7/21/2019 1-In Vivo Cusp Fracture of Endodontically Treated Premolars Restored With MOD Amalgam or MOD Resin Fillings

http://slidepdf.com/reader/full/1-in-vivo-cusp-fracture-of-endodontically-treated-premolars-restored-with-mod 1/5

I n v i v o c u s p f r a c t u r e o f

e n d o d o n t ic a l ly t r e a t e d

p r e m o l a r s r e s t o r e d w i t h M 0 Dam algam or M 0D res i n fillin gs

E . K . H a n s e n

Depar tment o f Techno logy, Roya l Denta lCo l lege, Copenhagen, Denmark

H a n s e n E K . In vivo c u s p f ra c t u r e o f e n d o d o n t i c a l l y t r e a t e d p r e m o l a r s r e s t o r e d

w i t h M O D a m a l g a m o r M O D r e s in fi ll in g s . D e n t M a t e r 1 9 88 : 4 : 1 69 - 17 3 .

A b s t r a c t - T h e f r e q u e n c y o f c u sp f r a c tu r e o f e n d o d o n t i c a U y t re a t e d p r e m o l a r s

w a s i n v e s t ig a t e d i n a r e t r o sp e c t i v e s tu d y . A f t e r e n d o d o n t i c t h e r a p y , t h e t e e t h

w e r e e i t h e r r e s t o r e d w i th a M O D a m a l g a m f il li n g o r w i th a n e n a m e l - b o n d e d

M O D r e s in f i ll in g . A v e r y h ig h f r e q u e n c y o f c u sp f r a c t u r e w a s f o u n d i n

p r e m o l a r s r e s t o r e d w i t h a m a l g a m : n e a r l y o n e - t h i r d f r a c t u r e d w i t h in 3 y e a r s

a f t e r e n d o d o n t i c t r e a t m e n t . T h e f r e q u e n c y o f c us p f ra c t u r e d i f f e re d a m o n g t h e

4 a m a l g a m - r e s t o r e d t e e t h ; t h e l o w e r fi rs t p r e m o l a r h a d a 1 5 - y e a r s u r v iv a l r a te

o f 7 4 % , i n c o n t r a s t to a n a v e r a g e o f 32 % f o r th e o t h e r 3 p r e m o l a r s . N o r e si n -

r e s t o r e d p r e m o l a r f r a c t u r e d d u r i n g t h e f i rs t 3 y e a r s , a n d t h e d i f fe r e n c e b e t w e e n

a m a l g a m a n d r e s i n - r e s t o r e d t e e t h w a s h i g h l y s ig n i fi c a n t a t t h e 0 - 3 y e a r i n te r v a l.

H o w e v e r , f r a c t u r e o f re s i n - r e s to r e d p r e m o l a r s d i d h a p p e n i n t h e f o ll o w i n g 3 - 1 0

y e a r i n t e r v a l. F r o m a p e r i o d o n t a l p o i n t o f v i e w , a lo w f r e q u e n c y o f c u sp

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

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

t e m p o r a r i l y r e s t o r in g e n d o d o n t i c a l l y t r e a t e d p r e m o l a r s w i th M O D c a v i ti e s.

Key words: endodont i c therapy, restorative

dentistry, amalgam, enamel-bonded resin, tooth

failure.

E. Kei th Hansen, Helsing6rsgade 7, DK-3400Hi l ler6d, Denmark.

Received Apri l 27; accepted July 24, 1987.

E n d o d o n t i c t h e r a p y c a u s e s a p r o -

n o u n c e d w e a k e n i n g o f t h e t o o t h a n d a

c o n s e q u e n t h i g h r i s k o f c u sp o r c r o w n

f r a c t u r e . G h e r e t a l . ( 1 ) s t u d i e d t h e

c l i n ic a l f e a t u r e s a s s o c i a t e d w i t h t o o t h

f r a c t u re a n d f o u n d t h a t 7 1 % o f t h e

f r a c t u r e d t e e t h h a d b e e n e n d o d o n t i -

c a l l y t r e a t e d .

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

b e c a u s e t h e f r a c t u r e u s u a l l y e x t e n d s

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

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

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

t h a t t h e t o o t h h a s t o b e e x t r a c t e d . I f t h e

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

f o r t h e d e n t i s t i s b o t h t e c h n i c a l a n d b i o -

l o g i c a l i n n a t u r e , i . e . t h e t e c h n i c a l d i f fi -

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

i t se l f a n d , b y i m p r e s s i o n - t a k i n g , t h e

b i o l o g i c a l r i sk o f f u r t h e r d a m a g i n g t h e

p e r i o d o n t a l t is s u e s (2 ) . E v e n i f t h e d e n -

t i s t s u c c e e d s i n f a b r i c a t i n g a w e l l -

a d a p t e d r e s t o r a t i o n , t h e p a t i e n t m a y

f a c e a n o t h e r p r o b l e m . M a n y i n v e s t i g a -

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

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

i n f l a m m a t o r y p e r i o d o n t a l r e s p o n s e ( 3 -

7 ) . A s a c o n s e q u e n c e o f t h i s , i t h a s b e -

c o m e a c c e p t e d p r o c e d u r e t o m a i n t a i n

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

a r e a w h e n e v e r p o s s ib l e . H o w e v e r , i n

c a s e s o f c u s p f r a c t u r e , o n e n e a r l y a l -

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

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

p o s s i b il i ty o f p e r m a n e n t i n j u r y t o t h e

p e r i o d o n t a l t is s u e s.

I n o r d e r t o p r e v e n t t o o t h f r a c t u r e ,

t h e o p t i m a l r e s to r a t i o n o f e n d o d o n t i -

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

c a s t i n l a y t h a t p r o t e c t s t h e c u s p s ( 8 ) ,

b u t m a n y d e n t i s ts d o n o t f i n d i t a c c e p t -

a b l e t o f a b r i c a t e t h e f i n a l r e s t o r a t i o n

b e f o r e p e r i a p i c a l h e a l in g h a s b e e n c o n -

f i r m e d w i t h r a d i o g r a p h s 6 - 1 2 m o n t h s

l a t e r. H o w e v e r , o n e o f t h e c u s p s , o r t h e

c r o w n i n w h o l e , m a y a c t u a l l y f ra c t u r e

d u r i n g t h i s o b s e r v a t i o n p e r i o d . S t i ll a n -

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

a r e e x p e n s i v e a n d q u i t e a f e w p a t i e n t s

c a n n o t a f f o r d t h e m . I n t h e s e c a s e s, t h e

d e n t i s t h a s b u t t w o c h o i c e s : a m a l g a m

o r c o m p o s i t e r e s i n .

T h i s r e t r o s p e c t i v e s t u d y w a s u n d e r -

t a k e n t o e x a m i n e w h e t h e r , a n d t o w h a t

e x t e n t , t h e u s e o f a n e n a m e l - b o n d e d

r e s t o r a t iv e r e s i n i n M O D c a v i ti e s o f e n -

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

d u c e d t h e f r e q u e n c y o f to o t h f r a c t u r e

w h e n c o m p a r e d t o e n d o d o n ti c a ll y

t r e a t e d p r e m o l a r s r e s t o r e d w i t h a

M O D a m a l g a m f i ll in g .

M a t e r ia l a n d m e t h o d s

T h e m a t e r i a l w a s c o l le c t e d fr o m M a y

1 9 8 6 t o F e b r u a r y 1 9 8 7 f r o m 8 d e n t i s t s

w o r k i n g a s g e n e r a l p r a c t i t i o n e r s . T h e

d a t a w e r e d e r i v e d f r o m c l in i c a l e x a m -

i n a t i o n s a n d r e v i e w o f t h e p a t i e n t s '

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

T h e l i m i t i n g c r i t e r i a f o r a c c e p t a n c e

o f d a t a w e r e t h e f o l lo w i n g : ( i) a n M O D

c a v i ty in a n e n d o d o n t i c a l l y tr e a t e d p r e -

m o l a r e i t h e r r e s t o r e d w i t h a m a l g a m o r

r e s t o r e d w i t h a c o m p o s i t e r e s i n a f t e r

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

( i f ) n o w e a k e n i n g o f a n y o f t h e c u s p s

c a u s e d b y a C l a s s V r e s t o r a t i o n ; ( i i i )

n o r m a l o c c l u s io n a n d a r t i c u la t i o n ; a n d

( i v ) c o m p l e t e p e r m a n e n t d e n t i t i o n i n

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

a t le a s t o n e m o l a r i n e a c h q u a d r a n t i n -

v o l v e d i n t h e o c c l u s i o n . T h e f o l l o w i n g

i n f o r m a t i o n w a s re c o r d e d : n a m e o f t h e

12 DentalMaterials4:4. 1988

7/21/2019 1-In Vivo Cusp Fracture of Endodontically Treated Premolars Restored With MOD Amalgam or MOD Resin Fillings

http://slidepdf.com/reader/full/1-in-vivo-cusp-fracture-of-endodontically-treated-premolars-restored-with-mod 2/5

1 7 0 H a n s e n

individual tooth, date of endodont ic

therapy, restorative material, and date

of control. For restorations with a com-

posite resin: type of cavity preparation

(bevel or butt-joint), use of an i nterme-

diate layer of low-viscous resin, and ap-

plication technique (bulk or incre-

ment). In cases of fracture, the dentists

were asked to record the date of regis-

tration of fracture, whether the fracture

involved the facial cusp, the lingual

cusp, or the crown as a whole, and also

whether the fracture resulted in extrac-

tion of the tooth. Informa tion was ob-

tained on 222 endodontic ally treated

premolars restored with either a MOD

amalgam or an enamel -bonded MOD

resin filling. It should be emphasized

that the restorative resins in this study

were applied after previous acid-etch-

ing of the ena mel, but without use of a

dentin- bonding agent.

Trial time of the endodontically

treated premolars was defined as the

time elapsing between the date of en-

dodontic therapy and (a) the date of

fracture; (b) the date of last contact ; (c)

the date of withdrawal; or (d) the

date of final registration. Total trial

time was arranged into intervals of one

year and, for each interval, the effec-

tive numb er of teeth exposed to risk of

fracture was calculated. The cumula-

tive survival rate was then calculated

using life table analysis (9, 10). Ana-

lyses of differences between the cum-

ulative survival rate of each of the 4

premolars and of differences between

MOD amalgam and MOD resin restor-

ations were tested at the 5% level of

significance by means of Chi-square

tests (10).

Resu l ts

Table 1 shows the num ber of endo don-

tically treated premolars restored with

Table 1. Number of endodontically treatedpremolars restored with a MOD amalgam orwith an enamel-bonded MOD resin filling.Number of fractures are shown in paren-theses.

Tooth MOD restorationsnumber*

Amalgam Resin

14, 24 48 (27) 23 (2)15, 25 70 (45) 11 (3)34, 44 13 (3) 2 (0)35, 45 50 (27) 4 (0)

Total 181 (102) 40 (5)

* = Viohl's two-digit system.

10 0

8 O

L UI- -

r

6o

U .I

40

g(. 9

20

%

9 ".

' , . ' \

\ - . .\ \ " - %

\ \ " ' . .

\ \ " ' ., . . . . . . . . . .

I I I I I I I _ Y E A R S A F T E R

2 /. 6 8 10 121 4

TREATMENT

Fig. 1. Cumulative survival rate of endodontically treated premolars restored with MODamalgam fillings. - . . . . lower first premolars; . . . . . . lower second premolars; - - = upperfirst premolars; . . . . upper second premolars.

a MOD amalgam or with an enamel-

bonded MOD resin filling.

F r a c t u r e p a t t e r n . Less than 10% of the

fractures included the crown as a

whole, i.e. usually only one of the cusps

was lost. When the latter occurred, the

facial cusp of the upper first premolar

fractured in 52% of the cases, in con-

trast to 29% for the upper and lower

second premolar. This difference was

statistically significant at the level of p

<0.05. The lower first premolar only

fractured lingually. The cusp fracture

nearly always ended subgingivally, and

3 of the teeth had to be extracted be-

cause of vertical root fracture.

M O D a m a l g a m . Within the first year

after endodontic therapy, 13% of the

premolars fractured and nearly one-

third failed during the first 3 years. Th e

cumulative survival rates for each of

the 4 premolars are shown in Fig. 1; for

the sake of clarity, 95% confidence in-

tervals are omitted. The lower first pre-

molar had the highest 15-year survival

rate (74%), while the upper second

premolar showed the lowest survival

rate (26%). No statistically significant

difference was found between the sur-

vival rates of the 2 upper premolars an d

that of the lower second premolar (p

>0.1), while the difference between

these 3 teeth and the lower first premo-

lar was statistically significant at the

level of p < 0.05.

M O D r e s i n . The restorative resins were

all chemically activated (Table 2); the

"unknown" resin was assessed as being

a chemically activated macrofilled com-

posite because of the surface texture,

and the fact that this restoration was

made in 1974, i.e. before both micro-

filled, hybrid, and light-activated com-

posites were marketed. Tooth failure

was independen t of the type of compos-

ite resin used (Table 2); cusp fracture

was thus found with both Adaptic and

Concise (macrofilled), Silar (micro-

filled) and P-10 (hybrid). The vast ma-

jority of the resin-restored teeth were

upper premolars, among which all 5

fractures were found (Table 1).

A bulk application technique was

used in 4 of the 5 fractured teeth; as to

the fifth fracture, no inf ormation on ap-

plication technique was obtaina ble.

Bevel preparation, both occlusally

and proximally, followed by applica-

Table 2. Restorative resins used and numberof fractures.

Material Type Number Fractureof teeth

Adaptic Ma 1 lConcise Ma 20 2P-10 Hy 9 1Silar Mi 9 1Unknown Ma 1 0

Ma = macrofilled; Mi = microfilled;Hy = hybrid.

7/21/2019 1-In Vivo Cusp Fracture of Endodontically Treated Premolars Restored With MOD Amalgam or MOD Resin Fillings

http://slidepdf.com/reader/full/1-in-vivo-cusp-fracture-of-endodontically-treated-premolars-restored-with-mod 3/5

F r e q u e n c y o f c u s p f r a c t u r e i n v i v o 171

t i o n o f a l o w - v i s c o u s r e s i n , w a s u s e d i n

3 0 o f t h e 4 0 r e s i n - r e s t o r e d p r e m o l a r s ;

n o i n f o r m a t i o n o n b e v e l / b u t t - jo i n t an d

l o w - v i s c o u s r e s i n w a s o b t a i n a b l e f o r t h e

r e m a i n i n g 1 0 fi l li n g s . F o u r o f t h e 5 f r a c -

t u r e s w e r e f o u n d i n t e e th w i t h b e v e l e d

c a v i t y m a r g i n s .

A m a l g a m v s . r e s i n . A s m e n t i o n e d e a r -

l i e r , t h e c u m u l a t i v e s u r v i v a l r a t e o f

a m a l g a m - r e s t o r e d l o w e r f ir st p r e m o l a r s

w a s s i g n i f i c a n t l y h i g h e r t h a n t h e s u r v i -

v a l ra t e s o f t h e 3 o t h e r p r e m o l a r s ( F i g .

1 ) . L o w e r f i r s t p r e m o l a r s a r e t h e r e f o r e

n o t i n c l u d e d i n t h e s t a t i st i c a l a n a l y s i s o f

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

M O D a m a l g a m a n d M O D r e si n -r e -

s t o r e d t e e t h . A s e p a r a t e a n a l y s i s o f

l o w e r f i r st p r e m o l a r s i s m e a n i n g l e s s b e -

c a u s e o f th e s m a l l n u m b e r o f o b s e r v a -

t i o n s ( T a b l e 1 ) .

T h e p o o l e d c u m u l a t i v e s u r v i v a l r a t eo f t h e u p p e r f i r st p r e m o l a r s , t h e u p p e r

s e c o n d p r e m o l a r s a n d t h e l o w e r se c o n d

p r e m o l a r s i s s h o w n i n F ig . 2 .

C h i - s q u a r e a n a l y s i s i n a 2 x 2 c o n -

t i n g e n c y t a b l e r e q u i r e s t h a t t h e e x -

p e c t e d f r e q u e n c y i n e a c h c e l l n o t b e t o o

s m a l l ; th e i n t e r v a ls a n a l y z e d w e r e

t h e r e f o r e r e s t r i c t e d t o 0 - 3 y e a r s , 3 - 6

y e a r s , a n d 6 -- 10 y e a r s . A n a l y s i s b e y o n d

1 0 y e a r s w a s n o t m a d e b e c a u s e o n l y 8

r e s i n r e s t o r a t i o n s w e r e o l d e r t h a n 1 0

y e a r s , a n d o n l y 4 r e s t o r a t i o n s w e r e o l -

d e r t h a n 1 1 y e a r s . T h e a n a l y s i s ( T a b l e

3 ) s h o w e d a h i g h l y s i g n i f ic a n t d i ff e r -e n c e b e t w e e n t h e s u r v i v a l r a t e o f a m a l -

g a m a n d r e s i n - r e s t o r e d p r e m o l a r s a t p

< 0 . 0 0 1 ; t h e m a i n r e a s o n w a s t h a t n o

r e s i n - r e s to r e d t o o t h f r a c t u r e d d u r i n g

t h e f i r st 3 y e a r s . T h e r e s i n - r e s t o r e d p r e -

m o l a r s h a d a s l i g h t ly b e t t e r s u r v i v a l

r a t e d u r i n g t h e 3 ~ 5 a n d 6 - 1 0 y e a r in t e r -

v a l s ( F i g . 2 ; T a b l e 3 ) , b u t t h i s d i f f e r -

e n c e w a s n o t s t a t i s t ic a l l y s i g n i f ic a n t ( p

> 0 . 0 5 ) .

Discussion

L i k e a l l r e t r o s p e c t i v e s t u d i e s , t h i s i n -

v e s t i g a ti o n h a s a n i n h e r e n t d i s a d v a n -

t a g e i n t h a t t h e d a t a o b t a i n e d f r o m r e -

v i e w o f t h e p a t i e n t s ' r e c o r d s o n l y p a r -

t ia l ly a n s w e r e d t h e q u e s t io n s a s k e d .

M a n y e s s e n t i a l d e t a i ls m a y b e l o s t i n a

r e t r o s p e c t i v e s t u d y b e c a u s e m o s t p a -

t i e n t r e c o r d s d o n o t c o n t a i n a l l t h e i n -

f o r m a t i o n n e e d e d f o r a c a r e fu l i n v e s ti -g a t i o n . T h i s p r o b l e m d o e s n o t p r e v e n t

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

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

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

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

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

n u m b e r o f r e s i n - re s t o r e d t e e t h w a s

r a t h e r s m a l l .

L a b o r a t o r y s t u d i e s h a v e s h o w n t h a t a

n o n - b o n d e d i n t r a c o r o n a l r e s t o r a t i o n

d o e s n o t s t re n g t h e n t h e t o o t h , a n d t h a t

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

w i t h M O D c a v i t ie s r e s t o r e d w i th a m a l -

g a m o r w i th a n o n - b o n d e d c o m p o s i ter e s i n is s i m i l a r t o t h a t o f p r e m o l a r s w i t h

a n u n f i l l e d M O D c a v i t y ( 8 , 1 1 , 1 2 ).

S e v e r a l a u t h o r s h a v e p u b l i s h e d p a p e r s

o n t h e r e i n f o r c i n g ef f e ct o f a n e n a m e l -

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

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

i n g a g e n t , a s in v e s t i g a t e d in t h e p r e s e n t

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

R e e l & M i t c h e l l ( 1 3 ) , E a k l e ( 1 4 ) a n d

S t a m p a l i a e t a l . ( 1 5 ) d i d n o t f i n d a s ig -

n i f i c a n t i n c r e a s e i n t h e f r a c t u r e r e s i s -

t a n c e , i n c o n t r a s t w i t h S i m o n s e n e t a l ,

( 1 1 ), D o u g l a s ( 1 2 ) a n d M a c k e n z i e ( 1 6) ,

w h o a ll f o u n d t h a t p r e m o l a r s w i th e n -a m e l - b o n d e d c o m p o s i t e r e s t o r a t i o n s

w e r e s t r o n g e r t h a n t h o s e e i t h e r re -

s t o r e d w i t h a m a l g a m o r l e f t u n r e s t o r e d .

H o w e v e r , m e t h o d s u s e d i n v i t ro t o

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

w i th a n M O D p r e p a r a t i o n m a y n o t r e -

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

I n t h e p r e s e n t i n v e s t ig a t i o n o n l y 3 o f

t h e 1 0 7 f r a c t u r e s w e r e s o v e r t i c a l t h a t

t h e t o o t h h a d t o b e e x t r a c t e d . T h i s l o w

f r e q u e n c y o f v e r t i c a l fr a c t u r e i s n o t i n

a c c o r d a n c e w i t h th e i n v i t ro r e s u l t s p r e -

s e n t e d b y S t a m p a l i a e t a l. ( 1 5 ) ; t h e s e

a u t h o r s f o u n d t h a t a l l e x c e p t o n e o f 22

f r a c t u r e s o c c u r r e d a s a m i d d l e s p l i t o f

t h e t o o t h t h r o u g h t h e p u l p a l f lo o r o f

t h e c a v i ty p r e p a r a t i o n . T h e d i s c r e p a n c y

b e t w e e n t h e r e s u l t s o f t h e p r e s e n t s t u d y

a n d t h e r e s u l t s p u b l i sh e d b y S t a m p a l i a

e t a l . ( 15 ) m a y v e r y w e l l b e c a u s e d b y

t h e d i f f e r e n t d i m e n s i o n s o f t h e M O D

c a v i t ie s . A f u r t h e r p o s s i b l e e x p l a n a t i o nh a s b e e n g i v e n b y C r a i g ( 1 7 ) , w h o

p o i n t e d o u t t h a t i n v i t ro t e s t i n g o f a r i -

g i d ly s u p p o r t e d t o o t h i g n o r e s t h e r e -

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

A l s o , i t d o e s n o t s e e m v e r y l i k e ly , co n -

s i d e ri n g t h e c o m p l e x o c c l u s a l f u n c t io n ,

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

c o m p l e t e ly r e p r o d u c e d i n v i t ro w i t h t h e

t e s t m e t h o d s u s e d ( 1 1 -1 6 ) .

T h e m o s t a s t o n i s h i n g f i n d i n g i n t h e

p r e s e n t s t u d y W a s t h e v e r y h i g h f r e -

q u e n c y o f c u s p f r a c t u r e o f t h e a m a l -

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

o n e - t h i r d f r a c t u r e d w i t h in 3 y e a r s a f t e re n d o d o n t i c t r e a t m e n t ( T a b l e 3 ) . T h e s e

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

r e s u lt i n p e r m a n e n t i n j u r y to t h e p e r i o -

d o n t a l t i s s u e s n o t o n l y b e c a u s e o f t h e

f r a c t u r e i t s e l f , b u t a l s o b e c a u s e e v e n a

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

e v e r b e s u r r o u n d e d b y t h e sa m e

h e a l t h y p e r i o d o n t a l t is s u e s a s th e n a t u -

r a l t o o t h s u r f a c e i t s e l f (3 - 7 ) .

T h e f re q u e n c y o f fr a c t u r e d i f fe r e d

a m o n g t h e 4 a m a l g a m - r e s t o r e d p re m o -

l a r s (F i g . 1 ) . T h e h i g h 1 5 - y e a r s u rv i v a l

r a t e o f t h e l o w e r f i rs t p r e m o l a r ( 7 4 % )

c o m p a r e d t o a n a v e r a g e o f 3 2 % f o r t h eo t h e r t h r e e p r e m o l a r s ( F i g s . 1 a n d 2 ) is

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

f o r m a n d t h e l o c a t io n o f t h e t o o t h . A s

t o t h e l a t t e r , L e i n f e l d e r ( 1 8 ) h a s p r e -

s e n t e d a w e a r f a c t o r o f c o m p o s i t e r e si n

a s a f u n c t i o n o f l o c a t i o n : t h e l o w e r f i r st

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

1 x , t h e u p p e r f ir s t p r e m o l a r 3 x , a n d

t h e tw o s e c o n d p r e m o l a r s 4 x . T h e s e

w e a r f a c t o r s , b e i n g a f u n c t i o n o f l o -

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

w i t h t h e d i f f e r e n t f r e q u e n c i e s o f c u s p

f r a c tu r e o f t h e 4 p r e m o l a r s f o u n d i n t h e

p r e s e n t s t u d y ( F i g . 1 ) .

Table 3 . C hi - square analys is o f surv ival r a t es ( cusp/crown f r ac ture) of endod ont i ca l ly t r ea t ed perm olar s r es tor ed wi th M OD amalgam f il li ngsor wi th enam el -bond ed MO D res in f il li ngs.

Years af tert r e a t m e n t

M O D a m a l g a m r e s to r a t io n s M O D r e si n r e s to r a t io n s

1~ dx Ux l'x l'~-d ~ lx d~ u~ 1'~ l' x -d~ ;(2

0-3 168 53 9 163.5 110.5 38 0 1 37.5 37.5 16.5093-6 106 17 11 100.5 83.5 37 3 5 34.5 31.5 1.3756-10 78 19 9 73.5 54.5 29 2 19 19.5 17.5 2.144

Total Chi-squ are 20.028

1• = intac t at beg inning of interval ; d x = fai l lures dur ing interva l ; ux = withdrawn and los t cases dur ing interval ; 1 'x = effective num bersexposed to r i sk of f r ac ture .

12"

7/21/2019 1-In Vivo Cusp Fracture of Endodontically Treated Premolars Restored With MOD Amalgam or MOD Resin Fillings

http://slidepdf.com/reader/full/1-in-vivo-cusp-fracture-of-endodontically-treated-premolars-restored-with-mod 4/5

172 H a n s e n

100

80

IL l

t Y

<

> 6 0

W>

~ 40<

IE

20

I I I

2 4 6 8

YEARS AFTERI I t

10 12 14 TREATMENT

Fig . 2 . Pooled cumulative survival rate of endodontically treated upper first premolars, up-per second premolars and lower second premolars. 9 = MOD amalgam restorations; o =enamel-bonded MOD resin restorations. Vertical bar = 95% confidence interval.

The frequency of facial cusp fracture

of the upper first premolars (52%),

compared with 29% for the upper and

lower second premolars, may be re-

lated to the anatomical form of both

the pulp chamber and the cusps (19).

The difference between the height of

the 2 cusps is more pronounced in the

upper first than in the upper second

premolar, and the occlusal slope of the

facial cusp is more steep (19), render-

ing the facial cusp of the upp er first pre-

molar more susceptible to fracture than

the lingual cusp. As to the 2 lower pre-

molars, endodontic therapy will most

often result in a weak lingual cusp.

Another interesting fact arises from

Fig. 2, which shows the cu mulat ive sur-

vival rates of amalgam and of resin-

restored premolars. The 3-year survival

rate of resin-restored teeth was mark-

edly better that that of the amalgam-

restored teeth. The difference between

the short-term survival rate of amalgam

and of resin-restored premolars can be

illustrated by the fact that this differ-

ence would still have been statistically

significant (p = 0.02) e ven if 5 of the 38

resin-restored teeth had fractured dur-

ing the first 3 years after endodontic

treatment.

After 3 years, cusp fracture of resin-

restored premolars happened with

nearly the same frequency as amalgam-

restored teeth. The combined use of

bevel and a low-viscous resin could no t

prevent tooth failure. This confirms the

i n v i t r o results published by Reel &

Mitchell (13) and by Douglas (12), who

did not find a significant difference be-

tween the fracture resistance of MOD

cavities with beveled or with butt-joint

cavity margins.

There are 2 more variables in the

present study which should be dis-

cussed, i.e. the application technique

and the fact that the restorative resins

were used without a dentin-bonding

agent.

As to the application technique, no

information was obtainable on one of

the 5 fractures; the other 4 failures

were found in premolars where the re-

storative resin had bee n applied with a

bulk technique. In this context it is in-

teresting that the polymerization con-

traction of bulk-applied restorative re-

sins in MOD cavities causes a defo rma-

tion of the cusps (20-22). The fractures

found in the resin-restored premolars

may have been initiated by an incom-

plete cusp fracture caused by the

stresses induced in the enamel during

the polymerization contraction of the

restorative resin. A possible solution to

this problem may be to use an oblique

incremental technique, which reduces

the wall-to-wall polymerization con-

traction (23) and thereby the cuspal de-

formation (21, 22).

No den tin-bond ing agent was used in

the resin-restored premolars and it is

thus possible that the fracture resis-

tance could have bee n increased. How-

ever, the i n v i t r o results published on

the effect of these bonding agents are

contradictory: Douglas (12) a nd Eakl e

(14) found that a den tin-bon ding agent

increased the fracture resistance of

MOD-prepared premolars, while Reel

& Mitchell (13) did not find a signifi-

cant improvement. Also, no commer-

cial dent in-bondi ng agent is as yet

strong enough to totally prevent the

formation of a contraction gap (24).

Furthermore, even strong bonding

agents have only a mediocre effect on

the high-viscous composites intended

for use in posterior teeth (25). Thus, it

is possible, but not evident, that the

frequency of cusp fracture found in the

present study could have bee n reduced

had a dent in-bond ing agent been ap-

plied.

In conclusi on, the possibility of using

enamel-bonded composites as tempor-

ary restorations for endodontically

treated premolars should be Consid-

ered. There are, of course, still many un-

solved problems with regard to the use

of composite resins in posterior teeth

and especially in large MOD cavities;

wear resistance and marginal leakage,

just to mention two of the problems.

However, from a periodontal point of

view, the low frequency of cusp frac-

ture carries great weight.

A c k n o w l e d g e m e n t - This paper was sup-ported in part by the Research Foundationof the Danish Dental Association.

R e f e r e n c e s

1. Gher ME, Dunlap RM, Anderson MH,Kuhl LV. A clinical survey of fracturedteeth. J D e n t R e s 1986:6 5 : 825. Abstr.891.

2. Wunderlich RC, Caffesse RG. Perio-dontal aspects of porcelain restorations.

D e n t C l in N o r t h A m 1985:29 : 693-703.3. App GR. Effect of silicate, amalgam,

and cast gold on the gingiva. J P r o s t h e t

D e n t 1961: 11 : 522-32.4. Silness J. Periodontal conditions in pa-

tients treated with dental bridges. III.The relationship between the locationof the crown margin and the periodontalcondition. J P e r i o d o n t R e s 1970: 5:225-9.

5. Renggli HH, Regolati B. Gingival in-flammation and plaque accumulation bywell-adapted supragingival and subgin-gival restorations. H e l v O d o n t o l A c t a

1972: 16 : 99-101.6. Maruyama T, Simoosa T, Ojima H.

7/21/2019 1-In Vivo Cusp Fracture of Endodontically Treated Premolars Restored With MOD Amalgam or MOD Resin Fillings

http://slidepdf.com/reader/full/1-in-vivo-cusp-fracture-of-endodontically-treated-premolars-restored-with-mod 5/5

Frequency of cusp fracture i n v i v o 1 7 3

M o rp h o l o g y o f g i n g i v a l c a p i ll a r i e s a d j a -

c e n t t o c o m p l e t e c r o w n s . J Prosthet

Dent 1976: 35: 1 7 9 -8 4 .

7 . Va l d e rh a u g J . Pe r i o d o n t a l c o n d i t i o n s

a n d c a r i o u s l e s i o n s fo l l o wi n g t h e i n se r -

t i o n o f f i x e d p ro s t h e se s : a 1 0 -y e a r fo l -

l o w-u p s t u d y . Int Dent J 1980: 30: 2 9 6 -

304.

8 . H o o d J A A . M e t h o d s to i m p r o v e f r a c-t u r e r e s i s t a n c e o f te e t h . I n : V a n h e r l e G ,

S m i t h D C , e d s . Posterior composite re-

sin dental restorative materials. T h e

Ne t h e r l a n d s : Pe t e r Sz u l c , 19 8 5: 4 4 3 -5 0 .

9 . C u t l e r S J , E d e r e r E M a x i m u m u t i li z a -

t i o n o f t h e l i f e t a b l e m e t h o d i n a n a l y z in g

su rv i v a l . J Chronic Dis 1958: 8 : 699-

712 .

1 0 . Tb y l s t ru p A, R 6 1 1i ng I . Th e l i f e t a b l e

me t h o d i n c l i n i c a l d e n t a l r e se a rc h .

Community Dent Oral Epidemiol 1975:

3 : 5 -1 0 .

1 1. S i m o n s e n R J , B a r o u g h E , G e l b M .

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

re s i n i n C l a s s I I r e s t o ra t i o n s . J Dent Res

1983: 62: 2 5 4 . Ab s t r . 7 6 1 .1 2. D o u g l a s W H . M e t h o d s t o i m p r o v e f ra c -

t u r e r e s i s t a n c e o f t e e t h . I n : V a n h e r l e G ,

S m i t h D C , e d s . Posterior composite re-

sin dental restorative materials. T h e

Ne t h e r l a n d s : Pe t e r Sz u l c , 1 9 8 5 : 4 3 3 -4 1 .

1 3 . R e e l DC , M i t c h e l l R J . F ra c t u re re s i s -

t a n c e o f t e e t h r e s t o r e d w i t h C l a s s I I

c o m p o s i t e r e s t o r a t i o n s . J Dent Res

9 1984: 63: 2 7 6 . Ab s t r . 9 5 0 .

1 4. E a k l e W S . F r a c t u r e r e s i s t a n c e o f t e e t h

r e s t o r e d w i t h C l a s s I I b o n d e d c o m p o s i t ere s i n . J Dent Res 1986: 65: 1 4 9 -5 3 .

1 5 . S t a m p a l i a LL , N i c h o I l s J I , B ru d v i k JS ,

J o n e s D W . F r a c t u r e r e s i s t a n c e o f t e e t h

w i t h r e s i n - b o n d e d r e s t o r a t i o n s . J Pros-

thet Dent 1986: 55: 6 9 4 -8 .

1 6. M a c k e n z i e D E T h e r e i n f o r c i n g e f f e ct o f

me s i o -o e c l u so d i s t a l a c i d -e t c h c o mp o s i t e

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

t e e t h . Br Dent J 1986: 161: 4 1 0 ~ .

1 7. C r a i g R G . O p e n d i s c u s s io n o f D o u g l a s /

H o o d p a p e r s . I n : V a n h e r l e G , S m i t h

D C , e d s . Posterior composite resin den-

tal restorative materials. T h e N e t h e r -

l a n d s : Pe t e r Sz u l c , 1 9 8 5 : 4 5 1 -2 .

1 8. L e i n f e l d e r K E C o m p o s i t e r e s i n s. Dent

Clin North Am 1985: 29: 3 5 9 -7 1 .1 9 . C a r l se n O. Ta n d mo rfo l o g i sk e sk i t s e r .

C o p e n h a g e n : M u n k s g a a r d , 1 9 8 6 .

2 0 . C a u s t o n B E , M i l l e r B , S e f t o n J . T h e

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

t e r i o r c o m p o s i t e r e s t o r a t i o n s : a n in vitro

s t u d y . Br Dent J 1985: 159: 3 9 7 -4 0 0 .

2 1 . J e n s e n M E , C h a n D C N . P o l y m e r i z a -

t i o n c o n t r a c t i o n a n d m i c r o l e a k a g e . I n :

V a n h e r l e G , S m i t h D C , e d s. Posterior

composite resin dental restorative mate-

rials. T h e N e t h e r l a n d s : P e t e r S z u l c ,1985: 243-62 .

2 2 . M c C u l l o c k A J , S m i t h B G N . In vitro

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

b y a d h e s i v e r e s t o r a t i v e m a t e r i a l s . Br

Dent J 1986: 161: 4 0 5 -9 .

2 3 . H a n s e n E K . E f f e c t o f c a v i ty d e p t h a n d

a p p l i c a ti o n t e c h n i q u e o n m a r g i n a l a d a p -

t a t i o n o f r e s i n s i n d e n t i n c a v i t ie s . J Dent

Res 1986: 65: 1319-21 .

2 4 . H a n s e n EK , A s m u s s e n E . C o m p a r a t i v e

s t u d y o f d e n t i n a d h e s i v e s . Scand J Dent

Res 1985: 93: 2 8 0 -7 .

2 5 . H a n s e n E K . E f f e c t o f t h r e e d e n t i n a d -

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

l i g h t -c u re d c o mp o s i t e s . Scand J Dent

Res 1986: 94: 8 2 -6 .