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is iave i^ϊi re ates o prostheses for use as sαa or hare t ssue re lacements in any part of the bαsy. frvr€ t tϊcula ly > _t it dis l ses porous implants which are b ologi all com atible in the body and promote bone and tissue i growt aαd &z$ &m® &» his inventio al o * ela es to a sj>et-~hod for rod cing the novel prosthetic de ices isc ose herein,

BA€KSBOffND ART

_% ϊn cases where an en ire tooth/root _f a section of bone or any hard tissue structure or defect must be replaced oc repaired, ol^gical compatibility and adequate ingrowth and tachm n of surrounding body tissue and bone must be assured. 0

U.S. patent application No. 214,572, filed

December 8, 1980, to Bruins st al. and assigned to Medical

Biological Sciences Inc. _* he assignee herein, approaches these problems of cc-πpatibilty and tissue ingrowth by

25 providing prosthetic deirices comprising seleσted-sised polymethylmethacrylate (PMMA) beads modified with small amounts of barium sulfate and coated with and physically bonded together by means of a polymerized hydrox ethyl aathacrylate (PHEMA) coating. The resulting bonds between

30 the PEEMA coated PMHA particles provide a basic founάation for porous implants having exceptional strength. Adequate bone _* and tissue ingrowth is insured by tha use of the hydrophilic PHEMA coating which is wetted by the body fluids.

35

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O PI

SUMMARY OF THE INVENTION

e present invention provides a prosthesis cc-a risiisg a co glomerat on of modified PMMA bea s which ? ar-j. not* initially _* h nd -:! together _* Specifically, *-3oάifie≤ ^β ?HM& beadε according to che i en i ^o n are des ibee ≤ loose, individual PMMA beads coased with P3EMA and further modified with barium sulfate for x-ray identification.

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The loose, individual modified PMMA beads may be inserted into areas of bene defects, such as cavities, or acke nto any hard issue part of the body in which repair, ^construction, or repl cemen is indicated. Areas ts where the loose, individual modified PMMA beads may be used include, for example, the third molar socket where no replacement molar is desired; furcations or bony recessions between adjacen teeth roots and infra-bony pockets caused by gum and bone disease _* Non~sral

20 applications include; fracture healing, bone cancer replacement, bony buildup in plastic surgery, filling of defective bone areas and replacement of metal implants, as well as replacement of asty failing metal implants,

25 DETAILED OB3CR2T5I ^Q 8 OF TEE ISV5NTION

The prosthesis of this invention comprises a conglomer ion of modified PMMA beads which, in individual, loose form, may, initially, be packed into

30 cavities or other areaε of hard tissue defect or disease by means of a dental tool such as, for example _* the type ose *to transfer silver amal is. When a void zn a hard tissue area is completely filled with the loose, individual modified PMMA beads* the surrounding soft

35 tissue is then sutured over the beads to completely

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es&o ssse i.es. Osc the beads coπse into contact wisl-t «ac oth * foEseεiasgf psres that are readily wettable ^■ j &l3θd and baasSy ££_£& ^• &&♦ la this way,, bone grow xs ^ros-^E-ad an tsαise ecessi n prevented. As the heal ng ϋ. £©e-«?s rog esses. _* ingrow h of surrounding bone and/or tfdsae. t roughout sue ^j _n «rβ i«: β of the packed b«ads l#ass to the. ffarasi-ioα of a prosthesis coaprising a cσr# ;i-ϊS3e_c i jft of ise 1?WHA e s _*

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9trκf εsoϋ.£is.d *?~x& jsaratijl - articles of fea?ium sulfate are cs i&ce ia .* sκrθϊS-&£.s jsisai-lar to that isclo ed in the x llGi&n s* &z&wt plica ion No, 214,572, filed December & _* S Q _t which is h ewith Incorporated by reference, in S ssrώer to preven b ta iaag of the MMA beads , the relative &a iuιn sulf&ta cs tβftrt of the implants is increased* while -the amount of SEM&, ^' is -decreased and pressure avoided. j iy 'clam s f orsesl isy rise coated BMMA particles are broken ^* «g ay phys c meaas, .such as a mortar and pestle _*

^• She loose, non-bonded .modified P.MMA beads

^■ e -aprising the hard: tissue implants of this invention are produce according to he following method. PMMA beads are thoroughly mixed w fch between about 10 and 20% y S Olesae, preferably 9%, and between about 21.5 and 43% by vaigfat of .7 ic on - r less than 1 jsicron - particle-size a ium sulfate _* preferably _? the size of the jPiMϋA beads is chosea with a -view towards the development Φf pore sizes that promote bone growth. Dnder various 0 -embodiments of the in en io , the PMMA beads may be about t e 20 to 24 a∑esh size Iparticle diameters between about IQϋ and 840 microns) or about the 24 to 30 mesh s ze (particle diameters between about 590 and ?0δ microns) whi h are most easily transferred and packed into a void 5 in hard tissue areas,, a ύ which form a pore size which

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£θs.& e-&σiie ^ w . The PMMA may contain small amounts of & lasfcisisec or a eo-aono er.

Se '^an about four nd seven percent, preferably ≤„re sy veight b s2 on the 2MMA) of monσmeric t 'άroxyetbΛ CH2_HA} is then added to the PK&ή. •&S - a i. _ca -iisate mixture and the total mixture is then thoroughly TZZ. c d and combined to ef ect a uniform coating α£ ^ s 555MA aitds, The KEKA has a nigh grade of purity - about 98.4% sini-nuπ. ani is lightly inhibited from poXymarisinc zsv trace a ouπcs of an inhibitor such as the methyl ether cf. hydrcquinαne {M3HQS „ The HEMA is ef rably modifi oy the addition of a cross-linking agent s ch as triethyleneglycαl dimethaσr late, which com rises between about 1 and 54 of the HEMA, preferably 5%.

The mixed PMMA beads are subsequently heated ^■ while da at layer of about 1/16" to 1/8* in thickness is a silicone rubber mo or on a non-polar surface such as Teflαa, polyethylene or polypropylene, that does not heat ϊi ta the alternating field and whose surface acts as a release agent _* The heat treatment is carried out in a dielectric oven such as a Model MBS-1, manufactured by .T. Rose and Associates of Troy, New York, until εost of t e hy≤roxy th l ethacrylate is polymerized. The heating step is, for example, about 1 1/2 minutes in duration when '£.&.*£ upper electrode is in a position 1/4 ^w aisve the top of the beads. The PMMA beads are then allowed tc cool to an sϊsbx nt temperature between acout 70° tc S- ^r £ and any eύsi s are broken up using a tso ar and estls and £«ir ^! sequa-.'L _* ly by screening.

Since the resulting modified PMMA beads may contain residual amounts of monomeric KEMA* the beads re

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t en boiled in water for about 2 to 3 minutes in ordsr to π^tra t any rssaain Bg monomer. The PMMA beads aκ% th«n s ea ou and air d ie . _* or force dried under tem era res that r sot high enough to cause -mel ing.

he loose, »σn*bon βd modified PMHA bea s have a w&ter-v-st able. PHEMA coating into which the ba i cs sulfate pa-ticlsg. are imbedded _* All ?£ the barium sulf is a ache so the PMMA oea s and thus there ar« no free ^■ ar idiSfS O -baxixsa sulf e r maining, he osrium sulfate saust be present in a a-BOunt to substantially prevent bonding between the -PHM& -particles. Therefore if the amount o£ PHEMA coating is increased, a corresponding increase in the amount, of barium sulfate used is required,

When the PMMA beads are to be packed into voids in hard tissue areas, it is advantageous that the PHEMA coating is wetteα and swollen by water so that the beads become slightly adherent and can be more readily handled in clumps by a means of a dental tool, such as, for example, the type used to transfer silver amalgam _*

Bone surfaces which will be adjacent to the prosthesis are advantageously pretreated in various ways. preferably, any tartar or debris on the bone surface, as well as all diseased bone adjacent to the prosthesis should be removed. This may be accomplished by using, for example, a round dental burr, in oral applications, it is also desirable to remove any diseased bone, as well as all the tartar and ebris on the tooth roots adjacent to the bone defect, by scaling and curettaging the root surfaces with ₄ either a periodontal instrument or an ultrasonic sealer. The cleaned root surface is then treated with a mild acid solution such as, for example, a 50% aqueous solution of citric acid or phosphoric acid, for about two

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us i es, followed by rittsiB with water. The roild acid reasaaen s&∑v&s c collaoe ise the root and thus promote r eafcirach-aa-i «.

Z-z is nde stooi th t the foregoing detailed d scri tion is p i e by way of illustration and SSiafc -several ra difiσati-oπs may fee made therein without departing from the ciscloε^ invention.

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