In orthodontics it is known that, because of wear on the teeth and the loss of individual teeth, the original vertical dimension of the dental arches is lost over time. The consequence of such an abnormal vertical dimension of the dental arches is mainly the shifting of the caput mandibulae out of its physiological position, with consequent disorders of temporo-mandibular joint function, which often causes neuralgia and painful muscular spasms with possible postural imbalance.

With the object of restoring the correct vertical dimension of the dental arches, it is currently known to interpose thicknesses between the teeth, also known by the name of bite splints, generally consisting of a layer of resin or hardened silicone materials. These conventional solutions nevertheless have the drawback that identification of the height and position to be restored is done with the material for formation of the bite splint, normally a wax, that is still in the plastic or deformable state; this does not allow the patient to establish what is the degree of squeezing necessary to restore the original height of the arches. Thus it is possible that after hardening of the wax, the thickness obtained may still be such as not to allow the defect on the articulation of the dental arches to be evaluated exhaustively, with the consequent need to repeat the whole operation from the start.

In addition to the bite splints recalled above, of the static type in that they operate according to pre-established shapes and dimensions, there also exist dynamic bites, consisting of small bags filled with pre-established and no longer modifiable amounts of a liquid, usually water. Nevertheless, if on the one hand the static bite splints described

have the drawback of a dimensional rigidity that does not allow any corrections of height that may be necessary to be performed, those of a dynamic type, being prepared with pre- established amounts of liquid, add to the preceding drawback that of not permanently preserving the position that is to be given to the dental arches.

It is therefore the main object of the present invention to overcome the above mentioned drawbacks of the prior art, by providing a device and a method suitable for performing correct restoration of the height of the dental arches, with the possibility of making dimensional adjustments and modifications, followed by permanent maintenance of the desired height, once it has been reached.

These and other objects are achieved with the device, the method and the cushion of claims 1,9 and 16, respectively. Further preferred embodiments of the invention are apparent from the remaining claims.

With respect to known static bite splints, the device and the method of the invention offer the advantage of allowing the patient to control the degree of compression exerted thereby on the material that forms the final cushion, so as to be able to stop at the desired time or, if need be, make the necessary changes or modifications with respect to previous measurements.

Moreover, unlike current dynamic bite splints, the cushion of the invention allows the correct dimensioning reached to be made permanent, so as to give stability to the system in its final state in the patient's mouth.

These and other objects, characteristics and advantages are apparent from the description that follows of a preferred embodiment of the device, the cushion and the method of the invention illustrated, by way of non-limiting example, in the figures of the attached plates of drawings. In these figures, which form an integral part of the present description: Figures 1 and 2 are a plan view of the device of the invention; - Figure 3 is a plan view of a variant embodiment of the device of the preceding figures; Figures 4 to 7 illustrate the various stages of the method of the invention; and Figures 8 and 9 illustrate the cushion of the invention bearing the impressions of the top and bottom teeth.

The device of the invention illustrated in Figures 1 and 2 consists in a sheath or bag 1 of flexible, transparent material (for example a PVC for medical use), shaped so as to adapt to the shape of the dental arches clenched thereon (Figure 4). This sheath is filled in a controlled manner with a fluid or liquid 10, consisting of a resin of photopolymerizable material. For this purpose, the introduction of the above mentioned liquid 10 into the sheath 1 is carried out by means of a syringe 6, the neck 7 of which is applied to a corresponding connection 8 provided on said sheath 1. When this has been filled to the desired extent, the syringe 6 is removed from the connector 8, which is subsequently closed with a stopper 9.

In the embodiment illustrated in Figure 3, the sheath 1 of flexible, transparent material is integrated with a reservoir 3, made in one piece with said sheath and pre-filled with the liquid 10. The reservoir 3 is in turn put into fluid communication with the sheath 1 through a channel 4. According to this variant, said liquid 10 is pushed from the reservoir 3 toward the sheath 1, through manipulation of the said reservoir with the fingers.

In both these embodiments, therefore, the reservoir 3 or the syringe 6 are provided to introduce into the sheath 1, destined to form the cushion 5 of Figure 8, amounts of photopolymerizable resin, initially in the liquid state, which can be controlled and modified at will.

The method illustrated in Figures 4 to 7 is performed with the version of Figures 1 and 2 of the device of the invention, but it can obviously also be realised with the sheath 1 provided with a reservoir 3, with the condition that, in this case, at the end of injection of the liquid 10 into the sheath 1, said reservoir is simply clamped with tweezers and then cut at the channel 4, so as to separate it from the rest of the device.

At the start, as shown in Figure 4, the sheath 1 is initially placed empty between the patient's dental arches, and clasped between the teeth with the connector 8 protruding out of the mouth. Subsequently the syringe is applied on the same connector 8 (Figure 5) so as to inject the liquid 10 of photopolymerizing material into the sheath 1 (Figure 6). Once the desired amount of this liquid has been introduced into said sheath 1 of flexible, transparent material, and the desired height has thus been given to the dental arches, the sheath itself is closed with the stopper 9 and hardening of the liquid 10 is then performed by means of a photoactivating device 11 (Figure 7). Once hardening has been achieved,

the sheath 1 is torn, so as to free the cushion 4 that has formed through hardening of the material 10, whilst said sheath was kept clenched between the teeth.

From the aforegoing description, it can be understood that the invention allows the amount of liquid 10 to be introduced into the sheath and destined to form the cushion to be modified at will. In this manner controlled volumetric expansion of said sheath 1 is achieved, producing raising of the dental articulation until a position judged to be ideal both by the patient and by the operator is reached. For its part, the liquid material 10 introduced creates a thickness between the teeth, thus giving more or less the desired increase in the vertical dimension of the dental arches. The amount of sheath-filling material, quantifiable from the measuring scale on the syringe or on the reservoir 3, makes it possible to repeat the operation, for example with another material, thus reproducing the same volumetric expansion. For this reason it is possible, for example, to fill the sheath 1 with 2.5 ml of any liquid, leaving the patient the necessary time to search dynamically for the most comfortable height and position of the cushion to be formed.

By subsequently filling another sheath with 5 ml of resin, it can immediately be reproduced and then hardening of the resin can be performed.

Thanks to the described connection between the sheath 1 and the syringe or reservoir 3, and also taking advantage of closing of the inlet 8 or 4 for feeding of the liquid 10 into said sheath positioned between the teeth, the patient is able to bite on the dynamic cushion thus formed, also for the time necessary for the operator to evaluate and establish whether to maintain, increase, or decrease the height reached, restoring any vertical dimension lost over time and giving the joint a tension-free state of rest.

Since it is always possible, however, in the initial phase, to remove or add liquid 10 to the sheath through the described system of connection between the syringe or reservoir and the sheath itself, further adjustments of this height are nevertheless permitted, should this be necessary.

Once the desired objective has been reached and taking advantage of the photopolymerizable nature of the liquid 10, as well as the transparency of the material forming the sheath 1, the resin forming this liquid can be hardened, so as to capture permanently the ideal condition established by the operator and the patient. In fact, once the desired degree of hardening has been reached, formation occurs inside the sheath 1 of

a cushion 5 which has impressed upon it the profile of the dental arches, in the position thereof which has been judged correct.

It is important to observe that the procedure according to the invention takes place substantially in two stages, the first dynamic and the second static.

The dynamic stage takes place when, with the sheath 1 filled with the material 10 still in the liquid state, the patient bites a deformable sheath which adapts to the mouth according to the neuromuscular position preferred by the patient. After remaining for a period of about half an hour or more in this dynamic state, if need be increasing or decreasing the vertical dimension by filling or partially emptying the sheath, the patient forgets or relaxes any articular anomaly and recovers the correct position of the temporo- mandibular joint. During this stage, in which the jaw movement is sought in three dimensions, it is possible to perform tests to check the correctness of the new position reached, such as for example electromyographic, kinesiological and postural tests etc. and, by no means last, an aesthetic evaluation.

Finally, the correct mandibular-articular position thus reached can be captured permanently during the static phase of the procedure, by hardening the fluid material inside the sheath, so as to generate a cushion of compact material bearing the upper (Figure 8) and lower (Figure 9) impression of the dentition. Once suitably finished, this cushion can be used immediately by the patient, or sent to the laboratory as the articular key for the construction of bite splints or prostheses in general, or other items, always also having available the cushion since it is formed of a definitively polymerized resin.

This also makes it possible to file the cushion obtained, which could prove useful as a valid pre-post procedure test comparison that can be used, for example, in a legal setting.

This finishing of the occlusal impressions of the teeth impressed on the cushion 5 is achieved in particular by lateral milling with a cutting or abrasion gradient equal to the degree of the patient's movements of laterality (15-25° on average) so as to flare the seat of the cusp of the teeth left impressed on said resin, allowing the jaw to be able to disengage and move laterally, though maintaining the contact of centric neuromuscular relationship which has been recorded with said cushion and which is impressed on the resin forming same.

Modifications can be made to the invention as described and illustrated above to realise variants which nevertheless come within the scope of the claims that follow. Thus, for example, in place of the material 10 which can be photopolymerized by means of a photoactivating device 11, it is possible to use a self-polymerizable material, obtained by composing or combining two or more components. In such a case, the sheath 1 does not need to be made of a transparent material. Furthermore, differently to what is shown, the syringe 6 could be provided with a needle. Lastly, the stopper 9 can be replaced by use of a neck 8 of material that that can be closed, for example by folding on itself.