1 2
which a sufficient number of apatite nuclei are pro
PROCESS OF MAKING BIOCOMPATIBLE GLASS duced by suitable thermal treatment, so that the growth
CERAMIC of the bone can take place in a known manner on such
nuclei. Thus it can be assumed with some degree of cer
BACKGROUND OF THE INVENTION tainty that such a glass ceramic material will grow to
. gether with the existing bone in situ.
1. Field of the Invention T,, , „„ Ju.i i. ^ _, ... ... The glass ceramic materials proposed by Hench et
The present invention relates to a novel and useful , . , . _■• j ^ , .,
. . ^ . , - , ■ al., however, have serious disadvantages which can
glass ceramic material, to a process for the manufac- . . , .
r .» ... . . , . ,n cause their use in the animal or human organism to be
ture thereof, and to the use of the resultant material, in 10 , 6
particular, as bone replacement material. come a senous source of danSer for the animal or Per"
2. Description of the Prior Art son beanng the implant, especially when implanting For osteoplastics and osteosynthesis there are em- large rePlacement pieces.
ployed, in addition to bone transplants, also metals SinCe il is known that the ratio of the two ions Na+
such as, for instance, silver and tantalum, metal com- '5 and K+ to each other is a decisive factor for proper
pounds such as, for instance, the surgical alloy steel functioning of the nerves and muscles in the animal or
"Vitallium" or the chromium-cobalt alloy "Protasul ganism, even relatively small variations and displace
1," and plastics such as, for instance, polyethylene, ments, in particular of the potassium ion concentration
methacrylates, or silicone rubber. will change the excitability or responsiveness of the
While the tolerance of the body for some of the said 2^ nerves and thus will lead to serious impairment of the
implants in the animal or human organism can be con- heart. Said ratio of sodium to potassium ions is all the
sidered satisfactory, none of the said materials or the more important because the extracellular potassium
materials known or tried out up to the present time are ion concentration, which in general is the only impor
able to grow together with the bone in the living organ- tant factor, constitutes only about 2 percent of the total
lsm- 25 potassium content of an organism. Disturbances in this
As is known, the substance of animal or human bone smali amount Qf extracellular material which, as a
consists essentially of hydroxyapatite (Ca.[(OH)- whole, constitutes only about 2 g. to 3 g. of potassium
(P04)3D which is permeated, in an intimate mixture, ions can be caused by even only relativeiy small shifts
by albuminoids (collagen). The great difference in in the potassium content of the blood or lymph,
chemical composition between the bone-replacement 30 ... must alsQ fee made wUh fe_
material and the bone itself is the reason why the syn- . ,+ , „+ . ... .
. , , . , , , spect to the Mg-^ and Ca^ ions which are also present
thetic bone-replacement materials known up to the . iU . ,, . , • ,, •
, r . -iU »u c ^ in the animal and human organism in a substantially inpresent time do not grow together with the mass of the .,, . . . & . ......
bone variable ratio and in a concentration which is also in
Therefore, up to now it has been only possible, by 35 variable. Changes and shifting of said ratio necessarily
suitable shaping of the implant, to obtain a certain me- result in severe damaSe in the organism in question,
chanical anchoring, as a result whereof the tissue close The glass ceramics proposed by Hench et al. are pre
to the bone simply envelopes the replacement material. Pared from Pure sodium-calcium glasses.
The contact thus produced between the artificial im- 11 is self-evident that, in view of the known capability
plant and the bone, however, always remains weak and 40 of 8lass to act as ion exchanger, there exists a potential
in particular cannot be subjected to the usual forces or of sodium Na+ ions and calcium Ca2+ ions which, one
stresses. the one hand, will greatly change, by leaching out, the
It is already known that regeneration of bone sub- concentration of these two ions at the area surrounding
stances proceeds from the mineral hydroxyapatite. This the glass ceramic implant and which, on the other
substance evidently acts here as point of attachment for 45 hand, will also considerably reduce by exchange ad
the albuminoids of the bone substance. Starting from sorption the concentration of the ion antagonists, for
hydroxyapatite nuclei, a complete bone is thus regener- instance, of potassium K+ ions and magnesium Mg2+
ated and built up. At the same time, connections to and ions. Thus it is to be expected that, when implanting
with the bone fragments which are still present are also larger replacement pieces, the effect on the specific ion
formed, i.e. formation of callus takes place. 50 concentration will extend, as a function of the geomet
Now, in itself, it would be possible to use apatite in ric shape of tne impianti to more remote organs and
sintered form as bone-replacement material. This their functions. As a result thereof a high displacement
method would, however, have the definite disadvan- of the ionic ratios js tQ be expected especiaiiy when the
tage that in order to obtain sufficient initial stability of ceramics are used in the form of s sintered or
the prosthesis or prosthesis part, there would have to be 55 ^ ... i e -n a fonn whjch js ticularl fa_
introduced very large quantities of apatite which ex- , , - ... j- ,
, , , .. . . .. \, ... . „ vorable for technical-medical reasons.
ceed by far the quantities required for the synthesis of . .
... , j r- i j Another substantial disadvantage of the known glass
a bone. Under such conditions, regeration and final de- , , °, „ , .
velopment of a bone replacement capable of bearing fT-T^" T/ te"denucj: to^OTm nuclelloads, however, will require too much time. 60 This leads to extremely long and technically expensive L. L. Hench, R. J. Splinter, T. K. Greenlee, and W. C. recrystallization processes. Furthermore, the number Allen have proposed, in an article entitled "Bonding of nuclei formed Per unit of volume is verv diff,cult to mechanisms at the interface of ceramic prosthetic ma- control technologically since it is dependent on numerterials," the use, as bone replacement, of apatite-con- ous imponderable factors such as the degree of purity taining materials which, as such, possess; sufficient 65 of the chemical starting materials, the prior heat treatstrength properties, so that, upon their intergrowth, full ment or thermal antecedents of the glass, the material load-bearing capacity is obtained immediately. In said of which the crucible consists, the Constance of the article, there are proposed glass ceramic materials in heating program, and others.
