Modular apparatus for realization of connection structures for mobile dental prostheses.

The present patent application for industrial invention relates to a modular apparatus used to fix mobile dental prostheses.

In particular, the present invention has been devised in order to optimize the technology known as "overdenture".

"Overdenture" refers to a system composed of a removable prosthesis that can be firmly fixed to the user's jaw bone or jaw by means of two more cooperating "male-female" connections.

In such a context the male part is surgically implanted into the patient's bone, whereas the female part is incorporated into the prosthesis.

The connection implanted into the patient is generally formed of two or more pins (or screws) with vertical axis that are suitably spaced and fixed in the jaw bone or jaw in such manner that the upper ends protrude shortly from the mucosa.

In some cases said protruding ends of the screws are connected by means of a metal bar, suitable shaped to follow the curvature of the dental arch, and therefore adapted to protrude shortly from the mucosa.

In such a context the female connection incorporated in the removable prosthesis must be provided with a seat compatible with dimensions and profile of said bar protruding from the mucosa (or of any pins or screws).

This condition is necessary to obtain a firm coupling, of basically male-female type, between the connection implanted into the patient and the corresponding seat obtained at the base of the prosthesis.

In other instances, instead, the protruding ends of the screws implanted into the patient are provided with corresponding spheres that are adapted to become the connection points of the removable prosthesis.

Said spheres are adapted to cooperate with corresponding covers incorporated at the base of the prosthesis in positions exactly corresponding to the ones occupied by the spheres in the patient's bone.

In fact, said covers are adapted to be firmly "snap-fitted" with the spheres, when the prosthesis is energetically engaged against the patient's mucosa.

In the presence of such a technology, the fixing covers provided in a removable prosthesis must be connected by a metal structure, which is likewise incorporated into the prosthesis, and adapted to increase the mechanical resistance of the latter.

The first part of such a structure is a metal profile inserted at the base of the prosthesis, which is shaped in such manner to follow the curvature of the latter in longitudinal direction.

Such a longitudinal metal profile is provided with one or more pins that cross the thickness of the prosthesis almost completely, reaching immediately under the point where false teeth are joined.

Moreover, it must be considered that the metal profile is also the fixing point of said Teflon covers adapted to provide connection of the entire prosthesis on the spheres protruding from the user's jaw bone or jaw.

The most delicate aspect of such known technology is certainly the realization of the metal part incorporated into each prosthesis, both when it cooperates with said bar connection implanted into the patient and when it cooperates with a connection with spheres.

In fact, it is evident that a removable prosthesis will be correctly fixed to the patient's bone only in the presence of perfect correspondence, with possibility of precise coupling, between the connection incorporated in the prosthesis and the connection implanted into the patient. In such a perspective, in order to make a removable prosthesis the dental technician must make a wax model of said metal part to be incorporated into the prosthesis.

During this first operation, the dental technician can use moldable wax to exactly determine the shape and dimensions of the future metal part of the prosthesis.

Once this first operation has been completed, the wax model is used to create a mold where fluid metal is cast.

So, the metal that sets inside the mold can perfectly reproduce, without error, the shapes that were very carefully given to said initial wax model.

While such a production process is extremely reliable, it is easy to understand that its main critical aspects are related to the complexity of the operations that must be carried out and the long time they require.

The purpose of the present invention is to simplify and shorten the operations that are necessary for the realization of the metal structure, i.e. "connection", adapted to be incorporated in a removable prosthesis.

Moreover, it must be noted that the apparatus of the invention can be used to provide a connection for removable prostheses of the type adapted to cooperate with spheres protruding from the patient's mucosa.

More precisely, the present invention intends to eliminate the traditional operations that considerably impair the work of the dental technician, i.e. realization of wax model, realization of mold and execution of metal casting.

The apparatus of the invention, in fact, is formed of modules that are directly made of metal, which can be rapidly assembled by the dental technician in order to realize a connection ready to be exactly incorporated into the prosthesis and perfectly compliant with the requirements of precise coupling with the sphere-type connection implanted into the patient.

Another advantage of the modular apparatus of the present invention is that it allows the dental technician to give each connection a profile that exactly reproduces the normally curvilinear profile of the prosthesis.

For explanatory reasons the description of the invention continues with reference to attached drawing, which only has an illustrative, not limiting value, wherein:

- figures 1 A, 1 B and 1 C respectively consist in an axonometric view, a plan view and a side view of the first part of the apparatus according to the present invention;

- Figures 2A, 2B, 2C and 2D are an axonometric view and three different views of the second part of the apparatus of the invention;

- Figures 3A, 3B, 3C and 3D are an axonometric view and three different views of the third part of the apparatus of the invention;

- Figures 4A, 4B, 4C and 4D are an axonometric view and three different views of the fourth part of the apparatus of the invention;

- Figures 5A and 5B are two axonometric views showing the cooperation modes of said parts of the apparatus of the invention.

Referring to the aforementioned figures, the modular apparatus of the invention is composed of the following modules, which can be used from time to time in the most suitable number of specimens.

The first of said modules consists in an elongated narrow metal frame (1 ) and also provided with a central window (F) for its entire length, as shown in figs. 1 A to 1 C.

It is made with a thin moldable metal plate and comprises two identical parallel longitudinal sections (1 a) joined at the ends by two identical basically semicircular sections (1 b).

The second module of the apparatus of the invention consists in a cover (2) of the type that can be fixed to the spheres adopted in the connections implanted into the patient.

The peculiarity of said cover (2) is that it is provided, towards the top, with an annular groove (2a) that is bordered in lower position by the upper flat border (2b) of the cover (2) and in upper position by an eccentric head (2c), as shown in figs. 2A to 2D. The third module of the apparatus of the invention consists in a pin (3) formed of a truncated-pyramidal stem (3a) provided towards the bottom with an annular groove (3b) comprised between an upper circular flange (3c) and a lower eccentric head (3d), as shown in figs. 3A to 3D.

The fourth module of the apparatus of the invention is basically identical to said third module, with the only difference that the upper truncated-pyramidal stem (4a) of said pin (4) is inclined with respect to the lower section of the same, the one housing the annular groove (4b) and determined by the corresponding circular flange (4c) and eccentric head (4d), as shown in figs. 4A to 4B.

Moreover, it must be considered that the eccentric head (2c) provided on top of the cover (2) has the same shape and dimensions as the eccentric heads (3d, 4d) provided on the bottom of said pins (3, 4), and the annular groove (2a) of the cover (2) has the same shape and dimensions as the grooves (3b, 4b) provided on the pins (3, 4).

It must be further considered that said eccentric heads (2c, 3d, 4d) have higher length and lower width than the center distance between said two longitudinal sections (1 a) of the frame (1 ) and said grooves (2a, 3b, 4b) have suitable height to allow for insertion of at least one of said longitudinal (1 a) or semicircular (1 b) sections of the frame (1 ).

So, the height of each groove (2a, 3b, 4b) must be equal to or multiple of the thickness of said frame (1 ).

Likewise, it must be noted that the upper border (2b) of the cover (2) and the circular flange (3c, 4c) of the pins (3, 4) have identical circumference and higher diameter than the center distance between the longitudinal sections (1 a) of the frame (1 ).

After describing the modules of the modular apparatus of the invention, it is necessary to explain the modes for mutual cooperation and adjustability to the structure and profile of a removable dental prosthesis.

Fig. 5A shows a possible assembly of said modules, which provides, in particular, for cooperation of two specimens, with different length, of said first module (1 ), one specimen of said second module (2) and two specimens of said third module (3).

Fig. 5B is the same as Fig. 5A, with the only difference that it shows a structure with two specimens of said fourth module (4).

In both cases, said cover (2) is combined with two adjacent specimens of the frame (1 ), also acting as connection means, and said cover (2) is already connected to a pin (P) of the type implanted in the patient's bone.

In order to assemble the parts of the apparatus of the invention, it is necessary to marginally overlap the two frames (1 ), in such manner that one of the semicircular sections (1 b) of the first of said frames (1 ) is engaged above the identical semicircular section (1 b) of the second frame.

Successively, said cover (2) must be inserted, from below upwards, through the two overlapped curved sections (1 b) of the adjacent frames (1 ); in such manner that the cover (2) simultaneously crosses the central windows (F) of the latter.

However, it must be noted that said eccentric head (2c) provided on top of said cover (2) has higher length than the center distance between said two longitudinal sections (1 a) of the frame (1 ), but lower width than said center distance.

Therefore it is evident that the cover (2) can be inserted into the frame (1 ) only if the eccentric head (2c) is in such a position that its longitudinal axis is aligned with the longitudinal axis of the frame (1 ).

In such a way, the eccentric head (2c) can be brought at a higher height than the two overlapped frames (1 ), until the point in which said semicircular sections (1 b) of the latter are engaged from opposite sides into the annular groove (2a) of the cover (2).

Now the installer must simply rotate the cover (2) by 90° so that the eccentric head (2c) is in orthogonal position with respect to the two frames (1 ). In view of the above, the cover (2) is firmly fixed between the two frames (1 ); in fact, its downward extraction would be prevented by the interference exerted by said eccentric head (2c) against the upper side of the first of the two overlapped frames, and likewise its upward extraction would be prevented by the interference exerted by said upper border (2b) of the cover (2) against the lower side of the second of said frames (1 ).

It must be noted that such a triple union can be obtained in view of the fact that the height of the groove (2a) of the cover (2) is basically double than the thickness of each of said frames (1 ).

Another operation that must be carried out by the installer refers to the insertion of two specimens of pins (3) inside said two frames (1 ) already joined by said cover (2).

More precisely, the two pins (3) are engaged in correspondence of the semicircular sections (1 b) of the two adjacent frames (1 ), i.e. in correspondence of the ones that are not yet engaged in the groove (2a) of said cover (2).

The insertion of said pins (3) must be carried out from up down, but the insertion and fixing modes inside the frame (1 ) are identical to the ones described above with reference to said cover (2).

It is understood that the eccentric head (3d) provided on the bottom of said pins (3) must be inserted through the central window (F), in such a position that its longitudinal axis is aligned with the longitudinal axis of the frame (1 ).

In such a way, the eccentric head (3d) can pass through the frame (1 ) until the flange (3c) provided under the truncated-pyramidal stem (3a) of the pin (3) does not interfere with the upper side of the frame (1 ), basically at the height of the corresponding semicircular section (1 b).

Now, a simple rotation by 90° of the entire pin (3) allows for firmly fixing the same inside the corresponding end of the frame (1 ).

The accidental uncoupling of said pin (3) is prevented by the insertion of said semicircular sections (1 b) of the frame (1 ) inside the groove (2a) of the pin (3), and also by the interference exerted against said frame (1 ) respectively from down up and from up down, by the bottom lever (3d) and the circular flange (3c) of the pin (3).

As anticipated, once the assembly of the parts is completed, the metal structure shown in Figs. 5A and 5B can be manually shaped by the dental technician, by adjusting the mutual inclination of the two frames

(1 ); this is done in order to give a "broken" profile suitable to exactly reproduce the curvilinear direction of the prosthesis where the metal structure will be incorporated.

Moreover, it must be noted that the possibility to make such a "broken" profile exactly compliant with the curvilinear profile is also guaranteed by the fact that said frame (1 ) is made in multiple specimens with different length, from which the dental technician can choose the most suitable one from time to time.

For the same purpose, the frame (1 ) is also made in a slightly arched version, wherein said longitudinal sections (1 a) are given a small degree of curvature.

Finally, it must be noted that the fourth module (4) of the apparatus of the invention is perfectly alternative, in terms of use and functionality, to the third module (3) shown in Figs. 3A to 3D.

Evidently, also the choice of using either one is left to the dental technician according to the specific requirements of the prosthesis to be made.

As shown in Figs. 5A and 5B, the third and fourth module (3, 4) can be made in multiple alternative versions, which only differ in the width of the section of the truncated-pyramidal stems (3a, 4a).