www.scielo.br/jaos
Effect of different ferrule designs on the fracture
resistance and failure pattern of endodontically
ceramic crowns
Haneef SHERFUDHIN1, Joseph HOBEICH2, Carlos Augusto CARVALHO3, Moustafa N. ABOUSHELIB4, Walid SADIG5,
Ziad SALAMEH6
1- BDS, MDS, Assistant Professor, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Saudi Arabia.
2- DUA, DSc, Assistant Professor, Department of Fixed Prosthodontics and Occlusion, Saint Joseph University, Beirut, Lebanon.
3- DDS, MSc, PhD student, Department of Operative Dentistry, Endodontics and Dental Material, University of São Paulo, Bauru School of Dentistry, Bauru,
SP, Brazil; and PhD student, Department of Fixed Prosthodontics and Dental Materials, Policlinico Le Scotte, University of Siena, Italy.
4- DDS, MSc, PhD, Dental Biomaterials Department, Faculty of Dentistry, Alexandria University, Egypt.
BDS, MSc, Professor, Department of Prosthetic Dental Sciences, College of Dentistry,King Saud University,Riyadh, Saudi Arabia.
6- DDS, MSc, PhD, Assistant Professor/Researcher,Eng.A.B Research Chair for Growth Factors and Bone Regeneration, King Saud University, Riyadh, Saudi
Arabia; Research Department, School of Dentistry, Lebanese University, Beirut, Lebanon.
Corresponding address: Carlos Augusto Carvalho - Julia Miranda 18 - 36.400-000 - Conselheiro Lafaiete - Minas Gerais - Brasil - Phone: +55 31 37633077
- Fax: +55 31 37637070 - e-mail: phdcar@gmail.com
!
ABSTRACT
O
bjective: This study investigated the effect of different ferrule heights on endodontically
! ! "#
Ivoclar-Vivadent) luted with self-polymerized resin cement (Multilink, Ivoclar Vivadent)
while the coronal section was restored with hybrid composite core build-up material (Tetric
Ceram, Ivoclar-Vivadent), which received all-ceramic crown. Different ferrule heights were
investigated: 1-mm circumferential ferrule without post and core (group 1 used as control),
a circumferential 1-mm ferrule (group 2), non-uniform ferrule 2-mm buccally and 1-mm
lingually (group 3), non-uniform ferrule 3-mm buccally and 2-mm lingually (group 4), and
$ %&'
groups were investigated by applying axial load to the ceramic crowns (n=10). Data were
analyzed statistically by one-way ANOVA and Tukey’s post-hoc test was used for pair-wise
comparisons (D*++%& ' $ $
load of all tested groups (P<0.780). The control group had the lowest fracture resistance
(891.43±202.22 N) and the highest catastrophic failure rate (P<0.05). Compared to the
$ / $
$ $ 6
specimens. Conclusions: Within the limitations of this study, increasing the ferrule length
6 $
; $
of these restorations under function.
Key words: Endodontics. Post. Material resistance.
J Appl Oral Sci.
28
2011;19(1):28-33
"## # ## # $ % # # $ # $$ % &% $$ ' &
height is necessary to achieve such protective
effect20. Recent clinical studies reported that the
? 6
clinical success rate of endodontically treated
events were due mainly to post debonding3,9. An
in vitro study reported that incomplete crown
ferrule was associated with greater variation in load
capacity after chewing simulation19, while other
studies found no effect of different ferrule heights in
6,22,24.
The aim of this study was to evaluate the fracture
resistance and failure pattern of endodontically
treated mandibular premolars restored with
$
posts and all-ceramic crowns. The null hypothesis
was that different ferrule heights do not improve
the fracture resistance or the failure pattern of the
tested restorations.
INTRODUCTION
Endodontically treated teeth often loose
substantial tooth structure from previous caries,
pre-existing restorations, and/or endodontic
treatment18, which reduce tooth bulk and thickness
of healthy dentin resulting in increased chances
of fracture under function8. Controversy exists
as to whether endodontic procedures are the
primary cause for loss of strength. Panitvisai and
Messer23 (1995) 6
increased with increasing the extension of cavity
preparations and was greatest when endodontic
access was incorporated into a preparation. It
has been reported that endodontically treated
teeth and their contralateral vital pairs exhibited
similar biomechanical properties, such as punch
shear strength, toughness, and load required for
fracture28.
Although the insertion of a post does not
strengthen or reinforce endodontically treated
teeth11,12/ ?
retention of the core material which in turn is used
@ 15. For the inserted post
to perform its function, several variables must be
put into consideration such as post length, diameter,
geometric design, and surface configuration15.
Additionally, special attention should be given to
the material the post is made of in order to ensure
adequate distribution of the absorbed stresses and
to prevent root fracture during29. Regarding with
consideration to the well-known success of metallic
posts there are now many concerns regarding the
associated inhomogeneous stress distribution,
biological side effects due to microleakage and
/ 6 B
an all-ceramic restorations5.
'
composite (FRC) posts helped improving stress
distribution because their elastic modulus is similar
to that of dentin as indicated by several clinical
and laboratory studies10,17,33. FRC post systems
showed more frequent favorable failure modes
than did metal post systems11,14 G $
posts proved effective in withstanding compressive
loads in posterior teeth1, they behave differently
in anterior teeth where non-axial biting forces
? 6@?
more effective27. Recent studies15-30 suggested that
$
and strengthening of endodontically treated teeth
under full coverage crowns.
A ferrule or encircling band of cast metal
around the remaining coronal surface can provide
protective reinforcement to endodontically treated
teeth by encapsulation of the remaining coronal
structure and by resisting functional lever forces
during mastication. A minimum 1 to 2 mm of ferrule
J Appl Oral Sci.
MATERIAL AND METHODS
Preparation of specimens
extracted for orthodontic reasons. All external
debris were removed with an ultrasonic scaler, and
@ #+@$
verify the absence of cracks, defects and dental
caries. Teeth were stored in a 0.5% chloramine
T (Prolabo, Paris, France) in saline solution.
Buccolingual and mesiodistal coronal dimensions
plus root length of all selected teeth were measured
using a digital caliper (Digimatic Calipers, Mitsutoyo,
Tokyo, Japan) and only teeth with the following
mean dimensions were selected: 14.1 mm root
length, 7.3 mm buccolingual width, and 4.9 mm
mesiodistal width.
Standardized root canal preparations were made
using the following procedure: initial probing using
#+ Q @ / / U $ /
Switzerland); the root canal length was established
$ ? @ $
from the apical foramen. The specimens were then
prepared endodontically with a stepback procedure
with size 45 (Flex R file; Union Broach, York
PA). After intermittent rinsing with 2.5% sodium
hypochlorite solution, the endodontic treatment
was completed using manual lateral condensation
method (AH Plus, Dentsply, De Tray, Konstanz,
Germany).
After endodontic treatment, each root was thinly
covered with a silicone impression material (Aquasil,
Dentsply) to simulate thickness of periodontal
ligament22. All specimens were embedded in selfpolymerized acrylic resin (Orthoresin, Dentsply,
Degudent GmbH, Postfach 1364, D-63403 Hanau,
Germany) poured into a mold while maintaining 2
mm below the cervical line exposed. The teeth were
29
2011;19(1):28-33
SHERFUDHIN H, HOBEICH J, CARVALHO CA, ABOUSHELIB MN, SADIG W, SALAMEH Z
with a diamond bur so that it was covered with at
least 2 mm of resin composite occlusally.
Post cementation was carried out with selfpolymerized resin cement (Multilink, Ivoclar
Vivadent) following manufacturer’s instructions.
Silane coupling agent (Monobond-S, IvoclarVivadent) was applied on the post surface for 60
s and then air-dried. After post cementation, the
surrounding dentin surface was etched with 36%
phosphoric acid (Total Etch, Ivoclar-Vivadent) for
15 s, washed with water spray and gently airdried. One coat of adhesive resin (Excite, IvoclarVivadent) was applied using a microbrush and light
polymerized for 20 s (Astralis 10, Ivoclar-Vivadent).
Then core build-up was performed using hybrid
composite resin (Tetric Ceram, Ivoclar-Vivadent)
in 1-mm-thick increments and light polymerized
(Astralis 10; Ivocar-Vivadent) for 40 s until the
core was restored to predetermined dimensions.
' $
matrix to allow for shape consistency between
specimens. The dimensions of the prepared cores
$
+@$
%
A single-phase impression was made using polyvinylsiloxane impression material (Virtual, IvoclarVivadent) and master dies were fabricated with
type 4 die stone (Jad Stone, Whip Mix, Louisville,
Kentucky, USA). A press ceramic (e max, A3,
Ivoclar-Vivadent) was selected to fabricate allceramic crowns of the restored specimens. Crown
dimensions were standardized by using a mold
for the external shape of each specimen. The
$
6 ;!~ $$/;?
Vivadent) for 20 s, rinsed off, air dried, silanized
for 60 s and air dried. Dentine primer liquids were
mixed and applied on the whole prepared tooth
surface for 15 s. Resin cement was dispensed from
the automix syringe directly into the inner surface of
the crowns which were seated and held in position
@ {+_@ ?
immediately with a micro brush. Exposed margins
were covered with glycerin gel and rinsed off after
complete polymerization of the resin cement. The
specimens were stored in distilled water at 37°C
for 7 days prior to testing.
embedded along their long axis using a surveyor
(Ney Surveyor; Dentsply).
Full crown preparation
The teeth were randomly divided into 5 groups of
10 teeth each. Crown margins were prepared under
constant water cooling and using 2.5x optical loops.
A new diamond point (Lot-NR 1599, DFS Dental and
Technical Products, GmbH, Germany) was attached
to the milling machine (K9 Milling Apparatus-990,
Kavo, Germany) for every group. The MRD gauged
diamond had a self-limiting tip, which produced a
1-mm-deep chamfer and the margins and the angle
of convergence were standardized.
G /
@ $ $
1): Group 1 (control): 1 mm circumferential ferrule
$ $ ?$ _`
{#
resin core; Group 3: non-uniform ferrule height (2
# $&
and resin core; Group 4: a non-uniform ferrule
height (3 mm buccally and 2 mm lingually) with
_ ` % ?
Post-space preparation
In the control group, excess gutta-percha was
removed to a depth of 2 mm from the coronal
surface of the preparation, using a carbide bur
(171L-012, Brasseler, USA). The coronal walls
were etched with 36% phosphoric acid (Total Etch,
Ivoclar-Vivadent, Schaan, Liechtenstein) for 15
s, washed with water spray and then gently airdried. One coat of adhesive resin (Excite, IvoclarVivadent) was applied using a microbrush and light
polymerized for 20 s (Astralis 10, Ivoclar-Vivadent).
A hybrid composite resin (Tetric Ceram, IvoclarVivadent) was applied and light polymerized for
40 s.
For the remaining groups, post space was created
using no. 1 Peeso reamer (Union Broach Co., Long
Island, NY, USA) and corresponding calibrating drill
! ! /"#/;? | ?&? $}
mm of apical gutta-percha intact. A translucent
$ !
! "# ;? | ?/ ~/ &
was used. Each post was cut to a suitable length
Figure 1- Schematic representation of the different tested groups
J Appl Oral Sci.
30
2011;19(1):28-33
"## # ## # $ % # # $ # $$ % &% $$ ' &
Table 1- Failure load (standard deviation) and failure type of tested groups
Group
Failure load (N)
Number of favorable fracture
Number of catastrophic fracture
Group 1 (Control)
891.4 (203)a
7 (70%)
3 (30%)
Group 2
1011.5 (289)a
10 (100%)
0 (0%)
Group 3
952.8 (246)a
10 (100%)
0 (0%)
Group 4
909.2 (226)a
9 (100%)
1 (10%)
Group 5
996.7 (279)a
9 (90%)
1(10%)
6LPLODUVXSHUVFULSWOHWWHULQGLFDWHVQRVLJQL¿FDQWGLIIHUHQFHEHWZHHQGLIIHUHQWWHVWJURXSV
was comparable to that of the other groups that
? / $
failure rate (70%) in the control specimens in the
form of vertical root fracture. The groups restored
/ /
complete favorable fracture in the form of cervical
fracture above the cervical line, previous data are
summarized in Table 1.
In all specimens, the cemented ceramic crown
was fractured without evidence of debonding
of either the crown or the cemented post. The
internal surface of the fractured ceramic fragments
demonstrated evidence of resin cement and part
of the core material indicating cohesive fracture of
the resin core.
Fracture resistance
All specimens were subjected to cyclic loading
according to the following regime: sinusoidal load
between 50 and 200 N at a rate of 2 hertz. All
specimens received 15,000 cycles and surface
damage was prevented by insertion of a 0.5 mm
silicon sheet between the occlusal surface of the
ceramic crown and the loading indenter (3 mm
diameter) of the pneumatically activated loading
machine. After completion of cyclic loading, a
universal testing machine (Instron 8500 Plus,
Instron, 100 Royal St. Canton, MA, USA) was used
to deliver a compressive load to the specimens at a
crosshead speed of 1 mm/min at 45 degree angle to
the long axis of the teeth (root apex tilted lingually)
until failure. Load-time curves were recorded using
a universal testing machine’s computer software.
The load was measured in Newton. The failure load
of the specimen was determined when the forceversus-time graph showed an abrupt change in
load, indicating a sudden decrease in the specimen’s
resistance to compressive loading.
After loading, the failure mode recorded for each
?
above the cement-enamel junction (repairable) or
catastrophic fracture of the root below cementenamel junction (non repairable). These inspections
were made using a stereomicroscope (Stereoscopic
zoom microscope, SMZ-1000, Nikon, Japan) and
during inspection, the teeth were trans-illuminated
with a fiber optic cable. Complete or partial
debonding of the crown or of the post and core
were also considered as favorable failure modes.
Data were analyzed statistically by one-way ANOVA
and Tukey’s post-hoc test was used for pair-wise
comparisons (D=0.05).
DISCUSSION
Considering the results obtained in this study,
different ferrule heights did not improve the
fracture resistance or the failure pattern of the
tested specimens. On the other hand, the use of
of dentin changed the catastrophic failure type of
the control group to almost complete favorable
fracture for the other four groups. The proposed
hypothesis was thus accepted. The dynamic cyclic
loading program was intended to quickly screen any
possible weakness in the cemented restorations.
Providing occlusal protection prevented generation
of cone cracks in the brittle ceramic crowns which
was the reason why all specimens survived without
failure. Longer periods of cyclic loading are required
to shed light on the long-term performance of these
restorations, but investigating this issue was not
within the scope of this study7.
The results of the fracture resistance test showed
that the amount of residual coronal structure
(ferrule height) did not increase significantly
the fracture resistance of endodontically treated
teeth. These results are in agreement with those
of previous studies2,6,22; while contrary results
were reported by other authors25,34. This could be
@
the forces and distributed the loading stresses over
RESULTS
All specimens survived the cyclic loading program
without any sign of external failure. Statistical
? $
the failure load of the tested groups and the control
group restored without fiber post (P<0.780).
Although fracture resistance of the control group
J Appl Oral Sci.
31
2011;19(1):28-33
SHERFUDHIN H, HOBEICH J, CARVALHO CA, ABOUSHELIB MN, SADIG W, SALAMEH Z
stress distribution that occurs at the post-dentin
interface24,34 . This could explain why all favorable
fractures were limited to the cervical portion of the
root including the core-dentin interface, since the
stresses were concentrated in the cervical area and
the outer root surface. Supporting this opinion is
the cohesive fracture of the resin core material,
which remained attached to the fractured segments
of ceramic crowns, thus indicating good bond
strength between the core build up material and
the cemented ceramic crown. The limited number of
$
the complexity of functional loads in the oral
environment may be some of the shortcomings of
the present study. Further investigations including
$ $
studies are recommended to complement the
present study.
a bigger surface area of the tooth structure similarly
for all tested groups7,16. These results may also be
resin composite core exerted a reinforcing effect by
supporting the remaining tooth structure regardless
of the ferrule design6,27. These non-metallic post
systems have gained widespread popularity in
recent years because of other advantages such
as their superior esthetics, ease of retrievability,
and simple application technique, which allow the
clinician to complete the procedure in a single short
appointment6.
According to the results of the present study,
$ &
revealed higher catastrophic failure rate compared
to the other groups, which indicates that insertion of
endodontically treated teeth even if the failure load
remains relatively not effected27,30. The presence of
a uniform 1-mm-thick coronal structure (group 2)
resulted in the highest fracture resistance value,
especially when compared to the control group,
which is in agreement with the results of previous
studies31,32.
A point of clinical relevance is that the fracture
resistance of specimens with non-uniform coronal
structure (group 3 and 4) was lower than the
specimens without a ferrule (group 5), with
consideration to maintaining as much as possible
of sound tooth structure. It could be advised to
adjust the coronal structure evenly to provide a
6 /
improve the fracture resistance of endodontically,
treated teeth. Further research is needed to fully
cover this issue21,26.
Lithia disilicate-based all-ceramic crowns were
$ 6@
$ }++!&/ $ 6
acid, readily silanized and bonded with any suitable
resin cement. It has also been reported that the
mean chewing force of adults ranges between 7 to
15 kg, and the maximum biting force could reach
up to 90 kg34. As the fracture loads in all groups in
the present study were found to be greater than the
ordinary chewing force, and even greater than the
maximum biting force, their mechanical strength
could be considered satisfactory from a clinical
point of view10.
In terms of the failure modes, the obtained
results are in accordance with those of previous
studies15,27/
$
posts resulted in more favorable fracture patterns4
while the specimens restored without posts showed
a higher incidence of catastrophic failure. It could
reinforced post systems offered more homogenous
stress distribution due to their modulus of elasticity
close to that of dentin resulting in a better
J Appl Oral Sci.
CONCLUSION
Within the limitations of this study, it may be
concluded that increasing the ferrule length did not
improve the fracture resistance of endodontically
treated teeth restored with glass ceramic crowns.
; $
of catastrophic failure of these restorations under
functional loads.
REFERENCES
1- Akkayan B, Gülmez T. Resistance to fracture of endodontically
treated teeth restored with different post systems. J Prosthet
Dent. 2002;87:431-7.
2- Al-Hazaimeh N, Gutteridge DL. An in vitro study into the effect of
the ferrule preparation on the fracture resistance of crowned teeth
incorporating prefabricated post and composite core restorations.
Int Endod J. 2001;34:40-6.
3- Cagidiaco MC, García-Godoy F, Vichi A, Grandidni S, Goracci C,
!
affects the 3-year survival of endodontically treated premolars.
Am J Dent. 2008;21:179-84.
4- Cagidiaco MC, Radovic I, Simonetti M, Tay F, Ferrari M. Clinical
teeth: 2-year results. Int J Prosthodont. 2007;20:293-8.
% ` /
J Am Dent Assoc. 1996;127:1397-8.
6- Dikbas I, Tanalp J, Ozel E, Koksal T, Ersoy M. Evaluation of
the effect of different ferrule designs on the fracture resistance
of endodontically treated maxillary central incisors incorporating
/
Dent Pract. 2007;8:62-9.
7- Duret B, Duret F, Reynaud M. Long-life physical property
preservation and postendodontic rehabilitation with the
Composipost. Compen Contin Educ Dent Suppl. 1996;20:S50-6.
8- Eakle WS, Maxwell EH, Braly BV. Fractures of posterior teeth
in adults. J Am Dent Assoc. 1986;112:215-8.
9- Ferrari M, Cagidiaco MC, Grandidni S, De Sanctis M, Goracci
C. Post placement affects survival of endodontically treated
premolars. J Dent Res. 2007;86:729-34.
10- Ferrari M, Vicchi A, Mannocci F, Mason PN. Retrospective
G
2000;13:9B-13B.
32
2011;19(1):28-33
"## # ## # $ % # # $ # $$ % &% $$ ' &
11- Fokkinga WA, Kreulen CM, Vallittu PK, Creugers NH. A
structured analysis of in vitro failure loads and failure modes of
// ;!
2004;17:476-82.
12- Goodacre CJ, Spolnik KJ. The prosthodontic management of
endodontically treated teeth; a literature review. Part I. Success
and failure data, treatment concepts. J Prosthodont. 1994;3:24350.
13- Guzy GE, Nicholls JI. In vitro comparison of intact
endodontically treated teeth with and without endo-post
reinforcement. J Prosthet Dent. 1979;42:39-44.
14- Hayashi M, Takahashi Y, Imazato S, Ebisu S. Fracture
resistance of pulpless teeth restored with post-cores and crowns.
Dent Mat. 2006:22:477-85.
15- Heydecke G, Butz F, Strub JR. Fracture strength and survival
rate of endodontically treated maxillary incisors with approximal
cavities restoration with different post and core systems: an invitro study. J Dent. 2001;29:427-33.
# ; / U Q/ ? ` ' 6
length and crown ferrule on the resistance to cyclic loading of
bovine teeth with prefabricated titanium post. Int J Prosthodont.
1999;12:78-82.
# /` / $
post-resin core unit: a scanning electron microscopy evaluation.
Dent Mat. 2004;20:176-83.
18- Nagasiri R, Chitmongkolsuk S. Long-term survival of
endodontically treated molars without crown coverage: a
retrospective cohort study. J Prosthet Dent. 2005;93:164-70.
19- Naumann M, Preuss A, Rosentritt M. Effect of incomplete
crown ferrules on load capacity of endodontically treated maxillary
/ /
ceramic crowns: an in vitro evaluation after chewing simulation.
Acta Odontol Scand. 2006;64:31-6.
{+$ /GU;/ $U/` $$ G/ B
Effect of no ferrule on failure of teeth restored with bonded posts
and cores. Gen Dent. 2004;52:143-6.
{#$ / $U/GU;/` $$ G/ B
;6 $
fracture resistance of restored endodontically treated anterior
teeth. J Prosthet Dent. 2006;95:290-6.
22- Oliveira JA, Pereira JR, Lins do Valle A, Zogheib LV. Fracture
resistance of endodontically treated teeth with different heights
composite resin core by intermittent loading. Oral Surg Oral Med
Oral Pathol Oral Radiol Endod. 2008;5:52-7.
J Appl Oral Sci.
{! ? !/ 6
to endodontic and restorative procedures. J Endod. 1995;21:5761.
24- Pegoretti A, Fambri L, Zappini G, Bianchetti M. Finite element
$
Biomaterials. 2002;23:2667-82.
25- Pierrisnard L, Bohin F, Renault P, Barquins M. Corono-radicular
$
element analysis. J Prosthet Dent. 2002;88:442-8.
26- Salameh Z, Ounsi HF, Aboushelib MN, Sadig W, Ferrari M.
Fracture resistance and failure patterns of endodontically treated
$
with a zirconia-ceramic crown. J Dent. 2008;34:842-6.
27- Salameh Z, Sorrentino R, Ounsi HF, Goracci C, Tashkandi E,
Tay F, et al. Effect of different all-ceramic crown system on fracture
resistance and failure pattern of endodontically treated maxillary
$
2007;33:848-51.
28- Sedgley CM, Messer HH. Are endodontically treated teeth
more brittle? J Endod. 1992;18:332-5.
29- Shillingburg HT, Hobo S, Whitsett L, Jacobi R, Brackett
S. Fundamentals of fixed prosthodontics. 3 rd ed. Chicago:
Quintessence Publishing; 1997. p.194-209.
30- Sorrentino R, Aversa R, Ferro V, Auriemma T, Zarone F, Ferrari
/'
stress distributions in endodontically treated maxillary central
incisors restored with different post, core and crown materials.
Dent Mater. 2007;23:983-93.
31- Sorensen JA, Engelman MJ. Ferrule design and fracture
resistance of endodontically treated teeth. J Prosthet Dent.
1990;63:529-36.
32- Sorensen JA, Martinoff JT. Intracoronal reinforcement and
coronal coverage: a study of endodontically treated teeth. J
Prosthet Dent. 1984;51:780-4.
33- Toksavul S, Zor M, Toman M, Gungor MA, Nergiz I, Artunç
C. Analysis of dentinal stress distribution of maxillary central
incisors subjected to various post-and-core applications. Oper
Dent. 2006;31:89-96.
34- Tortopidis D, Lyons MF, Baxendale RH, Gilmour WH. The
variability of bite force measurement between sessions, different
positions within dental arch. J Oral Rehabil. 1998;25:681-6.
35- Varvara G, Perinetti G, Di Iorio D, Murmura G, Caputi S. In
vitro evaluation of fracture resistance and failure mode of internally
restored endodontically treated maxillary incisors with differing
heights of residual dentin. J Prosthet Dent. 2007;98:365-72.
33
2011;19(1):28-33