in vivo fractures of ally treated posterior teeth restored with amalgam

8/3/2019 In Vivo Fractures of ally Treated Posterior Teeth Restored With Amalgam

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v i v o f r a c t u r e s o f e n d o d o n t i c a l l y t r e a t e de r io r t e e t h r e s t o r e d w i t h a m a l g a mIn vivo fractures of

he cum ulative survival rate (retention of bo th cusps)

years after e nd odo ntic th era py, 5 7% were lost after 10

ptable m aterial for restoration of endod ontically treated

E r i k K e i t h H a n s e n ' , E r i i t A s m u s s e nN i e l s C . C i i r i s t i a n s e n ^I n s t i t u t e s of ^ D e n t a l M a t e r i a l s a n d T e c h n o l o g y ^ P r o s t h e t i c D e n t i s t r y , R o y a l D e n t a l C o l l e g e ,C o p e n h a g e n , D e n m a r k

K e y w o r d s : a m a lg a m ; c a v i ty p r e p a r a t io n ; e n d ot i c t h e r a p y ; t o o t h f r a c t u r e .D r. o d o n t . E r ik K e i th H a n s e n , H e ls in g o r s g a d e 7D K - 3 4 0 0 H i lle r o d , D e n m a r k .A c c e p t e d for p u b l ic a t io n S e p t e m b e r 1 5 , 1 9 8 9

In a previous, retrospective investigation (3), theequency of cusp and crown fracture of endo don-

was to exam ine the cum ulative survival rates (rettion of both cusps) of endodontically treated pmolars and molars restored with MO/DO or Mamalgam without cuspal overlays, and to elucidthe fracture pattern of these amalgam-restoteeth.i W a t e r i a l a n d m e t h o d sThe data were collected from January to Octo1988 from 91 dentists working as general prtitioners. The results from the previous investigat(3) were updated and included in the present stuAll data were derived from clinical examinatiand review of the patients' dental records and radgraphs.The criteria for including data were: (i) an endontically treated premolar or first or second mowith an MO, a DO, or an MOD amalgam res to


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H a n s e n e t a i .one tooth in the prem olar region or 2 in the anteriorregion; and (vi) at least one molar in each q ua dra ntinvolved in the occlusion. Endodontically treatedteeth without antagonist were not included.The dentists were asked to record the followingdata on a registration form: tooth number, date ofendodontic therapy, cavity type (MO, DO orM O D ) , and the date of control or last contact. Incases of fracture, the dentists were asked to recordthe date of tooth failure and whether the facial cusp,the lingual cusp, or the whole crown (total fracture)was lost. Finally, the dentists were asked to recordwhether the fracture was supragingival, subgingi-v a l , at or beyond the alveolar crest, or whether thefracture was so vertical that the tooth had to beextracted. In this article, fractures at or beyond thealveolar crest, but not vertical fractures resulting inextraction, are referred to as subcrestal, even thoughsome of these fractures may have had a fracturelevel slightly above the alveolar crest.

The trial time was defined as the time elapsedbetween the date of endodontic therapy and thedate of fracture; the date of final registration; thedate of withdrawal (change of cavity, change ofrestorative material, extraction of the antagonist);or the date of last contact with the patient. In theanalyses, no distinction was made between MO andDO restorations: only between MO/DO and MOD.When MO/DO restorations had been replaced byM O D fillings, the teeth were recorded as withdra wnMO/DO teeth and re-entered as new MOD teeth.The total trial time was set to 20 years with intervalsof 1 year. For each interval, the effective number ofteeth exposed to risk of fracture was calculated. Thecumulative survival rate, i.e. retention of both cusps,for each tooth number with an MO/DO or MODcavity was then calculated by means of life tableanalysis (9). The classification based upon toothnu m be r and cav ity type gave 16 different c om bi-

Table 1. Number of endodontically treated teeth (n ) in the survival analysesdistributed on cavity type and fracture mode. The number of fractures arethose found within 20 years after endodontic therapy

oothnumber*

nCavity

MO/DOtypeMOD

FacialMO MOD

FractureLingual

MO MOD

modeTotal

MO MODVertical

MO MOD4567456

7 96 4986 44 38 56 8

13 22031945 725123

215

5471323

3 4261243

121 0

1 0 2310 7211 55

10429

6 72

35

215

7622282

113

133711

nations of tooth and cavity type: 4 premolars 4 molars, each with 2 cavity types. Differencestween these 16 combinations were analyzed log-rank tests (9) at the 5% level of significaAnalyses of the fracture pattern were done wKruskal-Wallis one-way analysis of variance, Mann-Whitney U-test, Fisher's exact probabtest (10) and the Jon cke era -T erp stra test (11);latter analysis can be described as a Kruskal-Wtest for trend. The significance level for the fracpattern was set to 1%; the reason for this wilexplained in Results. Most of the analyses wcarried out with 2 computerized statistical progr( S A S , version 6.03, SAS Institute, Gary, NG, Uand M EDST AT, version 2.1, Astra, Gopenh aDenmark). The 95% and 99% confidence l iwere calculated using MEDSTAT.

R e s u i t sData were obtained on 1695 endodontically treteeth with MO/DO or MOD cavities; all teeth wrestored with amalgam. However, 56 teeth wrejected because the cavity type or the date of endontic therapy or control was not recorded orcause of cuspal overlay. A further 55 sets of were partly rejected because some of the denmisunderstood the instructions and only recorfractured teeth, not fractured and non-fracturerandom. These 55 teeth were excluded from Table 2.

Group

Cumulative survivalTooth number*

Cavity typeMO/DO MOD

rates

3

(%); 95% confidence limits in

Cumulative survival rateyears 10 years

parent

(%)20 yea

4 44 51 74 71 61 44 6

9 3 ( 8 4 - 1 00 )9 5 ( 9 0 - 1 0 0 )9 5 ( 8 9 - 1 0 0 )8 6 ( 7 7 - 9 5 )8 6 ( 7 8 - 9 4)8 6 ( 7 8 - 9 4)9 3 ( 8 6 - 1 0 0 )

8 9 ( 7 7 - 1 0 0)9 0 ( 7 8 - 1 0 0 )9 0 ( 7 6 - 1 0 0 )8 1 ( 6 7 - 9 6 )8 0 ( 6 8 - 92 )8 1 ( 6 9 - 9 2 )8 0 ( 6 2 - 9 7)

8 5 ( 6 0 -8 2 ( 6 1 -7 4 ( 4 6 -7 3 ( 4 2 -7 1 ( 4 6 -6 7 ( 4 5 -6 4 ( 2 0 -

154 44 51 71 64 64 7

8 7 ( 7 4 - 1 0 0)8 3 ( 7 2 - 9 3)8 1 ( 7 3 - 8 8 )7 7 ( 6 6 - 8 9)8 7 ( 8 2 - 9 2)8 0 ( 7 4 - 8 6)8 9 ( 8 0 - 9 8)

6 7 ( 4 6 - 88 )6 2 ( 4 4 - 8 1)5 8 ( 4 7 - 6 9 )5 4 ( 3 5 - 7 4 )6 6 ( 5 7 - 7 6)5 8 ( 4 9 - 68 )5 9 ( 4 1 - 7 8 )

5 3 ( 1 8 -4 9 ( 9 - 84 7 ( 3 0 -3 6 ( 1 3 -3 4 ( 1 8 -3 4 ( 7 - 63 1 ( 2 - 6

1 41 5

7 5 ( 6 7 - 8 3 )7 0 ( 6 3 - 7 7)

5 0 ( 3 & - 6 1 )3 9 ( 3 0 - 4 8 )

2 8 ( 1 2 -2 7 ( 1 3 -

AB

9 0 ( 8 7 - 9 3) 8 4 ( 8 0 - 8 8 ) 7 4 ( 6 8 -


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H a n s e n e t a i .F r a c t u r e p a t t e r n - i o c a t i o n o f f r a c t u r eThe fracture level for 60 teeth was not recorded.Because of the consequent uncertainty, in the follow-ing analyses the level of significance was set to 1%.Apart from one tooth (upper first molar), therewas no statistically significant difference between theperiodontal damage caused by fracture of MO/DOteeth and that caused by fracture of the correspond-ing MOD teeth; in some case the periodontal dam-ages were slightly m ore severe for M O /D O teeth th anfor MOD teeth, but in other cases the reverse wasfound . T he only statistically significant differencewas found for the u pp er first mo lar, as mo re subgingi-val fractures were seen with MO/DO cavities thanwith MOD cavities (/^ = 0.009). However, we couldnot find any explanation for that. This statisticallysignificant difference for the upper first molar may bea type 1 error, because only 25 MO /D O fractureswere recorded (19 fractures in the survival analysis,4 in the partly rejected gro up, and 2 with unknownfracture level). If the latter 2 fractures had been su-pragingival, the level of pro bab ihty would hav e been0.04 instead of 0.009. M O /D O and M O D cavitieswere therefore pooled (Table 3).

The difference between the number of fracturesin Table 1 (/z = 532) an d in Table 3 (;z = 510) canbe explained as follows: 6 fractures, including 1vertical failure, happened 20 years or more afterthe endodo ntic the rapy; the 55 teeth, excluded fromthe survival analyses, were included in the analysesof the fracture levels; vertical fractures are not in-cluded in Table 3; and 60 fractures had no recordedfrac ture level (532 + 6 + 55 - 23 - 60 = 510).

There were only minor differences between thefracture levels with facial and total failure ( P = 0 . 4 1 ,two-tailed) (Table 3). Th e 2 failure modes weretherefore pooled. Table 3, which does not includevertical fractures, shows that JinguaJ failures mostlyere subgingival, in contrast to facial and total

0.001. This was

n Supra-gingival

Fracture levelSubgingival

Supracrestal Subcrestal*

F r a c t u r e p a t t e r n - e f f e c t o f t o o t h p o s i t i o n i n j a wThejonckheera-Terpstra test (11) showed a statcally significant trend in both the upper and lojaw: the more posterior the tooth, the more nounced the periodontal damage caused by tfailure (P< 0.001). In order to further examinepreviously mentioned pooling of MO/DO M O D cavities, the Jonc khe era-T erpstra test also carried out with the 2 cavity types separaThe trend was still statistically signif(P< 0 .0 0 2 ) .Th e results of the analyses (pooled M O /D O MOD cavities) are presented in Table 4. Twas no statistically significant difference betweenperiodontal damage caused by tooth failure ofper and lower molars (P =0 .04 ) (if vertical frachad been excluded, P would have been 1.00).trend shown by the Jonc khe era-T erps tra testcaused by supragingival fractures being more quent for premolars than for molars, and subcrfractures being more frequent for molars thanpremolars (Table 4).In the upper jaw this trend was primarily cauby lingual fractures being more severe in the mregion th an in the premo lar are a (/*< 0.001),the high frequency of vertical fractures for the usecond molar also played a role in this trend. pooled facial and total failures had no such tin the upper jaw (P= 0.0 9) .W ith regard to the lower jaw , facial/total lingual fractures were most severe in the molagion (P


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F r a c tu r e o f a m a l g a m - r e s t o r e d e n d o d e n t i c a l ly t r e a t e d twer one, tha n in the m olar region, while subcrestal

large 2 0-yea r investigation like this one could

Several laboratory studies have shown that cavity

the cavity is enlar ged (12 -17 ). M ost of these instudies concentrate on a very relevant clinical

Hood (16) found that the deflection of premolarendodo ntically treated premolars with M O D

s an L^ factor, w hich m eans tha t dou bling theAn endodo ntically treated posterior tooth m ay

ps (and the reb y the risk of fracture) m ay beior tooth tha n in a vital one. Th e increased cavity

Dentin preservation during endodontic treatmentbeen very muc h discussed. Both the cavity dep thL) and the thickness of the cusp (t) have a very

creasing the thickness of the cusps results in redudeflection under a given occlusal loading, but may interfere with optimal access to the root canIn our opinion, optimal access is the major poinconcern because an unsuccessful endodontic trment represents a much higher risk than fractura weak cusp.As to cusp fracture, the most essential problemthe periodontal dam age that the fracture may c(Tables 3, 4). The optimal restoration of an endontically treated posterior tooth should therebe a cast inlay with cuspal overlays or, if necessa full crown (16-18). However, cast restoratare generally not fabricated before the periaphealing has been confirmed with radiographs 6months later. But it may take 2-3 years, or emore, before the healing has been verified (During this observation period, or if the patcannot afford a cast restoration, the dentist hadeal with the risk of cusp or tooth fracture. study shows that this risk depends on the cavity and the position of the tooth.

For all 8 posterior teeth, there was a mardifference between the cumulative survival rate a MO/DO cavity and that with a MOD cavity (1 , Table 2). This is in good agreement withpreviously mentioned laboratory studies (12and one of the few clinical articles on this ( 2 0 ) . The high failure rate of MOD restored tecompared with that of MO/DO restored testrongly indicates that every effort should be mto maintain at least one marginal ridge in endotically treated teeth.

In this context it is interesting that many dentend to use operative trea tm ent of proxim al clesions at a rather early stage. Thylstrup et al. found that of 1080 proximal caries lesions, treoperatively on the basis of radiographic and/or cical observations, less than 10% of the caries lesshowed true cavitat ion. Nonoperative treatmshould therefore be considered more often, pecially for endodontically treated teeth. When dent cavitation occurs, the use of a tunnel preption may be better than the preparation of a contional MOD cavity.

Two teeth in the upper jaw had a diverging fture pattern, 'one of them being the upper first molar with MOD cavity. This study shows when this tooth fractures, most of the failuresfound facially. The cause for this is presumablyanatomical form of the pulp chamber and the sslope of the facial cusp, as already discussed viously (3).


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H a n s e n e t a l .1). Nearly half of the extractions caused by verticalfracture were upper second molars, even thoughthis tooth accounted for less than 8% of all theendodontically treated teeth in our study. If thistooth fails, between 14% and 60% have to be ex-tracted in contrast with 1-5% for the other posteriorteeth (99% confidence limits).

One of the causes for the high frequency of verti-cal fracture in the up per second mo lar is presumablythe anatomy of this tooth: 2 facial roots and onelingual root may be predisposing for a mesiodistal,vertical split through the pulpal floor in contrastwith the lower molars, where the 2 roots are placedperpendicularly to the weakened facial and lingualcusp. One m ight argue that the same high frequencyof vertical fracture should have been expected forthe upper first molar because it has the same basicanatomy as the second molar, but there are 2 essen-tial differences. The first molar is nearly alwayslarger, and thereby stronger, than the second molar.Furthermore, the load applied to the latter, moreposterior tooth during masticatory functions ishigh er, a nd the reb y also the risk of fatal failure.

The presence or absence of third molars was notrecorded in our study. An occlusal contact area inthe third molar region may very well reduce thefunctional load on the second upper molar. Thehigh frequency of vertical fracture for the lattertooth may therefore be caused by the anatomicalform, the posterior position of the tooth, the lack ofthird molar contact, or any combination of these 3variables. Whatever the cause, endodonticallytreated upper second molars seem to represent byfar the most threatened tooth, irrespective of MO/DO or MOD cavity type.

Our registration forms also did not include infor-mation on post reinforcement. Posts are generallyconsidered to increase the strength of endodontical-ly treated teeth. But the rationale for using postshas been questioned by Sorensen & Martinoff (1),who found that intracoronal reinforcement withposts did not result in a significant increase of thelinical success rate; they concluded that dentistshould focus less on factors that influence retention

ent study confirms this conclusion of Sorensen &The periodontal damage was generally more se-

l cusp or the crown totally fractured (Table 3).

ture alone. But total crown fractures were mohorizontal ones.The main problem, apart from vertical fracwas lingual failures, which resulted in significamore periodontal damage than did facial or crown fracture. Subgingival and subcrestal linfractures were, however, much more frequenthe molar region than in the premolar area, wespecially the lower premolars had a high frequof lingual failures with supragingival fracture lOne should therefore be most concerned aboutlingual cusp of molars and upper premolars becof the high risk of periodontal damages in casfracture.Both in vivo studies (2, 22) and in vitro invetions (17, 18, 20) have shown a markedly bsuccess rate for teeth with large cavities if the care protected with overlays. The present sshows that cuspal protection is important wamalgam is used both as temporary and permarestoration material. Lingual cusp coverageamalgam will probably be accepted by mosttients if they are properly informed about the pedontal consequences of tooth failure. Presumaone should also cover the facial cusp of the usecond molar in order to reduce the risk of verfracture. But we do not know whether that hinder a fatal tooth failure. A cast inlay with cuoverlays, fabricated immediately after the endotic treatment, may be the best solution for tooth.Protecting the facial cusp of teeth more anteriplaced than the second molar with a 2-3 mm lof amalgam may be hard to accept for manytients. In these cases, the patient has to acqept eithe risk of tooth failure or the immediate fabricaof a cast restoration without the normal observaperiod.

Our final conclusion is that amalgam withcuspal overlays, especially in MOD cavities, is uceptable for restoration of endodontically treposterior teeth, whether the am algam is used temporary or permanent restorative material . cusps should be covered with a 2-3 mm layeamalgam in order to reduce the risk of tooth failAn alternative treatment option, enamel-bondedsin, will be discussed in a later article.

Acknowledgements - The authors want to thandentists who collected the information on which


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F r a c t u r e o f a m a i g a m - r e s t o r e d e n d o d o n t ic a i iy t r e a t e d t

SORENSEN JA , M A R T IN O F F J T . Intracoronal reinforcementand coronal coverage: a study of endodontically treatedteeth. J Prosthet Dent 1984; 51 : 780-4.G H E R M E , D U NL A P R M , ANDERSON M H , K U H L LV. A clin-ical survey of fractured teeth. J Dent Res 1986; 65 :8 2 5 , Abstr . No. 891.. HANSEN E K . In vivo cusp fracture of endodontically treatedpremolars restored with MOD amalgam or MOD resin fill-ings. Dent Mater 1988; 4: 169-73.. SiLNESS J. Perio don tal con ditions in patien ts treate d withdental bridges. HI. The relationship between the location ofthe crown margin and the periodontal condition. J PeriodontRes 1970; 5: 225-9.. REN G G LI H H , REG O LA TI B . Gingival inflammation andplaque accumulation by well-adapted supragingival andsubgingival proximal restorations. Helv Odontol Acta 1972;16 : 99-101.. MARUYAMA T , SIMOOSA T, OJIMA H . Morphology of gingivalcapillaries adjacent to comp lete crowns. J Prosthet Dent 1976;

3 5 : 179-84.7 . VALDERHAUG J . Periodontal conditions and carious lesionsfollowing the insertion of flxed prostheses: a 10-year follow-up study\ Int D ent J 1980; 30: 296-304.8. LANG NP, K I E L RA , A N D ERH ALD EN K . Clinical and micro-biological effects of subg ingiva l restorations with ov erh an-ging or clinically perfect margins. J Clin Periodontol 1983; 10 :563-78.9. PETO R , PIKE M C , ARMITAGE O, et al. Design and analysisof rando mized clinical trials requiring prolonged observationof each patient. Br J Cancer 1977; 35: 1-39.

SiEGEL S. Nonp aram etric statistics for the behavioral sciences. N ewYork: McGraw-Hill, 1956.H O LLA N D ER M , WO LFE DA. Nonparametr ic stat ist icalmetho ds. New York: Jo hn Wiley & Sons, 1973.

1 2 . MoNDELLi J, STEA GA LL L , ISH IK IRIA MA A , N A V A RRO MSoARES FB. Fracture strength of human teeth with capreparations. J Prosthet Dent 1980; 43 : 419-22.1 3 . LARSON T D , DOUGLAS W H , GEISTFELD RE. Eflect of pared cavities on the strength of teeth. Oper Dent 1982 - 5 .

1 4 . MoRiN D, D ELO N G R , D O U G LA S WH. Cusp reinforcemby the acid-etch technique. J Dent Res 1984; 63 : 18.1 5 . DOUGLAS WH. Methods to improve fracture resistancteeth. In: VANHERLE G, SMITH DC, eds. Posterior co

resin dental restorative materials. The Ne the r l ands : Pe t e r Publishing, 1985: 433-1 .1 6 . H O O D JAA. Methods to improve fracture resistance of t

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1 8 . SALIS SG, H O O D J A A , STOKES A N S, KIRK EEJ. Patternindirect fracture in intact and restored human premteeth. Endod Dent Traumatol 1987; 3: 10-4.19. BYSTROM A, HAPPON EN R -P , SJOGREN U , SUND^VISTHealing of periapical lesions of pulpless teeth after end otic treatment with controlled asepsis. Endod Dent Trau1 9 8 7 ; 3: 58-63 .

2 0 . C A V E L W T , K E L SE Y W P, BLANKENAU RJ. An in vivo sof cuspal fracture. J Prosthet Dent 1985; 53 : 38-42.2 1 . TH Y LSTRU P A, BILLE J , Q V IST V. Rad iograph ic and obsetissue changes in approximal caries lesions at the timoperative treatment. Caries Res 1986; 20 : 7584.2 2 . LiBERMAN R , JuDES H, CoHEN E, E L I I. Re sto ratioposterior pulpless teeth: amalgam overlay versus cast onlay restoration. J Prosthet Dent 1987; 57 : 540-3 .


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in vivo fractures of ally treated posterior teeth restored with amalgam

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