Hibrid-kompozid ve farklı bonding ajanların kullanıldığı kök kanal tedavili dişlerin, bukkal va palatinal tüberkül kırılma dirençleri

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Introduction
Endodontically treated teeth are structurally different from unrestored vital teeth and require specialized restorative treatment (1). Loss of dentin including anatomic structures such as cusps and arched
roof of the pulp chamber may result in tooth tissue
fracture after the final restoration (2). In particular,
occlusal forces may result in cuspal fractures in rootfilled posterior teeth (3). Cusps deform due to occlusal forces and lateral excursions, even though intact
teeth are stiff (4), and the stress generated during friction between ocluding surfaces is mainly absorbed
in the periodontal ligament (5). Caries, trauma and
the excessive removal of dentine during root canal
treatment produce a substantial reduction in tooth
strength and increase cuspal fracture under occlusal
load (6,7).
Therefore, intracoronal reinforcement of teeth, especially posterior ones, is important in order to protect them against fracture (8). An optimal tooth restoration material should mimic structural, mechanical
and physical characteristics of dentin and enamel
(9).
The use of resin composites for restoring posterior
stress-bearing cavites has increased significantly in
recent years (10). The mechanical properties of resinbased composite mainly depend on its microstructure
and composition. The microstructural characteristics
involve the type, size and quantity of filler particles. These characteristics are directly related with the
composition of the composite (11).
Resin composites with dentin bonding agents are
materials that are considered good candidates for the
direct restoration of endodontically-treated teeth.
When it comes to strengthening the tooth structure
and increasing its fracture resistance, the role of resin
composites with dentin bonding agents has generally
been accepted (12).
* Dental Service, Turkish Army Land Forces
**Department of Conservative Dentistry and Endodontics, Gulhane Military
Medical Academy
Reprint request: Elif Aybala Oktay, Dental Service, Turkish Army Land
Forces, Ankara, Turkey
E-mail: eaybala@yahoo.com
Date submitted: August 18, 2009 • Date accepted: February 04, 20102 • March 2010 • Gulhane Med J Oktay and Sahinkesen
Recently self-etch adhesive systems have been widely utilized due to their simplified application procedures and low-technique sensitivity when compared
to etch and rinse adhesives (13). Self-etch adhesive
systems can generally be classified as either a one-step
(all-in-one) adhesive system or a two-step adhesive
system, based on whether or not a bonding agent is
applied (14). In addition, a two-step adhesive system
reportedly exhibited relatively higher bonding performance of resin to tooth than a one-step self-etch
adhesive system (15).
Clinically, it is important when replacing significant amounts of tooth structure that the restoration
will be functional and not fracture when strong occlusal contacts are present. The purpose of this study
was to compare the fracture resistance of the buccal
cusps and palatal cusps of root-filled maxillary premolar teeth with mesial-occlusal-distal (MOD) cavities restored with new-generation dentine bonding
adhesives.
Material and Methods
A hundred intact, noncarious, nonrestored double
rooted human mature maxillary premolar teeth freshly extracted for orthodontic and periodontal reasons
were selected. The mesio-distal and bucco-lingual dimension of the crown and the cervico-apical length
of the roots were similar. Measurements were made
by the help of a hand length meter. Only sound teeth
with an average length of 20 mm-21 mm, a buccolingual coronal width of 8.5 mm-9 mm and a mesiodistal coronal dimension of 6.5 mm-7 mm were included in the study. Any calculus and soft tissue deposits
were removed from the teeth using a hand scaler, and
the root surfaces were examined in a stereomicroscope for any root fracture and crack. Canal morphology
was verified from standardized apical radiographs (70
kV and 0.08 s) both in the mesial-distal and buccolingual directions. Because of anatomic variability,
the teeth were prepared free hand. The MOD preparations were prepared using high speed diamond
rotating cutting instruments (11161791 QTY) under
constant water cooling. The MOD cavities were prepared so that the bucco-lingual width of the occlusal
isthmus was one-third of the width between buccal
and lingual cusp tips, and the bucco-lingual width
of the approximal preparations was one-third of the
bucco-lingual width of the crown. The approximal
boxes were prepared straight and their depth was limited to 2 mm coronally from the cemento-enamel
junction (Figure 1).
Endodontic access cavity preparation and root canal treatment were performed in three experimental
groups. After endodontic access cavities preparation, a
size 15 K-file was inserted into the canals until it was
visible at the apical foramen for determination of the
working length. The working length of each canal was
calculated to be 1 mm less than the length obtained
with this initial file. Root canal preparations were
performed using Hero 642 NiTi rotary instruments.
The recommended working speed was 300 RPM. All
canals were prepared to ISO size 30-0.04 taper. The
instrumentation was performed strictly according to
the manufacturer’s instructions. The canals were irrigated with 3 mL of 2.5% NaOCl solution after the
use of each instrument. Following biomechanical preparation, the canals were irrigated with 3 mL of 15%
EDTA solution for 30 seconds to remove smear layer.
Final canal irrigation was accomplished with 3 mL of
2.5% NaOCL solution. Instruments were withdrawn
when resistance was felt and changed for the next instrument. Canals were dried with absorbent paper points. Root fillings were completed using gutta percha
(4200A-B Grenoble France) and AH Plus (Dentsply De
Trey GmbH 78467 Konstanz, Germany) root canal sealer using lateral condensation. After root canal fillings
were completed, the test specimens were restored in
the following manner: the material used in this study
and their composition are shown in Tables I and II).
Group 1: According to application procedure of 36%
phosphoric acid, Prime&Bond NT (Dentsply, Caulk,
Milford, DE, USA) acid was applied. After washing
with pressured water spray for 15 seconds extra water
was removed with light air. The surface was moist.
Prime&Bond NT was applied with single usage brush
for 20 seconds. It was applied on all cavity with light
air for 5 seconds. Light was applied for ten seconds.
Total performance hybrid (TPH) spectrum composite
resin was applied on MOD cavity with mouth spatula. Filling was polymerized by applying light on it for
20 seconds.
Group 2: Cearfil Tri–S Bond (Clearfil S
3
Bond);
(Kuraray Medical Inc. Okayama, Japan) was used as
a one-step adhesive for the all-in-one adhesive sysFigure 1. Shape of open MODE. D: Bucco-lingual distance,
B: Distance between cusps, A: Width of occlusial cavity,
C: Approximate width of cavity
D
B
A
C
E
B = 3A
C = 2,83 - 3mm
D = 3C
= 8,5 - 9mm
E =2mmVolume 52 • Issue 1 Dentine bonding agents • 3
tem. After applying air in high pressure for 5 seconds
it was polymerized with light for 10 seconds. Later,
spectrum TPH composite was placed in cavity and
polymerized with light for 20 seconds.
Group 3: Clearfil SE Bond; Two-step adhesive system. Premier (Kuraray Medical Inc. Okayama, Japan)
was applied on cavity with single usage brush for 20
seconds and applied on cavity homogenously. Its polymerization was ensured with light for 10 seconds.
Later, spectrum TPH composite was placed in cavity
and polymerized with light for 20 seconds.
Group 4: (Negative control)
Group 5: (Positive control)
The teeth were randomly divided into three experimental groups and two control (positive and negative) groups of 20 teeth each. Negative control group
did not receive endodontic cavity preparation or root
canal treatment. Positive control group received endodontic cavity and MOD cavity preparation. Positive
and negative experimental control groups were also
divided into two subgroups of 10 teeth each. While
the buccal cusp fracture resistance was observed in
one of the subgroups, the palatinal cusp fracture resistance was observed in the other subgroup.
The teeth were stored in an incubator at 37 C˚ in
100% humidity until the execution of the mechanical
tests. All specimens were thermocycled for 500 cycles
between 5 and 55 C˚ using a dwell time of 30 s. Copper
rings, 25 mm in length and 10 mm in diameter, were
filled with self-curing acrylic resin to the level 2 mm
apical to the cemento-enamel junction. The copper
rings with the teeth were placed into a universal testing machine (Llyod, LRX, Fareham, Hants, England).
The buccal walls of the teeth were then subjected to a
slowly increasing force (1 mm/min) at the junction of
the buccal cusp and the filling material. The force was
applied at the middle mesio-distal width of the buccal
cusp and at a 135° angle to the long axis of the teeth.
Same procedures were applied for palatinal cusps of
the teeth. The force necessary to fracture each tooth
was recorded (Figure 2).
For statistical analysis, SPSS for Windows Ver.15.0
(SPSS Inc., IL, USA) and NCSS 2007 (NCSS Inc., Utah,
USA) were used. All descriptive statistics are shown
as mean±standard deviation. The normality of the
data from all teeth and from subgroups was assessed
Table I. Materials used and their composition
Adhesive system Primer (Self etching primer) Adhesive Resin Manufacturing firm
Clearfil SE Bond (two-step
adhesive system) (self-etch)
10-Methacryloyloxydecyl dihydrogen
phosphate (MDP)
2-Hydroxyethyl methacrylate (HEMA)
Hydropilicdimethacrylate dl-Camphoroquinone
N,N-Dietanol p-toluidine water
Methacryloyloxydecyl dihydrogen phosphate
(MDP)
Bis-PhenolA diglycidylmethacrylate (Bis GMA)
Hydroxyethyl methacrylate (HEMA)
Hydropilic dimethacrylate dl-Camphorquinone
N,N –Dietanol p-toluidine Silanated kolloidal
silica
Kuraray, Osaka, Japan
Clearfil S Bond (all-in one
adhesive system) (self-etch)
10- Methacryloyloxydecyl dihydrogen
phosphate (MDP)
Bis-Phenol diglycidylmethacrylate (Bis-GMA)
2- Hydroxyethyl methacrylate (HEMA)
dl- Camphoroquinone Etil alcohol,
WaterSilanated kolloidal silica
Kuraray, Osaka, Japan
Prime&Bond NT one bottle
(Total-etch)
Conditioner Dipentaeritilol pantaakrilt monofosfat (PENTA),
UDMA, Resin R5-62-1 T-Resin, D-Resin
Nanafiller
Acetone
Dentsply
Table II. The composite material used and its composition
TPH
Spectrum
0.8
(Baglass)
0.5 (SIO)
0.04-2
(SIO)
Barium
glass,
silica
78 to 79 Modified Bis-GMA urethane, boron silicate of silanated aluminum
and barium, silanated pyrolytic silica, camphoroquinone, EDAB,
butylated hydroxytoluen, and mineral dyes
Dentsply
Latin America
Petropolis, RJ,
Brazil
554143
Figure 2. The state of teeth placed on fracture plan4 • March 2010 • Gulhane Med J Oktay and Sahinkesen
graphically and by using the Shapiro-Wilk Test results. To find differences between specimens, a oneway analysis of variance (ANOVA) test was conducted on data that were normally distributed, and the
Kruskall–Wallis tests were used for non-normal data.
When significant differences were found, the reasons
for these differences were analyzed by post-hoc pairwise tests.
Results
The difference between buccal cusp 351 kgf and palatal cusp 320 kgf for fracture resistance was found
statistically insignificant (z=1.035; p=0.301). There
was statistically significant difference in fracture resistance between adhesives in hybrid composite group
(F=7.962; p=0.001) (Figure 3).
When control group was investigated internally,
578 kgf difference between control (-) group and control (+) group was found to be important (t=9.729;
p<0.001). Control (-) group had 5 times more fracture
resistance than control (+) group. In the control (-)
group the fracture resistance of buccal cusp was 973
kgf, whereas the fracture resistance of palatal cusp
was 492 kgf. A fracture resistance difference of 480
unit between buccal and palatal cusp was statistically
significant (Z=3.780; p<0.001) (Figure 4).
In the control (+) group fracture resistance of buccal
cusp was 169 kgf, whereas fracture resistance of palatal cusp was 138 kgf. Buccal cusp had higher fracture
resistance than palatal cusp. However the difference
between two groups was not statistically significant
(Z=1.587; p=0.123).
Discussion
Fracture of teeth is a frequent dental problem (16).
Clinicians often experience the clinical fracture of endodontically treated teeth (17). Many factors, such as
caries, abrasion, erosion, malocclusion, trauma, masticatory stresses, aging and dessication caused by endodontic therapy contribute to the fracture of cusps (18).
In addition, the tooth anatomy itself can be partially
responsible for susceptibility to cuspal fracture (19).
However, cavity preparation procedures for tooth
restorations seem to be the major cause in most cuspal
fractures (20). In particular, several studies have been
performed to assess the mechanical resistance to fracture of root-filled maxillary premolars (21,22).
The resistance of teeth to fracture and the stiffness
of cusps are reduced by cavity preparation, and the degree of reduction is related to the depth and width of
the occlusal cavity as well as to the additional preparation of interproximal surfaces (23-25). Access preparation for endodontic treatment causes a more severe
loss of stability, especially in combination with MOD
The difference (69 kgf) between Prime&Bond NT
and Clearfil Tri-S Bond was statistically insignificant
(p=0.051), whereas 112 kgf of difference between
Prime&Bond NT and Clearfil SE Bond was statistically significant (p=0.001). There was no statistically
significant difference between Clearfil Tri-S Bond and
Clearfil SE Bond (p=0.421).
When subgroups of buccal and palatal cusp in which
restorative materials with dental adhesives were applied to teeth together compared, buccal cusp showed
a lower fracture resistance than palatal cusp. However
14 kgf difference in terms of fracture resistance was
not statistically significant (t=0.328; p=0.746).
Also buccal cusp showed higher fracture resistance than palatal group in hybrid restorative material
Clearfil Tri-S Bond group; but 25 kgf difference had
no statistically significance (t=0.949; p=0.355).
In Clearfil SE Bond group, buccal cusp was found
more resistant than palatal cusp in hybrid restorative
material. The difference in resistance was statistically
significant (z=1.436; p=0.165).
Figure 3. The fracture resistance to buccal and palatal adhesives in
hybrid composite group
600
500
400
300
200
100
0
BUCCAL PALATAL
PRIME & BOND NT
(GROUP 1)
BUCCAL PALATAL
CLEARFİL TRI-S BOND
(GROUP 2)
HYBRİD
BUCCAL PALATAL
CLEARFİL SE BOND
(GROUP 3)
Figure 4. Investigation and comparison of hybrid composite and
control groups
800
700
600
500
400
300
200
100
0
HYBRID COMPOSITE (n=60) CONTROL
Group (-) n=20
CONTROL
Group (+) n=20Volume 52 • Issue 1 Dentine bonding agents • 5
appropriate to use the material for a standard bonding
system, and the evaluation will prove reliability of the
test material.
In this study, no significant difference was found
between buccal and palatal cusp fracture in test groups.
However, Clearfil SE Bond had statistically higher
fracture resistance than Prime&Bond NT. Although
Clearfil SE Bond had higher fracture resistance than
Clearfil S-Tri Bond, there was no statistically significance between these two groups.
Prime& Bond NT we used in our study showed the least buccal and palatal fracture resistance when compared with the other groups. The cause of the difference
was that in total-etching (Prime&Bond NT) adhesive
system phosphoric acid was used to etch the smear
layer following rinsing. A moist surface is required in
order to maintain a noncollapsed demineralized collagen network etched dentine. Usually these one-bottle
adhesive systems contain ethanol or acetone as a solvent. Prolonged and intensive contact with acetonecontaining products may lead to minute dissolution of
the outermost surface of calcium hydroxide materials.
The use of strong 36% phosphoric acid with
Prime&Bond NT, according to the manufacturer’s instructions, may be excessive in the absence of a smear
layer and smear plugs, possibly causing “over etching”
and subsequent collapse of the collagen network. This
situation may inhibit the penetration of adhesive resin
and result in a weak hybrid layer.
An adhesive interface represents the transition area
between materials with different moduli of elasticity;
as a consequence, the adhesive interfaces are considered the weak link of adhesive restorations which can
fail under load, leading to the mechanical failure of
the buccal and palatal. This kind of fracture pattern
was due to morphology of the MOD preparations, leaving limited amounts of residual tooth structure at
level of the cervical margin of the specimens.
Clearfil SE Bond showed the best fracture resistance among all bonding agents. Considering the clinical
advantages of the simplified all-in-one adhesive systems, the bond to enamel requires further improvement. When a self-etch adhesive two step in hybride
composite was used the increase in cuspal rigidity was
significantly greater than total-etch adhesive whereas
combination of nano composite and adhesives need
further investigation. We believe that further studies
should be made to investigate the accordance between
adhesives and composites. Thus, the use of composite
resin and a bonding system has become widely accepted for restorative treatment of nonvital teeth. Clinical
studies should be performed keeping in mind the accordance between composites and adhesives.