CONSERVATIVE DENTISTRY DB 213 - University of Babylon

63222_74_24117_983.pdf 1 C ON SE R V A T IV E DE N T I S T RY D B 2 13 NA M E : SMITA PRAKASH ID: S040102 PROGAMME: BSS II PDF created with pdfFactory Pro trial version www.pdffactory.com 2 D E N T A L AMA L G AM PDF created with pdfFactory Pro trial version www.pdffactory.com 3 I N T R O DU C T I ON D e n t a l a m a l ga m i s t h e m o s t w i de l y u s e d re s t ora t i v e m a t er i a l . I t ha s b e e n i n u s e f or o v er 1 5 0 y ear s . D e n t a l a m a l g a m i s a mi x t ure o f a s il v er a ll o y w i t h m e r c ur y . T he s i l v er a l l o y i s a f i n e po w d er t ha t i s c o m po s e d m o s t l y o f s i l v er , t i n and c o p per , an d s o m e t im e s z i n c , p a ll a d i u m or i n d i u m . W hen t h e s i l v e r a l l o y and m er c ur y a r e m i x e d , a c he mi c a l r e a c t i o n o cc u r s t h a t f or m s d e n t a l a m a l g a m . T h i s r e a c t i on be t w ee n a l l o y a n d m e r c u r y i s t e r m e d a s a m a l g a m a t i o n rea c t i on . A l t h o ugh s o m e f o r m s o f m e r c u r y a r e ha z ardou s , t h e m e r c u r y i n a m a l g a m i s c h e m i c a l l y b o und t o t h e o t her m e t a l s t o m a k e i t s t ab l e an d t here f ore s a f e f or u s e i n d e n t a l a p p l i c a t i o n s . D e n t a l a m a l g a m i s u s ed i n a ll s ur f a c e s o f p o s t er i o r t e e t h a nd o cc a s i ona l l y i n t he l i n gu a l p i t s o f an t er i o r t ee t h . A m a l ga m r e s t o r a t i on s a cc o u n t f or a s i gn i f i c an t por t i on o f a l l den t a l re s t ora t i o n s . H o w e v er , b e c a u s e o f i t s s il v e r y - gra y a p pearan c e , re s t ora t i o n s are l i m i t e d t o p o s t e r i o r t ee t h . T h e p o pu l a r i t y o f de n t a l a m a l g a m re s u l t s f ro m i t s c o s t - e ff e c t i v e n e s s , d u r a b i l i t y a nd t h e e a s e o f u s e . F ur t her m o r e , s ur v e y s ha v e s ho w n t h a t t h e per c e n t age o f f a il u re s a m ong a m a l g a m re s t ora t i o n s i s s m a l l e r t h a n t h a t w i t h a n y o t her re s t ora t i v e m a t e r i a l . H o w e v e r , t h e f a i l ure s t ha t d o o c c ur a r e m ore f requ e n t l y d u e t o i m p r o p e r de s i g n o f t h e c a v i t y p r e para t i o n a n d f au l t y m a n i p u l a t i o n o f t he m a t e r i a l . T h ere f o r e , e v er y s t e p , f r o m t h e t i m e t he a ll o y i s s e l e c t ed un t i l t h e re s t ora t i o n i s po l i s h e d h a s a d e f i n i t e e f f e c t o n t h e p h y s i c a l prop e r t i e s a n d p o t e n t i a l l y o n t he s u c c e ss or f a i l u r e s o f t h e r e s t o r a t i o n . ( P h il i p s M oore : 1 9 94)
. PDF created with pdfFactory Pro trial version www.pdffactory.com 4 T Y P E O F M A T E R I AL C L A S S I F I CA T I ON D e n t a l a m a l ga m i s c l a s s i f i ed i n t o 2 : 1 . L o w - c o pper de n t a l a m a l ga m 2 . H i gh- c o p per d en t a l a m a l g a m L O W -C O P PE R A M A L G A M T he s e are a l s o k no w n a s 'traditional', 'conventional' amalgam. Low-copper amalgams w ere u s e d ear l i e r o n . N o w l o w - c op p e r a m a l ga m ha s bee n rep l a c e d b y h i g h - c o ppe r a m a l g a m s . ( J F M c C a b e , A G W a l l s : 1 998
) H I G H - C O PP E R A M A L G A M T h i s i s t h e p r o du c t t h a t i s u s e d i n t he S O H c li n i c . H i g h - c opp e r a m a l ga m w a s d e v e l o p e d i n1 9 62
b y t h e a d d i t i o n o f s i l v e r - c o p per e u t e c t i c p a r t i c l e s t o l o w- c op p e r s il v er - t i n l a t he- c u t p a r t i c l e s . C o m pared t o l o w - c o pper a m a l g a m c o u n t e r p ar t s , h i g h - c opp e r a ll o y s e x h i b i t t h e f o l l o w i ng proper t i e s : grea t er s t re n g t h , l e s s t a r n i s h and c or r o s i on , l e ss c r e e p a n d l e ss s e n s i t i v e t o h a n d l i n g v a r i a b l e s a n d p r o d u c e be t t er l on g - t e r m c li n i c a l re s u l t s . H i gh- c o p per a m a l ga m r e s t o r a t i on s a l s o h a v e a m u c h l o w e r i n c i den c e o f m arg i n a l f a il ure c o m p ared t o l o w - c op p e r a m a l ga m . T h e c o pper c on t en t m a y v a r y f r o m on e bran d t o a n o t h e r . T h e r e are 2 ba s i c t y pe s o f h i gh- c o p p er a l l o y s : a d m i x ed a n d s i n g l e- c o m p o s i t i o n . ( J F M c C a b e , A G W a l l s : 19 9 8 ) A d mi x e d A ll o ys T h i s i s t he o l de s t t y pe o f h i gh- c o p p er a ll o y . T he a l l o y p o w der p u r c ha s e d f r o m t h e m an u f a c t u r e r i s a m i x t u r e o f p o w der s o f 2 a ll o y s . O ne i s t rad i t i o na l l o w - c o p per a ll o y . T h e o t h e r i s a p o w der - often a silver-copper eutectic. Addition of these two increases t he o v era l l c o pper c on t e n t. T h e t o t a l c o p p er c on t en t o f c o mm er c i a l a d m i x ed a ll o y s rang e s f ro m abo u t 9-20 %. T h e a ll o y p a r t i c l e s are e i t h e r s p h e r e s o r l a t he- c u t . ( J F M c C a b e , A G W a l l s : 199
8 ) S i ng l e - c o m p o s i t i on T h i s t y p e o f a m a l ga m ha s an i n c re a s e d a m ou n t o f c o p per i n t he s i l v er - t i n - c opp e r a l l o y p a r t i c l e s . I t c on t a i n s p o w d e r par t i c l e s o f o n l y o ne c o m po s i t i on . T h e c o p per c o n t en t v a r i e s r a ng i ng f ro m a b ou t 13-3 0 %. S o m e s i n g l e - c o m po s i t i on a ll o y s c on t a i n s m a ll a m o u n t s o f i nd i u m an d p a ll a d i u m . ( J F M c C a b e , A G W a ll s : 1 998)
PDF created with pdfFactory Pro trial version www.pdffactory.com 5 A ll o y P ar t i c l e s : T h e s h ape a n d s i z e o f t he a l l o y p o w de r p a r t i c l e s v ar y . T here a r e 2 t y p e s o f a l l o y p a r t i c l e s : L a t h e- c u t a l l o y s and s p her i c a l a ll o y s . 1 . L a t h e - c u t a ll o y s - are irregular in shape, they may be fine-grain or coarse-grain. T h e y a r e h ea t - t r e a t ed t o prod u c e a un i f or m c o m p o s i t i o n a nd r e gu l a t e p r o p er t i e s . T h e a l l o y m a y b e d i s pe n s e d i n t h e f or m o f pre w e i g h ed t a b l e t s o r pe ll e t s . T h e a bo v e i m ag e s h o w s l a t he- c u t T h e l a t he- c u t a l l o y par t i c l e s a re a ll o y p ar t i c l e s . p a c k e d i n t o c ap s u l e s ( s our c e : go o g l e im a g e) ( s our c e : goo g l e im ag e ) 2 . S p h e r i c a l a l l o y s - alloy particles are made in the form of small spheres. One m e t ho d o f p r e p a r i n g t h i s i s k n o w n a s a t o m i z i n g pro c edure . S pher i c a l a ll o y s a m a l g a m a t e v e r y r e a d il y . A m a l ga m a t i on c a n b e a cc o m p li s h e d w i t h s m a l l e r a m o u n t o f m e r c ur y t h a n t h a t requ i red f o r l a t h e - c u t a l l o y s . T h e i m ag e s h o w s s pher i c a l p ar t i c l e s o f S p h e r i c a l a ll o y s. ( s our c e : go o g l e im a g e s ) PDF created with pdfFactory Pro trial version www.pdffactory.com 6 P R O DUC T U S E D I N T H E S O H C L I N I C

· Brand - Contour Amalgam Regular

· Trade-name - Contour Amalgam Regular

· Company - 'Kerr'

· Supplier - South Austral

· 2 spill product

· $5200 per annum

( I n f or m a t i o n f r o m N a r a y an ; S O H s t a f f ) C o n t o ur C o n t o u r i s a d i s p e r s e d ph a s e (ad mi x ) a ll o y t ha t f ea t ur e s a f i r m pa c k w i t h s m oo t h c a r v i n g . I t h a s 7 0 % s ph e r i c a l a nd 30
% l a t he- c u t par t i c l e s . T h i s g i v e s a b e t t er c o n t a c t i n a n e a s y - t o - c ond e n s e f o r m u l a t i o n . C o n t o ur h e l p s a v o i d c h i p p i n g a n d f l a k i ng o f m ar g i n a l r i d g e s . T h e s e are s e l f - a c t i v a t i n g , r e - s e a l ab l e c ap s u l e s , t rad i t i on a l c o l o r - c o d i n g s y s t e m an d w or k s w i t h an y a m a l g a m a t o r . B e n e f i t s :

· Fast and easy, no activation step

· Reliable and consistent

· No tool required

· Efficient and compliant disposal

N O T E T y t i n i s a no t her p r o du c t bu t t h i s i s n o t u s ed i n t h e S O H c li n i c . I t i s n o t s p h er i c a l , no t a d m i x . It i s h y b r i d a m a l ga m . I t ha s a ll t h e f e a t ure s and ben e f i t s o f C o n t o u r prod u c t. I t ha s g o od and f i r m c o nden s a t i on r e s i s t a n c e , h a s s m o o t h f i n i s h i ng c har a c t er i s t i c s a n d p r o v i d e s e x c e ll en t m e c ha n i c a l p r o p e r t i e s . (http://www.kerrdental.com/products/aToZList/index.cfm) PDF created with pdfFactory Pro trial version www.pdffactory.com 7 S T O R A G E R E Q U I RE M EN TS A m a l g a m c a p s u l e s s hou l d b e s t ore d a t a t e m p e r a t u r e n o h i g h er t ha n

25°C.

( s our c e : N ara y a n ; S O H C l i n i c s t a ff ) CHE M I S T R Y A ND R E A C T IO N L O W - C O P P E R D E N T A L A M A L G AM C O M P O SI T I O N : T h e c o m p o s i t i on o f l o w - c o pper , 'traditional', 'conventional' amalgam alloy is based on G V B l a ck's composition of approximately 65% silver, 25% tin, less than 6% copper and s o m e t im e s 1 % z i n c . S E T T I N G R E A C T I O N : E x c e s s AgзSn + Hg -® unreacted Ag Sn + Ag Hg + Sn Hg 1 . W hen t h e li q u i d m e r c ur y i s m i x ed w i t h t h e a m a l g a m a l l o y , t he m e r c ur y i s bo t h a b s orbed b y t he p a r t i c l e s an d d i s s o l v e s t he s u r f a c e o f t h e p ar t i c l e s . 2 . S i l v er a n d t i n c o n t i nu e t o d i s s o l v e i n t h e li q u i d m er c u r y , w h i c h b e c o m e s s a t ura t e d w i t h s il v e r an d t i n . 3 . T h e ga mm a-1 ( A g- H g ) and g a mm a - 2 ( S n - H g ) p h a s e s be g i n t o p r e c i p i t a t e . P re c i p i t a t i o n i s a p r o c e s s i n w h i c h a s o l i d i s f o r m ed f r o m m a t e r i a l d i s s o l v e d i n a l i qu i d . 4 . P re c i p i t a t i o n o f t h e g a m m a - 1 a nd ga m m a -2 p h a s e s c on t i nu e s u n t i l t h e m er c u r y i s c o n s u m e d a nd a s o li d m a s s re s u l t s . T he s e t t i n g rea c t i on m a y t a k e a s l o ng a s 2 4 h o urs to complete, when strength reaches a maximum. (L W i l li a m s , W i l k i n s : 2004
) PDF created with pdfFactory Pro trial version www.pdffactory.com 8 H I G H - C O P P ER D EN T A L A M A L G A MS C O M P O SI T I O N : H i gh- c o p per a m a l g a m c on t a i n s 40-6
0 % s i l v er , 2 7-30 % t i n a nd 13-30 % c opp e r an d 1 % z i n c . S o m e t i m e s i t a l s o c o n t a i n s I nd i u m an d P a l l a d i u m . Ø Silver causes setting expansion and increases strength and corrosion re s i s t a n c e . Ø Tin causes setting contraction and decreases strength and corrosion re s i s t a n c e . Ø Copper increases strength, reduces tarnish and corrosion, reduces creep, a n d l o w e r s c a s e s o f m arg i na l l e a k ag e . Ø Zinc reduces oxidation of the other metals in the alloy. Recently, clinical re s e a r c h h a s s h o w n t h a t z i n c - containing dental amalgams have a longer c li n i c a l li f e e x p e c t a n c y t h a n n on z i n c a m a l ga m s . Ø Indium reduces creep and increases strength.

Ø Palladium reduces tarnish and corrosion.

( s our c e : http://www.dentalindia.com/ccamal/htm) S E T T I N G R E A C T I O N : T h e s e t t i ng re a c t i on o f h i g h - c opp e r a m a l ga m s i s a li tt l e m ore c o m p l e x t han i n l o w - c o ppe r a m a l g a m s . It s n o t a b l e f ea t ure i s t h e l a ck o f a ga mm a-2 ( S n - H g ) produ c t . E x c e s s A g S n C u ( t h e a l l o y ) + H g - - --- - > unrea c t e d a l l o y + A g H g + C u S n 1 . T h e a l l o y c on t a i n s 1 0 % t o 3 0 % c opp e r . 2 . S i l v er rea c t s i n t h e s a m e m a nner a s a l o w- c o p per a m a l g a m , f o r m i ng a ga mm a- 1 ( A g- H g ) prod u c t . 3 . T i n rea c t s w i t h c o p per t o f o r m s e v e r a l C u - S n r e a c t i on p r o d u c t s . N o S n- H g rea c t i on produ c t i s f o r m e d a s o c c u r s i n t h e l o w - c o pper a m a l ga m r e a c t i on . (L W i l li a m s , W i l k i n s : 2004
) PDF created with pdfFactory Pro trial version www.pdffactory.com 9 P R O PE R T I ES M E CHAN I CA L P R O P E R T IES 1 . S T R E N G T H T h e s t reng t h o f a n a m a l g a m re s t ora t i o n m u s t be h i gh e n o ugh t o r e s i s t t he b i t i n g f o r c e s o f o c c l u s i o n . T he s t r e ng t h o f t he a m a l g a m d e pend s o n t h e p ha s e s t h a t ar e pre s e n t . H a v i ng m o r e o f t h e s t rong e r ph a s e s re s u l t s i n a s t r o nger m a t e r i a l . T he t w o t y p e s o f s t ren g t h are c o m p r e s s i v e s t r e ng t h and t e n s i l e s t r e n g t h . D e n t a l a m a l g a m ha s h i g h c o m p r e s s i v e s t reng t h ( 3 8 0 M P a f or l o w - c o pper a m a l ga m a nd 4 1 4 M P a f o r h i gh- c o p per a m a l ga m s ) . H o w e v e r , t h e t en s i l e a n d s he a r s t r e ng t h s ar e c o m p ara t i v e l y l o w . T h e r e f ore , a m a l ga m s hou l d be s u p por t e d b y t o o t h s t r u c t u r e s f o r c li n i c a l s u cc e ss i n t he l ong t e r m . T h e r a t e a t w h i c h an a m a l ga m d e v e l op s s t r e n g t h i s a n i m p o r t an t c li n i c a l c h a r a c t e r i s t i c . S p h e r i c a l p ar t i c l e a l l o y s an d c o p p er - e n r i c h e d a l l o y s de v e l o p s t reng t h m o r e ra p i d l y t h an c o n v e n t i ona l l a t h e - c u t m a t e r i a l s . F i ne-gr a i n , l a t he- c u t prod u c t s d e v e l op s t ren g t h m o r e r a p i d l y t h an c oar s e-gra i n prod u c t s . I f t h e a m a l g a m re s t ora t i o n i s s u b j e c t e d t o c h e w i n g o r o t he r o r a l f o r c e s be f ore s u f f i c i en t s t reng t h d e v e l op s , i t i s a t r i sk f or f ra c t ure . PDF created with pdfFactory Pro trial version www.pdffactory.com 10 2 . CR E EP Cr eep i s a s l o w c hange i n s hap e c a u s e d b y c o m pre s s i on due t o d y n a m i c i n t r a - o r a l s t r e s s e s . Cr eep c a u s e s a m a l ga m t o f l o w , s u c h t h a t un s upp o r t ed a m a l ga m pro t r u de s f r o m t h e m a r g i n o f t h e c a v i t y . T he s e un s u p por t e d e dg e s are w ea k a n d m a y b e f ur t h e r w ea k ene d b y c or r o s i o n . F r a c t u r e c a u s e s t h e f or m a t i o n o f a 'ditch' arou n d t he m arg i n s o f t h e a m a l g a m re s t ora t i on . C r e e p a l s o c rea t e s o v erhang s on f i ll i ng s l e a d i ng t o f o o d t r a pp i ng & s e c on d ar y de c ay. The gamma-2 phase of a m a l g a m i s pr im a r i l y re s po n s i b l e f or t he r e l a t i v e l y h i g h v a l ue s o f c ree p e x h i b i t e d b y s o m e m a t er i a l s . V a l u e s f or s t a t i c c re e p f or a m a l ga m : Material type Creep (%) C o n v e n t i on a l l a t he-cut 2.5 D i s p e r s i on-modified, copper-enriched 0.2 C o p per-enriched, containing 0.5% palladium 0.06 PDF created with pdfFactory Pro trial version www.pdffactory.com 11 3 . D I M E N S I O N A L C H A N G E : T h e ne t c o n t r a c t i on or e x pan s i on o f a n a m a l g a m i s c a l l e d i t s d im e n s i on a l c h a n g e . D i m en s i o n a l c han g e i s n e ga t i v e i f t h e a m a l ga m c on t r a c t s an d po s i t i v e i f i t e x pand s d u r i ng s e tt i n g . I n g e ner a l , m o s t a m a l ga m s e x pan d or c on t ra c t o n l y s li g h t l y o v e r a ll d u r i ng s e tt i n g , b u t t h e A N S I/ A D A s pe c i f i c a t i o n N o . 1 req u i re s t ha t t he d im e n s i ona l c h a ng e b e an e x p a n s i o n or a c on t r a c t i on o f no m ore t h an 2 0 m i c r o m e t re s / c m . E x p a n s i o n c ou l d r e s u l t i n p o s t - p l a c e m e n t s e n s i t i v i t y o r pro t ru s i o n f r o m t he c a v i t y , w h e r e a s c on t r a c t i o n w o u l d l e a v e g ap s prone t o l e a k a g e b e t w e e n t h e re s t ora t i on a n d t h e t oo t h . D i m en s i o n a l c han g e i s a ff e c t ed b y m a n y f a c t or s , s u c h a s t he m e r c ur y / a l l o y ra t i o a s w e l l a s t r i t ura t i o n a n d c o nd e n s a t i on t e c hn i q u e s . D ur i n g a m a l g a m a t i o n rea c t i on , e x pa n s i o n a n d c o n t r a c t i o n o c c u r s im u l t a n eou s l y . T h e d i s s o l u t i on o f g a mm a p a r t i c l e s gen e r a l l y l ead s t o c o n t r a c t i on , w h erea s t h e f o r m a t i on o f g a mm a - 1 c a u s e s e x pa n s i o n . T h e o v era l l d im en s i o n a l c h an g e i s t h e r e f ore t h e s u m o f t h e s e t w o pro c e s s e s . I m pro p e r m a n i p u l a t i on t ha t a l t er s t h e ra t i o o f g a mm a t o ga mm a - 1 a nd η in the set amalgam therefore also will alter its dimensional change. PDF created with pdfFactory Pro trial version www.pdffactory.com 12 CH E M I CA L P R O PE R T I ES 1 . CH E M I C A L C O RR O S I O N ( T A RN I S H ) T arn i s h i n g s im p l y i n v o l v e s t h e l o s s o f l u s t e r f ro m t h e s u r f a c e o f a m e t a l o r a l l o y d u e t o f o r m a t i on o f a s u r f a c e c o a t i ng . T h e i n t egr i t y o f t h e a ll o y i s no t a f f e c t ed a n d s o no c h an g e i n m e c h a n i c a l prop e r t i e s i s e x pe c t e d . A m a l g a m rea d il y t ar n i s he s d u e t o t h e f o r m a t i on o f a s u l p h i de l a y er on t h e s ur f a c e . R e a c t i o n : A g + 1 + S -2 - - - - - -- > A g 2 S ( b l a c k f i lm ) 2 . E L E C T R O CH E M I C A L C O R R O S I O N G a l v a n i c c o r ro s i o n o c c u r s w he n t w o d i s s i mi l a r m e t a l s e x i s t i n a w e t en v i ron m e n t . E l e c t r i c a l c u r ren t f l o w s b e t w e en t h e t w o m e t a l s , c o r ro s i o n (o x i d a t i on) o f o n e o f t h e m e t a l s o c c u r s . T he li k e l i ho o d o f g a l v an i c c or r o s i on i n c r ea s e s i f t w o m e t a l l i c p h a s e s are pre s e n t i n a m e t a l . C o rro s i o n o cc u r s bo t h o n t h e s u r f a c e a n d i n t he i n t er i o r o f t he r e s t o r a t i on . S u r f a c e c o r ro s i o n d i s c o l or s an a m a l ga m re s t ora t i o n a nd m a y e v en l e ad t o p i t t i n g . S u r f a c e c o r ro s i o n a l s o f i ll s t h e t o o t h / a m a l g a m i n t er f a c e w i t h c o r ro s i on produ c t s , r e d u c i n g m i c r o l e a k a g e . I n t erna l c o r ro s i o n w ill l e a d t o m ar g i n a l brea k do w n an d f ra c t ure . A n a c i d i c e n v i ron m e n t p r o m o t e s ga l v an i c c o r ro s i o n . T h e a bo v e i m ag e i s o f a n a m a l ga m r e s t o r a t i o n t ha t h a s u n dergone g a l v an i s m . ( s our c e : go o g l e im a g e) PDF created with pdfFactory Pro trial version www.pdffactory.com 13 T H E R M A L P R O P E R T I ES 1 . T H E R M A L D I FF U SI V I T Y A m a l g a m h a s a re l a t i v e l y h i gh v a l u e o f t h e r m a l d i f f u s i v i t y . T h u s , i n c o n s t r u c t i n g a n a m a l g a m re s t ora t i o n , a n i n s u l a t i n g m a t e r i a l , den t i ne i s rep l a c ed b y a good t h e r m a l c o n d u c t o r . I n l arge c a v i t i e s i t i s ne c e s s ar y t o li n e t he b a s e o f t h e c a v i t y w i t h an i n s u l a t i ng , c a v i t y l i n i ng m a t er i a l p r i or t o c on d e n s i n g t he a m a l ga m . T h i s r e du c e s t he har m f u l e ff e c t s o f t her m a l s t i m u l i o n t h e p u l p . 2 . C O E F F I C IE N T O F T H E R M A L E X PA N SI O N T h i s v a l u e f or a m a l g a m i s a bou t t hree t im e s gra t e r t h an t ha t f o r den t i ne . T h i s c o u p l ed w i t h t he g r a t er d i f f u s i v i t y o f a m a l ga m , re s u l t s i n c o n s i d e r a b l y m or e e x pa n s i o n a nd c o n t r a c t i on i n t he re s t ora t i o n t ha n i n t h e s ur r o u nd i ng t oo t h w h en a p a t i en t t a k e s ho t or c o l d f oo d or d r i n k . S u c h a be h a v i or m a y c a u s e mi c ro l e a k a ge arou n d t he f i ll i ng s i n c e t here i s n o ad h e s i on be t w ee n a m a l ga m a n d t oo t h s u b s t a n c e . B I O L OG I C A L P R O P E R T I ES 1 . M E RCUR Y T O X I C I T Y I t i s a c o n c ern i n d en t i s t r y be c a u s e m e r c u r y a nd i t s c h e m i c a l c o m po u nd s are t o x i c t o t h e k i dne y s an d t h e CN S . M e r c ur y h a s a h i gh v apo r pre s s u r e and e v a p ora t e s a t r o o m t e m p e r a t u re . T he l ung s ab s orb m o s t o f t h e m er c ur y v a p o r i n a i r w h e n i n h a l ed . P roper h and l i ng an d s t orag e a l o n g w i t h p r o m p t c l ea n i n g o f a l l m e r c u r y s p i l l s w il l m i n i mi z e r i s k o f t o x i c i t y . 2 . A M A L G A M T A TT O O T h i s m a y o c c u r du r i ng a m a l ga m r e m o v a l w he n a r u bber da m i s n o t u s ed and t he par t i c l e s o f a m a l g a m are f l un g b y t he bu r i n t o t he g i ng i v a l t i ss u e s w here t h e y r e m a i n e m be d ded , b e c o m e f i brou s t i ss u e en c a p s u l a t e d , an d c orrode t o f o r m b l a c k c or r o s i on p r o d u c t s . T h e r e are n o k n o w n ad v er s e rea c t i o n s b u t i t i s e s t he t i c a l l y un p l e a s i ng . ( s o u r c e : g oo g l e i m a g e s ) PDF created with pdfFactory Pro trial version www.pdffactory.com 14 A D V A N T A G ES O F DE N T A L A M A L G AM

· It is durable.

· Least technique sensitive of all restorative materials. · Applicable to a broad range of clinical situations. · Newer formulations have grater long-term resistance to surface corrosion.

· It has good long-term clinical performance.

· Ease of manipulation by dentist.

· Minimal placement time compared to other materials. · Corrosion products seal the tooth restoration interface and prevent bacterial l ea k age . · It is a one-appointment placement (direct material). · Long lasting if placed under ideal conditions.

· Very economical.

· Self sealing

· Biocompatible

D I S A D V A N T A G ES O F D E N T A L A M A L G AM

· Some destruction of sound tooth tissue.

· Poor esthetic qualities.

· Long-term corrosion at tooth-restoration interface may result in 'ditching' leading t o r e p l a c e m e n t .

· Galvanic response potential exists.

· Local allergic potential.

· Concern about possible mercury toxicity that affects the CNS, kidneys and s t o m a c h .

· Marginal breakdown.

· Bulk fracture

· Secondary caries

· Sometimes excess Hg within the restoration may seep through the dentinal t ubu l e s , d i s c o l o r de n t i n an d re s u l t i n b l a ck i s h o r gr a y i s h s t a i n i n g o f t e e t h . S i n c e e n a m e l i s s e m i - t ran s l u c e n t , t h i s d i s c o l o r a t i o n i s n o t i n c o n s p i c u o u s . PDF created with pdfFactory Pro trial version www.pdffactory.com 15 E S T IM A T E D C O S T F O R O N E S T A N D A RD A PP L I C A T ION A bo tt l e o f 6 0 0 a m a l g a m c a p s u l e s c o s t s arou n d $10 0 0 A u s t h ere f o r e s i n c e o n e a m a l g a m re s t ora t i o n m o s t l y u s e s o n e a m a l g a m c a p s u l e , t he c o s t p e r s t an d ard a p p li c a t i o n w o u l d a ppro x i m a t e l y be $2 . 0 7 F J . ( s our c e : N ara y a n , F S M c li n i c s t a f f ) C L I N I C A L A PP L I C A T I O NS D e n t a l a m a l ga m i s u s e d i n t he f o l l o w i n g s i t ua t i on s :

· In individuals of all ages.

· In stress-bearing areas and in small-to-moderate sized cavities in the posterior t ee t h .

· Especially used in large MOD cavities.

· When there is severe destruction of tooth structure and cost is an overriding c o n s i dera t i on . · As a foundation for cost-metal, metal-ceramic and ceramic restorations. · When patient commitment to personal oral hygiene is poor. · When moisture control is problematic with patients.

· When cost is an overriding patient concern.

D e n t a l a m a l ga m i s no t u s ed w h e n : · Esthetics is important, such as in the anterior teeth and in lingual endodontic- a cc e s s re s t ora t i on s o f t h e a n t e r i or t e e t h . · Patients have a history of allergy to mercury or other amalgam components. · A large restoration is needed and the cost of other restorative materials is not a s i g n i f i c an t f a c t o r i n t h e t rea t m en t d e c i s i on . · When a women is breast feeding because mercury can be passed to the baby t h r o ugh bre a s t m i l k . PDF created with pdfFactory Pro trial version www.pdffactory.com 16 M A N I PU L A T I O N O F DE N T A L A M A L G AM T h e m a n i p u l a t i o n o f a m a l g a m i n v o l v e s f i v e m a j o r s t ep s : 1 . P ropor t i on i ng and d i s p e n s i n g 2 . T r i t u ra t i o n 3 . C o n de n s a t i o n 4 . C ar v i ng 5 . P o li s h i n g P ropor t i on i ng and d i s p e n s i n g A l l o y / m er c u r y r a t i o s v ar y be t w ee n 5 : 8 a n d 10 : 8 . T h o s e mi x e s c on t a i n i ng g r a t er q u an t i t i e s o f m er c u r y are 'wetter' and are used with hand mixing. Those containing s m a l l er q uan t i t i e s o f m e r c u r y are 'drier' and are used with mechanical mixing. For a n y g i v en a l l o y / m e r c ur y ra t i o , t h e n a t u r e o f t he m i x m a y v ar y d e pen d i n g u pon t he s i z e a nd s hape o f t he a ll o y par t i c l e s . V ar i ou s m e t hod s o f d i s p e n s a t i o n are a v a il a b l e . T he m o s t a c c u r a t e m e t hod t o w e i g h t he m e r c ur y a nd a l l o y c o m p o nen t s i s u s i ng a ba l an c e . V o l u m e d i s p e n s e r s are a l s o c o m m o n . A n o t h er m e t hod o f d i s p e n s a t i on f o r t h e a l l o y i s preprop o r t i one d a s a p o w der i n a s m a l l s a c h e t or e n v e l o p e o r a s a t ab l e t i n w h i c h t he p o w der p a r t i c l e s are c o m p r e ss e d t og e t h e r . A n o t her c o n v e n i en t m e t h o d i n v o l v e s t he u s e o f e n c a p s u l a t ed m a t e r i a l s . E a c h c ap s u l e c on t a i n s bo t h a ll o y and m er c ur y i n p ropor t i o n s t h a t h a v e b e en de t e r mi n e d b y t h e m an u f a c t u r e r . T he t w o c o m pon e n t s a r e s e para t e d b y an i m pe r m eab l e m e m b rane t ha t i s s ha t t ered u s i n g a p u r po s e-bu i l t c a p s u l e pre s s or on s t ar t i n g t o v i bra t e t he c a p s u l e i n a m e c han i c a l mi x e r . C a p s u l e s w h i c h d o n o t requ i r e t he u s e o f a p r e s s are c a ll ed s e l f - a c t i v a t i n g c a p s u l e s . P ropor t i on i ng p l a y s a v e r y i m por t ant ro l e i n t he s u cc e ss o f a n a m a l g am re s t ora t i o n. PDF created with pdfFactory Pro trial version www.pdffactory.com 17 T r i t u ra t i on T r i t u ra t i on i s t h e mi x i ng o f a m a l g a m . AK A a m a l ga m a t i on r e a c t i on . M i x i n g c a n be do n e w i t h h a nd s , u s i ng a m or t a r and p e s t l e o r i n a n e l e c t r i c a ll y p o w ered m a c h i ne , w h i c h v i bra t e s a c ap s u l e c on t a i n i n g t he m er c ur y and a ll o y . T he t r i t u r a t i on t im e m a y ha v e an e ff e c t on t h e proper t i e s o f t h e f i na l s e t a m a l g a m . S o m e prod u c t s req u i re a t l ea s t 4 0 s e c o nd s t r i t ura t i o n i n o r d er t o a c h i e v e f u l l 'wetting' of alloy particles by mercury and o p t im a l p r o pe r t i e s i n a m a l g a m . T r i t u ra t i on b y ha n d i s no t e x t en s i v e l y p r a c t i c e d . I n s t e ad m i x i n g i s f ar m o re w i d e l y u s ed . M e c h an i c a l t r i t ura t i o n i s a l s o u s ed i n F S M t e a c h i n g c l i n i c . T h e ad v an t ag e s o f m e c h an i c a l t r i t u r a t i on are a s f o l l o w s : 1 . A un i f o r m re p rodu c i b l e mi x i s p r o d u c e d . 2 . A s h o r t er t r i t u ra t i o n t i m e c an b e u s ed . 3 . A gra t e r a l l o y / m e r c u r y ra t i o c an be u s e d . C o n de n s a t i on F o l l o w i ng t r i t u r a t i on , t h e m a t e r i a l i s p a c k ed o r c onde n s ed i n t o t h e pre p a r e d c a v i t y . T h e m a t er i a l i s c arr i e d i n t o t h e m o u t h b y a m a l g a m c arr i er s . A v a r i e t y o f m e t h od s ha v e b e en s ugg e s t ed t o c o nden s e a m a l ga m i n c l u d i ng u l t ra s o n i c v i b r a t i on and m e c h an i c a l c o n den s i ng t o o l s . T he m o s t w i de l y u s e d m e t ho d o f c o n d en s a t i on i s w i t h a h a nd i n s t ru m en t c a l l e d a n a m a l ga m c on d e n s e r . T h e s e are f l a t - e nde d a n d c o m e i n a v a r i e t y o f s t y l e s . T he s h a p e an d s i z e o f t he c onde n s e r s h o u l d b e c h o s e n w i t h t h e s i z e o f t he c a v i t y i n m i n d . T h e c o nden s er m u s t b e a b l e t o f i t w i t h i n t h e c a v i t y ou t l i n e a nd s h o u l d be a b l e t o g e t rea s o nab l y c l o s e t o t he p e r i p h era l m ar g i n o f t h e re s t ora t i on . I t i s be t t er t o u s e a s m a l l er d i a m e t er rou n d c ond e n s er o r an o v o i d i n s t r u m e n t t o f a c i l i t a t e t h e f i r s t s t a g e o f pa c k i ng . T he a m a l g a m i s p a c k ed i n i n c r e m e n t s , e a c h i n c re m en t b e i n g e q u i v a l en t t o t he v o l u m e o f m a t e r i a l w h i c h c a n be c arr i ed i n an a m a l g a m 'gun'. This is t he d e v i c e u s e d t o t ran s f er t he m a t er i a l f ro m t h e mi x i ng v e s s e l t o t h e p r e pared c a v i t y . D u r i ng c ond e n s a t i on , a f l u i d , m e r c ur y - r i c h l a y e r i s f o r m e d on t h e s u r f a c e o f e a c h PDF created with pdfFactory Pro trial version www.pdffactory.com 18 i n c re m e n t a l l a y er . T he c a v i t y i s o v er f i l l e d an d t he m er c u r y - r i c h l a y e r c ar v e d a w a y f r o m t he s ur f a c e . T h i s e ff e c t i v e l y redu c e s t h e m e r c ur y c on t e n t o f t he f i ll i n g t h u s i m pro v i n g i t s m e c h an i c a l proper t i e s . T h e t e c h n i qu e c ho s e n f or c o n d e n s a t i o n m u s t e n s ure t h e f o ll o w i ng : 1 . A d e q u a t e a d a p t a t i o n o f t he m a t e r i a l t o a l l pa r t s o f t h e c a v i t y ba s e and w a l l s . 2 . G oo d b o n d i n g b e t w e en t he i n c r e m en t a l l a y e r s o f a m a l g a m . 3 . O p t im a l m e c h a n i c a l p r o p e r t i e s i n t he s e t a m a l g a m b y m i n i m i z i ng poro s i t y a n d a c h i e v i ng f i n a l m e r c ur y c o n t e n t o f 44-48
% . T h e r e s h o u l d be a mi n i m a l t im e d e l a y b e t w e en t r i t ura t i o n an d c o n de n s a t i o n . I f c o n den s a t i on i s c o mm e n c e d t o o l a t e , t he a m a l g a m w il l ha v e a c h i e v e d a c er t a i n d e gre e o f s e t a n d a d a p t a t i o n , bo n d i ng o f i n c re m en t s a nd f i n a l m e c h an i c a l p r o per t i e s are a l l a ff e c t ed . B e l o w are t h e p i c t u r e s o f s o m e a m a l g a m c on d e n s e r s T h e p i c t u r e be l o w s h o w s a m a l g a m b e i n g c on d e n s e d i n t o t he c a v i t y . PDF created with pdfFactory Pro trial version www.pdffactory.com 19 C ar v i ng T h e p u r p o s e o f c a r v i ng an a m a l ga m r e s t o r a t i on i s t o r e m o v e t he m e r c ur y - r i c h l a y e r o n t he a m a l ga m s ur f a c e a n d t o rebu il d t h e a n a t o m y o f t he t o o t h , r e-e s t a b l i s h i n g c on t a c t w i t h t he o ppo s i n g d en t i t i on . C a r v i n g s hou l d be c ar r i ed ou t w h e n t he m a t e r i a l h a s rea c h ed a c e r t a i n degre e o f s e t . I f a t t e m p t s are m a de t o c ar v e t o o s o o n t here i s a d a nger o f 'dragging out' significant amounts of material from the surface. If carving is d e l a y ed t here i s a da n ger o f c h i pp i n g a t t h e m a r g i n s . It w il l be ne c e s s ar y t o c he c k t h e p a t t ern o f o cc l u s a l c o n t a c t s w h i l s t c ar v i ng a r e s t o r a t i on . W hen t h e a m a l g a m i s s t i ll s o f t , rubb i n g t he s ur f a c e w i t h c o t t on w oo l p r o d u c e s a m a t t f i n i s h , i f t h e s u b j e c t g e n t l y t a p s t he i r t ee t h t o ge t her o r m o v e s f ro m s i de t o s i d e , a n y a r e a s o f c o n t a c t w i l l s ho w u p . P o li s h i ng P o li s h i n g i s c ar r i e d o u t i n o r d e r t o a c h i e v e a l u s t ro u s s u r f a c e h a v i n g a m ore a cc e p t ab l e a p peara n c e a n d b e t t er c o r ro s i o n re s i s t an c e . T h e f i l li ng s s h o u l d n o t be p o l i s h ed un t i l t h e m a t e r i a l ha s a c h i e v e d a c e r t a i n l e v e l o f m e c h an i c a l s t r e n g t h ; o t her w i s e t here i s a d a nger o f f r a c t u r e a t t he m arg i n s . M a n y p r o d u c t s r e qu i r e a d e l a y o f 24
ho u r s b e t w een p l a c i n g a nd po li s h i n g . G ro s s i r reg u l a r i t i e s i n t h e s ur f a c e c an be redu c ed u s i ng m u l t i - b l ade d s t e e l bur s i n a s l o w ha n d p i e c e . T h i s s t age r e s u l t s i n a s m o o t h s u r f a c e c on t our . F i n e po li s h i n g t o prod u c e a l u s t e r i s t h en un d e r t a k en u s i n g grad e d abra s i v e s . P a s t e s a r e a p p l i e d u s i ng a rubb e r c a p o r br u s h . T h e a bo v e p i c t u r e s h o w s a m a l g a m re s t ora t i on b e i ng po l i s he d u s i ng a b r u s h . PDF created with pdfFactory Pro trial version www.pdffactory.com 20 C L I N I C A L H I N T S A ND T H I N G S T H A T M I G H T L E A D T O F A I L URES C AV I T Y D E SI G N · Amalgam has no intrinsic ability to bond to enamel and dentine, hence cavities h a v e t o b e u s e d w h i c h a r e u n d er c u t , i . e . , t h e c a v i t y i s w i d e r w i t h i n t he s t r u c t u r e o f t he t o o t h t h a n a t t h e s u r f a c e . T h i s i s d on e t o r e t a i n t h e m a t er i a l m e c han i c a l l y . A l l i n t ern a l l i ne an g l e s s ho u l d b e rou n ded t o mi n i m i z e i n t e r n a l s t re s s e s w i t h i n t h e re s t ora t i o n a n d t o f a c ili t a t e a d ap t a t i o n o f t h e m a t e r i a l t o t he c a v i t y w a l l s . T h e f l o or o f t he c a v i t y , bo t h t h a t o v e r l y i n g t he p u l p an d a t t h e g i n g i v a l e x t e n t s h ou l d b e f l a t t o per mi t c on d en s a t i o n o f a m a l ga m . · It is always necessary to remove unsupported enamel once any carious dentine h a s b ee n r e m o v e d . T h i s i s e a s y t o a c h i e v e on a c l e a r l y v i s i b l e c a v i t y s ur f a c e . F a i l ure t o r e m o v e u n s up p o r t e d e n a m e l w il l r e s u l t i n an i n t r i n s i c w ea k n e ss a t t h e m ar g i n s o f t h e r e s t ora t i o n . T he u n s upp o r t ed t i ss ue c ou l d f a il e i t h er d ur i n g f u n c t i on o r u nder t he p r e s s ure a pp li ed b y a s t e e l m a t r i x ba n d w h i l s t t he re s t ora t i o n i s b e i n g p a ck ed . I t c o u l d c a u s e m a r g i n a l d i t c h f o r m a t i on an d f a i l u r e o f t he r e s t o r a t i on . · An alternative form of amalgam retention is to prepare pits and grooves in the re m a i n i ng d en t i ne . T he s e a c t a s re t en t i v e f e a t u r e s i f po s i t i one d c orre c t l y i n r e l a t i o n t o t h e re m a i n i ng t o o t h t i s s ue s . A l t e r na t i v e l y de n t i ne p i n s c a n b e u s ed . N o w a da y s , t he m o s t c o mm on f o r m o f p i n i s s e l f - t h r e ad i ng p i n . P i n s w h i c h h a v e a s h o u l der w h i c h engage s t h e t oo t h t i s s u e b e f ore t h e t h r e aded s ha f t o f t he p i n c o n t a c t s t h e b a s e o f t he p i n ho l e c au s e l e s s d a m a ge t o t he t o o t h . P i n s n ee d t o b e p l a c e d w i t h c a r e t o a v o i d t he pu l p and t h e p e r i o d on t i u m . A l s o adequa t e s p a c e ne e d s t o b e a v a i l ab l e b e t w een t he p i n a n d t h e l o c a t i o n o f t h e s u r f a c e o f t he r e s t o r a t i on . F i n a l l y p i n s s hou l d no t b e p l a c ed t oo c l o s e t oge t h er . A l l d en t i n e p i n s w e a k e n t he re s t ora t i o n t here f ore s ho u l d b e u s e d s p ar i ng l y . M A T R I C ES I f an e x t erna l w a ll o f a t o o t h i s bre a c hed b y a c a v i t y a s t e e l m a t r i x ba n d n ee d s t o be a p p li e d t o t h e t o o t h t o p r o v i de a s ur f a c e aga i n s t w h i c h t h e a m a l g a m c an be c onden s e d . I n a dd i t i o n t he m a t r i x s h o u l d a d ap t v er y c l o s e l y t o t he g i ng i v a l m a r g i n o f t h e c a v i t y t o pre v e n t t h e p r o d u c t i on o f l ed g e s o f a m a l g a m ou t s i d e t he c a v i t y d ur i n g p a ck i n g . T h e u s e o f m a t r i x m a y a f f e c t t h e t o o t h . T h i s pr o b l e m c a n b e o v e r c o m e f i r s t l y b y a d ap t i n g t he m a t r i x t o t he t o o t h . I t i s burn i s h ed o u t w a r d t o t r y t o a c h i e v e c o n t a c t w i t h t h e a d j a c en t t o o t h . S e c ond l y , a w o ode n or m e t a l w ed g e s hou l d be i n s er t e d b e t w een t he t ee t h i f p o ss i b l e . T h i s h e l p s m a i n t a i n a d a p t a t i on o f t h e b a nd t o t h e t oo t h s ur f a c e c e r v i c a l l y a n d s epara t e s t ee t h s l i g h t l y . O n c e t he w ed g e i s i n p l a c e t h e m a t r i x c an be l oo s ene d s li gh t l y t o f a c il i t a t e bur n i s h i ng ag a i n s t t h e ad j a c en t t oo t h . R e m o v a l o f m a t r i x PDF created with pdfFactory Pro trial version www.pdffactory.com 21
b a n d s s h o u l d be c arr i e d ou t d u r i n g t h e c a r v i n g pro c e s s . T h e a m a l ga m m u s t be s u f f i c i en t l y s e t t ha t r e m o v a l o f t he b a n d w i l l no t re s u l t i n b u l k f a i l u r e o f t h e r e s t o r a t i on . T h e i m ag e s s h o w t he d i ff e r e n t t y p e s o f m a t r i x b and s . T h ere a r e m an y t y p e s b u t t he o n e t h a t i s c o mm o n l y u s ed i n t h e F S M d e n t a l c l i n i c dur i n g a m a l g a m r e s t ora t i o n i s t o f f l e m i r e m a t r i x b a nd. D ISP O S A L · All dental amalgam particles collected by any suction line configuration should be p l a c ed i n a n a i r t i g h t c o n t a i ner l ab e l e d 'contact amalgam'. · If the dental amalgam is removed by hand, the amalgam filling and teeth with filling s h o u l d be p l a c e d i n a i r t i gh t c on t a i ner l a b e l ed 'contact amalgam'. · If excess dental amalgam is generated during the placement of a filling, collect the e xc e s s d en t a l a m a l ga m i n a n a i r t i gh t c on t a i n e r l ab e l e d 'non-contact amalgam'. · Where separation between contact and non-contact amalgam is not required by the a p p r o v e d w a s t e c ar r i er , a l l a m a l ga m w a s t e s m a y b e p l a c ed i n a s i n g l e c on t a i ne r l ab e l e d 'scrap amalgam'. · All amalgam waste must be released to an approved waste carrier for recycling or d i s p o s a l . · Broken and unused amalgam capsules should be placed in an air tight container l ab e l e d 'non-contact amalgam' and released to an approved waste carrier for re c y c l i n g o r d i s p o s a l . · Empty amalgam capsules should be recycled or disposed with regular garbage. T h i s i s t he i m age o f a p r o p er a m a l g a m sc rap d i s po s a l b i n. ( s our c e : goo g l e ) PDF created with pdfFactory Pro trial version www.pdffactory.com 22
RU B B E R D A M A r u b ber s h i e l d i n g d e v i c e c a l l ed 'rubber dam' can be used during the application or re m o v a l o f a m a l g a m f i l l i ng . I t i s a c u s t o mi z ed rubb e r s h e e t t ha t f i t s o v er t he t e e t h he l d b y a c l a m p a n d f ra m e and i s u s e d f or m o s t f ill i n g s p r o c e d u r e s . I t redu c e s t h e e x p o s ure t o m e r c u r y an d a v o i d s s o li d s an d m a t e r i a l s f r o m b e i n g s w a ll o w e d . I t a l s o o v er c o m e s o b s t a c l e s l i k e a t o o t h b a t h e d i n s a l i v a , a t on g u e t ha t i n s i s t s on o b s t r u c t i ng v i s i on , a nd a b l e e d i ng g i n g i v a l . M o s t im por t a n t l y i t c re a t e s a d r y w o r k i ng area . A dr y , i s o l a t e d w or k f i e l d m e a n s : 1 . B a c t e r i a f ro m t h e s a l i v a w i l l no t g e t i n s i d e t he t ee t h . A n e a s i er t i m e c l e an i ng o u t t h e ba c t er i a a nd d e c a y f r o m i n s i de t he t o o t h . 2 . T h e r e s t ora t i on c a n b e p l a c e d i n a d r y e n v i r on m en t and s t r o nger bond s w i l l o cc ur w h en m o i s t u r e i s c o n t ro ll ed . 3 . P ro t e c t ed f r o m de b r i s or t i n y i n s t r u m en t s be i ng s w a l l o w e d . 4 . T o n gu e a n d o t h e r s t ru c t ur e s are p r o t e c t e d f ro m po s s i b l e d a m ag e . M o s t p a t i en t s l i k e r u b ber d a m s an d s a y t h e y c a n f e e l m o re r e l a x ed be c a u s e t he y d o n ' t h a v e t o c o n c e n t ra t e o n s t a y i n g o pen or p o s i t i o n i ng t he i r t o ngu e . The diagram shows rubber dam being used d u r i ng a r e s t o r a t i o n. A R T I CU L A T I N G P A P E R T h i s c a n b e u s e d t o d e t er m i ne t h e f a u l t s s u c h a s h i gh s p o t s s o t h a t t he r e s t ora t i o n c a n b e c a r v e d proper l y f o r op t i m u m f un c t i o n . PDF created with pdfFactory Pro trial version www.pdffactory.com 23
O t her rea s o n s f or f a i l u re · The manipulation of amalgam affects its strength. Inadequate condensation re s u l t s i n v o i d s , w h i c h w e a k en t h e s e t m a ss . M i x i ng t h e a m a l g a m f o r t o o l o ng or t oo s h o r t a t i m e a l s o w e a k en s t he f i n a l s t r e ng t h b y c ha n g i ng t h e ra t i o o f u n r e a c t e d ga mm a par t i c l e s t o t h e ga mm a-1 an d ga mm a r e a c t i on p r o d u c t s . I n ge n e r a l , t he m a n u f a c t urer's instructions for manipulation should be f o l l o w ed pre c i s e l y t o en s u r e m a x im u m s t reng t h . · Over triturated amalgam tends to crumble and is difficult to condense. It e x h i b i t s a s h o r t ened w o r k i n g t i m e . U n der t r i t u r a t e d a m a l ga m h a s a m u s h y- gra i n y f ee l b e c a u s e no t a l l p a r t i c l e s a r e b r o k e n do w n . T he m a s s i s d i f f i c u l t t o c o n den s e . E XP E R I E NC E O F AN O PE RA T OR S o m e o p e r a t o r s d i s c ourage t he u s e o f den t a l a m a l ga m be c au s e o f t h e p o s s i b i l i t y o f f a i l u r e s . A m a l g a m re s t ora t i o n requ i re s p r o per m a n i pu l a t i o n o f t h e m a t e r i a l and a v e r y t horou g h j o b o n t he p ar t o f t h e o p e r a t o r . E v er y s t e p f r o m t h e c a v i t y de s i g n t o t he u s e o f m a t r i x ban d a nd r u b ber d a m p l a y s a v er y i m po r t a n t r o l e . I m prop e r u s e o f m a t r i x b a nd s c a n f or m o v erha n g s . A m a l g a m requ i re s proper f i n i s h i n g a nd po li s h i ng . A m a l g a m re s t ora t i o n s a r e a l s o pro n e t o s e c o nd a r y c ar i e s a n d m a r g i n a l brea k do w n . F ur t her m o r e , w he n p a t i e n t b i t e t he y p l a c e a l o t o f f o r c e on t h e o c c l u s i o n w h i c h m a y l ea d t o per i o don t a l p rob l e m s . H o w e v er , s o m e op e r a t o r s t h i n k o t h e r w i s e . S o m e o f t he m s t i l l re c o mm end den t a l a m a l g a m be c a u s e a c c ord i n g t o t he m t h i s i s a v e r y go o d m a t er i a l f o r l a r g e M O D c a v i t i e s . T h i s i s b e c a u s e a m a l g a m h a s h i g h s t re n g t h . I t i s v er y c o s t -e f f e c t i v e and l on g - l a s t i ng . I t b e i n g a on e - a p po i n t m en t p l a c e m en t f ur t h e r m a k e s den t i s t s w or k e a s i e r . ( Z e e na t : B D S 4 , 20 0 5 ) M Y E XP E R I E NC E A S A N O B S E R VER F ro m m y o b s er v a t i on i n t h e c l i n i c I c a n c o n c l u d e t h a t a m a l ga m c a n b e a v e r y g o o d re s t ora t i v e m a t er i a l a l t h o ugh i t req u i re s a l o t o f w or k . A m a l g a m ne e d s t o b e m an i p u l a t e d prope r l y . E v en t he t r i t ura t i o n t i m e m a k e s a d i f f eren c e t o t h e re s t ora t i o n . T h e c a v i t y d e s i gn ha s t o be p er f e c t . M a t r i x ba n d s s h o u l d b e u s e d prop e r l y t o a v o i d o v e r h a n g s . Loo k i n g a t t h e h i g h c a s e s o f M O D c a v i t i e s i n our P a c i f i c R eg i o n , I t h i n k a m a l ga m f i ll i ng w ou l d b e t he be s t op t i o n s i n c e a m a l g a m h a s a l o n g l i f e - s p an (5-10 y e a r s ) pro v i d e d goo d ora l h y g i e n e i s m a i n t a i ne d a nd i t c an w i t h s t and f o r c e . H o w e v er , i f t h e c a v i t y i s n o t s o l a r ge t he n o t her m a t e r i a l s s u c h a s c o m p o s i t e s w h i c h h a v e go o d e s t h e t i c q u a l i t i e s c a n b e u s e d . PDF created with pdfFactory Pro trial version www.pdffactory.com 24
C O N C L U S I ON W i t h r e gard s t o t he i n f or m a t i o n g i v en i n t he p or t f o l i o , un d e r s t a nd i ng t h e c he mi c a l n a t ure and ph y s i c a l p r o per t i e s o f a m a t er i a l im pro v e s a c li n i c i an's ability to make g o od j u d g m en t . H i s t o r i c a l l y , a m a l ga m re s t ora t i on s ha v e be e n a m o ng t h e m o s t c o m m o n o f a ll d e n t a l re s t ora t i o n s . T h e u s e o f h i g h - c opp e r a m a l ga m s h a s i m pro v ed dra m a t i c a ll y t he c l i n i c a l l o n ge v i t y o f a m a l g a m ( 5 - 1 0 y e a r s u n der i de a l c ond i t i o n s ) . I t s m a j or a d v a n t a ge h a s b e en t h e d e c li ne i n t h e c a s e s o f m i c r o l e a k ag e . T he u s e o f pre c a p s u l a t e d a m a l g a m ha s r e du c ed s i g n i f i c a n t l y t h e r i s k o f e x p o s ure o f den t a l p e r s o n n e l t o m e r c u r y v apor . A s u cc e ss f u l a m a l g a m r e s t o r a t i on de p en d s o n t he prop e r t r i t u ra t i o n , c on d e n s a t i on , c a r v i n g a n d f i n i s h i n g o f a m a l g a m . I m prope r p l a c e m en t c an re s u l t i n l o s t c ha i r t i m e an d l e s s t han d e s i rab l e r e s u l t s . A l t ho u gh s m a l l a m o un t s o f m e r c ur y r e l ea s e f r o m a m a l g a m i s k no w n t o o c c ur , i t d oe s no t c a u s e an y m a j o r h ea l t h p r o b l e m s . H o w e v e r , i t m i gh t c a u s e m i l d a ll e r g i e s i n s o m e p a t i en t s . A l t h o ugh t h e r e are o t h e r a l t e r n a t i v e s t o a m a l g a m t h e y c a n n o t m a t c h a m a l g am's longevity, ease of manipulation and versatility. Hence dental amalgam w i ll be a par t o f den t i s t r y f or a l on g t i m e t o c o m e . PDF created with pdfFactory Pro trial version www.pdffactory.com 25
REC OM M END A T I ON I t ha s be e n i nd i c a t e d i n s e v e r a l l i t e r a t ure s t ha t t he f u t ure re s t ora t i v e m a t e r i a l o f c h o i c e w i l l n o l ong e r be d en t a l a m a l g a m . H o w e v er t he s e l e c t i on o f t he t y p e o f d e n t a l r e s t o r a t i v e m a t e r i a l i s d e pen d en t o n nu m ero u s f a c t or s . T h e f a c t or s t o c o n s i der i n c l u de t h e e x t en t o f t h e l e s i o n , t h e s t ren g t h o f re m a i n i n g t oo t h s t ru c t u r e , t he p r e f ere n c e o f t h e d e n t i s t i n u s i n g t h e m a t e r i a l an d t he f i na n c i a l c o s t o f t he pro c e dure . M o s t pe o p l e i n F i j i a nd e v e n t h o s e li v i ng i n o t h e r P a c i f i c I s l an d c o u n t r i e s are f ro m l o w - s o c i o e c ono mi c b a c k ground . T h e i r d i e t i n c l u d e s h i gh a m o u n t o f c arboh y dra t e s s u c h a s da l o , c a ss a v a , t a r o a n d r i c e . W i t h regard s t o t h e i r i n c o m e t h e y m a y no t b e a b l e t o a f f ord p r o p e r de n t a l c are a n d t h ere f o r e are a t a h i g h r i s k o f ha v i ng den t a l c a r i e s . T h e y p r e s en t t o t he c l i n i c w i t h l a rge M O D c a v i t i e s a n d t h e n e s t he t i cs m a y n o t c o n c ern t he m m u c h . T here a r e no c li n i c a l s c e n a r i o s o f a n y s e v ere m ed i c a l prob l e m s a ss o c i a t e d w i t h t h e u s e o f a m a l ga m a l t hou g h t here m i g h t b e s o m e mi n o r s i d e e ff e c t s i n s o m e p a t i e n t s . D e n t a l a m a l g a m i s u s er f r i e nd l y , s u i t ab l e t o a l l a ge grou p s , dura b l e an d v e r y c o s t -e f f e c t i v e a n d t h e r e f ore v er y s u i t a b l e t o t h e P a c i f i c I s l and e r s a s w e l l a s t he den t i s t s . F ur t her m o r e , i t i s s t r e ss b e ar i ng s o i t w i ll r e m a i n i n t he m a r k e t f or t he y ea r s t o c o m e . K e ep i ng t h i s i n m i nd I w ou l d re c o mm e n d t h e u s e o f den t a l a m a l ga m a s a r e s t o r a t i v e m a t er i a l . PDF created with pdfFactory Pro trial version www.pdffactory.com 26
RE F EREN CE 1 . Cr a i g R G , P o w er s J M , W a t c h a J C . D e n t a l M a t e r i a l s P rop e r t i e s and M an i p u l a t i on. 8 th ed. Mosby; 2004. 2 . M oore P. E l e m e n t s o f D en t a l M a t e r i a l s f o r D en t a l H y g i e n t i s t s a n d D e n t al A s s i s t a n ts. 6 th ed. USA: W.B. Saunders Company; 1994. 3 . M c C abe J E, W a ll s A G . A p p l i e d D e n t a l M a t e r i a ls. 8 th ed. Blackwell publishing; 1 9 98
. 4 . G l ad w i n M , B a g b y M . C l i n i c a l A s p e c t s o f D en t a l M a t e r i a l s - T he o r y , P r a c t i ce a n d C a s es. 2 nd ed. USA: Lippincott Williams and Wilkins; 2004. 5 . http://subrav.tripod.com/amalfail.htm#tarnish 6 . http://www.yourhealthbase.com/amalgams.html 7 . http://dentistry.ouhsc.edu/intranet-web/Courses/OPDT8451/OpDent1_00- 0 3 / B onded A m al 8 . http://www.health.gov/enviroment/amalgam/amalgamu.htm 9 . http://www.medsci.uu.se/occmed/webkurs/trends/hg.htm 1 0 . http://www.mercuryfreemow.com/ 1 1 . http://wwwwsda.org/dentists/s-wastewater.view 1 2 . h tt p : //www.health.gov/environment/amalgam1/selection.htm 1 3 . http://www.ec.gc.ca/MERCURY/EN/longd2.cfm 1 4 . http://www.maxillofacialcenter.com/BondBook/mucosa/amaltattoo.html 1 5 . http://www.dentalindia.com/ccamal.html 1 6 . Dr L een u R a j u : D en t a l M a t er i a l s M anu a l 1 7 . Z e e na t - BDS 4 (2005) PDF created with pdfFactory Pro trial version www.pdffactory.com 27
A P P E N D I X PDF created with pdfFactory Pro trial version www.pdffactory.com 28
DHG 2 4 4 M e t a l s i n d e n ti s t r y O b j e c t i v e s 1 . Define: a . alloy b . dental amalgam c . casting d . wroughting e . solder f . margination of the amalgam restoration g . finishing of an amalgam restoration h . recontouring of the amalgam restoration i . polishing of the amalgam restoration 2 . State components of the amalgam restoration. 3 . Identify advantages and disadvantages of the amalgam restoration. 4 . Describe mercury and identify potential hazards associated with this metal. 5 . Identify safety measures to be taken when working with mercury according to ADA and O S HA s t a n d a r d s . 6 . Describe properties that the following metals contribute to the dental amalgam: a . silver b . tin c . copper d . zinc 7 . Define and describe the significance of mercury to ally ratio in the dental amalgam. 8 . Define trituration and describe factors affecting a proper mix of the amalgam. 9 . Describe condensation of the amalgam and the objectives for this step of the amalgam p l a ce m e n t p r o c e du r e . 1 0 . Describe the setting of the amalgam including chemical process and time span. 1 1 . Describe factors affecting dimensional changes in the amalgam restoration. 1 2 . Define metal creep and explain the significance in the amalgam restoration. 1 3 . Discuss factors affecting the resulting strength of the amalgam restoration. 1 4 . List the classification of dental casting gold alloys and their recommended uses. 1 5 . Identify various metals used in the manufacture of gold lloy and discuss the properties t h a t e ac h c on t r i b u t e t o t h e r e s u l t i n g a l l o y . 1 6 . Describe the steps followed in casting the gold alloy for restorative products. 1 7 . Discuss uses of the gold alloy in dental restorations and the advantages and disadvantages o f t h i s m e t a l . 1 8 . D e s c r i b e a nd d e m o n s t r a t e s t e p s i n p o l i s h i n g a m a l g a m s . PDF created with pdfFactory Pro trial version www.pdffactory.com