clinical calcium phosphate application

7/25/2019 Clinical Calcium Phosphate Application

1/4

eramics hlternational

19 (1993) 363-366

R e v i e w a p e r

C l i n i c a l A p p l i c a t i o n s o f

C a l c i u m P h o s p h a t e

B i o m a t e r ia l s A R e v i e w

K l a a s d e G r o o t

B i o m a t e r i a l s R e s e a r c h G r o u p , D e p a r t m e n t o f B i o m a t e r i a l s ,

S c h o o l o f M e d i c i n e , Le i d e n Un i v e r s i t y , Bu i l d i n g 5 5 , R i j n s -

b u r g c r we g 1 0, 2 33 3 AA Lc i d c n , Th e N e t h e r l a n d s

( Re c e i v e d 2 8 M a y 1 9 9 2 ; a c c e p t e d 1 2 S e p t e m b e r 1 9 9 2 )

Abstract I t h a s b e e n k n o w n f o r m o r e t h a n t w e n t y y e a r s t h a t

c e r a m i c s m a d e o f c a l c iu m p h o s p h a t e s a l t s c a n b e u s e d

s u c c e s s f u ll y f o r r e p l a c i n g a n d a u g m e n t i n g b o n e t i ss u e , t '2 Th i s

c a n b e u n d e r s t o o d f r o m t h e s t r u c t u r e o f b o n e i t s e l f : i t is a

c o m p o s i t e s tr u c t u re , c o n s i s ti n g o f a c o n t i n u o u s p h a s e ( m a d e o f

c o l l a g e n o u s p r o t e i n s a n d o t h e r b i o l o g i c a l p o l y m e r s , a n d

phys io log ica l f lu id) , i n wh ich sma l l ca l c ium ph osp ha t e c rys t a l s

a r e d i s p er s e d . T h u s b i o c e r am i c s m a d e o f c a l c iu m p h o s p h a t e a r e

n o t f o r e i g n a n d h e n c e a r e b i o l o g i c a l l y c o m p a t i b l e w i t h l i v i n g

b o n e . I n t h i s p a p e r , s e v e r a l a s p e c t s o f b i o c e r a m i c s o f c a l c i u m

p h o s p h a t e s a r e d i s c u s s e d , n a m e l y , t h e i r p h y s i c a l - c h e m i c a l

s t r u c t u r e , m e c h a n i c a l p r o p e r t i e s , a n d b i o d e g r a d a t i o n , t h e i r u s e

a s c o a t i n g s o n m e c h a n i c a l l y s t r o n g s u b s t r a t e s , a n d t h e i r c l in i c a l

u s es .

p h o s p h a t e s a t r o o m t e m p e r a t u r e , a m o n g t h e m b e i n g

s e v er a l t h a t a r e t h e r m o d y n a m i c a l l y s t a b le o n l y a t

h i g h t e m p e r a t u r e s .

A f e w c a lc i u m p h o s p h a t e s a lt s h a v e b e e n s i n t er e d

i n t o a b i o c e r a m i c , s i n t e r i n g b e i n g a h e a t t r e a t m e n t

i n v o l v i n g t h e t r a n s i t i o n o f a v e r y f i ne p o w d e r

(p a r t i c l e s i z e ab o u t 1 bm o r l e s s ) i n t o a s o l i d o r

p o r o u s f o r m . T a b le 1 p r e s e n ts t w o c o m m o n

s y n t h e t i c r o u t e s , a n d T a b l e 2 s h o w s t h e c l a s si f i c a ti o n

i n t e r m s o f p o r o s i t y . T h i s c l a s s i f ic a t i o n i s o f i n t e r e s t

f o r b o t h m e c h a n i c a l p r o p e r t i e s a n d b e h a v i o u r i n

t e r m s o f b i o d e g r a d a t i o n .

T h e s o l u b i l i t i e s o f v a r i o u s c a l c i u m p h o s p h a t e s

d i f f e r g r e a t l y : n o t o n l y a r e t h e c h e m i c a l c r y s t a l l o -

g r a p h i c a l s t r u c tu r e s t h e m s e l v e s i m p o r t a n t , b u t

v a r i a b l e s s u c h a s p H , t h e s p e c i f ic n a t u r e o f t h e b u ff e r,

t e m p e r a t u r e , p o r o s i t i e s ( o r , b e t t e r , s p e c if i c s u r f a c e s)

a r e a l s o s i g n i f i c a n t . T a b l e 3 s h o w s t h e d i f f e r e n c e s

c l e a r l y f o r t h r e e v a r i a b l e s : c r y s t a l l o g r a p h i c s t r u c -

t u r e , p H , a n d s p e c if ic n a t u r e o f t h e b u f fe r . 4

C O M P A T I B I L I T Y O F C A L C I U M

P H O S P H A T E S U R F A C E S

P H A S E D I A G R A M S O F T H E S Y S T E M

C a O P a O s H 2 0

F o r t w o m a t e r ia l s , H A a n d f l -t r ic a l c iu m p h o s p h a t e ,

b i o d e g r a d a t i o n a f t e r i m p l a n t a t i o n h a s b e e n s t u d i e d

b y K l e i n

e t a l . 5

a n d b y v a n B l i t t e r s w i j k

e t a l . 6

T a b l e

P h a s e d i a g r a m s c l e ar ly s h o w t h a t t h e c o m b i n a t i o n o f

C a O , P 2 0 5 , a n d H 2 0 a l lo w s t h e e x i st e n c e o f m a n y

c a l c i u m p h o s p h a t e s al ts . N o t o n l y is w a t e r e s s e n t ia l

i n d e f i n in g t h e r m o d y n a m i c a l l y s ta b l e s a lt s, b u t t h e

t e m p e r a t u r e a l s o h a s a l a r g e e f f e c t .

A s i l l u st r a ti o n , s ev e r al p h a s e d i a g r a m s a r e s h o w n

in F igs 1 , 2 , 3 and 4 . 3 T h e y a r e e x p l a i n e d i n t h e

c a p t i o n s . I f o n e t a k e s i n t o a c c o u n t t h a t s o m e s o li d -

s t a t e t r a n s i t i o n s m a y o c c u r s l o w l y ( t h e t i m e r a n g i n g

f r o m d a y s t o m a n y y e a r s ) , t h e n i t is o b v i o u s t h a t , b y

s e l e c t e d h e a t t r e a t m e n t s , u n d e r c h o s e n v a p o u r

p r e s s u re s , it is p o ss i b le t o o b t a i n n u m e r o u s c a l c i u m

363

a b l e 1 . S y n t h e t i c r o u t e s f o r c a l c i u m p h o s p h a t e

m a t e r i a l s

( 1 ) S t a r ti n g p o w d e r o f t h e r e q u i re d s t o i c h i o m e t r y

( Ca l0 ( PO 4 ) e ( O H ) 2 f o r a p a t i t e ; Ca 3 (PO ~) 2 f o r t r i c a l c i u m

p h o s p h a t e ) , e i t h e r b o u g h t c o m m e r c i a l ly o r s y n t h e s iz e d

in t h e l a b o r a t o r y , r e s u l ts , a f t e r s i n t e r i n g a t 1 2 0 0 - 1 3 0 0 C

f o r s e v e r a l h o u r s , i n a s o l i d s h a p e . M i c r o p o r e s a n d

m a c r o p o r e s c a n b e i n t r o d u c e d a s d e s c r i b e d i n Re f. 1.

( 2 ) C a l c i u m c a r b o n a t e s h a p e s ( f o r e x a m p l e : c o r a l) c a n be

t r a n s f o r m e d i n t o c a l c i u m phosphate shapes a f t e r h e a t -

i n g in p h o s p h a t e - r i c h

aqueous solut ions under pressure

a t 3 0 0 - 4 0 0 C . ( E x a m p l e : I n t e r p o re . )

eramics h~ternational 0 2 7 2 - 8 8 42 / 9 3 /$ 6 . 0 0 ( (" 1 9 93 E l s e v i e r S c i e n c e P u b l i s h e r s L t d , E n g l a n d . P r i n t e d i n Gr e a t B r i t a i n


2/4

364

Klaasde root

C3 P - I- C4P ~

m _ _ A p

C a O + ~

C a O C 4 P A p C 3 P P 2 0 5

P 205 ( * 1 . )

Fig. 1. P hase diagram of C aO/P2 05 mixtures.

T ( * C )

4 1 6 0 0 1 5 0 0 1 4 0 0 1 3 0 0

I I I

r N A p + C a O

F:

2 - C 4 P

o

o. 1

m

L i q

o

= c : P

J 0 -

I I I I I . I

5 . 0 5 . 5 6 - 0 6 . 5 7 0

I 41T (K )

F ig . 2 . Phase d iagram of CaO/P20 s m ix tures show ing the

inf luence o f water pressure.

17OO

16O C

15O O

14OO -

1 3 0 0 -

_ L i q u i d 0 C31~+ L iq

eL ' C aP +

C 4 P - ~ C 3 P .

~ /

+ A p = ,~1

- C a O + C 4 P /

C 4P

+ A p

i 136C? ~ -

+

n

n

C a O + A p U

.~

O , C 3 P +

C2P

12 00 70 / 5 / i I A /p I I

6 0 5 5 \ 5 0

c4P P

C a O ( w t * l . )

+

L i q

Fig. 3. Phase diagram o f CaO/P205 mixtures.

17O O

1 6 0 0

1 5 0 0

1 4 0 0

13O O

Li(

m

C a O - I . - C 4 P

1 2 0 0

7 0 6 5

u i d o . C a P + L i q

c P

6 0 5 5 \

~O

_3

5 O

C4P C3P

C a O ( w t * 1 . )

Fig. 4. Phase diagram of

CaO/P20 s

mixtures (water pressure

500 mm Hg).

4 s h o w s t h a t b i o d e g r a d a t i o n i n c r e a s es w i t h p o r o s i t y

a n d t h a t H A d e g r a d e s h a r d l y a t a ll . V a n B l i t te r s w i j k

s t u d i e d H A i n m o r e d e t ai l a n d f o u n d t h a t t h e s u r fa c e

d i s s o lv e s a t a ra t e o f a b o u t 2 0 - 3 0 / l m p e r y e a r. T h u s

o n l y f o r s m a l l p a r t i cl e s ( le ss th a n s e v e r a l h u n d r e d

/ am ) is t h i s e f f e c t v i s i b l e . I n a l l c a s e s , a d i r e c t b o n d

b e t w e e n b o n e a n d c e ra m i c h a s b e en f o u n d b y m a n y

a u t h o r s .

Tab le 2 .

P o r o s i t i e s

M i c r o p o r e s :

diameter < 5 pm

Ma cropores: diam eter > 100 l~m

Dense: total volume of micro- a nd macropores: < 5%

T a b l e

3 . S o l u b i l i t y o f se v e r a l c a l c i u m

p h o s p h a t e s a s

f u n c t i o n o f p H a n d s p e c i f ic b u f f e r i n r e l a t i v e u n i t s

Buf fe r HA Tet raC P TCPc pH

Lactate 27 163 142 6, 2

Citrate 81 337 245 6, 2

Michael is 14 94 30 6, 2

Gom or is 9 140 37 6, 2

Lactate 27 100 93 7, 2

Citrate 38 86 91 7, 2

Michae lis 12 100 15 7 ,2

Gom or is 8 108 14 7, 2

Aq. dest 2, 3 4, 7 2, 7 - -

aHydroxylapat ite.

bTet racalc ium phosphate.

CTricalcium phosphate.


3/4

Clinical applications of cak ium phosphate hiomaterials

365

T a b l e

4 . B i o d e g r a d a t i o n o f H A a n d T C P ( i n

r a b b i t s )

M ate r i a l B iodeg rada t i on

( l o s s / 3 m o n t h s )

HA, 30vo1 macropores

HA, 30 vol macropores

+ 40 vo l m ic ropores

TCP, 30vo1 macropores

TCP, 30vo1 macropores

+ 40 vo l m ic ropores

O

0

15+_6

30 + 4

C L C I U M P H O S P H T E C O T I N G S

A s m e n t i o n e d i n t h e l i t e r a t u r e , 7 t h e f a t i g u e

b e h a v i o u r o f b u l k c a l c iu m p h o s p h a t e c e r a m i c s is

poor . C l i n i c a l u se ( s e e t he ne x t s e c t i on ) i s t he re fo re

l im i t ed . A n i n c re a s in g l y p o p u l a r w a y t o c i r c u m v e n t

t h is p r o b l e m is t o c o a t a s t r o n g s u b s t r a t e w i t h a t h i n

l a y e r o f c a l c iu m p h o s p h a t e . A c o m b i n a t i o n i s t h e n

o b t a i n e d t h a t n o t o n l y h a s g o o d b i o c o m p a t i b i l i t y

b u t a l so p o s s e s se s r e s i s ta n c e t o w a r d s f a t i g u e f a i lu r e .

T h e m e t h o d u s e d t o p u t a c o a t i n g o n t o a s u b s t r a t e

i s p l a s m a - s p r a y i n g , t h e p r i n c i p l e o f w h i c h i s d e p i c t e d

i n F i g . 5 . L i t e r a t u r e o n c a l c i u m - p h o s p h a t e - c o a t e d

i m p l a n t s c le a r ly s h o w s t h at , c o m p a r e d w i t h u n -

c o a t e d i m p l a n t s , t h e i r c l in i c a l p e r f o r m a n c e i s b e t t e r .

F o r e x a m p l e , c l i n i c a l s t u d i e s o n h y d r o x y l a p a t i t e -

c o a t e d t i t a n i u m h i p i m p l a n t s r e s u l t e d i n h i g h e r

H a r r i s - s c o r e s t h a n u n c o a t e d h i p i m p l a n t s . 8

A l t h o u g h t h e g e n e r a l c o n s e n s u s n o w i s t h a t

h y d r o x y l a p a t i t e c o a t i n g s d e g r a d e a f t e r i m p l a n t -

a t i o n , t h e q u a n t i t a t i v e r e s u lt s o f

i n v i v o

d e g r a d a t i o n -

r a t e s t u d i e s a r e n o t a l w a y s r e p r o d u c i b l e . D e g r a d -

a t i o n i s n o t o n l y a p r o p e r t y o f t h e c o a t i n g i t s e lf b u t

a l s o d e p e n d s o n t h e s p e c i f i c b i o l o g i c a l e n v i r o n m e n t

P l a s m a

s p r a y i n g

A n o d e

~ t P o w d e r

l l

\ -

- -

P l a s m a

Fig, 5. Schematic draw ing of plas ma-sp ray process. Between

anode an d cathode, a conti nuous electric discharge heats a gas

(introduced according to the arrow in the lower left-hand

corner), up to 20 000-30 000 K. This heated gas, called a 'plasma

has a very high speed (up to 1000km/h). A ceramic powder,

introduced in this fast-streaming and hot plasma, can thus be

deposited in a (partially) molten state onto a metallic or non-

metallic substrate. In this way, ceramic coatings of up to several

hundred/am can be obtained.

i n w h i c h t h e c o a t e d d e v i c e h a s b e e n i m p l a n t e d . S i n c e

t h is e n v i r o n m e n t i n t u r n m a y d e p e n d o n s p ec ie s , s it e

o f i m p l a n t a t i o n , s p e c i f ic t is s u e , a g e o f a n i m a l , s h a p e

a n d s u r f a ce m o r p h o l o g y o f th e i m p l a n t, a n d

o p e r a t i o n t e c h n i q u e ( w h i c h is p a r ti a ll y g o v e r n e d b y

s h a p e o f t h e i m p l a n t ) i t is o b v i o u s t h a t d i f f e re n c e s i n

d e g r a d a t i o n r a t e m a y b e f o u n d i f t h e e x p e ri m e n t a l

c o n d i t i o n s a r e n o t t h e s a m e .

B u t, e v e n t a k i n g t h i s i n t o c o n s i d e r a t io n , w e f o u n d

t h a t i m p l a n t s w i t h c o a t i n g s t h a t a r e t h e s a m e i n

t e rm s o f (i ) t h i c kne s s , ( ii ) de g re e o f c rys t a l l i n i t y , a nd

( i i i ) a d h e s i v e s t r e n g t h ( t h e c u r r e n t l y a c c e p t e d

p a r a m e t e r s f o r c h a r a c t e r i z i n g a n H A c o a t i n g ) a n d

t h a t a r e i m p l a n t e d i n t h e s a m e a n i m a l s p e c i e s

d e g r a d e d w i t h i n s i x m o n t h s i n o n e e x p e r i m e n t a n d

s h o w e d l i t t l e d e g r a d a t i o n i n a n o t h e r . A p o s s i b l e

e x p l a n a t i o n m a y b e a s f o l l o w s .

' D e g r e e o f c r y s t a l l i n i t y ' is n o t a f u l ly d e s c r i p t i v e

p a r a m e t e r o f t h e m o r p h o l o g y o f a c o a ti n g . A g i v e n

d e g r e e o f c r y s t a l l i n i t y c a n b e f o u n d b y d i f f e r e n t t y p e s

o f m o r p h o l o g y , a n e x a m p l e b e i n g t h a t t h e c o a t in g

c o n s is t s e i t h e r o f a c o n t i n u o u s a m o r p h o u s p h a s e

w i t h d i s c r e t e c r y s t a l l i n e p a r t i c l e s o r a c o n t i n u o u s

c r y s t a l l in e p h a s e w i t h d i s c r e te a m o r p h o u s a r e a s . I n

t h e f i r s t s i t u a t i o n , d e g r a d a t i o n o c c u r s b y r a p i d

d i s s o l u t io n o f t h e r e l a ti v e ly s o l u b le a m o r p h o u s

p h a s e , f o l l o w e d b y l o o s e n i n g o f c r y s t a ll i n e p a rt ic l es ,

w h e r e a s a c o a t in g o f th e s e c o n d t y p e w o u l d d e g r a d e

a t a r a t e g o v e r n e d b y d i s s o l u t i o n o f t h e r a t h e r

i n s o l u b l e c r y s t a l l i n e H A . I t i s o b v i o u s f r o m t h i s

e x a m p l e t h a t t h e ' d e g r e e o f c r y s t a ll i n it y ' c a n n o t b e

u s e d to p r e d i c t t h e d e g r a d a t i o n r a t e , t h a t a t t h e s a m e

d e g r e e o f c r y s t a l l i n i t y d i f f e r e n t d e g r a d a t i o n r a t e s

m a y b e o b s e r v e d , a n d t h a t c h a r a c t e r i z a ti o n o f a

c o a t i n g i n t e r m s o f t h i c k n e s s , d e g r e e o f c r y s t a l li n i t y ,

a n d a d h e s i v e s t r e n g t h i s n o t s u f f i c i e n t .

R e c e n t r e s u l t s h a v e s h o w n i n d e e d t h a t , w i t h t h e

s a m e d e g r e e o f c r y s t a l l i n i t y , d i f f e r e n t r e s o r p t i o n

r a t e s c a n b e f o u n d . K l e i n e t a l . ~1 f o u n d t h a t t h e

b e h a v i o u r o f t w o c o a t e d i m p l a n t s h a v i n g t h e s a m e

d e g r e e o f c r y s t a l l in i t y b u t o b t a i n e d w i t h d i f f er e n t

p l a s m a - s p r a y c o n d i t i o n s w a s q u i t e d i f f e r e n t : " o n e

d e g r a d e d s i g n i f i c a n t l y f a s t e r t h a n t h e o t h e r .

C L I N I C L U S E

I n p r e v i o u s s e c t i o n s , i t h a s b e e n s h o w n t h a t b u l k

c e r a m i c s o f c a l c i u m p h o s p h a t e a r e s t ro n g i n

c o m p r e s s i o n , w e a k i n t e n s i o n , a n d n o t r e s i s t a n t

t o w a r d s f a ti g u e f a il u re . H e n c e b u l k i m p l a n t s c a n

o n l y b e u s e d i n i n s t a n c e s w h e r e n o m e c h a n i c a l l o a d s

o t h e r t h a n c o m p r e s s i o n ( o r n o l o a d s a t a ll ) a r e

p r e s e n t . T h i s l i m i ts t h e u s e o f b u l k b i o c e r a m i c s o f

c a lc i u m p h o s p h a t e - - d e n s e o r p o r o u s - - t o s m a ll

i m p l a n t s , s u c h a s g r a n u l a t e t o r e p a i r o r a u g m e n t


4/4

3 6 6

T a b l e 5 . C l i n i c a l a p p l i c a t i o n s i n o r a l h e a d a n d n e c k

s u r g e r y

1) Craniofacial appl ications

A) Augmenta t ion B) Reco ns t ruc t ion

Ridge Per iodontal

Mand ibu la r Mand ibu la r

Zygomat i c O r thognat i c

Ch in Bone gra f t i ng

Cranioplastry

2) Prosthe tic implants

A) Subper iosteal

B) Endosteal

Endosseous

Endodont ic

Or thodont i c

C) Transosseous implants

Transmandibular

3) Otological applications

A) Oss icu la r B) Cana l wa l l

s m a l l b o n y d e f e c t s , a n d i m p l a n t s t o r e p l a c e m i d d l e -

e a r o s s i c l e s .

H y d r o x y l a p a t i t e - c o a t e d i m p l a n t s a r e s tr o n g e r :

t h e y c a n b e m a d e b i g ge r a n d u s e d f o r l o a d - b e a r i n g

s it e s. A v e r y s u c c e s s f u l e x a m p l e i s a t i t a n i u m

a r t if i c i al h i p j o i n t , c o a t e d w i t h H A . T a b l e 5 g i v e s a

s u m m a r y o f c li n ic a l ap p l i c a t i o n s , b a s e d o n t h e

c o n s i d e r a t i o n s o f th e p r e v i o u s p a r a g r a p h s , ~ 2 e s p e c i-

a l ly f o r h e a d a n d n e c k s u r g e r y .

C O N C L U D I N G R E M A R K S

B i o c e r a m i c s o f c a l c iu m p h o s p h a t e a r e b i o a c ti v e ,

w h i c h m e a n s t h a t t h e y c a n b o n d w i t h b o n y t i ss u es .

T h e y c a n be p r o d u c e d e i th e r as ' p e r m a n e n t '

i m p l a n t s - - m e a n i n g t h a t su c h i m p l a n t s w il l s t a y f o r

a t le a s t fi ve t o t e n y e a r s - - o r a s " d e g r a d a b l e '

i m p l a n t s - - d i s a p p e a r i n g w i t h in a f e w m o n t h s , D e -

g r a d a b l e i m p l a n t s c a n b e u s e d f o r r e p a i r o n l y ,

w h e r e a s p e r m a n e n t i m p l a n t s a r e s u i ta b l e f o r b o t h

r e p a i r o f b o n e a n d p e r m a n e n t a u g m e n t a t i o n . T h i s is

o b v i o u s i f o n e c o n s id e r s t h a t a u g m e n t i n g b o n e

w h e r e i t w a s n o t b e f o r e w i ll b e a t e m p o r a r y s u c c e s s

K l a a s d e G r o o t

w i t h b i o d e g r a d a b l e b i o c e ra m i c s . C o a t i n g s o n m e t a ll ic

a n d c o m p o s i t e s u b s t r a t e s a r e o f g r e a t i n te r e s t : t h e y

a l l ow o s s e o i n t e g r a t i o n , e v e n i f t h e c o a t i n g s t h e m -

s e lv e s d i s a p p e a r a f t e r o n e o r t w o y e a r s . I t c a n b e

c o n c l u d e d t h a t b i o a c t iv e b i o c e r a m i c s h a v e a c o n -

s i d e r a b l e f u t u r e i n s u r g i c al d i s c i p l i n es t h a t a r e

c o n c e r n e d w i t h r e p la c i n g , r e c o n s t r u c t i n g , o r a u g -

m e n t i n g p a r t s o f t h e h u m a n s k e l e t o n .

R E F E R E N C E S

1. D E G R OO T, K . , B io c e ra m ic s c o n s i s t in g o f ca l c iu m

phospha te sa l t s . Biomater ia ls , (1 9 8 0 )47 -5 0 .

2 . D E G RO OT , K. , Med ica l appl ica t ions of ca lc ium phos-

phate bioceramics. J . Ceram. Soc , Japan, 99 (1991) 943-53.

3 . A M E R I C A N C H E M I C A L S O C I E T Y , Phas e Di agr ams

. for Ceramists, 5 (1983) 320-3.

4 . K L E I N , C . P . A . T ., D E B L I E C K - H O G E R V O R S T , J . M .

A . , W OL KE , J. G . C . & D E G RO OT , K . , S tud ie s o f t h e

solubi l i ty ofd i f fc rent ca lc ium p hosph a te ce ram ic part ic les #t

l i lro. Biom aterials,

I 1 (1990) 509-12.

5 . KL EIN , C . P . A . T . , D R IESSE N , A . A ., D E G R OO T, K . &

VA N D EN HO OF F, A ., B io d e g ra d a t io n b e h a v io u r o f

var ious ca lc ium phospha te mate r ia ls in bone t i ssue . J .

Biomed. Mater . Res . , 17 11983)769-84.

6 . V A N B L I T T E R S W l J K , C . A ., G R O T E , J . J ,, K U Y P E R S ,

W. , D A EMS, W. T . H . & D E G ROOT, K . , Ma c ro p o re

t i ssue ingrowth: a quant i ta t ive and qua l i ta t ive s tudy on

hydro xyap a t i te ce ramic . Biomater ia ls , 1 (1986) 137-43.

7 . D E P U T T E R , C.. D E G R O O T , K . & S IL L E V I S S M I T T , P .

A. E. , Transmu cosa l implants o f dense hydrox ylapa t i te . J '.

Prosthet. Dent. , 49 (1983) 87-96.

8 . GEESINK, R. G. T. , Exper imenta l and c l in ica l exper ience

with hy droxy lapa t i te -coa ted h ip implants .

Orthopaedics,

12k (1989) 1239-42.

9 . G EESIN K , R . G . T ., D E G R OO T, K . & K LEIN , C . P . A . T . ,

Chem ica l implant f ixa t ion using h ydrox yapa t i te coat ings:

the deve lopmen t of a human to ta l h ip prosthesis for

chemica l f ixa t ion to bone using HA coa t ings on t i tan ium

subst ra tes .

Clin. Orthop. ,

225 (19871 147-70.

10. DH ER T, W. J . A ., KL EIN , C. P. A. T. , W OL KE , J. G . C.,

V A N D E R V E L D E , E . A ., D E G R O O T , K . & R O Z I N G , P .

M., A mechanical investigation of fluora patite , magnesium

whit locki te , and hydroxylapa t i te p lasma-sprayed coa t ings

in goats. J. Biomed. Mater . Res . , 25 (1991) 1183-200.

I I . KLEIN , C . P . A . T . , WOLKE, J . G . C . , D E BLIEC K-

H O G E R V O R S T , J . M . A . & D E G R O O T , K . , H e a l

t rea tment inf luencc p lasma-sprayed C a / P coatings. Paper

presented a t Third World Conference on Biorna te r ia ls ,

Bcrlin, 1992.

12. D E G RO OT , K. , Effec t of porosi ty and physicochemica l

proper t ies on the s tab i l i ty , resorp t ion , and s t rength of

ca c ium phosph a te ce ramics. Ann . N Y A cad. Sci., 523 (1988)

227-33.

clinical calcium phosphate application

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