6 April 1972] 15818/73 Heading A5R A former for use in the preparation of dentures comprises a tray which approximates the shape of a finished denture and carries false teeth on its inner surface, at least part of the outer surface of the tray being formed of a formable material so that the tray can be conformed to the shape of a patients gum or model thereof with the formable material retaining the conformed configuration. A former 20 for an upper denture includes a tray 21 having outer and inner flexible walls 24 26 a palate portion 28 and a lower part 29 having pockets to receive false teeth 42, the tray being formed e.g. by vacuum moulding from a sheet of plastics material having little elastic memory. A formable material 48 is secured to the outer surfaces of walls 26, 28 so that the tray can be deformed into contact with the gums and palate (as shown in outline). Preferably the material 48 is heat-formable, and the former is immersed in hot water prior to being moulded by finger-pressure to the patient's gums and palate. A mouldable spacer may be inserted between the former and the patient's gums. To form a denture a first layer of dentureforming material capable of cold-curing to a rigid acrylic polymer is distributed over the palate and gum portions of the former. A preformed shim of acrylic or non woven polyester is positioned over the material. A second layer of a denture-forming material capable of cold curing to a semi-rigid acrylic polymer is distributed over the shim and the assembly inserted into the patient's mouth and moulded in situ to the gums and palate. A multi-layer shim may be used in which case it is enclosed within the first layer. The tray 21 may be formed from a copolymer of ethylene and vinyl acetate and the formable material may be a wax. [GB1432664A]

Description

o»*j*w r nya ηή'ϊ ϊρηπ no»© Method and apparatus for the in-situ formation of dentures SIDNET SCHNEIDER and HARRY SELIG KATZ C: 40093 41944/2 This invention relates to a tray suitable for use in the in-situ formation of an artificial denture.

U.S. Patents 3,460,252 and 3,621,575 describe various means and methods for forming a denture in-situ in the mouth of a dental patient. These patents also disclose the possibility of altering the shape of the tray which carries the false teeth to conform more closely to an individual patient's mouth by cutting and bending the tray and then attempting to retain the shape against the material's elastic memory by the use of adhesive tape. The formable tray of this invention may be used in the making of a denture as described, for example, in the above mentioned U.S. Patents.

The invention provides a tray for use in the preparation of a denture, which tray is contoured to approximate the shape of a finished denture and carries false teeth on a part of the inner surface thereof, wherein at least part of the outer surface of the tray is formed of a formable material (as hereinafter defined) so that the tray can be conformed to the shape of a patient's gum or model thereof with the formable material retaining the conformed configuration, said false teeth being formed of a material different from said formable material.

The invention also provides a method of making a conformed tray suitable for use in the preparation of a denture, which method comprises applying pressure to a tray of the invention, which tray is spatially separated from a patient's gum or a model of a patient's gum by a spacer of a shapeable material, whereby to 41944/2 The conformed tray produced in accordance with this method can then be. used to prepare a denture by a method which comprises applying pressure in the mouth of a patient to a layer of a curable resinous, denture forming material carried by the conformed tray.

The term n ormable material" as used herein means a material which has little or no elastic memory, i.e. it is capable of being moved from a first position to a second position and of retaining said second position. Included within the term nformablen is "heat-formableB which means formable or shapeable at temperatures above room temperature (about 20°C) but not at room temperature Suitable formable materials include metals such as lead and aluminium and heat-formable materials such as plastics compositions and waxes. The preferred materials are formable and also spreadable or flowable at the operating temperature. A preferred material is a petroleum derivative micro-rcrystalline box-wax, well known in the dental art and sometimes known as "boxing-wax", which is readily formable and spreadable at only moderately elevated temperatures of 110 to 160°F (44 to 71°C) , yet it has fairly good shape-retaining properties at and below room temperature. An especially preferred box-wax has a Vicat softening point above 135°F preferably 135 to 155°F (57 to 68°C) , and a melting point about 170°F (about 77°C) .

The tray may be adapted to carry false teeth by having an inner basic tray, suitably of a plastics material, which basic tray carries false teeth in a trough-shaped portion of the inner surface thereof, 41944/2 to hold the teeth in position and which basic tray has a coating of the formable material over at least part of the outer surface thereof. Preferably the basic tray comprises inner and outer flexible walls, the walls having formable material over essentially all their outer surfaces. The plastics material is · . preferably a sheet material which inherently or by reason of its thinness is capable of being stretched but at the same time possesses sufficiently low elastic memory that it will hot work against or force the conformed formable material from its conformed configuration. Suitable sheet materials are polymeric materials having a Vicat softening point (ASTM D-1525) of 100°F to 160°P (about 38 to 71°C) , preferably 120°P to i40°F (49 to 60°C) , and a modulus of elasticity (ASTM D-747) of 500 to 9,000 p.s.i., preferably 1,000 to 4,000 p.s.i. Suitable polymeric materials include copolymers of ethylene and vinyl acetate (EVA) containing 65% to 88% ethylene arid 12% to 35% vinyl acetate, preferably 67% to 80% ethylene and 20% to 33% vinyl acetate. A particularly preferred ethylene/vinyl acetate copolymer containing about 72% ethylene and 28% vinyl acetate and having a Vicat softening point of about 125°p (about 52°C) and modulus of elasticity of about 1,700 p.s.i. may be obtained under the trademark and identi ication "ALATHON" EVA 3175.

The thickness of the outer walls of the basic tray is preferably from 3 to 12 mils , more preferably 4 to 8 mils . 41944/2 Another particularly preferred EVA material is a copolymer containing 82% ethylene and 18% vinyl acetate, of density 0.94 gm/cc, melt index 2.5 and in sheet form of 6 mil thickness.

The invention also provides a method of producing a tray for the in-situ formation of a denture which method comprises vacuum forming a basic tray from a sheet of plastics material sufficiently thin to have little elastic memory over a die shaped in the form of a gum and having false teeth thereon, and coating the outside of the basic tray having the teeth therein with the formable material. If desired, part of the basic tray can be cut away and/or replaced by sheet plastics material of different thickness. For example when the coating of formable material has been built up, part of the basic tray can be removed to leave a flange not greater than half the size of the walls of the tray forming the trough. While the coating may be built up by the addition of strips of formable material, preferably to form a continuous coating, it is preferred to make the coating by dipping the basic tray into a molten formable material, e.g. molten wax. The coating on the biting surface of the teeth is preferably removed or this area is not coated at all, so that a firm "bite" can be made during actual formation of the denture when 1 the tray is conformed to a patent's mouth.

When preparing the basic tray there is preferably used a die comprising a block having a lower supporting base portion and having as an upper portion a replica 41944/2 portion having a channel comprising a bottom contoured to fit the base of a set of false teeth and adjacent the outer gum side and bordering on said channel a ridge portion replicating the portion of natural gums between natural teeth and the main outer gum side, said die having a plurality of holes therethrough to enable vacuum forming of a sheet of plastics material thereover.

Various embodiments of the invention will now be described by reference to the accompanying drawings, in which: Pig. 1 is a perspective view showing a formable upper tray with teeth therein.

Fig. 2 is a perspective view showing a formable lower tray with teeth therein.

Fig. 3 is a section taken along line 3-3 of Fig. 2 with dotted lines illustrating the changed outline of the section after conforming of the tray.

Fig. 4 is a plan view showing a formable upper §ray having a set of pre-cast false teeth therein.

Fig. 5 is a view showing a tray in elevation and in section taken along line 5-5 of Fig. 4 with dotted lines illustrating the changed outline of the section after conforming of the tray.

Fig. 6 is an exploded view illustrating the formation of a conformed upper tray and showing a model of the gum of a patent (A) , a shaped spacer (B) which is placed over said model and a formable tray (C) placed over said spacer.

Fig. 7 is a perspective view showing a shaped spacer for use in forming a conformed lower tray. 41944/2 Fig. 8 is a perspective view illustrating: the forming of a conformed upper tray.

Fig. 9 is a top view of a die block for use in forming a basic tray. ~ Fig. 10 is a side elevation of the die block shown in Fig. 9.

Fig. 11 is a perspective view partly in section illustrating a plastics sheet vacuum-formed over a die block with false teeth thereon.

Fig. 12 is a top view of a pre-cast set of false teeth.

Fig. 13 is a representative vertical section through a finished denture while still within a conformed tray taken at a point similar to the section of Fig. 5.

Fig. 14 is a section of a finished denture while still within a conformed tray, taken along the line 14-14 of Fig. 13.

Fig. 15 is a top view of an improved formable tra , and Fig. 16 is a section along the lines 16-16 of Fig. 15.

A generally preferred type formable tray in accordance with the invention is shown in Figs. 1-5, Figs. 1, 4 and 5 showing a formable tray 20 for making an upper denture and Figs. 2 and 3 showing a formable tray 22 for a lower denture. The formable tray 20 .includes a basic tray 21 which comprises an outer uprising flexible wall 24, and an inner flexible wall 26, and a palate portion 28. The inner flexible wall 26 can comprise portions which are only slightly uprising or even horizontal prior to conforming to permit the palate to be raised a fairly substantial amount during the conforming. The inner and outer walls are suitably inter-connected along an integral bottom portion 29. The basic tray 21 is preferably formed of a thin flexible plastics material which has little elastic memory. The preferred plastics materials are as hereinbefore described. The thickness of the palate portion will be less when the tray is produced by vacuum forming.

The tray is preferably prepared by vacuum forming from a sheet of material, although other known methods such as injection and blow moulding can be used.

The outer wall 24 and inner wall 26 together with the bottom portion 29 collectively form a trough 30 of which the upper portion is a gum-receiving portion 32 capable of receiving a patient's gum and of which the lower portion contains false teeth r the gum-receiving portion having a bottom defined by or including the exposed tops of the false teeth which are to be subsequently joined to denture-forming material.

The trough 30 including the lower portion thereof is relatively narrow at the forward position 36 of the tray and gradually increases in width along the side portion 38 of the tray towards the back teeth as shown particularly in Fig. 4, and such construction may be utilized to contribute to the snug holding of the teeth in the tray. Impressed within said lower portion of the trough 30 of the basic tray 21, as during moulding 41944/2 or at any other suitable time are indentations 40 preferably in the form of spaced pockets which desirably are openly interconnected continuously along the arch of the lower portion of the trough. The indentations 40 hold, and indicate the positions of the false teeth 42 within the basic tray 21 prior to making the dentures.

The teeth 42 can thus be supported and cannot readily move out of place in the basic tray. An adhesive is therefore not necessary, although one is desirably employed.

The false teeth employed in the invention and disposed within the indentations 40 may be provided as a single cast unit containing all necessary teeth as shown in the drawings, or may be provided by a plurality of sections containing one or more teeth, or may all be provided as individual teeth; the teeth may or may not be held by a binder material such as silicone rubber, as described in U.S. Patents Nos. 3,460,252 and 3,621,575. Small holes 101 {not shown except in Pig. 15) may be drilled or moulded into the centre top of each of the teeth to promote the strength of the bond between the teeth and denture-forming material.

Both the upper basic tray 21 and lower basic tray 23 desirably have a small outward step 44 which is more pronounced towards the rear of the tray than the front, and which may be more pronounced with respect to the outer walls 24 than the inner walls 26. The steps 44 allow for the natural stepping out of the gums from the teeth. When false teeth are to be positioned in the cavities 40 without being imbedded in a binder, then it will be evident that the step 44 will be more 41944/2 and 5. The trough 30 can be said to terminate at the back of the tray and the portion of the trough 30 between the last tooth on each side and the rearward edge 46 will be called the platform trough 47.

The rearward edge 46 of the tray extends across the rearward edge of the palate and the entire length of such rearward edge 46 is preferably turned up slightly to facilitate in controlling the flow of excess denture material out of the tray during the denture-forming operation.

The formable tray 20 has on the outside surfaces of the basic tray 21 a formable material 48 which can be formed or shaped and thus effect a repositioning and/or reshaping of outer uprising flexible wall 2&† the inner flexible wall 26 and palate portion 28, because said walls and palate portion are secured to the formable material 48 and are composed of a material of sufficiently, low memory that such walls and palate retain the new shape and/or position. As shown particularly in Pigs. 1-5, the formable material covers virtually all of the outside surfaces of the basic tray 21 or 23, except for the portion thereof containing the teeth or at least the lower parts of the teeth, but including preferably the outside surface of the platform trough 47. When the preferred box-wax is used as formable material, the thickness of the layer is preferably 1 to 2.5 mm. It is also possible to leave the upper region of the outer uprising wall 24 (and inner wall in the case of a lower tray) uncovered by the formable material to facilitate trimming thereof 41944/2 in the preliminary fitting of the tray, and such omission is permissible because the precise forming or adapting of such upper region of the tray is usually less important. When left uncovered such upper region of the basic tray 21 can be made more rigid or have a greater memory as by, for example, reinforcing with a thin strip of stiffer plastics material, as the general position or orientation of such upper region can be satisfactorily set by the shaping of the formable material secured to the balance of the uprising walls. The use of formable material 48 which is flowable and thus can be spread is helpful in reducing the number of different upper trays which must be made available to fit different patients. In this connection, it can be appreciated that the palate area is subject to fairly wide variations among different patients and it may not be always possible to conform the palate portion of a basic tray to the palate of every patient, especially those having the higher palates, simply by conforming the formable material. Accordingly, it is preferred to use a formable, preferably heat-formable , material which can be spread, in conjunction with an upper tray in which at least the palate portion of the basic tray can be spread or stretched to conform to the contours and surface area of the patient's palate. As a practical matter, such a formable tray can be constructed by employing a basic upper tray made from a sheet of a suitable plastics material which is capable by reason of its thinness and/or otherwise of being stretched while at the same time the material has a sufficiently configuration. The ethylene/vinyl acetate copolymers (EVA) hereinbefore mentioned, are rubbery type materials which can also be raised above their softening points at the same temperature that the preferred heat-formable material is made formable by heating. It will be evident that equivalent conformed trays or formers may be provided by any of a variety of other means. For example, instead of making the former entirely from the preferred thin EVA sheet material, a basic tray may be prepared from a thicker sheet of EVA or other material having, for example, a thickness of 15 to 30 mils, and the palate portion thereof cut away and replaced with a palate portion of a very thin EVA sheet, said replacement palate portion being joined to the resulting tray by heat sealing, bonding and the like. Any ridge line created in the final denture by the junction of the palate and remainder of the basic tray may be readily removed by conventional finishing techniques, e.g. grinding and polishing.

The formable material 48 may be joined and held to the basic tray 21 by any of several suitable means including the natural adhesion of the formable materials to the basic tray material or by means of an adhesive or bonding substance which is desirably not brittle and which therefore can be formed along with formable material.

While the invention has been largely described with reference to an upper tray and Figs. 1, 4 and 5, it will be evident that a lever formable tray 22 with its lower basic tray 23 shown in Figs. 2 and 3 may be analogously constructed, and like part numbers in Figs.

The formable tray 20 or 22 is used to obtain a former or conformed tray for use in making the final denture. The conformed tray may be very suitably prepared in either two general ways, i.e. by either conforming the formable tray to the gums (and palate in the case of an upper denture) of the patient in situ in the mouth of the patient or by conforming the tray to a dentist's stone model of the gums (and palate in the case of an upper denture) , said stone model being obtained in the usual way by taking an aliginate impression of the gums (and any palate) followed by casting of the impression in stone. In either case, the formable tray 20 or 22 is made into a conformed tray by the application of pressure to the formable parts of the formable tray 20 or 22 while in position over the gums or model of the gums while the tray and the gum or model are separated by the shapeable spacer. Suitably the formable tray is made formable by the suitable application of heat, for example, by immersing in hot water which is at a temperature at which the preferred wax-forming material attains its formable state, and which is also preferably at a temperature high enough to raise the preferred basic tray plastics sheet material above its softening point, e.g. a water temperature of from 120° to 160°F (about 49 to 71°C) . Immersion times are typically 1/2 to 4 minutes.

As shown in an embodiment which is illustrated in Pig. 6, the upper formable tray 20 with the heat-formable forming material 48 in the formable state is conformation thereto by providing a shapeable spacer 56 intermediate said tray and stone impression. The spacer 56 is then positioned in contact with the stone impression and the tray gently positioned on the assembly and pressed down carefully over the spacer and the stone impression so that the spacer adopts the configuration of the stone impression and the inside of the tray conforms to the impression shape of the spacer. The end edges of the spacer preferably are about equidistant from the top of the wall positions of the tray, as illustrated in Fig. 8. Alternatively, the spacer may be fitted inside the tray and this assembly positioned on the stone impression. In either case, the tray which is still in formable condition by virtue of the heating thereof, is conformed to the gums and palate portion by the application of mild finger pressure to the formable material at appropriate locations as illustrated by the pressure arrows in Fig. 8. The tray thus processed conforms substantially to the gums and palate of the patient except that it differs therefrom spatially by the thickness of the spacer. The thus conformed tray is removed from the stone impression and cooled to a temperature at which the heat-formable material is no longer formable. Cooling may be accomplished simply by allowing the conformed tray to cool in the atmosphere to room temperatures but is preferably expedited by immersing the conformed tray in cold water for 1/2 to 5 minutes. The spacer may be separated from the tray before or after cooling. Typical differences between a formable tray 20 or 22 and a corresponding conformed are shown by dotted lines, and an upper conformed tray containing a finished denture is* also shown in Figs. 13 and 14.

The spacer employed in the present invention represents an important functional aspect thereof and is used in the tray-conforming operation to control and determine approximately the thickness of the final denture. Thus, the basic purpose of the spacer is to allow for and determine approximately the space to be later occupied by the denture-forming plastics material at least in the more critical areas which are adjacent the lower and middle regions of the inner wall 26 and the outer wall 24,and the palate in the case of an upper denture. The spacer may be of uniform thickness or it may be of non-uniform thickness to provide for areas in which it will be subsequently desired or required to have a lesser or greater thickness of the plastics denture material. In practice, satisfactory results have been obtained employing a spacer of uniform thickness. The relationships between the thickness of the spacer and the thickness of the plastics denture material in the final denture is indicated as approximate. Since the final denture-forming step exerts some expansive pressure on the wall of the tray, especially when a shim is employed in this denture-forming step, it will be evident that the spacer usually represents the minimum thickness of the denture. For example, when employing a spacer of uniform thickness using a shim in the final denture, it has been found that the thickness of an upper denture in the areas adjacent the inner wall and most of the spacer. The areas adjacent the outer wall of the tray (and the inner wall in the case of a lower denture) tend to be thicker than the spacer due to the flow of denture-forming material at these locations but such thickness can be controlled by the application of pressure to the tray during the denture forming process to squeeze out excess denture-forming plastics material, but in any event, the thickness of the spacer provides a very desirable control in arriving at a desirable thickness for such areas. However, the very front of the denture adjacent the front of the outer wall of the tray may be of a thickness about equal to or even somewhat less than that of the spacer (if the spacer is not made thinner in such area) because it is a part of the preferred technique in forming the denture to squeeze out an extra amount of denture-forming material to make this area particularly thin for comfort and cosmetic reasons.

With some patients having high centre palates it may not be always possible to completely conform the tray to the palate areas resulting in a small air space during the conforming process and accordingly a greater thickness of denture plastic in such areas will result. However, even in such cases a very satisfactory denture may be produced. Similarly, undercut and other unusual isolated irregular areas in the gums of the patient are disregarded in the conforming operation and result in areas of greater thickness because such areas are filled as is, of The spacer may be made from any of several suitable materials and may be preformed to adapt to the shaping of the tray or may be a sheet material which can be shaped under mild pressure to take the shape of the tray. When employing a sheet material, it is preferred to employ a material which has satisfactory drape properties so that it will approximately conform to the shape of the tray and gums and palate of the patient without substantial bunching or overlapping, thereby avoiding the production of an untrue conformation in the tray.

A sheet material providing satisfactory results is a sheet of pure gum rubber. A suitable spacer having a uniform thickness of about 0.0625 inch may be made simply by cutting an arch-shaped piece from a commercially available sheet of pure gum rubber. Another suitable spacer is similarly made from 0.05 to 0.125 inch thick "Minicel" L-200 cross-linked polyethylene foam.

In general, it is preferred to use a spacer which has been preformed to the internal shape of the basic tray and accordingly fits just inside the tray substantially in contact with the inside of the inner and outer walls and palate in the case of an upper denture.

Such preformed spacers may be readily prepared from strips of the same box-wax which is preferred as the formable material, by vacuum forming and the like from wax sheets or by casting or moulding by suitable techniques and is preferably 0.05 to 0.10 inch in thickness. To assist in preventing sticking to the tray and to facilitate separation from the tray, it is preferred to coat the underside or contacting surfaces of a wax spacer with a layer of lacquer or upper denture is illustrated in Pig. 6 and a preferred preformed wax spacer 58 of analogous construction for use in forming a lower denture is shown in Pig. 7.

A further particularly preferred embodiment is illustrated irt Figs. 15 and 16. A basic tray 21 for an upper denture is vacuum formed over a set of false teeth 42 set ori a die (see Figs. 9, 10 and 11 , and the description hereafter) having,; a gum shape. The die is preferably provided with a handle (not shown) with which the vacuum formed basic tray 21, now containing the teeth 42, can be dipped into molten box-wax, until a layer 4$, of 2 to 3.8 mm thickness, of formable material builds up on the outside of the basic tray 21. After cooling, the basic tray 21 is scored with a sharp knife so that part of the outer and inner walls thereof can be removed to leave just an arch-shaped section having a flange 102 of about 1/8 in. on the outer wall 24a and from 1/8 to up to 1/2 in. where a palate portion is included on the inner wall 26a and holding the false teeth. The box wax layer 48 can be cut away from the part containing the teeth as shown in Fig. 16. The formable layer 48 is sufficiently strong to support the pressure in the final denture-making step and the removal of part of the basic tray ensures that there is no problem about stretching and conforming the formable tray to the shape of the patient's mouth.

It will be appreciated that other trays fall within the scope of this invention. Thus, for example, a set of teeth may be used having a preformed flange of pigmented denture-forming material together with a The formable tray 20 after conforming to the balance of the first-layer material to the tray.

A second layer of denture-forming material constituting a liquid pigmented material capable of cold curing to a semi-rigid or semi-hard acrylic polymer is then deposited and distributed over the shim and the resulting assembly inserted into the mouth of the If desired, the gums and palate of the patient may be lightly coated with a light, mineral or other oil or petroleum jelly to reduce the effects of heat of curing. The preferred denture-forming materials are as described in said U.S. Patent 3,621,575 and the amounts thereof and the volume proportions of first layer rigid material to second layer semi-rigid material are preferably the reduced amounts disclosed in German Offenlegungsschrift 2,213,364, except that a small amount of a light oil, preferably a natural oil, desirably peppermint oil, may be incorporated into at least the second layer denture- forming materials. Thus, the first layer material may be preferably prepared by adding 3.7 cc of liquid acrylic monomer to which 3-5 drops of peppermint oil has been added to 5.2 gms of the pigmented resin powder, both said liquid and powder obtained under the trademark nDUR LMER,, . The secbnd layer material is preferably prepared by adding 6.0 cc of liquid monomer to which 3-5 drops of peppermint oil has been added to 7.75 gms of the pigmented resin powder, said liquid component obtained as special order component 2-A and said powder component obtained as special 'order component 3-A, both from the American Consolidated Manufacturing Company of Philadelphia, Pa. The peppermint oil may be any commercially available type and the amount generally of any oil such as peppermint oil may vary from 1% to 5% based on the total weight of the liquid monomer component used in forming the denture.

The denture formed in situ in the tray and in the mouth of the patient is removed from the mouth after curing of the denture-forming material which takes typically about - permit easier working in the mouth as desired or required to ensure proper positioning and squeezing out of excess material. The resulting denture as formed in the tray is illustrated in Figs. 13 and 14 wherein the conformed tray 60 is shown in dotted line outline. The denture 62 has the shim 64 embedded therein between a first layer 66 of. rigid material and a second layer 68 of semi-rigid material, and the conformed tray is readily separated from the denture which may be finished by polishing and the like.

The preferred basic trays 21 and 23 may be prepared by vacuum forming. Heretofore, a tray for in-situ denture formation was made by vacuum forming over a one-piece block having the general shape of a set of false teeth and then later inserting or casting a set of false teeth in the cavities or depressed pocket portions thereof.

However, this method is not really suitable when the basic tray is formed from the preferred thin EVA sheet.

As illustrated in Figs. 9-12 inclusive, a die block 70 similar to that previously used is preferably employed except that the teeth are absent and replaced by a teeth-holding channel generally designated 72 which preferably constitutes an outline of the bottom of a set of false teeth 74 which can be positioned and held on the die block 70 by the channel 72. A die block 70 for an upper basic tray therefore comprises, as shown particularly in Figs. 9 and 10, a slightly enlarged replica of the natural gums 76 comprising the teeth-holding bottom portions 78, outer gum side 80 and inner gum side 82, and an impressed replica of the palate 84 which is of the die block constitutes a base 86 which is sufficiently high to ensure good vacuum forming.

The gums and palate also contain a plurality of holes 88 which are drilled entirely through the block to ensure good vacuum forming. The teeth holding channel 72 has a bottom 90 adapted to mate and support the bottom or base of the teeth which are preferably slightly concave and accordingly the channel bottom is preferably slightly convex.

Hence, the bottom essentially comprises a plurality of contiguous indicia 91 which are preferably convex in shape. The channel at its side which is adjacent the outside gum side 80 terminates at a side wall or ridge line 92 which is preferably continuous although its depth may be very shallow or virtually non-existent at the points where each centre of the outside edge of a false tooth will rest. The side wall or ridge line 92 preferably increases in depth proceeding away from these points and forms a plurality of protuberances 94 which essentially replicate the portion of natural gums which protrude between natural teeth. The outline of the ridge line therefore essentially corresponds to the outline formed by the front portion of the bottom of the false teeth and can be said to comprise the protuberances 94 and arch-like ridge portions 95 which join the protuberances. In practice, the cast set of false teeth 74 shown in Fig. 12 may be held on the die block 70 solely by the ridge line 92 inasmuch as such ridge line 92 and its protuberances 94 prevent the false teeth from being pushed off the die block during vacuum forming and the protuberances 94 similarly secure the false teeth against undesired lateral movement. It is therefore not necessary that the side of the channel adjacent the inner side gums terminate in an inner side wall or inner ridge line although the same is preferred as shown at 96 in Fig. 9. However, if desired, small pins or pegs (not shown) of 2-4 millimetres in height above the die block may be secured between front teeth in the interproximal region, e.g. between the second bicuspid and first molar on each side, to further provide against movement. In general, the inner ridge line 96, including its protuberances 98, are preferably of shallower depth than the corresponding outer ridge line 92 and its protuberances 94, and again the depth at the points of maximum distance from the imaginary longitudinal centre line may be very shallow or non-existent.

The die block 70 is preferably of dentist's stone and may be prepared using conventional techniques from a set of already made dentures by taking a standard impression thereof in a material such as alginate. Prior to taking the impression the outer gum wall of the denture may be built up or cut away in order to introduce dimensions desired in the final die block. After taking the impression of the denture, it is cast in stone to obtain a stone model of the denture from which the teeth are then removed by cutting, grinding or similar means. The ridge line 92 with its protuberances 94 and optionally the inner ridge line 96 and its protuberances 98 may be small knife or by equivalent means to form the desired die block. The holes 88 may be drilled through the formed die block by conventional procedures. A die block for a lower tray may be similarly prepared from a set of lower dentures. The shape of the arch of the false teeth and accordingly the trays provided by the invention preferably conform to the anatomical curve. A number of such die blocks of varying size can be used to make different sized basic trays.

The basic tray 21 may be prepared using the die block 70 by first placing thereon a set of false teeth such as the false teeth 74 shown i Pig. 12. The false teeth 74 are appropriately secured in the channel 72 of the die block 70. When preparing the tray from the preferred ethylene/vinyl acetate sheet material of preferred 6 mil thickness, or other sheet material which can be easily deformed because of its nature and/or thinness, it has been found desirable to coat the preferred pre-cast acrylic false teeth with a pressure-sensitive or other adhesive so that the basic tray material will be removably bonded or secured to the teeth and thereby prevent the flow of denture-forming material over the teeth during the preparation of the denture. It is not necessary to coat the entirety of the teeth but at least the surfaces near the gum line are desirably entirely coated with the adhesive. A suitable such adhesive is a cyanoacrylate based adhesive obtained under the trade designation "Eastman 910" ("Eastman" is a Registered Trade Mark). The die block 70 with the adhesive-coated teeth secured h n e 2 of the die block is ositioned on the suction plate of a conventional vacuum forming machine, a sheet of suitable plastics material 100 placed thereover, and the vacuum former operated to conform under heat and preassure the sheet 100 to the false teeth holding die block whereby the indicia or pockets 40 of the basic tray are formed around the teeth which are adhered thereto by reason of the adhesive,. and in general the substance or outline of the basic tray 21 with, teeth therein is produced.

The false teeth thus come away from the die block when the sheet material is removed therefrom and the resulting crude basic tray with teeth therein is converted to the basic tray by simply cutting away excess sheet material. The preferred basic trays do not hold their shape well on their own at this point and are preferably placed on a suitable holding block (not shown) , and converted to the preferred deformable tray 20 by coating the walls and palate thereof with the deformable material. In the preferred embodiments this may be accomplished by coating the preferred box-wa on the walls and palate using a hot spatula or more preferably by dipping into molten wax. The preferred box-wax has a natural adherence for the sethylene/vinyl acetate sheet material so that the use of an adhesive is not necessary. A additional advantage of forming an upper tray by vacuum forming of a thin, e.g. 6 mil, sheet of the preferred ethylene/vinyl acetate materials is that the sheet portion over the palate is stretched during the vacuum forming to an even thinner sheet having only about 40% to 75% of stretched during the conforming step to limited extent usually desired to conform the same sufficiently ^ to most palate variations.

While it is desirable to form the denture in situ in the mouth of the patient, the conformed tray may be used to form a denture outside the mouth using the stone model of the patient's gums by placing the conformed tray and stone impression in an articulator known in the art and proceeding to form the denture therein using cold-cured denture forming material.

It will also be evident that various features collectively incorporated into the preferred embodiments of the invention may be used individually or together with other features not involved i this invention to gain advantages in the formation of dentures, and the modifications, if any, in the structures disclosed herein to carry out such variations will readily occur to those skilled in the art* For example, advantages may be gained by employing a tray in which either the inner or outer wall portion are made formable. In an upper tray advantages can also be gained when only the inner wall and palate integral therewith are made formable. Similarly, an upper tray in which only the outer wall portion is formable may be used in forming a fully adapted or conformed tray or former by taking an impression of only the palate and inner gum side in such a tray using an impression material such as alginate while separating the impression material and gums and palate of the patient with a spacer in accordance with such a modification of the invention disclosed in the German Offenlegungsschrift said application and herein are of similar structure and accomplish essentially the same purpose.

It will also be evident that the various improvements provided by the present invention may be realized in general in the formation of dentures, particularly the in situ formation of dentures involving methods utilizing a device or assembly carrying false teeth and having wall means establishing a gum-xeceiving portion or trough adapted to hold denture-forming material which is curable at mouth temperatures to take the shape of, and fit to, a patient's gum, including especially devices or assemblies in which inner and outer removable wall portions form the gum-receiving trough and in which the curable denture-forming material functions to join together the resulting artificial gum and false teeth. 41944/2

Claims (37)

1. A tray for use in the preparation of a denture, which tray is contoured to approximate the shape of a finished denture and carries false teeth on a part of the inner surface thereof, wherein at least part of the outer surface of the tray is formed of a formable material (as hereinbefore defined) so that the tray can be conformed to the shape of a patient's gum or model thereof with the formable material retaining the conformed configuration, said false teeth being formed of a material different from said formable material.

2. A tray according to claim 1 which comprises ah inner basic tray, which basic tray carries false teeth in a trough-shaped portion of the inner surface thereof, said trough-shaped portion having indentations therein to hold the teeth in position and which basic tray has a coating of the formable material on at least part of the outer surface thereof.

3. A tray according to claim 2 wherein the basic tray comprises inner and outer flexible walls, the walls having formable material over essentially all their outer surfaces*

4. A tray according to claim 3 wherein the basic tray extends over the total area of the tray and has formable material over essentially the total outer surface thereof.

5. A tray according to any one of claims 2 to 4 wherein the basic tray is made from a copolymer of 65 to 80% ethylene and 35 to 12% vinyl acetate. 41944/2

6. A tray according to claim 5, wherein the copolymer comprises about 82% ethylene and about 18% vinyl acetate and has a density of 0.94 gm/cc and a melt index of 2.5.

7. A tray according to claim 5 or 6 wherein the basic tray is made from a sheet of said copolymer 4 to 8 mil thick.

8. A tray according to any one of the preceding claims wherein the tray is suitable for use in the preparation of an upper denture and comprises a formable palate portion.

9. A tray according to any one of the preceding claims wherein the formable material is heat-formable (as hereinbefore defined) .

10. A tray according to claim 9 wherein the formable material is a petroleum derivative micro- crystalline box-wax.

11. A tray according to claim 10 wherein the box-wax has a Vicat softening point of 135 to 155°F. (approx. 57 to 68°C) .

12. A tray according to any one of the preceding claims which carries a full set of false teeth.

13. A tray according to claim 12 wherein the set of false teeth is removably secured to a trough portion of the tray by an adhesive.

14. A tray according to claim 1 substantially 4. IV.1973 for underlined as hereinbefore described with reference to any one figures. of Figures 1 to 6, 15 and 16 of the accompanying drawings.

15. A method of producing a tray as claimed in claim 2 which method comprises vacuum-forming a basic 41944/2 tray from a sheet of plastics material sufficiently thin to have little elastic or plastic memory over a die shaped in the form of a gum and having false teeth thereon and coating the outside of the basic tray having the teeth therein with said formable material.

16. A method according to claim 15 wherein the coating is of a heat-formable wax and the coating is built up by dipping the basic tray into molten wax.

17. A method according to claim 15 wherein the coating is built up from strips of formable material.

18. A method according to claim 15, 16 or 17 wherein the coating is removed from the biting surface of the teeth or no coating is applied thereto.

19. A method according to any one of claims 15 to 18 wherein after the coating of formable material has been built up, part of the basic tray is removed to leave a flange not greater than half the size of the walls of the tray forming the trough.

20. A method according to any one of claims 15 to 19 wherein there is used a die comprising a block having a lower supporting base portion and having as an upper portion a replica of a natural gum comprising inner and outer gum sides and a teeth-holding gum bottom portion, the bottom portion having a channel comprising a bottom contoured to fit the base of a set of false teeth and adjacent the outer gum side and bordering on the channel a ridge portion replicating the portion of natural gums between natural teeth and the main outer gum side, the die having a plurality of holes therethrough to enable 41944/2

21. A method according to claim 20 wherein the channel in the die comprises a plurality of contiguous convex indicia adapted to mate with the concave base portions of a set of false teeth.

22. A method according to claim 20 or 21 wherein the die comprises an impressed replica of a palate integral with the inner gum side.

23. A method according to any one of claims 20 to 22 wherein the die is substantially as hereinbefore described with reference to Figures 9 to 11 of the accompanying drawings.

24. A method according to claim 15 substantially as hereinbefore described with reference to Figures 15 and 16 of the accompanying drawings.

25. A tray when produced by a method as claimed in any one of claims 15 to 24.

26. A method of making a conformed tray suitable for use in the preparation of a denture which method comprises applying pressure to a tray as claimed in any one of claims 1 to 14 and 25, which tray is spatially separated from a patient's gum or a model of a patient* s gum by a spacer of a shapeable material, whereby to conform to the gum or model thereof that part of the tray formed of the formable material.

27. A method according to claim 26 wherein the formable material of the tray is heated to make it formable and is then afterwards cooled to retain the conformed shape.

28. A method according to claim 26 substantially as hereinbefore described with reference to Figures 6 41944/2

29. A conformed tray when made by a method as claimed in any one of claims 26 to 28.

30. A method of preparing a denture which comprises applying pressure in the mouth of a patient to a layer of a curable, resinous, denture-forming material carried by a conformed tray as claimed in claim 29.

31. A method according to claim 30 wherein the curable denture-forming material comprises a first layer of a material capable of curing to a rigid polymer adjacent the conformed tray, a second layer of a material capable of curing to a semirigid polymer, and a shim intermediate the two layers in at least that portion to be moulded over the patient's gum.

32. A method of preparing a denture according to claim 30 substantially as hereinbefore described with reference to Figures 13 and 14 of the accompanying drawings .

33. A denture whenever prepared by a method as claimed in any one of claims 30 to 32.

34. An assembly suitable for use in the preparation of a conformed tray as claimed in claim 29 which assembly comprises a tray as claimed in any one of claims 1 to 14 and 25 and a spacer of shapeable material provided with a layer of non-stick or mould-release material on the surface to be contacted by the tray.

35. An assembly according to claim 34 wherein the spacer is of box-wax. 41944/2

36. An assembly according to claim 34 substantiall as hereinbefore described with reference to Figures 6 to 8 of the accompanying drawings .

37. A kit suitable for use in the preparation of a denture which kit comprises a tray as claimed in any one of claims 1 to 14 and 25, a deformable spacer sheet, a shim, a first de ture-forming material curable to a rigid polymer and a second denture-forming material curable to a semi-rigid polymer. For the Applicants DR. REI HOLD COHK AND PARTNERS HE/AA