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Endodontics

storing teeth that are endodontically treated

gh existing crowns Part iii: Material usage

 E

Witherspoon, BDSc, MS^/Charles W Berry, MS, PhDVGiancarlo G. Romero, DDS,

Objective: This study was undertaken to determine if any current materiais can prevent coronai ieal

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• Trautmann et al

TABLE  Complete-coverage crown restoration

groups

Crown type

Porcelain (Duceram*)-fused-to-

high-noble metal (Orion*)

Porcelain (Düceram*)-fused-to-

noble metal (Lunar*)

All-metal,

 gold (Oro B-2*)

All-porcelain (Empress^)

All-metal, high noble (Orion*)

Total

*Degussa-Ney Dental.

 Empress (Ivoclar Nor ti i America).

Tooth type

Anterior

10

10

0

10

0

3 0

Posterior

10

10

10

10

10

50

Total

2 0

2 0

10

2 0

10

8 0

interface between the endodontic access opening and

the crown material cannot be neglected.

The fact that bacterial contamination is the etio-

logic factor that will challenge the seal of the root

canal filling secondary to coronal leakage is well

known. Grossm an, Seltzer,'' and Mortensen et al '

indicated that the assessment of bacterial leakage is a

clinically reliable test. This resulted in further studies

that used bacterial species to assess the seal of root-

filled canals.8'13.17-23

The purpose of this study was to determine if any of

the dental materials in current clinical use has the

abil i ty to prevent coronal leakage in restored

endodontic access openings in permanently fixed

crowns following NSRCT.

METHOD AND MATERIALS

  pecimen preparation

 

total of 60 extracted mandibular first molars and 36

extracted maxillary central incisors were used. Proxi-

mal and facial radiographs were made using size 2

Kodak Ultraspeed film (Eastman Kodak). Teeth were

evaluated to determine root curvature and canal mor-

phology. Those exhibiting unusual anatomy, severe

curves, root caries, cervical defects, immature apices,

previous root canal therapy, and large coronal restora-

tions were excluded from the study.

Gross tissue debris was removed carefully from the

teeth, which were then immersed in 10 mL of 5.25%

sodium hypochlorite (NaOCl) (Clorox) for a 5-minute

soak. The teeth were stored in distilled water contain-

ing dissolved thymol crystals (Sigma Chemical) and

allocated randomly to 1 of the 8 complete-coverage

restoration groups (Table 1).

Crowns were p repared as described by Rosenstiel et

al.̂ * A high-speed handpiece with water spray and

fine-diamond cutting burs (Nos. 856, 850, 909, 368,

and 847, Brasseler) were used. The operator was cali-

brated for crown preparation, and the final prepara-

tions were evaluated by 2 prosthodontists.

The laboratory work for the crowns was performed

by a prosthodontist, who followed the manufacturer's

recommendations in the manipulation of the metals

and porcelain. Impressions of the crown preparations

were made with a polyvinyl siloxane impression mater-

ial (Extrude, Kerr) with 12 teeth per plastic tray.

Crown castings were made with silky rock-ADA type

IV stone material (Resinrock, Whip Mix). Once die

spacer was placed uniformly throughout the die prepa-

rations, the crown forms were waxed with Gator Dip

Wax (Whip Mix), invested, and cast. The various mate-

rials were used in accordance with the manufacturer's

recommendations. All crowns were cemented perma-

nently with Panavia 21 Dental Adhesive (J Morita),

and mixed according to the manufacturer's recommen-

dations. The crowned teeth were left in an incubator at

37''C for

 

week.

After a  1 week  incubation, straight-line endodontic

access openings were m ade with a high-speed handpiece

used with copious water spray and a combination of

Nos.

  4 and 6 round diamond burs (Brasseler), trans-

metal, and safe-ended Endo Z burs (Dentsply Maillefer).

The openings followed the recommended outline form

for maxillary central incisors and mandibular molars.

The working length of the root canal was determined by

subtracting 1.0 mm from the p oint where a No. 10 K-

type file (LD Caulk) was observed at the apical foramen.

The canals were cleaned and shaped with a combination

of Orifice Shapers and ProFile NiTi rotary files of .04

and .06 taper (Dentsply-Tulsa Dental), while 5.25%

NaOCl was used as an irrigant. Once the instmmenta-

fion was completed to the coronal or middle third of the

root, the canals were irrigated first with 5 mL of 5.25%

NaOCl for a period of

 

minute, then vWth 5 mL of 17%

R-ethylene diamine tetraacetic acid (REDTA) (Roth

Drug) for 2 minutes, and finally with 5 mL of 5.25%

NaOCl for 1 minute to remove the smear layer. Canals

were dried with paper points. Teeth from 8 complete-

coverage restoration groups (Table 1) were allocated ran-

domly to

 

of

 5

 access restorative modalities (Table 2).

Sixteen teeth were allocated as positive or negative

controls:

1. Positive control group (intact crown): 5 posterior

teeth (1 of each crown type) and 3 anterior teeth (1

of each crown type)

2.  Negative control group (unrestored accessed crown):

5 posterior teeth (1 of each crown type) and 3 anter-

ior teeth (1 of each crown type)

28

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Trautmann   et al •

E 2 Restorative ma terials

Restorative

 material

 (Tytin FC*) and varnish

 (Tytin FC*) and bonding

 (Panavia21t i

Light-cured  resin (Prodigy*) and

onding  agent (Optibond Solo*)

Dual-cured resin (Corestore*) and

bonding

 agent (Optibond Solo*)

Glass-ionomer cem ent (Fuji IX GP

otal

*Kerr.

 J.  Morita.

»GO

 America.

Tooth/crown  type

Anterior

6

6

6

6

>   6

30

Posterior

10

10

10

10

10

50

Total

16

16

16

16

16

80

Crown  line

  Sterile  TSB

 i

1 (TSB) Tryp t icase soy

  b roth.

  Leak age

apparatus.

Once restored, all teeth were placed in the incubator

Leakage assessm ent apparatus

  acterial leakage model

 P roteus vul-

  (2.0 mL of 24-hour growth in trypticase soy

broth [TSB]), was placed in the coronal reservoir of

each test assembly with a long-tipped Pasteur pipette.

An aseptic placement technique was used under a vac-

uum. The inoculated tooth-and-tubing assembly was

inserted in to a presterilized test tube (17 x 100 mm)

containing 2 mL of sterile TSB. The test tube was

loosely covered with a plastic cap and briefly agitated

to remove air bubbles.

The TSB was incubated at 37°C for 30 days and

observed weekly for turbidity, indicating microbial

penetration. The number of tubes exhibiting growth

was recorded. The microorganisms were inoculated

onto agar plates and observed for purity by gross

appearance and gram stained to determine contami-

nation by species other than P vulgaris.

The inoculated TSB in the coronal reservoirs was

replaced every 7 days. After 30 days, the test assem-

blies were removed, rinsed with sterile saline, and sub-

sequently exposed to 2 méthylène blue for 30 days.

Statistical evaluation

The outcomes of the bacterial leakage study were eval-

uated with a chi-square test to compare the influence

of  1)  type of restoration,  2)  type of crown, and  3)

type of tooth (anterior versus posterior) on the inci-

dence of turbidity. For

  1 tailed

  tests and where

expected cell counts were fewer than 5, Fisher's exact

tests were utilized.

 International

29

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• Trautmann et al

RESULTS

A total of 51%  of specimens (41/80) demonstrated bac-

terial leakage. A cbi-square test of independence did not

indicate a statistically significant association between

the presence of turbidity (indicating bacterial leakage)

and tbe restorative materials used (P

 

0.995). All mate-

rials leaked in at least 50% of tbe specimens: amalgam

and bonding agent (8/1 6); amalgam and varnish (8/1 6);

light-cured composite (8/16); glass-ionomer cement

(8/16); and dual-cured composite (9/16; 56%).

No statistically significant association between

crown type and bacterial leakage (as evidenced by the

pres enc e of turbidity) w as found (P = 0.149). Tbe

greatest incidence of bacterial leakage was observed

for all-porcelain crowns (14/20; 70%), wbile tbe low-

est incidence of leakage was observed among all-metal

noble crow ns (2 /1 0; 20% ). All otber crown types

exhibited a 50% incidence of turbidity (1 0/20 for both

types of porcelain-fused-to-metal crowns and 5 /10 for

all-metal gold crowns).

To allow further investigation of possible associa-

tions between bacterial leakage and crown type, porce-

lain-type crowns were grouped togetber and compared

to all-metal crowns grouped togetber. Fisher's exact

test revealed some evidence tbat porcelain-type

crowns were more susceptible to bacterial leakage

tban were all-metal crowns (P = 0.077). Specifically, 7

of 20 all-metal crowns (35%) sbowed turbidity, while

34 of 60 porcelain-type crowns (57%) sbowed turbid-

ity. The presence of turbidity among all-porcelain

crowns was then compared to the presence of turbidity

among all otber types of crowns in tbe study. All-

porcelain crowns bad a significantly higher risk of tur-

bidity; teeth witb all-porcelain crowns had an odds

ratio of 2.85 for tbe presence of turbidity compared to

teeth witb crowns tbat were not all-porcelain   [P

0.046 for

  1 tailed

 Fisber's exact test).

A chi-square test of independence demonstrated a

statistically significant association (P = 0.009) between

tbe occurrence of turbidity and type of tootb; anterior

teetb demonstrated a greater frequency of bacterial

leakage (21/30; 70%) than did posterior teetb (20/50;

40%).

  Specifically, anterior teetb were 3.5 times as

likely to show signs of bacterial leakage than were

posterior teeth.

To investigate the difterence between anterior and

posterior teeth in the incidence of turbidity, tbe pres-

ence of turbidity among all-porcelain crowns was

compared to tbe presence of turbidity among porce-

lain-fused-to-metal crowns separately for anterior and

posterior teetb. Among anterior teeth, all-porcelain

crowns bad the same incidence of turbidity (7/10;

70%) as porcelain-fused-to-metal crowns (14/20;

70%).

  However, Fisher's exact test indicated tbat pos-

terior teeth with all-porcelain crowns exhibited a sig-

nificantly greater incidence of bacterial leakage (7/10;

70%) than did posterior teeth with porcelain-fused-to-

metal crowns (6/20; 30%) (P = 0.045).

Teeth were examined for signs of turbidity at 1-

week intervals over a 4-week period during tbe course

of the study. Of tbe 41 teeth demonstrating bacterial

leakage during the study, tbe greatest proportion of

turbidity was observed after 1 week

  (17/41;

 41% ). Tbe

number exhibiting turbidity declined over tbe course

of tbe study, as 9 of 41 (22%) exbibited turbidity at

both weeks 2 and 3 and only 6 of 41 (15%) demon-

strated bacterial leakage at tbe fourth week.

All positive controls showed no turbidity (0% ), and

all negative con trols show complete turbidity (100% ).

DISCUSSION

Wben cballenged witb bacteria, all materials in tbis

study sbowed significant leakage (51 % ). Tbis finding

was comparable to that of previous studies.*•' '• '*

Although tbe difterence was not statistically significant,

all-metal crowns leaked less than did crowns com-

posed of porcelain. Anterior crowns leaked the most,

regardless of tbe type of crown or restoration used.

The purpose of tbis study was to determine if any of

tbe dental materials in current clinical use bas the abil-

ity to prevent marginal leakage of tbe res torations in the

endodontic access cavities of permanently fixed crowns.

Tbe results indicated that all materials will leak, and

none of tbe tested restorations prevented tbe penetra-

tion of mobile bacteria into tbe root canal

 filling

 space.

Proteus vulgaris

  is a highly motile microorganism

tbat grows easily and remains viable in a simple

medium for extended periods. Furtberm ore, tbe size of

P

  vulgaris

 is comparable to tb at of other microorgan-

isms tbat have been identified to be of significance in

periradicular lesions.^^  Pivteus vulgaris is comparable

by gram-stain to endodontic pathogens, wbicb makes

it an effective organism relevant for tbe bacterial leak-

age model. Because its efticacy bas been demonstrated

in prior studies, tbis microorganism was chosen for

measuring bacterial leakage.* '*'^^'2'

Nonsurgical root canal tberapy must be regarded as

incomplete unti l a proper coronal restoration is

placed. Tbe final restoration is essential to establishing

a barrier between tbe periradicular tissues and the oral

cavity.' - An unfavorable coronal restorative material

will disrupt the seal of tbe root canal, bringing about

contamination of an otherwise favorable NSRCT.^*

Furthermore, tbe tecbnical quality of coronal restora-

tions has been identified as significant, and more

important tban tbe tecbnical quality of tbe root treat-

ment, to apical periodontal health.^'-^i Tberefore,

 

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Trautmann et al

Since the original use of adhesive restorations by

  Although the nature of the bond between resin

and amalgam. '^''*'' This study

The concept that volumetric changes in resin

we ttability of the dentin substrate, In spite of

terial leakage,*'* ' These d ata agree with p revious

The ease of use and delivery makes glass-ionomer

or choice as a perm anent restorative material,' ' This

Another aspect of coronal leakage that is important

ide molecules have been found beneath

crow ns within 1 week, *' ** Therefore, the integrity

tissues.

 ON LUSION

fixed crowns that have undergone nonsurgical root

canal therapy. The fol lowing conclusions were

reached:

1, All restorative materials leaked. There was no sta-

tistically significant difference among materials,

2,

  All-metal crowns showed less leakage than did

porcelain-containing crowns; however, these differ-

ences were not statistically significant,

3,

  Anterior crowned teeth had significantly more

leakage than did posterior crowned teeth.

Further evaluation of these findings is warranted to

identify a leakproof restorative material and technique.

  KNOWLEDGMENTS

The authors acknowledge the support of the following companies:

Degussa-Ney Dental for providing all necessary materials and met-

als;

  Ivoclar North America for providing all porcelain and materials;

and Kerr Mfg and GC America for providing all restorative materials.

This research was supported in part by the Intramural Grant of the

Baylor College of Dentistry, a member of the Texas A&M University

System, Health Science Center.

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