US 2347567 A
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Description (OCR text may contain errors)
April 25, 1944. E. J. KREssE DENTAL IMPLANT Filed March ll, 1943 EDwAR J. KRESSE INVENTOR.
` @ta/w57! Patented Apr. 25, 2.9214
UNITED STATES PATENT QFFICE DENTAL IMPLANT Edward J. Kresse, Denver, Colo.
Application March 11. 1943, Serial No. 478,823
This invention relates, in general, to dentistry and has reference more particularly to improvements in materials from which to manufacture implants for use in mounting articial teeth, but which can also be used in traumatic bone surgery.
It has long been the custom to mount crowns on the natural roots which have iirst been prepared by grinding, cleaning and filling according to an established asceptic surgical procedure. Such practice has been largely discontinued for reasons that will not be pointed out herein.
As early as 1909 the use of a peculiarly constructed metal frame for insertion into the alveolus of an extracted tooth or in a cavity drilled in the jaw bone, was suggested as a bearing for` an artificial tooth (Patent 943,113). Since that time a large number of experiments have been carried out which show that implants for the mounting of crowns and for bone surgery are likely to cause sepsis and necrosis unless the material employed is selected with great care.
A metallic alloy sold under the name of Vitallium and composed of 65% cobalt, 30% chromium and 5% molybdenum has been found to be a suitable material for implants as it does not set up any appreciable electrolytic action which, if present, is objectionable as it produces metallic salts in the local tissue iluid which causes excessive cellular proliferation and in general inhibits osteoblastlc activity.
It is the object of this invention to produce a suitable nonmetallic material for use in makin surgical implants that will not produce any electrolytic action and in the body of which certain germicides can be incorporated which will be released graduallv through osmotic action, and in suilicient quantity to inhibit sepsis and necrosis.
It has been found that certain plastic substances, such, for example, as methyl methacrylate. polymers when mixed with a germlcide have osmotic properties which allow the germicide to slowly pass out in suiilcient quantity to inhibit sepsis. Such implants keep tissues and surrounding bone clean and healthy, thereby permitting full osteoblastic activity and osteogenesis to proceed in' a normal way.
Another object is to vproduce an implant that shall be provided with a drainage opening extending the entire length and through which iluids from the bottom of the alveolus can escape.
A further object is to produce an implant with means for making an operative connection with a tool for rotating it when it is inserted.
The above and any other objects that may berial, such as stainless steel, gold or silver.
come apparent as the description proceeds are u attained by means of a construction and an arrangement of parts that will now be described in detail, and for this purpose reference will new be had to the accompanying drawing in which:
Figure 1 is a cross section through an upper jaw bone showing an implant in place therein;
Figure 2 is a side elevation of the implant;
Figure 3 is an end view of Figure 2;
Figure 4 is a longitudinally diametrical section taken of Figure 3;
Figure 5 is a fragmentary diametrical section to an enlarged scale; and
Figure 6 is a longitudinal section similar to that shown in Figure 4 and shows a slightly modiiled construction.
In the drawing reference numeral 5 designates the jaw bone and 6 the eshy covering thereof, while reference numeral I designates the implant and 8 a crown secured to the implant.
In order to illustrate one speciiic use of the material that forms the subject of this invention a dental implant constructed therefrom will be described. 'I'he material is a plastic in the poly. mer or monomer of which a chemical having germicidal properties or actions has been incorporated in a manner which will hereinafter be referred to in greater detail. The plastic which has been employed in this invention and which is illustrative of plastics of a type suitable for this purpose is a methyl methacrylate which is furnished by the manufacturer in two parts, one of which is a powder and the other a liquid monomer, such plastics are thermoplastic and can be molded in a suitable metal mold. In the present instance, a two-part mold has been employed.
'I'he implant has the general appearance of a wood screwland in the drawing the threads have been designated by reference numeral 9. During the molding operation the implant is provided with a drainage opening III that extends the entire length thereof and may be formed by a tubular metal member such as that designated by reference numeral l I, although if plastics of sufcient hardness are used, such openings may be formed in the plastic implant itself. The larger end of the implant is provided with a ferrule l2 which is made from some noncorrodible mate- In order to turn the implant during the operation of inserting it in the alveolus, it is provided in addition to the drainage tube I i, with one or more short tubes i3 that are placed adjacent the drainage tube and soldered or welded thereto or they may be secured to the drainage tube by a wire wrapping as it is only necessary that they be held in position during the molding operation since after the plastic has set, it will securely hold the several tubes in position.
Since the process of molding plastics is well understood. it will not be described herein. In the present case it merely involves a two-part mold having an opening of the size and shape desired. When the materials forming the plastic are mixed, certain chemicals having germicidal properties such as silver nitrate, iodine crystals, thymol iodide, sulfa derivatives, formalin derivatives, either in the form of a fine powder of uniform of varying size, or as a liquid are mixed with the monomer and after the plastic has been molded and set, such germicldes arequite uniformly distributedthroughout the entire mass. The presence of these germicides produce a plastic that has osmotic properties and therefore when the implant is in position the fluids from the socket gradually absorb sumcient quantities of germicide to inhibit sepsis or necrosis.
The method of inserting the implants is that after the tooth has been extracted, a suitable tap is employed for cutting threads in the walls of the alveolus, after which the implant is positioned on the end of a tool I4, having a plurality of prongs I5 positioned to engage in the openings in tubes II and I3. The tool I4 forms what may be termed a screw driver and enables the operator to place the implant in position. After the implant has been positioned in the alveolus, the tool is removed, leaving the central drain opening I free to permit the escape of fluids and in this way the production of pressures at the bottom of the alveolus is prevented. The germicides that have been incorporated in the plastic prevent sepsis and promote osteoblastic acitivity and the new bone thus formed' lls the grooves between the threads and provide a firm and rigid support for the implant.
For the purpose of hastening and expediting the osmotic process foreign objects such as fine particles of rubber of the type employed in vulcanized dentures may be mixed with the polymer or monomer before the materials are molded and this produces a plastic body of such porosity as may be desired. These have been indicated by dots in the sections and have been designated by numeral I6. However, when germicides of crystals form are employed, these will leave pores of microscopic size as they dissolve, thereby providing a multitude of passages that gradually extend inwardly and through which the germicide is liberated in sumcient quantity to prevent sepsis. Increased porosity may also be obtained by other means such as mixing other than'the normal monomer with the polymer or mixing organic plastics therewith, and it may also be obtained in the fabrication of the plastic by other chemical or physical treatments.
After the implant has been positioned and the new bone growth has formed so as to hold it rigidly and after all danger of irritation and decomposition has passed, a crown I3 may be attached by mean/s of prongs such as those indicated by reference numeral I5 in Figure 4.
From the above description it will be apparent that the implant that has been described and which is illustrative of surgical implants made from the material that forms the subject of this invention is: first of all, a nonmetallic implant, and since the material is a nonconductor of electricity and is of uniform composition, it cannot produce electrolysis. Another important feature of distinction is that it comprises in its'body a 75 material having germicidaproperties which produce porosity and which gives to the material osmotic characteristics that permit the germicide to be slowly delivered to the enclosing membranes; this a property that is not present in metallic implants. The amount of porosity can be regulated in the manner above pointed out.
Although the implant which forms the subject of this invention has been described in connection with dentistry, it is also equally suited for use in traumatic bone surgery where ordinary metal implants often produce necrosis. The shape of the implant and the size, shape and pitch of the threads, can, of course, be varied as`well as its size and since the material of which it is formed is very strong, it is highly suitable for connecting pieces of bone that have been broken because the properties that make it suitable for dental implants are of equal value wherever implants are indicated in connection with any other portion of the body.
It is to be understood that any suitable plastics can be employed, either thermosetting or thermoplastic.
TheA roots of the teeth are separated from the jaw bone by a layer of peridontal tissue which is elastic and serves to absorb shock. In Figure 6 an enlarged sectional view of the assembly is shown in which the center dowel'pin I5 is shown as extending almost entirely through the entire length of the drain tube II, or through the opening where no drain tube is used. Between the dowels I5 and the sides of the tube an elastic cement I1 is positioned and a layer of this cement is positioned between the tooth 8 and the implant as shown at I8. The elastic cement may be of natural rubber, a synthetic rubber or plastic and serves the double purpose of securing the tooth to the implant and as a shock absorber corresponding in function to the peridontal tissues. Instead of having the elastic connection in the implant the dowels may be mounted elastically in the tooth.
Having described the invention what is claimed as new is:
1. A material for'use in making surgical implants comprising a thermoplastic of the methyl methacrylate type having incorporated therein a solid water soluble chemical having germicidal properties, the chemical being present in sufficient quantity to produce a porous structure after the germicide has been dissolved and removed by osmotic action.
2. A material for use in making surgical irnplants comprising methyl methacrylate and a water soluble germicide` chemical in crystal form. the latter being present in the implant in sufcient quantity to produce continuous, inwardly extending passages as the germicide is dissolved.
3. A material for use in making surgical implants comprising a thermoplastic of the methyl methacrylate type with which is mixed particles of dental vulcanite in sufilcient quantity to produce a porous structure, and a water soluble chemical having germicidal properties.
4. A non-metallic material for use in making surgical implants comprising a thermo responsive plastic, free from rubber, in which is incorporated a germicidal chemical in crystal form, the crystals being present in suiiicient quantity to produce continuous passages as the chemical dissolve whereby the germicide will be slowly dissolved and released when subjected to the action of body iiuids.
EDWARD J. KRESSE.