Abstract:
A dental casting alloy based on Ni and Ti and having addition of cast of Mo, Fe, Cu and Co has the following composition in weight %:Ti: 40-50 % Mo 0.2-20 % Fe 0.1-1.5% Cu. 0.1-1.0% Co 0.1-0.5% Ni balance to a total of 100%; the alloy has advantages over prior alloys for dental castings including a high level of fluidity, a low shrinkage percentage, a low melting temperature and super elasticity

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to a dental technique and alloy that can be used in orthopaedic stomatology, and especially in dental castings, restorations and cast removable partial devices, including dental prostheses and dentures.  
         BACKGROUND ART  
         [0002]    The prosthetic device or false tooth application allows to solve tooth defects of the enamel and restore the integrity of the dental arch. Depending on the pathology, its severity and progression, the prosthesis design is selected on the basis of what is already currently used in modem dental, prosthodontic practice.  
           [0003]    Considerations of the requirements of dental alloys used for prosthetic devices are: their strength, wear resistance, hygienic and esthetic properties, biocompatibility with the dental tissues, cost aspects and a number of others.  
           [0004]    The alloys used until now are in certain ways acceptable with respect to the above-mentioned requirements, in relation to specific tooth defects and types of prosthetic device.  
           [0005]    On the other hand, there are substantial disadvantages associated with currently used alloys that diminish their applications and the patients&#39; satisfaction. For example, various alloys used in the same patient have different galvanic potentials which can be harmful to human health.  
           [0006]    The important requirement for a dental casting alloy is its technological effectiveness when a prosthesis is fabricated. Currently, parameters such as: the preparation of the alloy and the ratio of components, the purity of the furnace environment, the casting settings and so on play a key function in producing quality castings. The production cost and consumer prices are directly related to the limits on possible variations of these parameters.  
           [0007]    Material science offers new and more perfected casting alloys and casting materials that characterize the technical level for the proposed invention.  
           [0008]    There is known the stomatological cast alloy [1] that contains 23% of Ni; 23% of Cr; 5% of Si, Mn, Al, Nb and the rest is Fe. As compared to stainless steel this alloy has improved corrosion resistance and fluidity which is important for casting of prosthetic devices of small dimensions and volume. The disadvantage of this material is the low level of biomechanical compatibility.  
           [0009]    There is also known the stomatological cast alloy [2] “BUGOGEN . . . CCS VAC” (KXC) that contains in its composition the following components: Co -63%; Cr-27%; Mo-5%; Ni-3.5%; Si, Mn, C-1.5%. This alloy is oriented to manufacture a unit-cast high-duty removable partial prosthetic device including splinting apparatuses, crowns and tooth bridges. An advantage is the optimal correlation on high ultimate strength and plasticity. The oxide film which is formed on surface of the alloy allows deposition of a ceramic coating on it. The disadvantages are the low biomechanical compatibility and high specific gravity. This alloy is not exposed to stamping, bending or soldering.  
           [0010]    There is known the stomatological cast alloy [1] “NiCr-DENT No S vas”, that contains in its composition the following components: Cr-25%; Mo-9.5%; Si, Mn, S-4%; the remainder being Ni. The alloy is characterized by high yield point, high hardness, possibility to be machined with drills of usual instrumental steel, high-tensile oxide film under good adhesion toward metallic basis and ceramic coating. The disadvantages of this alloy are the low biomechanical compatibility, high specific gravity, and the complexity of technology that requires the formation of a deep vacuum.  
           [0011]    Taking into consideration the mentioned criteria for the choice of stomatological or dental casting alloys, the presence of titanium in their composition may improve their properties. A dental casting alloy [3] composed of Ni and Ti, in a ratio of approximately 50% each, was chosen as a prototype for the alloy of the invention.  
           [0012]    The prosthetic devices made of this prior prototype alloy practically have no shrinkage, they fit on to gypsum models easily thus allowing to reduce the thickness and degree of teeth preparation intended for use with prosthetic devices. Also, these prosthetic devices are not affected by oxidation, thus increasing their service life. The disadvantages of the prototype alloy are low elasticity and low biomechanical compatibility. The fine-structured elements of the prosthetic devices are affected by high-level mechanical loads, for example, the frames of removable partial prosthetic devices, and since they are not elastic, they are weak. In order to increase the strength of the partial prosthetic devices it would be necessary to increase the volume of material and thus to increase the weight of the prostheses.  
         DISCLOSURE OF THE INVENTION  
         [0013]    The technical advantages of the invention are an increase in the elastic properties of the new alloy, its related biomechanical compatibility, strength characteristics and strain wear resistance.  
           [0014]    These technical advantageous results are achieved by a dental casting alloy based on Ni and Ti, with additions of the following alloying elements or components: Mo, Fe, Cu and Co at the following weight percentages:  
                                                       Ti:    40-50%           Mo:   0.2-2.0%           Fe:   0.1-1.5%           Cu:   0.1-1.0%           Co:   0.1-0.5%           Ni   the remainder to 100%                      
 
           [0015]    Thus in one aspect of the invention there is provided a dental casting alloy of the aforementioned composition.  
           [0016]    In another aspect of the invention there is provided a dental prosthesis cast from the dental alloy of the invention.  
           [0017]    In another aspect of the invention there is provided use of the dental alloy of the invention in the manufacture of a dental prosthesis.  
           [0018]    In another aspect of the invention there is provided in a method of implanting a dental prosthesis in a patient in need of such prosthesis, the improvement where the prosthesis is of a dental alloy of the invention.  
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0019]    [0019]FIGS. 1, 2 and  3  are views of partial metal frames of the removable prosthetic devices cast from the alloy of the invention.  
         [0020]    [0020]FIG. 4 is a view of a partial prosthetic device cast from the invented casting alloy. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]    Suitably the dental casting alloy of the invention comprises, in weight %:  
                                                       Ti:    44-46%, preferably about 45%           Mo:   0.2-2.0%, preferably 0.5 to 1.5%           Fe:   0.1-1.5%, preferably 0.3 to 1%           Cu:   0.1-1.0%, preferably 0.3 to 0.8%           Co:   0.1-0.5%, preferably 0.2 to 0.4%           Ni   balance to 100%                      
 
         [0022]    Amounts of Mo below the aforementioned lower limit render the alloy difficult to machine or extrude while amounts above the aforementioned upper limit render the alloy too brittle.  
         [0023]    Amounts of Fe below the aforementioned lower limit reduces the plasticity unfavourably, while amounts above the aforementioned upper limit increase the plasticity to an unfavourable level.  
         [0024]    The presence of the elements Mo, Fe, Cu and Co in this Ni—Ti alloy imparts properties which are different and superior to those of the prototype. This provides the attainability of the mentioned results. The complex study and testing for this alloy, the comparative evaluation of its technical characteristics have defined its several technological and functional merits:  
         [0025]    1. High level of fluidity. This allows the casting of removable prosthetic devices of intricate and thin configurations (FIG. 1- 3 ) without a vacuum and under high homogeneity of the alloy structure.  
         [0026]    Low shrinkage percentage. This provides the possibility to maximize the technological accuracy of the alloy to fit dental models, and the intra-oral fitting of the prosthetic devices including the supporting surfaces of the teeth. The shrinkage is essentially zero.  
         [0027]    Lower melting temperature. This results in less demand on mold materials and on casting settings, the melting temperature is 1130 to 1210° C.  
         [0028]    Superelasticity. This terminology corresponds to a rubber-like behavior of the alloy when alternating strain loads are applied and relieved. The value of the maximum strain of the invented alloy that is returned after the load release may reach up to 2.5% and it may correspond to the elasticity of live tissues. This coincidence (relating to strain characteristics), minimizes and practically excludes macro displacements and overloads on the interface “alloy-organism tissue”. In turn, this elasticity property reduces damage to the surrounding tissues of the prosthesis, including damage that takes place with repeated loads. This elasticity allows for the reduction of the volume of the alloy which is required to perform the function and thus reduces the weight of the prosthetic device. This last advantage is amplified with a lower specific gravity of the invented alloy.  
         [0029]    2. The available physical and mechanical merits of the invented alloy influences its consumer preference:  
         [0030]    a) The cast removable partial prosthetic devices exhibit stable and lasting retention of the clasps on the residual supporting teeth.  
         [0031]    b) There is an improvement on uniformity and the distribution of the masticatory-forces along the length of the tooth arch and alveolar ridge.  
         [0032]    c) There is a possibility to abandon the dampers or resilient attachments used to reduce the masticatory forces for patients with gum or periodontal disease.  
         [0033]    d) There is a reduction of the harmful action of the prosthetic device retentive clasps or loading on the supporting teeth.  
       EXAMPLE  
       [0034]    The achieved technical results using the invented casting alloy for dental prosthetic devices are confirmed by the Engineering Medical Centre (Tomsk), the Scientific and Research Institute of Medical Materials of the Siberian Physical and Technical Institute (Tomsk) and at the Siberian Medical University.  
         [0035]    An example on the use of the invented alloy is shown with the case history of patient identified as SCH, 45 years old, who sought a dental consultation. The diagnosis after examination was:—Generalized disease of the gum (periodontitis) of the upper jaw which is complicated with a bilateral (Class II) partial absence of the posterior teeth of the lower jaw and mobility levels II &amp; III (advanced mobilities) of the remaining teeth of the maxilla.  
         [0036]    As part of the dental treatment, the invented dental casting alloy was employed in an experimental trial. The composition was as follows in weight %: Ti-45%; Mo-1.0%; Fe-0.5%; Cu-0.5%; Co-0.3%; the balance to 100% was Ni. This alloy was processed by means of induction casting.  
         [0037]    Using the method of induction centrifugal casting the prepared alloy was poured into a unit-cast removable prosthetic device or mold with T-shaped so-called “clammers”.  
         [0038]    After accomplishing the anti-inflammation treatment of periodontal therapy, the teeth with the mobility levels of III (advanced mobilities) were extracted. The cast prosthetic device was applied using supports from rests on three teeth, formula 4,2⊥5 (with mobilities of II and ⅓ of radicular bone loss).  
         [0039]    Good retention of the partial prosthetic device was achieved and normal function during the mastication was restored. The positive results were documented over 9 months.  
       REFERENCES  
       [0040]    Literature used for invention disclosure:  
         [0041]    1. Stomatological cast alloys. Reclama TOO “Denta”, Novosibirsk, Ob&#39;edineniya str., 39;  
         [0042]    2. C. D. Bogoslovski, High quality casting in Dental Prosthesis Technique, Moscow, “Medecina” 1977, page 25;  
         [0043]    3. U.S. Pat. No. 2,111,722, A61 13/20, Method to produce cast metallic frame of Dental Prosthesis (prototype).