AU7154381A - Method and capsule for storing and mixing the two cooperativebasic materials of dental amalgam and method in manufacturingthe capsule - Google Patents

Description

METHOD AND CAPSULE FOR STORING AND MIXING THE TWO CO- -OPERATIVE BASIC MATERIALS OF DENTAL AMALGAM AND METHOD IN MANUFACTURING THE CAPSULE

The present invention relates to a method for stor¬ ing and mixing two co-reactive basic materials for den¬ tal amalgam, usually a silver alloy (in a typical case containing - apart from silver - also tin, copper and zinc), known in the art as alloy, functioning as one component and pure mercury as the second component.

The invention also relates to a capsule for stor¬ ing and mixing the two co-reactive components by employ¬ ing the method in accordance ith the invention, and furthermore relates to a method in manufactu ing this capsul e.

In -the sphere of dentistry many proposals have been made for capsules whereby quantities proportioned in advance of .the two co-reactive components are stored in the capsule separate from each other and can be brought together and mixed directly in the capsule so as to react with each other whilst forming amalgam directly prior to the use thereof.

The capsules now available on the market include a chamber for each component with an openable point of separation between the chambers. Several different prin¬ ciples are employed to open the point of separation.

In one embodiment (U.S. patent specification 3 275 302) a ball or disc which rests on a seating be¬ tween the chambers forms the point of separation between the chambers, the said separation being opened by shaking the capsule so as to mix the components with each other. The ball or disc at the same time forms a mixing body, known as a pistil , when the capsule is shaken during mixing. One significant disadvantage of this capsule consists in the fact that the capsule is regards its position; it must not be turned upside down before mixing is to take place.

In another embodiment (U.S. patent specification 3 357 545) the capsule contains two portions which are adjustable relative to each other with an aperture be¬ tween the chambers formed by the sections which can be opened and. closed by turning or moving the sections re¬ lative to each other.

It is also known (U.S. patent specification 3 625 349) that _.in a capsule which consists of two rota able components arranged excentrical ly relative to each other, mercury is provided in a small bag of plastic foil which is broken up by rotating the sections rela¬ tive to each other in order that the mercury will be pressed out of the bag and through an aperture between the sections is pressed into a chamber which contains the alloy.

Capsules having two sections which are telescopical ly displaceable mutually are also known wherein the sec- tions are pressed telescopically together in order that a membrane between the chambers which functions as the point of separation will be broken, either because one section is pressed directly against the membrane (U.S. patent specification 3 451 540) or by one section pres- sing on the mercury which in turn presses against the membrane (U.S. patent specification 3 595 439) . The membrane can also be shaped like a small bag of plastic foil which contains the mercury and which rests loosely in a chamber which contains the alloy. The plastic bag is broken up in that the capsule sections are pressed telescopically together when the components are to be mixed with each other.

Apart from the fact that these known dental cap¬ sules are complicated in design, in certain cases ex- tremely complicated, and hence relatively expensive to

O. produce, which is a distinct disadvantage, when - as here - they are to be throwaway capsules they suffer from the disadvantage that a particular manipulation of the capsule is required before the components can mix, and moreover a manipulation which in some cases requires the exercise of quite a great deal of force. If the mercury is located in a small plastic bag inside the chamber for the alloy, there is also the shortcom¬ ing that the plastic foil remains in the resultant amal¬ gam in the form of one or more pieces and has to be separated from the amalgam when this is removed from the capsule for use.

A dental capsule has been proposed which does not require any special manipulation before the mixing of the components (Swedish patent application 7906465-5). The capsule comprises a chamber for each component, and the chamber which contains the alloy also contains a rammer which when the capsule is shaken knocks re¬ peatedly against a displaceable separating wall between the chambers. By this means the separating wall is pressed successively into the chamber containing the mercury, thus opening up passages which permit the mer¬ cury, during the movement of the separating wall , to be forced past the said wall into the chamber with the alloy. However, this capsule is just about as complica¬ ted as the capsules described above and furthermore requires fairly high precision during manufacture.

One problem which has either not been considered at all or only inadequately in the case of the dental capsules described above is that mercury in extremely fine-particulate form can penetrate outwards between the sections rotatable or telescopically displaceable relative to each other, or in the joint between the sec¬ tions of the capsule which have to be separated in order to take out the finished amalgam. When mixing of the components takes place whilst the capsule is being shaken at high frequency, which is performed in special shaking devices available for the purpose, the mercury is flung out in the form of microscopically small drop- lets which have a very large cumulative surface and thereby a correspondingly high vaporisation- ate . It is known that the daily respiration of air contaminated by mercury vapour can result in chronic mercury poisoning, and consequently the fact is not unknown that in dental surgeries there is some risk of such poisoning, even though the frequency of its occurrence is assumed to be low. This occupational hygiene health risk is hence probably slight, but even so having regard to its con¬ sequences, it is well worth taking into account when designing dental capsules particularly since mercury can cause damage also in other ways, namely by giving rise to allergic reactions in certain persons.

The problem of mercury leakage from dental capsule during shaking of the capsule in order to prepare the amalgam has been discussed in the literature and has al been subject to investigations and proposals have also emerged for a dental capsule which is designed to eli¬ minate the risk of mercury escape. This dental capsule (German laid-open specification 28 31 005.6) is relativ ly simple in design. One chamber has a welded-on or glued-on cover with a breakage point, and in this cham¬ ber which contains the alloy, the other chamber is loca¬ ted in the form of a bag of thin plastic foil which en¬ closes the mercury. When the capsule is shaken the bag is broken open against the end walls of the capsules and when the amalgam is ready the cover is broken away from the rest of the capsule at the breakage point using a special puncturing device. Apart from the fact that in this case too there is the disadvantage of encountering foreign substances in the amalgam, i.e. the disintegrate plastic bag which can be in the form of one or more pieces, the attachment of the cover whilst providing a breaking point after the capsule has been filled with the components does involve some complication, as does the breaking up of the cover which cannot be performed just as comfortably as when separating two components which are pushed together.

The object of the present invention is to make poss¬ ible to store and mix the two co-reactive components for dental amalgam, which simultaneously satisfies all the requirements which could be imposed, namely: that storage and mixing can occur in a capsule of simple design, so that the capsule can be produced at low cost and is thus quite suitable for throwaway use ; that filling of the capsule with the two components can be undertaken in a simple manner using an auto¬ mated method; that the components can be kept separate in a rel i- able manner even during storage in the capsule for a long period; that the components can be merged together in the capsule by a simple manipulation of the capsule without any noteworthy amount of force being re- quired; that the mixing can take place by shaking in the capsule without risk of the material forcing its way out of the capsule; and that the mixing can take place without foreign ob- je^'cts coming into contact with the components or being mixed into the material .

This object is achieved in a surprisingly simple • manner by means of the method in accordance with the invention for storing and mixing the two co-reactive basic materials for dental amalgam, which is character- ized in that the basic materials are stored in a packag known per se, consisting of an elastically flexible length of tube bent into V-shape, which is sealed at th ends and in which the fold between the arms forms a point of separation between the basic materials accommo¬ dated one in each arm of the length of tube, and in tha the basic materials, after straightening out the length of tube, are mixed with each other by a shaking movement which has one component in the axial direction of the straightened tube length.

The capsule proposed for working this method is of a type which is previously known per se (U.S. patent specification 3 478 871), which has hitherto not been employed for storage and mixing of the two co-reactive basic materials for dental amalgam, and which consists of an elastically flexible length of tube bent into V- -shape, with the arms sealed at the ends, each forming a chamber, and with the tip between the arms forming a point of separation between the chambers, said point of separation being openable by straightening out the lengt of tube. In the known embodiment the point of separation between the chambers is provided for in a known manner by pressing together the tube length at the V -point, but such pressing together cannot provide an effective and reliably sealing point of separation for mercury which has the ability to make its way past even the smallest gaps, if the wall thickness of the tube length is not absolutely uniform, which is difficult to accom¬ plish in practice unless production of the tube is made considerably more expensive. Thus, the known capsule is not suitable for the storage of the basic materials for dental amalgam in which one material is me rc u ry . In orde to improve the sealing effect at the point of separation so that not even mercury can make its way past the point of separation, there is provided, in accordance with the

Bu invention, at a capsule of the type referred to, the improvement that the point of separation at the tip of the Y-shaped capsule comprises two transverse compres¬ sion points in which the opposite flat wall sections of the length of tube are pressed against each other, with a section located between the compression points, which is flattened in relation to the original cross -secti onal shape of the length of tube.

To produce this capsule the invention provides a method in which an elastic flexible length of tube is bent into V-shape with the arms each forming a chamber and with the tip between the arms forming a point of separation between the chambers. The novel and charac¬ terizing feature is that the length of tube prior to bending is pre-shaped into a section at the longitudinal centre of the length of tube by providing two transverse compressions which are mutually separated by an inter¬ mediate section.

It is preferred if the interven ng section of the tube length is flattened during the execution of the compression operations at the same time as the wall sec¬ tion, which should be located on the inside of the V, is being arched aroun the intended axis of bending. To illustrate the .present invention this will be described in greater detail in the following as to an embodiment with reference to the accompanying drawing in which

FIG 1 is a side view of the basic material for the capsule, a length of plastic tubing or plastic hose, FIG 2 is the side view of an introductory step dur¬ ing the production of the capsule in accordance with the invention, of the tube length in FIG 1 consist¬ ing in pre-shaping of that section of the tube length which is to form the fold, FIG 3 is an axial sectional view on a larger scale of the preformed section,

FIG 4 is a side view of the capsule after filling but before closure,

FIG 5 is a perspective view of the capsule ready

FIG 6 is a perspective view of the capsule straigh tened out so-as to mix the components, FIG 7 is a perspective view of the capsule in the state as shown in FIG 6 together with a holder to which it is to be applied for shaking in a conven¬ tional amalgam mixer, and

FIG 8 is a perspective view of the capsule placed in the holder.

The capsule for working the method in accordance with the invention is made from an elastic bendable tub (hose) of thermoplastic material, preferably polypropen it is however also possible to use e.g. polyethylene, polyester or nylon. The tube should preferably be abso¬ lutely transparent (glass clear). The thickness of the tube wall should be selected empirically and is depen¬ dent on which plastic material is involved; suitable external and internal diameters for a polypropene tube can be 4.9 and 4.1 mm respectively. The tube length sho be selected with regard' to the quantity of the two com- ponents which are to be stored and mixed in the capsule and to the stroke of the mixer to be used.

Referring to FIGS 1 to 3 of the drawing, the lengt of tube is illustrated in FIG 1 and denoted there by 10, and during the manufacture of the capsule in accordance with the invention this tube length is pre-shaped in a section roughly at the centre according to FIGS 2 and 3. Deformation of a section of the tube length at the cent of its length is undertaken by means of a plunger, this giving two compressions 10 A with a transverse section 10 B located between these compressions, which is β flattened in comparison with the original cross-sectional form of the tube length, whereby the wall section on the top side is curved essentially cyl indrical ly around a transverse axis to the tube length. The section 10B is of the order of 2.5 to 3 mm.

The tube length thus pre-shaped is bent into V-shape as shown in FIG 4 with the curvature of section 10B loca¬ ted on the inside, thus providing two arms 11 and 12 which are open at their free ends at 13 and 14 respective ly and which are interconnected at their other ends at the tip of the V J5 which is formed by the pre-formed central section of the tube length and which has two folds where the indentations 1 OA have been made, with the opposite flat wall sections of the length of tube pressed against each other and with the fold separated at the tip of the V by the intermediate section 10B. The folds form the point of separation between the two chambers formed by the arms 11 and 12 and thanks to pre- -shaping during the provision of the two points of com- pression 1 OA this point of separation provides a com¬ plete seal between both chambers in the arms even in the case of a component such as mercury which is so diffi cul t to seal .

To ensure that the tube length will retain the V-shape according to FIG 4, means can be provided for holding together the arms 11 and 12 and these means can comprise a strip of tape or string placed around the arms, an enveloping sleeve made -of paper, plastic or the like, or a plate of cardboard or plastic with a number of holes in which a* V-shaped length of tube as shown n FIG 4 can be placed in each hole. Also a metal bar or clip can be used. In FIG 5 such means have been indicated diagrammatical ly by dashed lines 16.

FIG 4 shows that the V-shaped capsule has been filled with the two components which are to be ored therein. The chamber formed by the arm 11 has been fill through the open end 13 with alloy, denoted by 17, whil the chamber formed by the arm 12 has been provided with a droplet of mercury 18 through the open end 14 of this 5 arm. Then the amount of alloy and the amσunt of mercury are of course proportioned in the manner required for the dental amalgam which is to be formed by mixing the components with each other.

After the capsule has been filled the two arms 11

10 and 12 are closed at the ends 13 and 14 by a transverse seal 19 and 20, provided by means of heat or ultrasonic A marking can be provided in one of the transverse seal to identify the dental amalgam of which the two compo¬ nents are to form part. The appearance of the capsule

] S is now as shown in FIG 5 and this is the condition in which it should be for storage and distribution of the two components which are kept absol utely separate from each other by means of the effective point of separatio at the tip 15. Thus, there is no risk at all of the com 0 ponents being mixed as long as the capsule has the V- -shape illustrated.

When the amalgam is to be prepared the means 16 which maintain the V-shape, are removed and the capsule is straightened out to the shape shown in FIG 6. This 5 opens up. the point of separation formed by the fold 15 s that the alloy 17 and the mercury 18 come into contact with each other to be mixed in the straightened capsule. It should be noted here that an indentation 21 remains in the tube wall from the previously-formed fold, pro- 0 vided that the plastic material is of such a composition that after straightening of the length of tube there is a certain residual deformation on the part of the tube wall. Inside the capsule the indentation forms a thres¬ hold between the chambers formed by arms 11 and 12. 5 To enable mixing of the alloy and mercury to take place in amalgam mixers of existing types, which are adapted to the dental capsules currently available, a holder or adaptor of the type shown in FIG 7 can be used. This holder contains a channel 22 which is so dimensioned that it can envelop the straightened capsule which can be passed into the channel subject to some elastic deformation on the part of its walls. Since the straightened capsule can at the ends of the indenta¬ tion 21 exhibit a couple of slight bulges in the side, the channel 22 has a couple of recesses 22A to provide room for these bulges. The channel 22 is seated on a body 23 the shape of which resembles the dental capsules currently employed.

The holder can be located between the two holder arms, partially indicated by dashed lines at 24 in FIG 8 on a conventional amalgam mixer of any of the known makes (VIBROMIX, DENTOMAT, SILAMAT, DUOMAT). The capsule in- ^' serted in its holder in the amalgam mixer is made to perform a reciprocating movement as shown by the arrow 25 in FIG 8 or a reciprocating and simultaneously cir¬ cular motion as shown by the markings 26 in FIG 8, so that the alloy 17 and the mercury 18 will mix and react with each other during the formation of the amalgam. The threshold formed by the indentation 21 thereby serves to intensify the mixing in the capsule and to prevent the mixture from being compressed, which would make it diffi¬ cult to remove the amalgam from the capsule. The seals 19 and 20 which by nature are such that they project from the sides of the capsules prevent the capsule from sliding away from the channel 22 in its lengthwise di¬ rection during mixing. As the capsule is completely sealed, there is no risk whatever of mercury in finely- -divided form escaping from the capsule to the atmos¬ phere at mixing. When the amalgam-has^' been prepared, the capsule is opened merely by cutting off the length of tube at a suitable position, after which the amalgam can be re¬ moved from the capsule for i.ns.ertion by amalgam gum or conventional plug device.

The embodiment of the invention described indicate that the present invention provides an easily-handled a effective means, also a capsule which is surprisingly simple in the design and functional respects, for stor¬ ing and mixing basic materials for dental amalgam, by means of which the objects of the present invention men¬ tioned above can be achieved.

Claims (4)

1. CLAIMS 1. Method for storage and mixing two co-reactive basic materials for dental amalgam, c h a r a c t e r ¬ i z e d in that the basic materials are stored in _a— package known per se, consisting of an elastically flexible length of tube (10) bent into V-shape,-wtrfci. is sealed at the end (at 19 and 20) and in which the fold (15) between the arms forms a point of separation between the basic materials accommodated one in each arm (11, 12) of the length of tube, and in that the ba¬ sic materials, after straightening out the length of tube (10), are mixed with each other by a shaking move¬ ment (25, 26) which has one component in the axial di¬ rection of the straightened tube length.
2. 2. Capsule fo r storage and mixing of the two co- -reactive basic materials for dental amalgam, consisting of an elastically flexible length of tube (10) bent into V-shape, with the arms (11, 12) sealed (at 19 and 20) at the ends, each forming a chamber, and with the tip (15) between the arms forming a point of separation between the chambers, said point of separation being openable by straightening out the length of tube, c h a r a c ¬ t e i z e d in that the point of separation at the tip (15) of the V-shaped capsule comprises two trans- verse compression points (10A) in which the opposite flat wall sections of the length of tube (10) are pressed against each other, with a section (10B) located between the compression points, which is flattened in relation to the original cross-sectional shape of the length of tube.
3. 3. Method in manufacturing a capsule for storage and mixing of the two co-reactive basic materials for dental amalgam, in which an elastically flexible length of tube (10) is bent into V-shape with the arms (11 , 12) each forming a chamber and with the tip (15) arms forming a point of separation between the chambers, c h a r a c t e r i z e d in that the length of tube (10) prior to bending is pre-shaped in a section at the longitudinal centre of the length of tube by providing two transverse compressions (10A) which are mutually separated by an intermediate section (10B).
4. 4. Method as in cl aim 3, c h a r a c t e r i z e d in that the intermediate section (10B) of the length of tube is flattened during the provision of the compressio (10A), whilst simultaneously the wall section which should be located on the inside of the V, is being arched around the intended axis of bending.

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