The present invention relates to a method and an arrange¬ ment for lifting simultaneously at least two sections of a multi-section jaw model intended for dentotechnical pur¬ poses from a mount or like base on which the model sec¬ tions are detachably placed and aligned correctly in rela¬ tion with one another through the agency of at least one guide means.

When carrying out certain kinds of dental work, such as the manufacture of bridges and like constructions, the dental technician will work from a model of the patient's jaw. This model is produced by first taking an imprint of the patient's jaw and then making a cast from the im¬ print. The model is then placed on a mount and held in position thereon with the aid of guide means, which may have the form of pins provided on the model and received in corresponding holes in the mount.

In the manufacture of metal bridges for instance, an ad ^¬ vantage is gained when the bridge is cast in one single piece, since single-piece bridge casts afford many advan ^¬ tages in comparison with constructions which comprise a multiple of mutually soldered sections. This is due to the homogenous nature of a single-piece metal construction, which is not achieved with a bridge construction that com ^¬ prises a number of mutually welded sections, since the nature of the weld material in the joints between the sections is different to that of the actual bridge sec ^¬ tions .

In the manufacture of a bridge construction, the model is normally divided into a plurality of sections and each section is provided with at least one guide means for the

aforesaid purpose. Consequently, subsequent to producing a wax model of the bridge construction on the jaw model it is extremely difficult to lift up all of the various sections of the jaw model simultaneously from the mount. It is very difficult to lift the sections manually, parti¬ cularly if some of the guide means are not so readily re¬ leased as others. Should this be the case, the sec¬ tions can easily become displaced in relation to one another and may not be parallel with each other when lifted, which may result in deformation of the wax model. Should the wax model be deformed, the bridge construction produced therefrom will, of course, not fit the patient's mouth, which will in turn lead to additional work in making adjustments to the bridge, possibly requiring the bridge to be divided up into sections and resoldered to¬ gether, which is very undesirable for the aforesaid rea¬ sons.. A further problem resides in the difficulties ex¬ perienced when attempting to carry out similar operations by hand when fitting the cast skeleton framework to a bridge construction and placing facade material in posi¬ tion, this material often being porcelain, which is ex¬ tremely sensitive prior to being fired.

The object of the invention is to provide a method and an arrangement of the aforesaid kind with which these draw¬ backs are overcome and which will enable all the sections of a multi-section jaw model to be lifted simultaneously without risk of the various sections being displaced rela¬ tive to one another. This object is achieved with a method according to the invention having the character¬ izing features set forth in claim 1 and with the aid of a _l arrangement having the characteristic features set forth in claim 3.

Sui _t able embodiments of the invention are set forth in the

depending claims.

The invention will now be described in more detail with reference to the accompanying drawings, in which

Figure 1 is a front- view of a jaw model and support means in accordance with one embodiment of the invention;

Figure 2 is a top plan view of the jaw model and support means of Figure 1 and shows a mould for producing a mount for carrying the jaw model ;

Figure 3 is a top plan view of the support means illus¬ trated in Figures 1 and 2;

Figure 4 is a view which corresponds to Figure 2 but which shows a further embodiment of the support means;

Figure 5 is a perspective view of one embodiment of an inventive lifting device; and

Figure 6 is a sectional view taken on the line VI-VI in Figure 5.

Figure 1 illustrates a known jaw model 1 which is produced b taking an imprint of a patient's jaw and casting the model from the imprint. The model is intended to facilitate the work of the dental technician and is normally divided into a larger or smaller number of sections, not shown in the drawing. In order to enable these model sections to be held in precisely the correct position in relation to one another, the model sections are fitted detachably onto a mount or stand 2. The mount 2 is shown in chain lines in Figure 1, whereas Figure 2 illustrates the mount in the process of manufacture in a mould 3, which is described in

detail hereinafter. Each model section is provided with quide means 4 in the form of pins which are firmly at¬ tached to respective model sections and which project down into the mount 2, thereby ensuring that each model section is guided positively in relation to the mount. The guide pins 4 are received with a good fit in corresponding holes in the mount. This enables respective model sections to be removed readily from the mount 2, which is necessary when carrying out certain aspects of dentistry, such, as when manufacturing bridges and the like, while at the same time ensuring that the initial mutual relationship of model sections on the mount 2 will be maintained through¬ out the duration of the work.

The above described is well known to those skilled in this art, and the use of an arrangement of this kind will re¬ sult in the difficulties and problems recited in the introduction. These problems are solved in accordance with the invention, by placing a support means 5 between the jaw model 1 and the mount 2. As will best be seen from Figure 3, the support means 5 is essentially in the form of a closed loop 6 of substantially horseshoe con¬ figuration, and has gripping members 7 projecting later¬ ally therefrom. The illustrated embodiment of the support means 5 also includes a connecting part 8 which joins to¬ gether the two limbs of the horseshoe-shaped loop 6. The support means 5 is preferably made of metal, e.g. steel, so that the support means will be very stable. This enables the support means 5 to be moved safely, particularly when the gripping members 7 are used to lift the support means 5 and the jaw model 1 carried thereby, this use of the gripping members 7 being facilitated by the fact that they project laterally from the mount 2 and can be gripped manually with the hands or with the aid of a suitably configured tool.

Figure 2 illustrates the support means 5 located between the jaw model 1 and the mount 2. The method used conven¬ tionally for mounting the jaw model 1 onto the mount 2 involves placing the jaw model, provided with guide means for pins 4, over a mould 3 and then filling the mould with a solidifying substance, up to the undersurface of the jaw model 1. The solidified substance forms the mount 2. It will be appreciated that the substance from which the mount 2 is formed tends to adhere to the model 1 and to the guide means 4. In order to prevent this from happea- ing, there is used a suitable release agent. In the case of the illustrated inventive embodiment, the mould 3 is provided with grooves in which gripping parts 7 of the guide means 5 are fitted, so that the upper surface of the guide means 5 will lie in the same plane as the upper surface of the mould 3, which means that the guide means will be fully embedded in the mount 2 and will not inter¬ fere with the fit between the undersurface of the jaw model 1 and the upper surface of the mount 2.

As an alternative to placing the guide means 5 over the mould 3 when casting the mount 2, it is conceivable to produce a model of essentially the same configuration as the guide means 5 and to use this model to produce the requisite cavity in the mount 2. In this regard, the model support means, not shown in the drawing, is produced from some suitable plastics material and is mainly intended for one-time use only. In order to ensure that the cavity produced in the mount 2 affords sufficient space for the support means 5, the model support means is preferably made slightly larger than the actual support means 5. This will enable the support means 5 to be used even if small foreign particles are present in the cavity, such as dust and like dirt from the surroundings, without influencing the fit between the jaw model 1 and the mount

Figures 4-6 illustrate a lifting arrangement constructed in accordance with the invention. When using the illus¬ trated lifting arrangement, the aforementioned alternative is applied in which a model is positioned beneath the jaw model 1 when casting the mount 2. This model therewith has the form of a distance piece 9, as illustrated in Figure 4.

The distance piece 9 has the form of an essentially rectangular plate, which is larger than the intended mount 2 and which projects beyond the mount during the casting operation. The distance piece 9 is provided with a recess or cavity 10, shown in broken lines in Figure 4, which is positioned beneath the jaw model 1 when casting the mount 2. The guide means 4 will therewith project down through the cavity 10 in the distance piece 9, and into the mount 2. As will be seen from Figure 4, the cavity or slot 10 is arcuate in shape and has a size and configuration which corresponds essentially to the configuration of the jaw model 1. The slot 10, however, is narrower than the jaw model 1. When casting the mount 2 in the mould 3, the mould is filled with casting material up to the under- surface of the distance piece 9, and also up into the slot 10 in the distance piece, and into abutment with the undersurface of the jaw model 1.

When the mount 2 has hardened, it is removed from the mould 3 and the jaw model 1 and distance piece 9 lifted away from the mount 2.

When further work is to be carried out on the jaw model 1 , e.g. if a bridge construction is to be produced on the jaw model 1, the jaw model is divided into sections.

This further work is effected with the aid of an inventive lifting arrangement, illustrated more clearly in Figures 5 and 6. The lifting arrangement illustrated in Figures 5 and 6 comprises two mutually parallel plates 11 and 12 which abut one another in their starting position. The plate .11 is an alignment plate and when the lifting ar¬ rangement is used is intended to lie against the upper side of the mount 2 and therewith align the arrangement relative to the jaw model 1 and the mount 2. The align- ment plate 11 is provided to this end with an arcuate slot 13 whose size and shape correspond to the size and shape of the slot 10 in the distance piece 9. This en¬ ables the alignment plate 11 to be placed on the mount 2 for the purpose of aligning the lifting arrangement rela- tive thereto. Latching means (not shown) which extend beneath the mount 2 and prevent the alignment plate 11 from being lifted therefrom may also be provided, in order to maintain the correct mutual positions between the alignment plate 11 and the mount 2.

The plate 12 has the function of a support and lifting plate and, in the starting position, is intended to lie against the upper side of the alignment plate 11. The supporting and lifting plate 12 is also provided with an arcuate slot, referenced 14, whose shape and size corre¬ spond to the shape and size of the slot 13 in the align¬ ment plate 11 and is located directly above said slot. The two plates 11 and 12 have together a thickness which is equal to or slightly smaller than the thickness of the distance piece 9. Thus, when the lifting arrangement is placed on the mount 2 with the plates 11 and 12 in mutual abutment, the jaw model 1 can be placed in its correct position on the mount 2, without interference from the plates 11 and 12.

In order to enable the supporting and lifting plate 12 to be lifted relative to the alighment plate 11 and the mount 2 in a guided and aligned fashion, the alignment plate 11 has mounted thereon a number of posts 15 which extend upwardly from the plate 11 through corresponding holes in the supporting and lifting plate 12. The upper ends of the posts 15 are connected together by means of a trans¬ verse element 16, which may optionally be detachably fitted to the posts in order to facilitate access to the jaw model 1. In order to ensure that the supporting and lifting plate 12 is guided accurately in relation to the alignment plate 11 , guide sleeves 17 are arranged around the posts 15. The guide sleeves 17 are firmly attached to the supporting and lifting plate 12, and may, for in- stance, have the form of ball bushings which enable the plates to be guided accurately in relation to one another, which enable the ^" lates to move smoothly apart and which minimize the rist of the plates sticking due to uneven or oblique movement of one plate in relation to the other.

The supporting and lifting plate 12 is also provided with a handle 18 for facilitating the various manipulations carried out. During a lifting operation, the handle 18 is used to lift up the supporting and lifting plate 12, at the same time as the transverse element 16 is used to hold the alignment plate 11 down in its correct position against the mount 2. The guide sleeves 17 are operative in ensuring that the jaw model 1 , including all of the various sections thereof, will move uniformly away from the mount 2 parallel therewith, thereby avoiding the problems recited in the introduction. In order to adapt to jaw models of differing configurations, mutually dif¬ ferent distance pieces, alignment plates 11 and supporting and lifting plates 12 can be used, the slots or cavities of which are adapted to the configuration of the actual

model concerned. For example, the plates can be con¬ structed so that solely the centre parts of the plates are exchangeable against other plate centre parts having recesses which fit the model concerned. This has not been illustrated in the drawing, however.

It will be understood that the invention is not restricted to the aforedescribed embodiment and that modifications can be made within the scope of the following claims. For example, drive means may be provided for effecting the mutual movements between the alignment plate 11 and the supporting and lifting plate 12. These drive means may be mechanical, pneumatic, hydraulic or electrical drive means, or a combination of such means.