lPotential Use of One-Phase Poly (methyl methacrylate) in Dental Implants

8/12/2019 lPotential Use of One-Phase Poly (methyl methacrylate) in Dental Implants

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Journal of Dental Research

http://jdr.sagepub.com/content/55/2/272Theonline version of this article can be found at:

DOI: 10.1177/00220345760550021901

1976 55: 272J DENT RESHussein S. Zaki and Ihab L. Kamel

Potential Use of One-Phase Poly(methyl methacrylate) in Dental Implants

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International and American Associations for Dental Research

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P o t e n t i a l U s e o f O n e - P h a s e P o l y ( m et h y l m e t h a c r y l a t e )i n D e n t a l I m p l a n t sHUSSEIN S . ZAKI a n d IHAB L . KAMELB i o m ed i c a l E n g i n e e r i n g P r o g r a m and t h e D e p a r t m e n t o f M a t e r i a l s E n g i n e e r i n g ,D r e x e l U n i v e r s i t y , P h i l a d e l p h i a , P e n n s y l v a n i a 1 9 1 0 4 , USA

T h r o u g h c o m p o u n d i n g a n d m o l d i n g t e c h -n i q u e s , v a r i a t i o n o f p o r o s i t y and t h e r e s u l t -I n g e f f e c t o n t h e m e c h a n i c a l p r o p e r t i e so f o n e - p h a s e p o l y ( m e t h y l m e t h a c r y l a t e )(PMMA) w e r e s t u d i e d . C h a r a c t e r i z a t i o n o ft h e c o m p o s i t e s d e v e l o p e d w a s p u r s u e d b yc o r r e l a t i n g t h e m i c r o s t r u c t u r e w i t h t h e p h y s -i c a l and m e c h a n i c a l b e h a v i o r o f t h e m a t e r i a l .From t h e t h r e e compounding t e c h n i q u e ss t u d i e d , N a C l - f i l l e d PMMA p r o v e d t o h a v et h e b e s t o v e r a l l m e c h a n i c a l p r o p e r t i e s andc o n t r o l o f p o r o s i t y c o m p a r e d t o a w i d e r a n g eo f f i l l e r c o n t e n t .The u s e o f p o l y m e r i c t o o t h r o o t i m p l a n t ss h o w s s o m e a d v a n t a g e s o v e r m e t a l b l a d e sa n d p o r o u s c e r a m i c s . I n a d d i t i o n t o t o u g h -n e s s a n d b i o c o m p a t i b i l i t y , t h e y a l l o w e a s yc o m p o u n d i n g and h e n c e c a n b e t a i l o r e d t of i t a v a r i e t y o f c o n d i t i o n s . H e a t - c u r e d p o l y( m e t h y l m e t h a c r y l a t e ) (PMMA) i s t h e m o s tcommon p o l y m e r i n d e n t i s t r y , i n g e n e r a l ,a n d i n e n d o s s e o u s p o l y m e r i m p l a n t s , i n p a r -t i c u l a r . 1 - 1 3 The u s e o f m u l t i p h a s e a c r y l i cp o l y m e r s , h o w e v e r , i s n o t w i t h o u t some d i s -a d v a n t a g e s . I n s p i t e o f t h e r e l a t i v e s u c c e s sr ep o r t e d b y s e v e r a l i n v e s t i g a t o r s w i t h t h et w o - p h a s e s y s t e m a s an a n a t o m i c i m p l a n t 6 - 8o r a s a c o a t i n g o f t r i p o d a l v i t a l l i u m p i n s , 3 - 5d e f i n i t e s i g n s o f f a i l u r e w e r e a l s o r e p o r t e d .Bone r e s o r p t i o n i n f e c t i o n a n d s e v e r e o s t e o -m y e l i t i s w e r e d e m o n s t r a t e d b y Hamner,R e e d , a n d H a n d , 1 4 a n d Hamner and R e e d 1 5who u s e d h e a t - c u r e d PMMA i n e x a c t t o o t hr e p l i c a t i o n s . T h e s e a u t h o r s d e m o n s t r a t e dt h a t t h e p r i m a r y c a u s e o f f a i l u r e i n t h i s s y s -tem wa s r e l a t e d t o t h e p r e s e n c e o f e x c e s s i v eamounts o f r e s i d u a l monomer.

T h i s i n v e s t i g a t i o n was s u p p o r t e d , i n p a r t , b y N a t i o n a lI n s t i t u t e o f D e n t a l R e s e a r c h Grant N o . D E - 0 1 9 7 - 0 7 .R e c e i v e d f o r p u b l i c a t i o n J a n u a r y 2 0 , 1 9 7 5 .A c c e p t e d f o r p u b l i c a t i o n A u g u i s t 1 4 , 1 9 7 5 .2 7 2

I n t h e p r e s e n t i n v e s t i g a t i o n , t h e u s e o f ao n e- p h a s e p o l y m e r i c m a t r i x i s i n t r o d u c e d a sa n a l t e r n a t i v e f o r making a n i m p l a n t a b l ep r o s t h e s i s . The p r e s e n t c o m p o s i t e c a n b ea p p l i e d t o a v a r i e t y o f i m p l a n t d e s i g n s b yu s e o f a s i m p l e h o t p r e s s i n g t e c h n i q u e i n as p e c i a l l y d e s i g n e d d i e . P o r o s i t y i s n e e d e d i nt h e i m p l a n t e d p o r t i o n t o i n d u c e f ib r o u s o rb o n e t i s s u e i n g r o w t h t h a t w i l l g i v e s t a b i l i t ya n d s t r e n g t h t o t h e i m p l a n t . I n t h e p r e s e n tw o r k , t h e f o l l o w i n g t h r e e t e c h n i q u e s w i l l b ei n t r o d u c e d f o r c o n t r o l l i n g p o r o s i t y i n t h eh o t - m o l d e d P M \ A I A : ( 1 ) l i g h t s i n t e r i n g o fp u r e P M M A , ( 2 ) c o m p o u n d i n g a r e s o r b a b l ef i l l e r ( s y n t h e t i c h y d r o x y a p a t i t e ) , and ( 3 )compounding P w a t e r - s o l u b l e f i l l e r ( N a C b ) .The i m m e d i a t e o b j e c t iv e o f t h i s work w a st o e v a l u a t e t i l e m e c h a n i c a l a n d p h y s i c a lp r o p e r t i e s o f t h e a f o r e m e n t i o n e d c o m p o s i t e sa s r e l a t e d t o t h e n a t u r e o f t h e f i l l e r . Them i c r o s t r u c t u r e a s v i e w e d b y t h e s c a n n i n ge l e c t r o n m i c r o s c o p e ( S E M I ) w i l l b e u s e d i ne x p l a i n i n g t h e d i f f e r e n c e s i n t h e c o m p o s i t eb e h a v i o r .

M a t e r i a l s a n d M e t h o d sThe p r i n c i p a l m a t e r i a l u s e d i n t h i s i n v e s -t i g a t i o n w a s a d d i t i v e - f r e e PMMAa w i t h a na v e r a g e m o l e c u l a r w e i g h t o f 6 0 0 , 0 0 0 a n d

a v e r a g e p a r t i c l e s i z e s o f 3 5 , 1 5 0 , a n d 2 5 0m e s l i ( 4 2 0 , 1 0 0 , and 6 0 m i c r o m e t e r s ( t m ) ,r e s p e c t i v e l y ) . B e f o r e c o m p o u n d i n g , t h i sp o l y m e r p o w d e r wa s t h o r o u g h l y w a s h e d i nd i s t i l l e d w a t e r t o r e m o v e a n y s u r f a c e -a d s o r b e d i m p u r i t i e s o r w a t e r - s o l u b l e c o a t i n g ,d e c a n t e d , d r i e d i n a vacuum o v e n a t 1 0 0 Ff o r 2 4 h o u r s , a n d s t o r e d i n a d e s i c c a t o r u n t i li t w a s u s e d .Two f i l l e r s w e r e compounded w i t h t h ePMMfA i n t h i s w o r k : NaCl and s y n t h e t i c

a E s s c h e m C o . , E s s i n g t o n , P a .

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POLY(METHYL METHACRYLATE) IMPLANTS 2 7 3h i y d r o x y a p a t i t e ( t r i b a s i c c a l c i u m p h o s p h a t e ) .Reagent g r a d e NaCi was g r o t u n d a n ds c r e e n e d t o an a v e r a g e p a r t i c l e s i z e o f 7 5 ,1 0 0 , a n d 4 0 0 n m . T h - e s e p a r a t e c d p a r t i c l e sw e r e s u b s e q u e n t l y d r i e c l i n a v a c i u u m o v e na t 1 0 0 F f o r 2 4 h o u r s and s t o r e d i n a d e s i c -c a t o r . The h y d r o x y a p a t i t e w h l i l c l was s u p -p l i e d a s a v e r y f i n e p o w d e r ( 0 . 5 , m ) wasu s e d a s r e c e i v e d .The s y n t l h e t i c h y d r o x y a p a t i t e a n d ( l t h eNaCl w e r e c o m p o U n d e d s e ) a l r a t e l y w i t l h t h ep u r e P M I N I A , u l s i n g t h l i e e p o l y m e r p a r t i c l es i z e s . Amounts o f 5 , 1 0 , 1 5 , a n d 2 0 wtf i l l e r w e r e d r y m i x e d w i t l h P'MMA i n a t w i n -s l h e l l m i x e r f o r two h o u r s b e f o r e m o l d i n g .I n t l h e c a s e o f N a C l , a s e c o n d c o m p o i u n d i n gt e c l h n i q u e wa s f o l l o w e d t o i m p r o v e t h e u i n i -f o r m i t y o f t h e f i l l e r d i s t r i b u t i o n . A s p e c i f i e dwt0 4 o f N a C l w a s ( l i s s o l v e ( I i n d i s t i l l e dw a t e r a n t i s u b s e q j U e n t l y m i x e d l w i t h i t h e p o l y -mer p o w d l e r ; t l i . s u n i f o i - m r m i x t u r e w a sx c C U U M m ( t i e i l a n d t u i m b l e d i n a t U i l - i n s e l lmixer f o r two h l o u i r s b e f o r e m o l d l i n g .SAMPLF MOLDING A N T ) 1 E S I I T N G . \ O n e - i t c h 1d i a m e t e r c l o s e d ( l i e a n d a h l a n d l p r e s s ' weicu s e d f o r m o l d i n g a l l f u l l ) l ( l e n s e t e s t s a t m p l e sa t 3 3 3 0 F a n d 1 , 0 0 0 p s i ( F i g 1 ) The m o l d e ds a m p l e s were m a c l h i n e d t o p r e p a r e I X l -i n c l h c o m p r e s s i v e s t r e n g t l h s a m p l e s . ' 1 l h e s es a m p l e s w e r e w a s l h e d I i n d i s t i l l e d l w a t e r ,d r i e d , a n d l s t o r e d l i n a d e s i c c a t o r .L i g h i t l y s i n t e r e ( d PMMA s a m p l e s w e r e p r e -p a r e d i b v c o m p r e s s i o n m o l d i n g t h e p u i r ep o l y m e r p o w c l e r a t 1 , 0 0 0 p s i i n t h e a f o r e -m e n t i o n e d 1 - i n c l h ( l i e . The m o l d l i n g t e m -p e r a t u i r e was v a r i e d i n t t i . s t e c h n i q i u e f r o m1 7 0 t o 3 0 0 F a t 1 0 F i n c r e m e n t s . The d l e n -s i t y o f e a c h s a m p l e wa s c a l c u l a t e d a s a f u i n c -t i o n o f t h e m o l l i n g t e m p e r a t u i r e , u t s i n gw e i g l h t a n d l v o l u i m e d a t a . The f o l l o w i n g t w o -s t e p m o l d i n g t e c l h n i q u i e w a s a l s o t r i e d i no r d l e r t o i m p r o v e t h e m e c l h a n i c a l p r o p e r t i e so f t h i s p o r o u s , l i g l h t l y f u i s e d m a t e r i a l a t 1 8 0F : ( l ) c o m p r e s s i o n i m o l d i n g o f a s o l i dP ' . I M A c o r e a p p r o x i m a t e l y one h a l f t h e r e -- j u i r e d l r o o t d i a m e t e r , a n d ( 2 ) c o m p a c t i o na n d l i g h l t s i n t e r i n g o f t h e p o r o u i s m a t e r i a la l o u l n ( 1 t h e s o l i d l core t o t h e r e t l u i r e d s i z e .A w a t e r s o r p t i o n t e s t w a s p e r f o r m e d o n l von t h e f u i l l y c l e n s e s a m p l e s . T h e s e s a m p l e sw e r e s t o r e d i n a d e s i c c a t o r u - n t i l a c o n s t a n td r y w e i g h l t wa s r e a c l h e d . A f t e r t h e d e t e r m in a t i o n o f t h e d i y w e i g l h t , t h l e s a m p l e s w e r ei m m e r s e d i n a ( l i s t i l l e d w a t e r b a t h a t 1 0 0 F .E a c h s a m m p l e was s u l ) s e q u e n t l v w x e i g h e d e v e r v

b B u e h l e r L t d . , E v a n s t o n , I l l .

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F I G 1 . - C o m p r e s s i o n m o l d i n g e q u i p m e n t . A ,p i e s s ; B , t h e r m o c o u p l e p o t e n t i o m e t e r , C , h e a t -i n i g s l e e v e ; a n t i D , d i e .2 4 h o r I n I s f o r a i s e v e n - d a y p e r i o d and t h e n o nt h e 1 5 t h i a n d t h e 1 6 t h d a y . The p e r c e n ti n c r e a s e i n w e i g l h t w a s c a l c u l a t e d a c c o r d i n gt o t i l e f o l l o w i l - n g e q u a t i o n : C wt i n c i e a s e _

1 0 0 ; w l h e r e W i s w e i g h t a f t e r i m -r n i e r s i o n a n d I V W i n i t i a l w e i g h t .1 F h e c o m p r e s s i v e s t r e n g t h a n d m o d u l u s o fa l l s a m p l e s w e r e m e a s t u r e d on a c o n s t a n ts t r a i r n t e s t i n g m a c l i i n e a t a s t r a i n r a t e o f0 . 0 2 i n c i / m i n . A l l f u l l y d e n s e s a m p l e s weret e s t e d l i n a w e t c o n d l i t i o n a f t e r 1 6 d a y s ' s o a k -i l n g i n w a t e r . The t e s t wa s t e r m i n a t e d a f t e rt h e y i e l d p o i l n t was r e a c l h e d . I n a c c o r d a n c ew i t l A . S T N I s p e c i f i c a t i o n D 6 9 5 , t h e y i e l dp o i n t wa s t a k e n a s t h e f i r s t p o i n t on t h es t r e s s - s t r a i n d l i a g r a m a t w l h i c l h an i n c r e a s e i ns t r a i n o c c u t r r e d xw i t h o u i t an i n c r e a s e i n s t i - e s s .

R e s u l t sL I G T G L . Y S I N I E R F D PM I [ A . V a r i a t i o n i nc l e n s i t y a n i d s t r e l i g t h a s a f u i n c t i o n o f t h em o l d l i n g t e m l e r a t L u r e f o r t h e 3 5 - m e s h p o l -mer i s s h l o w n i n F i g u r e 2 . The d l e n s i t y i n -c r e a s e d a l m o s t l i n e a r l y t u p t o 2 9 1 0 F . A t t e m -

p e r a t u r e s g i e a t e i t h a n 2 3 0 F , t h e p o l y m e ra p p ) r o a c h e d i t s s o l i d d e n s i t y r a t l h e r q u i c k l y .B l e t w e e n i 1 8 0 a n d 2 0 0 F , t h e c o m p r e s s i v es t r e n i g t l h i n c r e a s e d l c o n s i d e r a b l y f r o m 3 , 0 0 0e I n s t r o n U n i v e r s a l T e s t i n g M a c h i n e , I n s t r o n C o r p . ,C a n t o n , N \ a s s .

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F I G 2 . - D e n s i t y and c o m p r e s s i v e y i e l d s t r e n g t h vs s i n t e r i n g temperature f o r3 5 - m e s h pure PMMA a t 1 0 0 0 p s i . W ' S o l i d c i r c l e s , p l o t i s r e f e r r e d t o r i g h t -hand o r d i n a t e a n d t r i a n g l e s , p l o t t o l e f t - h a n d o r d i n a t e u s i n g h o r i z o n t a la rrow s . V e r t i c a l arrow r e f e r s t o i n c r e a s e i n c i r c l e - p o i n t s t o h i g h e r l e v e l s o fs t r e n g t h due t o i n t r o d u c t i o n o f s o l i d c ore i n t h e s e s a m p l e s . )

t o 1 0 , 0 0 0 p s i . The e f f e c t o f t h e p o l y m e rp a r t i c l e s i z e on t h e p o r e s i z e and d i s t r i b u t i o nwhen s i n t e r e d a t 1 8 0 F i s shown i n F i g u r e 3 .From t h e s e m i c r o g r a p h s , i t i s a p p a r e n t t h a tt h e po r e s i z e r e m a i n e d l a r g e a f t e r s i n t e r i n go f t h e l a r g e p a r t i c l e s w h e r e a s t h e p o r o s i t ywas homogeneous w i t h t h e s m a l l e r p a r t i c l e s .F i g u r e 4 s h o w s t h e s t r u c t u r e o f t h e sames e q u e n c e o f p o l y m e r p a r t i c l e s i z e s as F i g u r e3 when s i n t e r e d at 2 0 0 F . I t can b e s e e nt h a t a t 2 0 0 F t h e f u s i o n a t t h e p a r t i c l e -p a r t i c l e i n t e r f a c e i s v e ry s i g n i f i c a n t andc l e a r l y s u b s t a n t i a t e s t h e i m p r o v e m e n t o f t h ec o m p r e s s i v e s t r e n g t h a t t h a t temp era t u re( F i g 2 ) .A c o m p a r i s o n b e t w e e n F i g u r e s 3 and 4a l s o i n d i c a t e s t h a t f u s i o n b e t w e e n t h e p a r-t i c l e s o c c u r r e d m u c h f a s t e r f o r t h e s m a l lp o l y m e r p a r t i c l e s t h a n f o r t h e l a r g e r o n e s .T h i s s h i o u i l d b e e x p e c t e d , h o w e v e r , s i n c e t h es m a l l p a r t i c l e s l h a v e a much l a r g e r a r e a o fs u r f a c e contact and h e n c e can b e f u s e d t o -g e t h e r a t a f a s t e r r a t e .PMMA-HYDROXYAPATITE C O M P O S I T E S . - F i g -ur es 5 an d 6 s h o w t h e c o m p r e s s i v e s t r e n g t h

as a f u n c t i o n o f t h e f i l l e r c o n t e n t . I n F i g u r e5 , t h e c o m p r e s s i v e s t r e n g t h i n t h e i n s t a n c e o ft h e 3 5 - m e s h p a r t i c l e s and h y d r o x y a p a t i t e i ss h o w n t o d e c r e a s e much f a s t e r w i t h an i n -crease i n t h e f i l l e r content, as compared w i t hthe s m a l l e r p a r t i c l e s i n F i g u r e 6 . E x p l a n a -t i o n o f t h i s d a t a b e c o m e s c l e a r when t h ep a r t i c l e - s i z e r a t i o o f t h e p o l y m e r t o f i l l e r i sc o n s i d e r e d . A t a h i g l h r a t i o or w i t l h l a r g ep o l y m e r p a r t i c l e s , s e g r e g a t e d f i l l e r d i s t r i b u -t i o n w i l l r e s u l t w l h e r e t h e f i l l e r a c t s a s ac o a t i n g t o t h e l a r g e p o l y m e r p a r t i c l e s . Whent h e f i l l e r h a p p e n s t o b e a c e r a m i c , t h e c o a t -i n g w i l l a c t a s an i n s u l a t o r t h a t i n t e r f e r e sw i t l h t h e c o m p l e t e f u s i o n o f t h e p a r t i c l e s .T h i s r e s u l t e d i n l o o s e l y h e l d p a r t i c l e s t h a ta l l o w e d a h i g h e r l e v e l o f w a t e r s o r p t i o n anda l o w e r c o m p r e s s i v e s t r e n g t h .The m i c r o s t r u c t u r e s o f a 1 5 wt h y -d r o x y a p a t i t e and d i f f e r e n t p o l y m e r p a r t i c l es i z e s a re shown i n F i g u r e 7 . A c o m p l e t e f i l l -er n e t w o r k w i t h s e g r e g a t e d p o l y m e r p a r -t i c l e s i s shown f o r t h e 3 5 - m e s h p o l y m e r ( F i g7 , c ) ; whereas a p a r t i a l n e t w o r k and a h i g h e rd e g r e e o f p o l y m e r f u s i o n i s a p p a r e n t f o r t h e

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p r o x i m a t e l y t h e s a m e s l o p e . T h i s s l o p e w a sf o u n d t o a p p r o x i m a t e t h e c o m p o s i t e l a w o fm i x t u r e s w i t h n o f i l l e r r e i n f o r c e m e n t : . c =r m V m ; w h e r e c r and am a r e t h e c o m p r e s s i v es t r e n g t h o f t h e c o m p o s i t e a n d m a t r i x , r e -s p e c t i v e l y , a n d V m i s t h e v o l u m e f r a c t i o n o ft h e f i l l e r . T h i s c a l c u l a t i o n a s s u m e d no l o a dt r a n s f e r a t t h e f i l l e r - m a t r i x i n t e r f a c e , n o r

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F i G 7 . - H y d r o x y a p a t i t e - f i l l e d PMMA, 1 5 w t ,( X 1 I O ) . A, 2 5 0 - m e s h ; B , 1 5 0 - m e s h , SEM; C , 3 5 -m e s h , SEM.

t i c l e s . E x c e p t i n F i g u r e 9 , a , the s a l t p a l t i t l es i z e was 1 0 0 t o 1 5 0 u m . I t c a n , r e a d i l y hes e e n t h a t r a n ( l o m d i s t r i b u t i o n l p r e v a i i l s f o rthe s m a l l p o l y m e l p ) a r t i d l e s w h i e r e a s a s e m i -s e g r e g a t e ( l d i s t r i b u t i o n was a p p a r e n t i n t h e. 3 5 - m e s l h p o l y m e r . S i m i l a r t o the c e r a m i c -f i l l e c l P \ I N I A , the f i l l e r d i s t r i b u t i o n i s c o n -t r o l l e ( 1 by the p ) o l y m e r - f i l l e r p a x r t i c l e s i z e ra -t i o . - I - l e l o l ) m e l p a r t i c l e f u i s i o I n , h o - s e x e ,was r e l a t i v e l y c o m p l e t e i n a l l the s a l t com-

p o s i t e s b e c a u L s e o f t h e l a r g e f i l l e r p a r t i c l e su i s e d I and the h i i g h e r c o n d u c t i x i t y o f t h e s a l tcompalred w i t l h the c e r a m i c .T o i m p r o v e the h o m o g e n e i t y o f the com-l ) o s i t e . p a r t i c u i l a i l y when u L s i n g l a 2 i g e p o l y -mer p a r t i c l e s , c o m p o u n d i n g o f t h e f i l l e r i na n i aqueous s o l u t i o n was t r i e d . F i g u r e 1 0s h i o w s the poie ( l i s t r i b u t t i o i n w i t l h t l i s t e c h -n i i u t i e u i s i n i g 3 5 - m e s h p o l y m e r p I a r t i c l e s . T h es l i t - s h a p e d pores i n t h i s m i c r o g r a p h a re d L u et o the ( l e f o r m a t i o n o f t l h e segregated s a l tco a t i n g on the l a r g e p o l y m e r p a r t i c l e s d t i r -i n i g l i o t c o m p l c t i o n .F i g u i l e 11 s h i o w s t i l e w a t e r s o r i ) t i o n d a l t af o r p u r e a n d ( I 1 5 w t h y d r o x y a p a t i t e - f i l l e ds a m l l e s . I n a l l s a m p l e s e x c e l t i n the c a s eo f the f i l l e d , 3 5 - n m e s l h composite, e q u i l i b r i u ms o r p t i o n wasc i a e h i c i e ( l by the I 5 t i ( l a ) , ofsoaking. Xn i n cr ease in the equilibrillm

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F I i . . 9 SEM m i c t o g r a p h o f N a C l - f i l l e d , 3 5 -mesh PMMA ( X I O O ) . A, 10 w t ' , o f 3 0 t o 5 0/ A m N a C I ; a n d B , 2 0 wt o f 1 0 0 t o 1 5 0 AmNaCI.w at et s o t r p t i o n w a t s a p p a r en t d t t e t o the f i l l e t -t h a t i n c r e i a s e i w i t l i the p o l y m e r p a t t i c l e s i z e .Y h l e s o r p t i o n l e x - e l reicl t e d c a t t a s t r o p ) h i c 1 l i m l -i t s w l h e n the 35-mesh polymer was u i s e d be-C t l U s e o f the f o t I m n a t i o n i o f a t s e g i - e g a t e t l S t t I u C -t t r e . I n t h i s l a s t i t n s t a n c e , the i n l i b i t i o n o fp a t t i c l e f t u s i o n l C a l l u s e d ano t r d e r o f m a i i i g n i t u i d ei n c t e a i s e i n the wi s te r sorptio n l e v e l a n I l dc o n s c ( i e q e n t l y a c a t a s t r o p h i c e f l e c t on i thes t r e n i g t l h o f t h e conmposite. I n a d d i t i o n , thewatet s o t r p t i o n c a t u s e d a t dcciase in t i e miod-t i l t i s of A l l s i a i p l e s to i a l e v e l t a n g i n g f t o n i t2 t o 24 x 1 ( ) l pSi.

Dis cus s io nA k l l t h l i i e e t e c h n l i q u e s presente in thiss e s t i g u a t i o n a i c h i c v e d the c o n t r o l o f p o r o s i t y

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f i l l e t , h l o w e v e r , r e s u l t e d i n a s t r o n i g e r c o m -p o s i t e c o m p a r e c l t o t h e l i g h t s i n t e e i n g t e c l h -n i q l u e . I n g e n i e t - a i l , l i g l h t s i n t e i i t i n g i s a s v e i - vs e n s i t i x e t o t h e c o m p ) o u l l l n d i g t e m p e i a t u r e .) 1 e s s u t r e . a t ( I m i i o l d i n i g c y c l e , a n d - e s L l t e d i n Ia v e r y weak m a t e t r i a l w h e r e l i g l h p o r o s i t y wasC l e s i r a b l e . I m n p i ovement o f t h e s t r I e n g t h a t al o w s i n t e r i n g t e m l ) p e l a t t i r e i s l n e e C d e d I i f t h ei m p ) l a n t e ( l i o o t i s t o s u l c c e e c d i n h e a t i n g t h ei n a . s t i c a l t o r y l o a d i t s w i t h l o u t p e r m , i n l e n t c l e f a o r -r n a t i o n . 1 h i s w s a s i c c a o m p l i s h e d b y t u s i n g as o l i d l P I M A \ c o i - e s u t i t o u n d e d b N 1 , a l i g h t l 1s i n t e t e d , p t o r i s S C e t t i o n . 1 l i . s t e c l h n l i qlle Wa sd e r n o n s t i a t e d l a t 1 8 0 a n t I i - e s u i l t e d I i n al h r e e f o l d i m r l ) i o \ e m e n t o f t h e c o r - u l p i e s s i x es t r e n i g t l i o f t h e m n a t e t i a l a s c o m p a r e d t o t i l et o t a l l v p o t o t i s o n - e ( F i g 2 ) I i h e t e c l h n i q u t i ea l s o h a t s t h e a d d e d a d v a n t a g e o f p r e v e n t i n gt h e p o s s i b l e c l o S u i r e o f t h e i o o t - p o e s u i n d c l e t -l o a d i n g h e f o r e d l o w i n g l ) o n e o i t i s s t u e i n -g t o x w t h . 1 h e m n a i n a d s v a n t a g e o f t h e l i g l i ts i u t e l - i i i g t e c h l i i i q i i e i n g e l l e i a l i s i t s . s i m -p ) l i c i t v ; 1 1 n a d d i t i x e s o 1 f i l l e s a i e u s e d l h e r ea n d t h l u l s , i n o c o m p l i c a t i o n i i a i s i n g f r o m a d -x e i s e t i s s t l e r e a c t i o n i s t o h e e x p e c t e d .C o m p o u n d i n g o f IiMMAx w i t h l l i y d i o x y -a p a t i t e p ) o x w d e r wa s n i o t a t i e a s s p i - o c e s s ( L u l et o t h e p ) o x w l e r s g r e a t a f f i n i t y t o a d s o r l ) wa-t e i r . C o n s e q t u e n t l y , a g g l o m e r a t i o n o f t l h ep ) o X c i l d i x a s ( 1 t l i t e a p ) p a r e n t p a r t i c u l a r l yw l t e n i a s m a l l p o l y m e r p a r t i c l e s i z e w a s u L s e d .W V i t h h i i g l h e r l o a d i n g a n d c l l a i g e r p o l y m e r p a t -t i t l e s , a g g l o m e r a t i o n o f h y d r o x y a p a t i t e wasn i o t a p ) p a r n c u t ) e c a u i s e o f t h e l a r g e p o r e sa x a i l a b l e f o t - t h e c e r a m i c f i l l e r . I n a ( d d i t i o n i ,




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F I G 11.-Water s o r p t i o n v s t i m e f o r pure polymer and h y d r o x y a p a t i t e -f i l l e d P M M A .t h i s f i l l e r f o r m e d a c o n t i n u o u s n e t w o r k o fi t s f i n e p a r t i c l e s , s u r r o u n d i n g t h e i n d i v i d u a lp o l y m e r b e a d s , a nd p r e v e n t e d t h e i r com-p l e t e f u s i o n . T h i s was an a p p a r e n t m a n i f e s -t a t i o n when 3 5 - m e s h p o l y m e r and 1 5 wtl o a d i n g was u s e d ( F i g 7 , c ) w h e r e t h e i n d i -v i d u a l p o l y m e r i c p a r t i c l e s a re c l e a r l y d i s -t i n g u i s h a b l e .

C o n t r a r y t o h y d r o x y a p a t i t e , compoundingo f a l l p o l y m e r p a r t i c l e s w i t h NaCl was s i m -p l e . I n t h e c a s e o f d r y m i x i n g , t h e pore s i z ewas c o n t r o l l e d b y t h e NaCl p a r t i c l e s i z e ,w h e r e a s t h e percent p o r o s i t y was c o n t r o l l e db y t h e s a l t c o n te n t o f t h e s a m p l e . I t wasa p p a r e n t t h a t ra n dom d i s t r i b u t i o n p r e v a i l e df o r t h e s m a l l e r p o l y m e r p a r t i c l e s w h e r e a ss e m i s e g r e g a t e d d i st r i b ut i o n r e s ul t ed i n t h ei n s t a n c e o f 3 5 - m e s h p a r t i c l e s . S i m i l a r t o t h ec e r a m i c - f i l l e d PMMA, t h e f i l l e r d i s t r i b u t i o ni s c o n t r o l l e d b y t h e p o l y m e r - f i l l e r p a r t i c l es i z e r a t i o . H o w e v e r , b e c a u s e o f t h e h i g h e rc o n d u c t i v i t y o f t h e s a l t compared t o h y -d r o x y a p a t i t e , t h e p o l y m e r p a r t i c l e f u s i o nwas r e l a t i v e l y c o m p l e t e i n a l l s a l t - f i l l e d com-p o s i t e s . The e f f e c t o f t h e p o l y m e r - f i l l e r par-t i c l e s i z e r a t i o on t h e f i l l e r d i s t r i b u t i o nagrees w i t h t h e p r o p o s e d model o f M a l l i a r i sand T u r n e r . 1 6 These a u t h o r s showed t h a twhen t h e f i l l e r p a r t i c l e s a re m u c h s m a l l e r

t h a n the p o l y m e r p a r t i c l e s , t h e f i l l e r f o r m sa c o a t i n g around t h e p o l y m e r w i t h a f i n a ld i s t r i b u t i o n r e s e m b l i n g a t h r e e - d i m e n s i o n a ln e t w o r k . The n e t w o r k b e c o m e s i n t e r c o n -n e c t e d when a c r i t i c a l volume f r a c t i o n o ff i l l e r i s r e a c h e d t h a t i s d e p e n d e n t on t h ep o l y m e r - f i l l e r p a r t i c l e s i z e r a t i o . These a u -t h o r s a l s o showed t h a t a c o n t i n u o u s n e t w o r kcan b e a t t a i n e d w i t h a very low volume f r a c -t i o n o f f i l l e r ( 2 t o 3 v o l ) i f t h e p o l y m e r -f i l l e r p a r t i c l e s i z e r a t i o i s h i g h ( e x p r e s s e d a sa b o u t 2 0 t o 3 0 ) . As t h e s i z e o f p o l y m e r andf i l l e r p a r t i c l e s a p p r o a c h one a n o t h e r , t h eamount o f f i l l e r r e q u i r e d f o r a c o n t i n u o u sf i l l e r p a t h w i l l i n c r e a s e u n t i l i t r e a c h e s t h era n dom d i s t r i b u t i o n v a l u e o f 3 5 t o 4 0 v o l .H e n c e , t h i s p o l y m e r - f i l l e r r a t i o s h o u l d a l -ways b e k e p t i n m i n d when i n t e r c o n n e c t i n gp o r o s i t y i s d e s i r e d .

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J Dent R e s M a r c h - A p r i l 1 9 7 6a s o l i d p o l y m e r c o r e and porous outer l a y e rs h o w e d improvement i n the o v e r a l l mechan-i c a l properties a n d g o o d p o t e n t i a l f o r a n a -t o m i c a l i m p l a n t s .The N a C l - f i l l e d P M I N I A was f o u n d t o g i v et h e b e s t o v e r a l l m e c h a n i c a l properties andc o n t r o l o f p o r o s i t y .The m e c l h a ni c a l p r o p e r t i e s o f t h e f i l l e d ,w a t e r - e q u i l i b r a t e d c omp o s i te s were c l o s e t ol i l e r a t u r e v a l u e s o f d r y P A X I M I A systems ex-cept f o r a n o t i c e a b l e d r o p i n t h i e i r m o d u l u s .I n t h e i n s t a n c e o f l i y d r o x y a p a t i t e , the 2 0 wtc / - f i l l e d PMMIA c o m p o s i t e s w i t h 3 5 - m e s hp a r t i c l e s i z e s u f f e r e d a s u b s t a n t i a l l o s s int h e i r m e c l h a n i c a l p r o p e r t i e s and p h y s i c a l i n -t e g r i t y a f t e r s o a k i n g f o r one week i n water.

P o l y m e r - f i l l e r p a r t i c l e s i z e ratio s h o u l d bet a k e n i n t o c o n s i d e r a t i o n i n compounding i no r d e r t o o b t a i n t h e d e s i r e d f i l l e r d i s t r i b u t i o n( e i t h e r random or n e t w o r k ) .

R e f e r e n c e s1 . S H K L A R , G . ; HODOSH, M . ; and P O V A R , M . : T i s -

s u e R e a c t i o n s t o P l a s t i c Tooth I m p l a n t s ,O r a l S u r g 2 2 : 3 4 9 - 3 5 7 , 1 9 6 6 .2 . H O D O S H , M . ; P O V A R , M . ; a n d S H K L A R , G . :

P l a s t i c Tooth I m p l a n t s w i t h Root C h a n n e l sand O s s e o u s B r i d g e s , O r a l S u r g 2 4 : 8 3 1 - 8 3 6 ,1 9 6 7 .

3 . HODOSH, M . ; P O V A R , M . ; MIRMAN, M . ; andS H K L A R , G . : P o l y m e t h a c r y l a t e C o a t e d V i t a l -l i u m P i n s as E n d o s t e a l D e n t a l I m p l a n t s i nP a p i o a nd G e l a d a B a b o o n s , O r a l S u r g 2 6 :5 5 4 - 5 5 9 , 1 9 6 8 .4 . SHKLAR, G . ; HODOSH, M . ; a n d POVAR, M . :T i s s u e R e a c t i o n t o P o l y m e r - C o a t e d V i t a l l i u mP i n I m p l a n t t s , J P r o s t h e t Dent 2 4 : 6 3 6 - 6 4 5 ,1 9 7 0 .5 . HODOSH, M . ; S H K L A R , G . ; a nd POVAR, M . : T h eC l i n i c a l Us e o f P o l y m e r - C o a t e d M e t a l P i n sa s E n d o s t e a l I m p l a n t s , J P r o s t h e t Dent 2 5 :8 5 - 9 1 , 1 9 7 1 .

6 . H O D O S H , M . ; P O V A R , M . ; a n d S H K L A R , G . :C o n t r o l o f P o r o s i t y i n P o l y m e r T o o t h I m -p l a n t s , J P r o s t h e t Dent 2 4 : 4 5 3 - 4 6 0 , 1 9 7 0 .7 . H O D O S H , M . ; P O V A R , M . ; a n d S H K L A R , G . ;P e r i o d o n t a l F i b e r A t t a c h m e n t t o P l a s t i cTooth I m p l a n t , J P e r i o d o n t o l , 3 9 : 1 8 7 - 1 8 9 ,1 9 6 8 .

8 . H o D O S H , M . ; P O V A R , M . ; a n d S H K L A R , G . :The A n a t o m i c A n o r g a n i c - B o n e P o l y m e t h -a c r y l a t e E n d o s t e a l D e n t a l I m p l a n t , O r a lS u r g 2 5 : 8 8 3 - 8 8 8 , 1 9 6 8 .

9 . HODOSH, M . ; SHKLAR, G . ; and P O V A R , M . :T o t a l l y S e l f - S u p p o r t i n g Tooth R e p l i c a P o l y -mer I m p l a n t , O r a l S u r g 3 3 : 1 0 2 2 - 1 0 3 0 , 1 9 7 2 .

1 0 . S A L K , G . H . : I m m e d i a t e P l a s t i c Tooth I m -p l a n t s : C a s e R e p o r t , J S C a l i f Dent A s s n 4 0 :3 7 9 - 3 8 5 , 1 9 7 2 .1 1 . A S H M A N , A . : A c r y l i c R e s i n Tooth I m p l a n t( C o n t i n u i n g R e p o r t ) , J P r o s t h e t Dent 2 9 :5 4 9 - 5 5 5 , 1 9 7 3 .1 2 . H O D O S H , M . ; P O V A R , M . ; and S H K L A R , G . :D e v e l o p m e n t o f S e l f - S u p p o r t i n g P o l y m e rTooth I m p l a n t , J Biomed Mater R e s 4 : 2 0 5 -2 1 6 , 1 9 7 3 .1 3 . L A W R E N C E , G . ; N A T H A N S O N , D . ; M Y E R S O N ,R . L . ; and H O D O S H , M . : P o r o u s Heat C u r e dPMMA f o r D e n t a l I m p l a n t s , 6 t h A n n u a lC o n f e r e n c e i n B i o m a t e r i a l s , C l e m s o n , S C ,New Y o r k : I n t e r s c i e n c e - J o h n W i l e y a n dS o n s , 1 9 7 4 .1 4 . HAMNER, J . E . ; R E E D , O . M . ; a nd HAND , A . R . :C l i n i c a l , R a d i o g r a p h i c , H i s t o l o g i c a n d E l e c -t r o i n M i c r o s c o p i c O b s e r v a t i o n s o f P l a s t i cTooth I m p l a n t a t i o n s i n B a b o o n s , O r a l S u r g3 0 : 5 5 5 - 5 7 0 , 1 9 7 0 .1 5 . HAMNER, J . E . , a n d R E E D , O . M . : The C u r r e n tS t a t u s o f A r t i f i c i a l Tooth I m p l a n t a t i o n ,A r i z Dent J 1 7 : 1 2 - 1 6 , 1 9 7 1 .

1 6 . M A L L I A R I s , A . , and T U R N E R , D . T . : I n f l u e n c eo f P a r t i c l e S i z e on t h e E l e c t r i c a l R e s i s t i v i t yo f C o m p a c t e d M i x t u r e s o f P o l y m e r i c andM e t a l l i c P o w d e r s , J A p p l P h y s i o l 4 2 : 6 1 4 - 6 1 8 ,1 9 7 1 .



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