in vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin.pdf

8/17/2019 In vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin.pdf

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w k ? f r a c t u r e s

of

e n d o d o n t i c a l l y t r e a t e d

s t e r io r t e e t h r e s t o r e d w i t h e n a m e l - b o n d e d

In vivo fractures of endodontically

the M O D resin-restored teeth was equal to that of M O /D O

a macrofilled or hybrid resin. It was also found that a beveling

erm ed iat e layer of low-viscosity resin resulted in a sign ificant

E r ik K e i th H a n s e n , E r ik A s m u s s e n

Ins t i tute

of

Dental Mater ia ls and Technolog

Royal Dental Col lege, Copenhagen, Denmark

Key words: ac id etch-res in technique; res in

t i o n ;

tooth t rac ture; cusp f rac ture.

Er i k Ke i t h Hansen , He is ingorsgade 7 , DK-3

H i l l e r o d , Denma r k

Accep ted

fo r

pub l icat ion Ap r i l

6,

1 9 9 0 .

her risk of fracture tha n does a vital one ( 1- 3) .

f end odo ntica lly treated teeth

t be decreased with an intra-co rona l am algam

amalga m-restored and non -etched resin-restored

An al ternat ive trea tment option, enamel-bonded

teeth are restored with an etch-retained resin f

instead of am alg am . This has been confirmed

in vivo study on endo dontically treated prem

restored with either amalgam or enamel-bo

resin (16): the survival rate (retention of both c

ofthe resin-restored teeth was markedly better

that of the teeth restored with am alg am . In

study (16), however, the number of resin-res

teeth was rath er sm all (n = 40) .

The purpose of this retrospective study was t

a more comprehensive knowledge ofthe cumul

survival rate and the fracture pattern of endo

tically treated posterior teeth restored with ena

bonded resin with or without the use of a de

bonding agent .

M a t e r i a l

and

m e t h o d s


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F r a c t u r e o f r e s i n - r e s t e r e d e n d e d o n t ic a l ly t r e a t e d t e e

The criteria for including data were: i) an endo-

The dentists were asked to record the following

endod ontic the rapy, cavity type (M O, D O, or

and the date of control or last con tact.

In cases of fracture, the dentists were asked to

The survival time was defined as the time elapsed

no distinction was made between MO and DO

D filhngs, the teeth were recorded as w ithdraw n

In the previously mentioned study on endodon-

lower M O D premo lars and upper and low

MOD molars ; and Group G consisted of upp

MOD premolars . The same grouping was us

in the present study. The cumulative survival ra

for each gro up w as calculated with life table analys

1 7 .

Differences between the three group s we

analyzed with log-rank tests (17) at the 5% level

significance. Analyses of the fracture pattern a

differences as to type of restorative resin and tre

ment of the cavo-surface margin were done wi

contingency tables, Kruskal-Wallis one-way anal

sis of variance, Mann-Whitney's U test, and

Fisher exact probability test (18). The significan

level for the use of low-viscosity resin and for t

fracture pattern was set to 1%; the reason for th

will be explained in Results.

Most of the analyses were carried out with

computerized statistical program (MEDSTAT, v

s ion 2 .1 , Astra , Gopenhagen, De nm ark).

R e s u l t s

Data were obtained on 213 endodontically treat

posterior teeth restored with resin, but 11 tee

were rejected because the cavity type or the date

endodontic therapy was not recorded or because

cuspal ove rlays. A further 12 sets of dat a were par

rejected because some ofthe dentists misundersto

the instructions and only recorded fractured tee

not fractured and non-fractured at random. Th

12 teeth were excluded from the survival analys

but included in the analyses of the fracture patte

Ta ble 1 shows the 190 teeth in the survival analy

distributed by cavity type and fracture mode.

In this article, no distinction is made betwe

teeth from the right side of the mouth and te

from the left side. In the tables, only right side to

numbers will be used.

S u r v iv a l ra t e r e t e n t io n of b o t h c u s p s )

Th e num ber of endodon tically treated teeth distr

uted by tooth number, cavity type, and fract

mode are shown in Table 1.

T he re was no statistically significant differe

between the cumulative survival rates of Groups

B and G (P = 0.98), i.e. teeth with an MOD cav

had the same failure rate as teeth with an MO/

cavity. The survival rates of the three groups

depicted in Fig. 1, and the 95% confidence interv

are shown in Table 2 for the 3-, 5-, and 10-y

surviv al rates. W ith no statistically significant dif

ence between the three groups, the pooled cumu


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H a n s e n A s m u s s e n

Ta b l e 1 . N umbe r of end odon t i ca l l y t r e a t ed t ee t h in

th e

su r v i v a l a n a l y s e s d i s t r i b u t e d

on

tooth num be r , cav i t y t y pe , and f ra c t u re m ode .

Tooth

n umbe r ^

Ca v i t y t y p e

Fractu re mode^

MO/DO

6

3

4

1

4

5

4

1

7

1

1

1

4

3

0

1

MOD

21

13

5

0

0

5

1

3

44

28

6

0

4

8

4

1

Fac ia l

L i n g u a l

Tota l

MO/DO

MOD

MO /DO

MOD

MO/DO MOD

14

15

16

17

44

45

16

47

14

15

16

17

44

45

46

47

2

1

f

2

1

1

5

4

2

1

'

=

No ve r t i ca l f r a c t u re s we re found .

-

=

Vioh l' s t wo - d i g i t s y s t em .

'

=

Use

of

den t i n - bon d i n g a g e n t .

survival rate will be used in the Discussion where a

comparison

is

m ade between

the

failure r ate of acid -

etch resin-restored teeth

and

amalgam-restored

teeth.

The cumulative survival rate of the resin-restored

teeth depended

on

several variables:

Restorative resins

- The

endodon tically treated

/o

100

L U

<

Z)

o

20

B

A

C

2 A 6 8 10 12

teeth

had

been restored with

20

different r

Analyses ofthe survival rates of 190 fillings w

many materials are not possible. The teeth

therefore first divided into

two

groups: Teet

stored with

a

chemically-activated

and

teet

stored with

a

light-activated resin.

Teeth restored with

a


had

a

5-year cumulative survival rate

of 92

contrast to 59% for teeth restored with a

activated material (the 9 5 % confidence limits

8 7 - 9 8 %

and

29-89%, respectively). This diffe

was highly significant

(P<

0.001). Even

the

10

survival rate

of

teeth restored with

a

chemi

Tab le 2 . Cumu la t i ve su rv i va l r a t e s of Groups A , B , and C w i t h 95 co

l im i t s in pa r e n t h e s i s .

Group

(n )

Toot h n um be r '

C a v i t y t y p e

MO/DO MOD

Cumu l a t i v e s u r v i v a l r a t e s (

3 y e a r s 5 y e a r s 10

A

(42)

B

( 4 1 )

C

14 ,

4 4 , 4 5

16 ,17

46 ,47

1 5

4 4 , 4 5

16 ,17

46 , 4 7

1 4 , 1 5

9 2 ( 8 1 - 1 0 0 ) 81 ( 6 ^ 9 9 ) 73 ( 4

8 9 ( 7 8 - 1 0 0 ) 8 5 ( 7 0 - 1 0 0 ) 7 8 ( 4 6

9 4 ( 8 9 - 9 9 ) 89 ( 8 1 - 9 6 ) 71 ( 5


4/9


5/9

u s s e n

o /

/o

1 0 0

8 0

60

O

2 0

J

1 I I I 1 I I

2

A 6 8 10

Y E A R S A F T E R T R E A T M E N T

12

3.

Comparison

of

survival rates

for

resin-restored

and

amal-

= Amalgam, Group A. AB = Amalgam,

B,

AC

=

Amalgam, Group

C. R =

Resin, Groups

A, B

d

C

pooled.

of fractures in the beveled and in

our

previous study

on

endodontically treated

(5), three analyses of

be made: tooth surface,

and

effect

of

tooth position

in

the jaw.

the two

first a nalyses w ere m ad e

in

this study

up more than 65%

Tooth surface - Most of the fractures involved the

For the

upper first premolar,

71% of

the pooled

of

facial cu sp frac ture

for the

other

pos-

not

statisti-

No difference was found

a light-activated resin

a


ma-

{P=0A6 .

Fracture level

-

There were more subgingival

and

for

teeth restored with

a

light-

for teeth restored with a chem-

(P= 0.048 ); this difference

as

not

considered

as

statistically significant

be-

l ingual

and

facial failure

was not

statistically s

cant (P=0.12) . There also was a tendency for

lar fractures to be more severe than pre

fractures ,

but a

detailed analysis

was not

because

of the

smal l number

of

m olar fra

(Table 1). None of the 32 fractures was so v

that the tooth had to be extracted.

D i s c u s s i o n

In a retrospective study, a registration form wi

many questions may result in a reduced resp

Furthermore, some

of the

answers

may

have

based upon memory,

not

upon actual know

Thus, several variables were not included i

registration form, first of all variables that may

been important

for the

assessment

of

th e

low

s

rate

of

the light-ac tivated resins,

e.g.

matrix s

(metal or clear strips), the use of light gu

wedges, the thickness of the increments, and

irradiation from

the

facial

and

lingual aspect

tooth.

Not

only this lack

of

information,

bu

the high proportion of unrecorded use of a

viscosity resin and unrecorded fracture level

for

a

cautious interpretation.

Nevertheless,

the

high failure rate

of

teet

stored with

a

light-activated material

is

aston

(Fig. 2); the statistical analyses show ed that

restored with a light-activated resin had n

three times

as

many fractures

as

expected

(the

ber

of

expected fractures

is

derived from

th

rank tests). It should once again be noted th

light-activated resins were applied with a lay

technique.

There

may be

several causes

for the low

su

rate of teeth restored with a light-activated

bu t the main one is presumably the initiati

the polymerization process: teeth restored w

chemically-activated microfilled resin

for

an

use had a higher survival rate than teeth res

with

the

corresponding l ight-activated materi

anter ior use (e.g. the chem ically-activated Si

the light-activated Silux);

and the

same

was

for resins intended

for

posterior

use (e.g. the

ically-activated resion P-10 vs the two ligh

vated resins, P-30 and P-50). Even old-fash

macrofilled resins like Concise

and

Adaptic

better survival rates than

did

modern l ight-acti

resins provisionally or finally accepted for pos

use by the Am erican De ntal A ssociation: E

Posterior, Fulfil, Heliomolar, Herculite,

and

O

sin,

all

of which were used

in the

present study

problem, polymerization of light-activated res


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ent in the cavity of an end odo ntically treated

When light-activated restoratives are used, most

There were 45 teeth which had been restored

The fracture resistance of teeth restored with re-

in vitro

studies, and the results are contradic-

F r a c t u r e o f r o s i n - r e s t o r e d e n d o i i o n t i c a i l y t r e a t e d

light-activated resin, and one cannot expect an

proved survival rate if the restorative resin is po

polymerized.

The use of an intermediate layer of low-visco

resin resulted in a pronounced improvement of

survival rate for teeth restored with a chemic

activated material, but not for teeth restored

a light-activated one. The cause for this differ

may be the following:

In vitro

studies have show n tha t an acid-et

enamel surface is fragile (23, 24): even a very

pressure may result in a significant reduction in

bond strength between resin and etched ena

But if the enamel has been covered with a

viscosity resin prior to application of the restora

resin, the risk of impairing the bond strength

be significantly reduced. An additional explana

could be that both the amount and the siz

marginal voids is increased when no intermed

resin layer is used (25). Marginal voids will re

the contact area between resin and enamel,

fewer sites are therefore a vailable to hinde r the w

to-wall shrinkage of the polymerizing restora

resin. The result may be the formation of a pa

or total gap between the restorative resin and

cavity wall, and thereby a diminished capabilit

the resin restoration to increase the strength of

tooth. The reason why the use of a low-visco

resin did not improve the survival rate of t

restored with a light-activated resin conceivabl

that an increased contact area between the rest

tive resin and the etched enamel is of no valu

the restorative material is pooriy polymerized.

The fracture resistance of prepared teeth wi

beveled cavo-surface margin has been tested

in

8 ,

11, 15). Th ese studies all show no , or on

sHght, improvement of the tooth strength, whic

in agreement with the present investigation.

The survival rate of the acid-etch resin-rest

teeth in this study may be compared with tha

the corresponding amalgam-restored teeth in

previous investigation (5). This comparison is

picted in Fig. 3 where the pooled 12-year surv

rate of the resin-restored teeth is applied. As s

amalgam-restored MO/DO teeth had a sl ig

better 12-year survival rate than that found for

pooled MO/DO and MOD res in-res tored teeth ,

the difference was not statistically significant

0.2). One may argue that a comparison betw

the survival rate of am algam -restored M O /

teeth and pooled MO/DO plus MOD resin-sto

teeth is incorrect, but as reported in Results,


7/9

(5). Teeth with MOD amalgam res-

a pro-

for the

MOD cavities;

one year, the difference betw een the

the two types of restora-

is statistically significant at the level of

0.05 (Group B) and below 0.001

Group C).

The

difference betw een

the

12-year

sur-

of

resin-

and

amalgam-restored

MOD

was highly significant at a level of proba bil i ty

3). It should be noted that the

of the

resin-restored

MOD

teeth

study w as obtained in spite of the po or results

the light-activated materials (Fig. 2).

The periodonal damage caused by the cusp frac-

of the

acid-etch resin-restored teeth

was not

as found in our previous study where

was used as the restorative material (5).

for

this

may be

that

the

strength-

of an etch-retained filhng will give a

in case of cusp failure. Th is

restorative resin is sufficiently

The fracture resistance of teeth re-

an insufficiently irradiated resin filling

to be equivalent to that of an unrestored

Our hypo thesis, insufficient poly me rizatio n

of

the light-activated restorations,

was sup-

by the fact tha t teeth res tored w ith these

had

more subgingival

and

subcrestal frac-

had

teeth restored with chemically-acti-

In the latter gro up, all but one fracture

the fractures of

the periodontal damage in

of tooth failure was less severe th an found for

in out previous study

5 :

.

The

acid-etch resin tech nique

may be a

better

for temporary or

of endod ontically treated

an MOD

.

Light-activated resins must

be

polymerized prop -

We suggest at least 60 s per increment .

. Th e increments in the proximal part of the cavity

be

less than

2 mm

thick.

.

Microfilled resins intended

for

anterior

use

not be used to restore posterior teeth.

.

The

acid-etched enam el should

be

covered with

of

low-viscosity resin.

cknowledgements - The authors want to tha

dentists who collected

the

information

on

whic

study is based. Th is investigation was supporte

the Research Foundation of De ntal Aktiesels

af 1934, the Insurance Association of Danish

tists in Hafnia Insuranc e, and the Research F

dation of the Dan ish D enta l A ssociation.

R e f e r e n c e s

1.

SoRENSEN JA, MARTINOFF JT. Intracoronal reinfor

and coronal coverage: A study of endodontically t

teeth.

J

Prosthet

Dent

1984;

51:

780-4.

2.

GHER M E , DUNLAP RM, ANDERSON MH, KUHL LV.

ical survey of fractured teeth. J Dent Res 1986; 65

Abstr. No. 891.

3. HOOD JAA. Methods to improve fracture resistance o

In : Posterior Composite Resin Dental Restorative Materi

VANHERLE and DC SMITH, Eds., The Netherlands:

Szulc Publishing Co., 1985, pp. 443 50.

4.

BLASER

PK,

LUND

MR,

COCHRAN

MA,

POTTER

RH.

of designs of Class H preparations on resistance of te

fracture. Oper Dent 1983; 8: 6-10.

5. HANSEN EK, ASMUSSEN E, CHRISTIANSEN NC. In viv

tures of endodontically treated posterior teeth restored

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6. SiMONSEN RJ, BAROUCH E, GELB M. Cusp fracture res

from composite resin in Class II restorations. J De

1983; 6 Z- 254, Abstr. No. 761.

7. LANDY NA, SIMONSEN RJ. Cusp fracture strength in

II composite resin restorations. J Dent Res 1984; 63

Abstr. No. 40.

8.

DOUGLAS

WH. Methods to improve fracture resista

t e e th .

In :

Posterior Composite Resin Dental Restorative M

G VANERLE and DC SMITH, Eds., The Netherlands:

Szulc Publishing Co., 1985, pp. 433 41.

9. TROPE M, MALTZ D, LANGER I, TRONSTAD L. Resista

fracture of restored endodontically treated premolars.

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10.

MoRiN DL, DOUGLAS WH, CROSS M , DELONG R . Bio

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measurement. Dent Mater 1988; 4: 41-8.

1 1 . JoYNT RB, WiECZKowsKi G JR , KLOCKOWSKI R, DAV

Effects of composite restorations on resistance to cuspa

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12. MoRiN D, DELONG R, DOUGLAS WH. Cusp reinforc

by the acid-etch technique. J Dent Res 1984; 63: 107

13. EAKLE WS . Fracture resistance of teeth restored with

II bonded composite resin. J Dent Res 1986: 65: 149

14. MACKENZIE DF. The reinforcing effect of mesio-occlus

acid-etch composite restorations on weakened po

teeth. Br Dent J 1986; 161: 410 4.

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stored with class II composite restorations. J Prosth

1989;^/.-

177-80.

16.

HANSEN EK. Visible light-cured composite resins: poly

ation contraction, contraction pattern and hygroscop

pansion. Scand

J Dent Res

1982;

90:

329-35.

17. PETO R, PIKE MC, ARMITAGE O, et al. Design and a

of randomized clinical trials requiring prolonged obser

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18. S I E G E L S.

Nonparametric Statistics

for the

Behavioral S


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R B . Fra ctur e strength of Class II prepa ration s with a pos-

terior resin. J Dent Res 1985; 64 : 350, Abstr. No. 1578.

. E A K L E WS. Increased fracture resistance of teeth: compari-

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fracture resistance of teeth with dentin adhesives and com-

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