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THE EFFECT OF DIFFERENT SURFACE TREATMENTS ON RETENTION OF GLASS FIBER POSTS, CARBON FIBER POSTS AND CAST METAL POSTS. AN IN-VITRO STUDY
By Dr. ROMESH SONI
Dissertation submitted to
Rajiv Gandhi University of Health Sciences, Bangalore
In partial fulfillment of the requirements for the degree of
MASTER OF DENTAL SURGERY
in
PROSTHODONTICS, CROWN&BRIDGE INCLUDING IMPLANTOLOGY
Under guidance of
Prof Dr. D. R. PRITHVIRAJ
DEPARTMENT OF PROSTHODONTICS,
GOVERNMENT DENTAL COLLEGE AND RESEARCH
INSTITUTE
BANGALORE-02
(2006-2009)
I
RAJIV GANDHI UNIVERSITY OF
HEALTH SCIENCES, BANGALORE KARNATAKA
DECLARATION BY THE CANDIDATE
I hereby declare that the dissertation/thesis entitled ‘‘THE EFFECT OF
DIFFERENT SURFACE TREATMENTS ON RETENTION OF
GLASS FIBER POSTS, CARBON FIBER POSTS AND CAST
METAL POSTS. AN IN-VITRO STUDY” is a bonafide work carried out by
me under the guidance of Dr.D.R.PRITHVIRAJ, Professor and Head,
Department of Prosthodontics, Government Dental College and Research Institute,
Bangalore.
Date:
Place: Bangalore Dr. ROMESH SONI
II
RAJIV GANDHI UNIVERSITY OF
HEALTH SCIENCES, BANGALORE KARNATAKA
CERTIFICATE BY THE GUIDE
This is to certify that this dissertation entitled “THE EFFECT OF
DIFFERENT SURFACE TREATMENTS ON RETENTION OF
GLASS FIBER POSTS, CARBON FIBER POSTS AND CAST
METAL POSTS. AN IN-VITRO STUDY” is a bonafide research work done
by Dr. ROMESH SONI in partial fulfillment of the requirement for the degree of
MASTER OF DENTAL SURGERY DEGREE IN
PROSTHODONTICS.
Date: Dr. D. R. PRITHVIRAJ, M.D.S
Place: Bangalore Professor& Head
Dept of Prosthodontics
Govt Dental College and Research Institute
Bangalore -02
III
ENDORSEMENT BY THE HOD,
DIRECTOR/HEAD OF THE INSTITUTION
This is to certify that this dissertation entitled “THE EFFECT OF
DIFFERENT SURFACE TREATMENTS ON RETENTION OF
GLASS FIBER POSTS, CARBON FIBER POSTS AND CAST
METAL POSTS. AN IN-VITRO STUDY” is a bonafide research work done
by Dr. ROMESH SONI under the guidance of Dr. D. R. PRITHVIRAJ,
Professor and Head, Department of Prosthodontics, Government Dental College and
Research Institute, Bangalore.
(Dr.D.R.Prithviraj) (Dr. S.S. Hiremath) Professor& Head Dean cum Director
Dept of Prosthodontics Government Dental College and
Research Institute, Bangalore.
Date: Date:
Place: Bangalore Place: Bangalore
IV
V
COPY RIGHT
Declaration by the Candidate
I hereby declare that the Rajiv Gandhi University of Health Sciences,
Bangalore, Karnataka shall have the rights to preserve, use and
disseminate this dissertation/thesis in print or electronic format for
academic/research purpose.
Date: Place: Bangalore Dr. ROMESH SONI
© Rajiv Gandhi University of Health Sciences, Karnataka
VI
ACKNOWLEDGEMENTS This dissertation has been one of the most significant academic challenges I
have ever had to face. Without the constant support, guidance and encouragement of
the following people, this study would not have been completed. It is to them I owe
my deepest gratitude.
It is my privilege and honor to express my sincere thanks and gratitude to
Dr. D. R. Prithviraj, Professor and Head, Department of Prosthodontics,
Government Dental College and Research Institute, Bangalore, for his continuous
support, guidance provided and constant encouragement shown to me. His wisdom,
knowledge, vision and commitment to highest standards inspired and motivated me in
shaping my outlook to this profession.
I avail this opportunity to thank Dr. Sounderraj, Professor, Dr. Prema,
Assistant Professor and Dr.Vishwanath, Assistant Professor, Department of
Prosthodontics, for their constant guidance and valuable suggestions during the course
of my study.
I am thankful to Dr S.S. Hiremath, Dean cum Director, Government Dental
College and Research Institute, Bangalore for providing the facilities needed for this
study.
I express my heartfelt thanks to Dr. Kalavathi, Dr. Anoop, Dr Nagaranjni,
Dr Reshma, lecturers, Department of Prosthodontics for their suggestions and co-
operation during my post-graduate study.
VII
I am also thankful to all the non-teaching staff and technicians in the
Department of Prosthodontics for their support and co-operation during the course of
my study.
I would like to thank Mr Rajesh, Manager, 3M ESPE, Bangalore who
allowed me to analyze my samples in their universal testing machine. My sincere
regards to Mr.Tejasvi, senior statistician for his help in preparing the statistical data
needed for this study.
My profound thanks and appreciation to my seniors Dr. Sarvan, Dr. Ankit
and Dr. Vishal, and to my colleague Dr. Sushma for their untiring stint of moral
support, encouragement, and help. I sincerely thank Dr. Sumit, Dr. Anish, Dr. Pooja
and Dr. Malesh for their constant help and support.
I thank my parents Mr. D.S. Soni & Mrs. Narender Kaur and my loving
brother Dr. Ankit Soni who has always supported, encouraged and believed me in all
my endeavors. At last but not the least, my wife Dr. Shilpa Soni whose belief in me
and my capabilities has encouraged and motivated me a lot.
Ultimately I thank the Almighty for his blessings and being besides me
through the thick and thin of life.
Date:
Place: Bangalore Dr.ROMESH SONI
.
VIII
LIST OF ABBREVIATIONS USED
ANOVA: Analysis of Variance
cm: Centimeter
EDTA: Ethylene diamene tertraacetic acid
FRC: Fiber reinforced composite
Kgf : Kilogram force
mm: Millimeter
PMMA: poly- methyl methacrylate
SD: Standard Deviation
SEM: Scanning electron microscope
IX
ABSTRACT Background and objectives: The present study was conducted with the purpose of
analysis of the effect of different surface treatments on retention of glass fiber posts,
carbon fiber posts and cast metal posts.
Method: Ninety extracted single rooted human teeth were selected. Each tooth was
cut with, a diamond rotatory cutting instrument, 1 mm coronal to the cemento-enamel
junction. Post spaces were prepared to 9mm in length for all the teeth with the specific
drill bit provided by the manufacturer for the specific size of post. Surface treatment
of the glass fiber post, carbon fiber post and cast metal posts with ethyl alcohol, resin
primer and air-borne alumina particle abrasion was done. Posts were luted with dual
cure resin cement. For the Retentive force test, a screw driven universal testing
machine was used to apply tensile load to the post. The force required to dislodge
each post from prepared post space was recorded.
Results: Air-borne alumina particle abraded cast-metal posts had the highest retentive
strength compared to all other surface treated or untreated posts used in the study
followed by primer treated cast metal posts and ethyl alcohol treated cast metal posts.
Airborne alumina particle abraded glass fiber posts and carbon fiber posts had the
next highest retentive strengths. Treating the surface of the posts with resin-primer
and ethyl alcohol produced no statistically significant difference in the retentive
strength of all the type of posts used in the study. There was no significant difference
in the retentive strength obtained between glass fiber posts and carbon fiber posts.
X
Conclusion: Within limitations of this study, it may be concluded that, air-borne
alumina particle abrasion increased the retentive strength of all the type of posts used
in this study. Surface treatment of the posts with resin-primer and ethyl alcohol
produced no statistically significant difference in the retentive strength.
Keywords: Retentive strength, Surface treatment, Airborne alumina particle abrasion,
Tensile load.
XI
CONTENTS
1. INTRODUCTION 1-2
2. OBJECTIVES 3
3. REVIEW OF LITERATURE 4-14
4. METHODOLOGY 15-25
5. RESULTS 26-37
6. DISCUSSION 38-42
7. CONCLUSION 43
8. SUMMARY 44
9. BIBILIOGRAPHY 45-47
XII
LIST OF TABLES
Sl. No
Tables
Page no
I Retentive strength of carbon fiber post treated with ethyl alcohol
28
II
Retentive strength of carbon fiber post treated with resin primer
28-29
III
Retentive strength of carbon fiber post air abraded with alumina
29-30
IV
Retentive strength of glass fiber post treated with ethyl alcohol
30
V
Retentive strength of glass fiber post treated with resin primer
30-31
VI
Retentive strength of glass fiber post air abraded with alumina
31-32
VII Retentive strength of cast metal post treated with ethyl alcohol
32
VIII Retentive strength of cast metal post treated with resin primer
32-33
IX
Retentive strength of cast metal post air abraded with alumina
33-34
X Means and standard deviations of each group
34
XI
Comparisons of the mean retentive strength of posts using ANOVA test.
34-35
XII
Multiple comparisons using Bonferroni method to find out
significant difference between type of post
35
XIII
Multiple comparisons using Bonferroni method to find out
significant difference between type of treatment.
36
XIII
LIST OF FIGURES
Sl. No
Figures
Page No
1
Armamentarium used for the study
20
2
Custom made device of stainless steel (lateral view)
20
3
Custom made device of stainless steel (superior view)
21
4
PMMA Blocks with sectioned teeth and prepared post
spaces
21
5a
Carbon fiber post luted with dual cure resin cement
22
5b
Glass fiber post luted with dual cure resin cement
22
5c
Cast metal post luted with dual cure resin cement
23
6
Induction Casting Machine
23
7
Universal Testing Machine
24
8a
Universal Testing Machine with the custom made device
24
8b
Universal Testing Machine with the dislodged post
25
XIV
LIST OF GRAPHS
Sl. No.
Graphs
Page no.
I.
Mean retentive strength of each group in bar diagram
36
II.
Main effects plot of retentive strength of each group
37
III.
Interaction plot of retentive strength between each group
37
Introduction
Restoring endodontically treated teeth is a challenge when insufficient coronal
tooth structure remains to support a restoration, and the post is commonly used to
retain the core. Post and core systems have been used to restore endodontically treated
tooth for more than 250 years.1
Post and core system are available in variety of materials. Cast metal post and
core foundations have a long history of successful use due to their superior physical
properties. However, esthetic properties of these materials are limited since gray
colored post and core is apparent when used to support translucent all-ceramic
restorations. Coupled with a high lip line, cast metal post and core foundations may
result in esthetic problems. Additionally, their high elastic modulus can cause stress
concentration within surrounding radicular dentin, resulting in root fractures.2
Prefabricated post systems are also popular because they can provide satisfactory
results, while saving time and reducing costs. However, prefabricated post should
adequately adapt to prepared root canal otherwise a cast post and core should be used.
Carbon fiber posts have also come into use for prosthodontic applications.3 In
general, the mechanical properties of a fiber reinforced composite material depend
strongly on load direction. The fatigue behavior of fiber reinforced composites which
are anisotropic is also vastly different from that of homogenous materials. In a
homogenous material under fatigue, a crack once initiated, often propagates quickly,
thus leading to sudden failure of the material. However, the damage process in
composite materials is complex, consisting of matrix cracking, interface debonding,
delamination, local fiber breakage and the microstructure of the material has a great
1
Introduction
influence on fatigue behavior. Further, properties such as biocompatibility and
corrosion resistance, make the carbon fiber post a potential replacement for
conventional metallic post in many clinical situations. However, the modulus of
elasticity of carbon fiber post is much greater than that of dentin. Also as with
metallic posts, the use of carbon fiber posts have generally limited esthetic
expectations. Their dark underlying color can adversely influence the shade of
overlying gingival tissue and prosthetic restorations.4 Post made up of tooth colored material such as glass fibers have become
popular because they increase the transmission of light within root and overlying
gingival tissues. Glass fiber posts are composed of glass fibers, inorganic filler, and a
resin matrix. The low modulus of elasticity of fiber reinforced epoxy resin post has
been reported to reduce risk of root fracture. In addition, the restoration of
endodontically treated teeth with metal free materials eliminates the potential hazards
of corrosion and hypersensitivity. Fiber reinforced posts also have advantage of easy
removal if endodontic retreatment is required.5
Many in-vitro studies have investigated various factors that affect retention of
a post. However, very few studies have been done to evaluate the effect of different
surface treatment on retention of Glass fiber post, Carbon fiber post and Cast metal
posts. Hence, this study was carried out to compare the effect of surface treatment
with ethyl alcohol, resin primer and air-borne alumina particle abrasion on the
retention of Glass fiber post, Carbon fiber post and Cast metal posts.
2
objectives
The objectives of this study are as follows-
1. To evaluate the effect of surface treatment by 57.1% Ethyl alcohol on
retention of glass fiber posts.
2. To evaluate the effect of surface treatment by Rely a Bond Resin Primer on
retention of glass fiber posts.
3. To evaluate the effect of surface treatment by Air borne Alumina Particle
Abrasion on retention of glass fiber posts.
4. To evaluate the effect of surface treatment by 57.1% Ethyl alcohol on
retention of carbon fiber posts.
5. To evaluate the effect of surface treatment by Rely a Bond Resin Primer on
retention of carbon fiber posts.
6. To evaluate the effect of surface treatment by Air borne Alumina Particle
Abrasion on retention of carbon fiber posts.
7. To evaluate the effect of surface treatment by 57.1 % Ethyl alcohol on
retention of cast metal posts.
8. To evaluate the effect of surface treatment by Rely a Bond Resin Primer on
retention of cast metal posts.
9. To evaluate the effect of surface treatment by Air Borne Alumina Particle
Abrasion on retention of cast metal posts.
10. To compare the effect of surface treatment by 57.1 % Ethyl alcohol, Rely a
Bond Resin primer and Air borne Alumina Particle Abrasion on retention of
glass fiber post, carbon fiber post and cast metal post.
3
Review of literature
Studies have been conducted to know the effect of different surface treatments
on the retentive strength of the different types of posts. Different materials and
methodologies have been tried by different authors to improve the retentive strength.
The related articles have been reviewed and presented here.
The authors6 in 1993 conducted a study to evaluate the effect of Ethylene
diamine tetraacetic acid (EDTA) in the post spaces. They concluded that EDTA was
too strong a solvent to remove the smear layer even for limited periods. The inorganic
smear layer may be removed but the adjacent dentin of the canal may also be
appreciably weakened by the EDTA because of deterioration of the inorganic matrix
of dentin.
The authors7 in 1994 conducted a study to evaluate the retention of posts
cemented with various dentinal bonding cements. The study compared the ability of
three resinous cement and a glass ionomer cement to retain the post in the root canals
of extracted endodontically treated maxillary canines. Resinous cements vary in their
ease of manipulation and in their ability to retain endodontic post. Their study
demonstrated that C & B metabond cement provided the greatest retention for the
cemented posts. The glass ionomer cement (Ketac-Cem) was equally or more
retentive than Panavia and All bond 2 resinous cement, respectively. Ketac-Cem
cement was also easier to manipulate.
The authors8 in 1995 conducted a study to evaluate the survival rate and
4
Review of literature
failure rate of two post designs – custom cast tapered posts and parallel sided serrated
posts. The result of the study showed loss of retention being the most frequent cause
of failure for both type of post, the incidence being higher for custom cast tapered
post.
The authors9 in 1997 conducted a study to evaluate the effect of different
surface textures on the retentive strength of tapered posts. Two sizes of tapered
titanium post were used: post No.1, 9 mm length, 0.5 mm base diameter; and post No.
3, 15 mm length, 1.1 mm base diameter were used. The various surface textures of the
tapered post used were smooth, smooth with grooves, sandblasted, sandblasted with
grooves. In addition, effect of size of post and roughening the dentinal walls of the
post spaces on retentive strength was also evaluated. They concluded that smooth post
showed the lowest retentive strength. Sandblasting the smooth post doubled its
retentive strength. The retentive strength of both smooth and sandblasted posts could
be further increased by the addition of circumferential grooves. Roughening the
dentinal walls of the prepared post space increased the retentive strength of
sandblasted posts with and without grooves even more. Larger posts demonstrated an
absolute retentive strength almost three to four times higher than smaller size posts.
The authors10 in 1997 conducted a study to evaluate cyclic fatigue testing of 5
endodontic post designs supported by four core materials. This study was examined
the ParaPost, and Volck) with four core materials (Tytin silver amalgam, Ti-core,
Ketac-Silver and G-C Miracle Mix). They concluded that all post/core samples with
Ti-Core composite and Tytin silver amalgam completed the test with no failures.
5
Review of literature
All post/ core samples with Ketac-Silver material failed before the 4,000,000 test
cycle configuration and all failures were core failures. All post/ core samples with G-
C Miracle Mix material failed in a similar manner. With this simulated fatigue test,
Ti-Core material and Tytin silver amalgam were superior to both G-C Miracle Mix
and Ketac-Silver materials.
The authors11 in 1997 conducted a study to evaluate the in-vitro performance
and the failure characteristics of the carbon fiber post and core system. This study
compared the composipost system (comprising a carbon fiber post, a composite core
material, and a low viscosity Bis-GMA bonding resin) against stainless steel post and
composite core, gold alloy post and gold alloy core combinations. They concluded
that the specimens restored with the Composipost system exhibited inferior strength
properties in comparison to the other post and core systems tested.
The authors12 in 1997 conducted a study to evaluate the root reinforcement
with a resin bonded preformed post. The result of the study showed that force needed
to fracture the roots in zinc phosphate cement group were lower than in the composite
cement group.
The authors13 in 1998 conducted a study to evaluate the retention of three
endodontic posts cemented with five dental cements. This study compared the
retentive values of three posts (Flexi-post, AccessPost, and ParaPost) cemented with
five cements; Flexi-flow cement (Composite resin cement), Zinc phosphate, Advance
6
Review of literature
cement (Glass ionomer cement), Duet cement (Glass ionomer hybrid cement) and
Ketac-cem (Glass ionomer cement). They concluded that Flexi-post dowel with Flexi-
flow cement obtained the highest retentive value. Parapost dowel with Duet cement
exhibited the lowest retention value. The Flexi-post dowel demonstrated higher mean
retention than Access post or Para post dowels; Access post dowel was higher than
Para post dowel. Flexi-flow cement had the highest overall mean retention followed
by, Zinc phosphate, Advance, Ketac-cem, and Duet cements.
The authors14 in 1998 conducted a study to evaluate the retention of parallel-
sided titanium posts cemented with six luting agents. Two resin-ionomer hybrid
cements and 2 resin cements were tested with corresponding dentin bonding agents. A
Glass ionomer cement was also tested, and Zinc-phosphate cement served as the
control. Samples were tested in an Instron universal testing machine to catastrophic
tensile failure. They concluded that Advance cement (resin ionomer cement) with
Prime and Bond systems was found to be statistically more retentive than all other
groups tested. Cement It (resin cement) with Bond It (dentin bonding agent) and
Permalute (resin cement) with Permalute Primers A and B systems (dentin bonding
agents) demonstrated significantly greater retention than the other cements. There was
no statistically significant difference among Ketac Cem cement, Resinomer, and
zinc-phosphate cement.
The authors15 in 1998 conducted a study to evaluate the retention of post
with Resin cement, Glass ionomer cement and Hybrid cement and they
7
Review of literature
concluded that retention of posts was better with resin and glass ionomer cements
than with resin modified glass ionomer cement. The relative low retention of hybrid
cements was attributed to inconsistent powder to liquid ratio and presence of air voids
in the post space.
The authors16 in 1998 conducted a study to evaluate the affect of cement
thickness on retention of endodontic posts with a composite resin luting cement and it
was concluded that changes in composite resin luting agent thickness of upto 500 μm
do not decrease the retention of endodontic post.
The authors17 in 2000 conducted a study to compare the tensile bond strength
of adhesive resin cement to different post materials. They concluded that Panavia 21
produced consistently higher bond strength to all types of post material due to the
presence of adhesive monomer MDP (10-Methacryloxydecyl dihydrogen phosphate).
C&B metabond had consistently high bond strength to metal alloys but lower bond
strength with the Zirconium groups.
The authors18 in 2001 conducted a study to evaluate the use of reinforced
composite resin cement as compensation for reduced post length. The retention values
of stainless steel posts (parallel-sided ParaPost and tapered Dentatus) luted with
Flexi-Flow titanium-reinforced composite resin and zinc phosphate cements were
evaluated. They concluded that Flexi-Flow reinforced composite resin cement
compensated for the reduced length of shorter parallel-sided ParaPost and tapered
8
Review of literature
Dentatus dowels.
The authors19 in 2001 conducted a study to evaluate the in-vitro fatigue
resistance of Glass ionomer cements used in post-and-core applications. This study
evaluated the fatigue resistance of 2 new Glass ionomer cements, Shoufu Hi-Dense
and Fuji IX GP, and compared their mechanical behavior as a core material under
masticatory load with a silver-reinforced glass ionomer (ESPE Ketac-Silver) and a
silver amalgam (Cavex Avaloy LC). They concluded that silver amalgam was
significantly superior to all glass ionomer cements tested. The silver-reinforced glass
ionomer showed the highest rate of defect formation. Shofu Hi-Dense and Fuji IX GP
showed significantly fewer defects than Ketac-Silver.
The authors20 in 2004 conducted a study to evaluate the diametral tensile
strength of a resin composite core with nonmetallic prefabricated posts. The aim of
this study was to determine the influence of different types of posts on the fracture
resistance of resin composite core material using the diametral tensile strength test.
They concluded that when used with the composite core material, Light-Post,
Dentorama post, and FiberKor resulted in the highest diametral tensile strength
values, whereas ParaPost resulted in the lowest values.
The authors21 in 2006 conducted a study to evaluate the effect of silane on the
bond strengths of fiber posts. Fifty-four extracted human maxillary central incisors
and canines were endodontically treated. D.T. Light Post (DT, Bisco), FRC Postec
(FR, Ivoclar Vivadent), and ParaPost Fiber White (PP, Colt`ene/Whaledent) were
9
Review of literature
inserted using the resin adhesive system provided by the respective manufacturer. For
half of the specimens in each group, the fiber posts were treated with a silane solution
(Monobond S, Ivoclar Vivadent). A push-out test was performed on three different
sections of each root to measure bond strengths. They concluded that the use of a
silane coupling agent did not increase the push-out bond strengths of the three fiber
posts used in this study. All posts bonded to root dentin at the same magnitude.
Bonding is more predictable at the most coronal level of the root.
The authors5 in 2006 conducted a study to evaluate the effect of different
surface treatments on retention of glass-fiber endodontic posts. The tapered post
received 1 of 4 surface treatments: cleaning with alcohol, cleaning with alcohol and
conditioning with ED-Primer, airborne-alumina particle abrasion, or air-borne
alumina particle abrasion and conditioning with ED-Primer. They concluded that the
air-borne alumina particle abraded posts had significantly higher retention compared
with the non-abraded posts. Treating the post surface with ED-Primer material prior
to cementation had no significant effect on retention.
The authors2 in 2006 conducted a study to evaluate the resistance of three new
esthetic post-and-core systems to compressive loading. Three experimental
groups consisted of a stainless steel post with composite-resin core group, zirconium
dioxide post with composite-resin core group, and zirconium dioxide post with
ceramic core group. The cast metal post and core group served as the control. They
concluded that the cast metal post with metal core and zirconia post with ceramic core
10
Review of literature
foundations were found to be more fracture resistant than the other post and core
groups. Aside from it’s desirable esthetic properties, the zirconia post with ceramic
core combination demonstrated high resistance to fracture.
The authors22 in 2007 conducted a study to evaluate the flexural modulus and
flexural strength of different types of endodontic post in comparison with human root
dentin. Fiber-reinforced composite (FRC) posts have an elastic modulus that more
closely approaches that of dentin while that for metal posts was much higher. The
flexural strength of fiber post and metal posts was respectively four and seven times
higher than root dentin.
The authors23 in 2007 conducted a study to evaluate flexural strength of
different fiber reinforced post systems. Eight types of fiber post were selected for this
study. Fiber Kor (Jeneric-Pentron), Para Post Fiber White (Coltene), Luscent Anchor
(Dentatus), Twin-Luscent Anchor (Dentatus), Style Post (Metalor), DT White-Post
(VDW), DT Light-Post (VDW) and ER Dentin Post (Brasseler) A universal testing
machine loading at an angle of 90◦ was employed for the three-point bending test.
The test was carried out until fracturing of the post. They concluded that the flexural
strength of the fiber reinforced systems ranged from 565 to 898MPa. DT White-Post
and DT Light-Post (898 and 842MPa, respectively) had significantly higher flexural
strengths than the other posts. Style Post (565MPa) showed a significantly lower
flexural strength than all other posts.
The authors24 in 2007 conducted a study to evaluate .the rotational fatigue-
11
Review of literature
resistance of seven post types anchored on natural teeth. They concluded that in
increasing order of magnitude, the resistances to fatigue loading were as follows:
Biopost (Zirconium oxides Y-TZP), Unimetric-T (Titanium), Unimetric-SS (Stainless
steel), Composipost (Carbon fibers), Easypost (Si–Zr fibers), Everstickpost (E-glass
fibers), DT Lightpost (Quartz fibers).
The authors25 in 2007 conducted a study to evaluate the effect of sandblasting
on adhesion of a dual-cured resin composite to methacrylic fiber posts. They
concluded that sandblasting increases the microtensile strength to methacrylate-
based glass fiber posts, thus eliminating the need for additional ‘‘chair-side’’
treatments like Silane application (Monobond S, Ivoclar Vivadent) or Adhesive
application (Unifil Core self-etching bond).
The authors26 in 2007 conducted a study to evaluate the fracture resistance of
anterior endodontically treated teeth prepared with a 2-mm ferrule, restored
with glass fiber and zircon posts and composite resin cores or cast posts and cores.
They concluded that the teeth restored with glass fiber and zircon posts
demonstrated significantly lower failure loads than those with cast NiCr post and
cores. All specimens failed via root fractures.
The authors27 in 2008 conducted a study to evaluate the effect of two fiber
post types and two luting cement systems on regional post retention using the push-
out test. The crowns of 24 recently extracted sound maxillary central incisors were
sectioned transversely 2mm coronal to the labial cemento-enamel junction, and the
12
Review of literature
roots were treated endodontically. Following standardized post space preparations,
fiber-reinforced posts (C-POST; AESTHETI-PLUS) were placed using two adhesive
systems (acid-etch one-step plus/C&B cement; self-adhesive RelyX Unicem), in four
equal groups. Push-out bond strength tests were performed at four sites in each root.
They concluded that AESTHETI-PLUS (quartz fiber-reinforced posts) showed
significantly higher push-out strengths than C-POST (carbon fiber-reinforced posts).
The authors28 in 2008 conducted a study to compare the tensile strength of
commercially pure titanium and type III cast gold-alloy posts and cores cemented
with zinc phosphate or resin cement. Forty-two extracted human canines were
endodontically treated. The root preparations were accomplished using Largo reamers
(10 mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the posts and
cores were made, and specimens were casted in commercially pure titanium and in
type III gold alloy. Fourteen titanium cast posts and cores were submitted to surface
treatment with Kroll acid solution and to scanning electron microscopy (SEM), before
and after acid etching. The groups were cemented with zinc phosphate cement or
resin cement (Panavia F). Tensile strengths were measured in a universal testing
machine at a crosshead speed of 0.5 mm/min. They concluded that there were no
significant differences among the groups tested. Retentive means for zinc phosphate
and Panavia F cements were statistically similar. The bond strength was not
influenced by the alloy, the luting material, or the etching treatment. SEM analysis
indicated that the etched surfaces were smoother than those that did not receive
surface treatment, but this fact did not influence the results.
13
Review of literature
The authors29 in 2008 conducted a study to evaluate the static and fatigue
fracture resistances of pulpless teeth restored with post–cores. Extracted human
premolars were restored with a combination of either a fiber post or metallic post and
a composite resin core. Teeth with full crown preparations without post–core
restorations served as a control. A 90◦ vertical or 45◦ oblique static compressive load
was applied to restored teeth, and fracture loads and modes of fracture were recorded.
Fatigue fracture tests were conducted by applying sinusoidal cyclic loads to restored
teeth from vertical or oblique directions. They concluded that in both static and
fatigue fracture testing under vertical or oblique loadings, the fracture loads of teeth
restored with fiber posts were significantly greater than those of teeth restored with
metallic posts. The fatigue limits of teeth restored with fiber and metallic posts were
112 kilogram force (kgf) and 82 kgf respectively under vertical loadings and 26 kgf
and 20 kgf under oblique loading.
14
Methodology
The present in-vitro study was carried out to evaluate the effect of different
surface treatments on the retentive strength of glass fiber posts, carbon fiber posts and
cast metal posts.
Materials and Armamentarium used (figure 1).
A. Materials used for specimen preparation 1. Custom made device of stainless steel- Hollow cubical mold without roof
of the following dimensions-
Length-40 millimeter (mm), Width-40mm, Height-25mm with uniform wall
thickness of 6mm. For easy holding of cubical mold during testing a 2mm
thick stainless steel plate was welded below it (figure-2 and 3).
2. Auto-polymerizing poly-methyl methacrylate resin (DPI-RR Cold cure,
DPI, Mumbai, India)
3. Extracted human teeth with single root canal.
4. Elastomeric impression material: Addition polyvinylsiloxane (Aquasil, Soft
Putty/regular set, Dentsply, Germany) 5. Petroleum Jelly (Nice chemicals Pvt. Ltd, Cochin)
B. Materials and armamentarium used for sectioning the teeth and
preparation of post spaces
1. Diamond burs (Preparation set, Shofu Inc, Kyoto, Japan) 2. Air-rotor hand piece (Pana-Air, NSK Nakanishi Inc, Tochigi-ken, Japan)
3. Endo-files (K-file, Dentsply DeTrey GmbH, Constance, Germany).
15
Methodology
4. Sodium Hypochlorite- 3% solution (Vensons India, Bangalore, India)
5. Drill Bit for preparation of post spaces – Size 2 (R.T.D, France)
C. Materials and Armamentarium used for post and cementation of posts
1. Glass Fiber Posts with diameter of 1 mm at apex –size 2 (D.T. Light post,
R.T.D, France)
2. Carbon Fiber posts with diameter of 1 mm at apex –size 2 (D.T. Carbon
post, R.T.D, France)
3. Ni-Cr alloy ( Wiron, Bego, Bremen, Germany )
4. Aluminium oxide blasting material-50µm (Korox 50, Bego, Bremen,
Germany)
5. Ethyl Alcohol 57.1% (Surgical Spirit, Reliance Pharmaceutical
Laborateries, Hyderabad, India)
6. Primer (Rely a Bond, Reliance products, U.S.A.)
7. Dual cure resin cement (Rely x ARC, 3M ESPE, U.S.A)
8. Phosphate bonded investment material (Bellasun, Bego, Bremen, Germany)
9. Silli Rings ( Ringless casting rings, Vijai Dental Products, Chennai, India )
10. Vaccum Mixing Machine (Wehmer, U.S.A.)
11. Burn-out Furnace (Sidesco, Bangalore)
12. Induction Casting Machine (Degutron, Degussa AG, Germany) (figure 6).
D. Instrument used for measurement of retentive strength
1. Universal Testing Machine with a cross head speed of 2mm/min. (Instron
33R 4467, Instron limited, Buckinghamshire, England) (figure 7).
16
Methodology
Method
1. Ninety extracted caries-free and visually assessed fracture free, human
maxillary anterior teeth and mandibular premolar teeth were selected. The selected
teeth were cleaned of both calculus deposits and soft tissue, and stored in distilled
water.
2. A thin layer of petroleum jelly was applied to the inner walls of hollow
cubical mold. Thereafter, the mold was filled with a mix of auto-polymerizing acrylic
resin. After polymerization, the poly-methyl methacrylate block (PMMA) was
removed from the cubical mold. The PMMA block was subsequently duplicated using
elastomeric impression material. All the PMMA blocks were tested for the fit in the
cubical mold. If there was any interference, it was removed by trimming. After the fit
of the PMMA blocks was checked, a hole was made in the center of these blocks.
Total ninety PMMA blocks were prepared for mounting the teeth. Notches were
prepared in root of the teeth to prevent dislodgement during testing and subsequently
each tooth was mounted in the hole made in the PMMA block till cemento-enamel
junction with a fresh mix of auto-polymerizing acrylic resin.
3. Each tooth was sectioned with a diamond rotatory cutting instrument under water spray, 1 mm coronal to the cemento-enamel junction. Roots with distinctly
oval canal and diameter of more than 2mm were excluded from the study. The pulpal
tissue was removed and canal was enlarged with Endo files up to size 40. 3% Sodium
hypochlorite solution was used to irrigate the canal throughout instrumentation.
17
Methodology
. 4. Specific drill bit of size 2 supplied for the prefabricated fiber post size 2 was
marked at 9mm length from the tip using permanent marker and post spaces of 9mm
in length were prepared(figure 4). New instrument was used for every 8 specimens.
Throughout the preparation, the post spaces were irrigated with 3% Sodium
hypochlorite solution. The prepared post spaces were dried.
5. Acrylic patterns of the post spaces of thirty specimens were made for cast
metal posts and were numbered. Subsequently they were invested and casted with Ni-
Cr alloy using an Induction Casting Machine.
6. All the specimens were divided into 9 groups. Each group contained 10
specimens.
GROUP 1- Carbon fiber posts cleaned with 57.1% ethyl alcohol for three minutes.
GROUP 2- Carbon fiber posts conditioned with resin primer for 60 seconds.
GROUP 3- Carbon fiber posts air abraded with 50µm alumina particles for 5 seconds
from a distance of 30mm.
GROUP 4- Glass fiber posts cleaned with 57.1% ethyl alcohol for three minutes.
GROUP 5- Glass fiber posts conditioned with resin primer for 60 seconds.
GROUP 6- Glass fiber posts air abraded with 50µm alumina particles for 5 seconds
from a distance of 30mm.
GROUP 7- Cast metal posts cleaned with 57.1% ethyl alcohol for three minutes.
GROUP 8- Cast metal posts conditioned with resin primer for 60 seconds.
18
Methodology
GROUP 9- Cast metal posts air abraded with 50µm alumina particles for 5 seconds
from a distance of 30mm.
7. All the surface treated posts were marked at 9 mm (millimeter) from the
apex using permanent marker and subsequently luted with Dual cure resin cement
(figure 5a,b,c). Cement was not light cured to standardize the study, as carbon fiber
post and cast metal posts were also used.
8. For the Retentive force test, a screw driven universal testing machine was
used to apply tensile load to the post at a cross head speed of 2mm/min (figure 8a,b).
The force required to dislodge each post from prepared post space was recorded. The
data was subjected to statistical analysis.
19
Methodology
Figure 1: Armamentarium used for the study
Figure 2: Custom made device (lateral view)
20
Methodology
Figure 3: Custom made device (superior view)
Figure 4: PMMA Blocks with sectioned teeth and prepared post spaces
21
Methodology
Figure 5a: Carbon fiber posts luted with dual cure resin cement
Figure 5b: Glass fiber posts luted with dual cure resin cement
22
Methodology
Figure 5c: Cast metal posts luted with dual cure resin cement
Figure 6: Induction Casting Machine
23
Methodology
Figure 7: Universal Testing Machine
Figure 8a: Universal Testing Machine with the custom made device
24
Methodology
Figure 8b: Universal Testing Machine and the dislodged post
25
Results
Retentive strength of Glass fiber posts, Carbon fiber posts and Cast metal
posts surface treated with ethyl alcohol, resin primer and airborne alumina particle
abrasion were compared. Retentive strength of Group 1 to 9 is listed in Table I to XI
respectively. Means and standard deviations of each group are listed in Table X.
Comparison of the mean retentive strength using two-way Analysis of Variance
(ANOVA) is listed in Table XI. From the two way ANOVA test we observe that
type of post is a significant factor influencing retentive strength and there is a
significant difference between the different posts (P<0.001). We also notice that
“Surface Treatment” is a significant factor influencing retentive strength and there is a
significant difference between the different surface treatments (P<0.001). Also, the
interaction effect of post and surface treatment is significant (P<0.001). In order to
find out among which of the posts there exist a significant difference, we carry out
post-hoc (multiple comparisons) test using Bonferroni method (Table XII)
From the multiple comparisons table we notice that there is a significant
difference in retentive strength between Carbon fiber posts and Cast metal posts
(P<0.001). We also notice a significant difference between Glass fiber posts and Cast
metal posts (P<0.001). There is no significant difference in retentive strength between
Carbon fiber posts and Glass fiber posts (P>0.05). Similarly, post-hoc (multiple
comparisons) test using Bonferroni method was carried out to find out among which
of the treatments there exist a significant difference (Table XIII).
We observe in Table XIII that there is a significant difference in the retentive
26
Results
strength between air borne alumina particle abrasion and ethyl alcohol treated posts
(P<0.001). We also notice a significant difference in the retentive strength between air
borne alumina particle abrasion and resin primer treated posts (P<0.001). There was
no significant difference between ethyl alcohol and resin primer treated posts
(P>0.05).
Retentive strength of each group is showed in the bar diagram in Graph-I.
From the Graph II we notice that type of post is the most important factor
influencing retentive strength followed by treatment. Among the different posts, cast
metal posts yields a higher retentive strength followed by carbon fiber posts and glass
fiber posts and this difference is found to be statistically significant (P<0.001).
Among the different surface treatments, abrasion yields a higher retentive strength
followed by ethyl alcohol and resin primer and this difference is found to be
statistically significant (P<0.001).
From the Graph III we notice that cast metal posts yields a higher retentive
strength compared to carbon fiber posts and glass fiber posts in all the three
treatments. Glass fiber yields the least retentive strength in all the three treatments.
27
Results
Table I (Group-1)
Sl No. Name of the specimen Maximum load (kgf)
1. Carbon fiber post treated with ethyl alcohol 4.662
2. Carbon fiber post treated with ethyl alcohol 6.404
3. Carbon fiber post treated with ethyl alcohol 4.814
4. Carbon fiber post treated with ethyl alcohol 3.363
5. Carbon fiber post treated with ethyl alcohol 7.249
6. Carbon fiber post treated with ethyl alcohol 8.491
7. Carbon fiber post treated with ethyl alcohol 8.139
8. Carbon fiber post treated with ethyl alcohol 9.292
9. Carbon fiber post treated with ethyl alcohol 8.691
10. Carbon fiber post treated with ethyl alcohol 7.882
Table II (Group 2)
Sl No. Name of the specimen Maximum load (kgf)
1. Carbon fiber post treated with resin primer 6.007
2. Carbon fiber post treated with resin primer 8.528
28
Results
3. Carbon fiber post treated with resin primer 5.293
4. Carbon fiber post treated with resin primer 5.971
5. Carbon fiber post treated with resin primer 5.771
6. Carbon fiber post treated with resin primer 6.572
7. Carbon fiber post treated with resin primer 8.381
8. Carbon fiber post treated with resin primer 3.668
9. Carbon fiber post treated with resin primer 4.068
10. Carbon fiber post treated with resin primer 8.226
Table III (Group 3)
Sl No. Name of the specimen Maximum load (kgf)
1. Carbon fiber post air abraded with alumina 13.648
2. Carbon fiber post air abraded with alumina 15.378
3. Carbon fiber post air abraded with alumina 13.328
4. Carbon fiber post air abraded with alumina 9.394
5. Carbon fiber post air abraded with alumina 12.114
6. Carbon fiber post air abraded with alumina 16.342
7. Carbon fiber post air abraded with alumina 9.584
8. Carbon fiber post air abraded with alumina 10.904
9. Carbon fiber post air abraded with alumina 12.134
29
Results
10. Carbon fiber post air abraded with alumina 10.575
Table IV (Group 4)
Sl No. Name of the specimen Maximum load (kgf)
1. Glass fiber post treated with ethyl alcohol 4.369
2. Glass fiber post treated with ethyl alcohol 6.829
3. Glass fiber post treated with ethyl alcohol 6.806
4. Glass fiber post treated with ethyl alcohol 4.771
5. Glass fiber post treated with ethyl alcohol 3.302
6. Glass fiber post treated with ethyl alcohol 5.467
7. Glass fiber post treated with ethyl alcohol 3.667
8. Glass fiber post treated with ethyl alcohol 4.322
9. Glass fiber post treated with ethyl alcohol 4.800
10. Glass fiber post treated with ethyl alcohol 5.378
Table V (Group 5)
Sl No. Name of the specimen Maximum load (kgf)
1. Glass fiber post treated with resin primer 6.295
2. Glass fiber post treated with resin primer 8.633
30
Results
3. Glass fiber post treated with resin primer 9.775
4. Glass fiber post treated with resin primer 2.911
5. Glass fiber post treated with resin primer 6.180
6. Glass fiber post treated with resin primer 6.227
7. Glass fiber post treated with resin primer 4.115
8. Glass fiber post treated with resin primer 6.772
9. Glass fiber post treated with resin primer 2.791
10. Glass fiber post treated with resin primer 4.376
Table VI (Group 6)
Sl No. Name of the specimen Maximum load (kgf)
1. Glass fiber post air abraded with alumina 10.071
2. Glass fiber post air abraded with alumina 12.284
3. Glass fiber post air abraded with alumina 11.070
4. Glass fiber post air abraded with alumina 11.199
5. Glass fiber post air abraded with alumina 11.768
6. Glass fiber post air abraded with alumina 15.724
7. Glass fiber post air abraded with alumina 13.572
8. Glass fiber post air abraded with alumina 10.611
31
Results
9. Glass fiber post air abraded with alumina 11.255
10. Glass fiber post air abraded with alumina 12.650
Table VII (Group 7)
Sl No. Name of the specimen Maximum load (kgf)
1. Cast metal post treated with ethyl alcohol 14.009
2. Cast metal post treated with ethyl alcohol 12.582
3. Cast metal post treated with ethyl alcohol 24.405
4. Cast metal post treated with ethyl alcohol 14.042
5. Cast metal post treated with ethyl alcohol 15.865
6. Cast metal post treated with ethyl alcohol 13.950
7. Cast metal post treated with ethyl alcohol 13.414
8. Cast metal post treated with ethyl alcohol 8.523
9. Cast metal post treated with ethyl alcohol 12.088
10. Cast metal post treated with ethyl alcohol 9.557
Table VIII (Group 8)
Sl No. Name of the specimen Maximum load (kgf)
1. Cast metal post treated with resin primer 16.373
2. Cast metal post treated with resin primer 17.241
32
Results
3. Cast metal post treated with resin primer 16.335
4. Cast metal post treated with resin primer 11.762
5. Cast metal post treated with resin primer 16.947
6. Cast metal post treated with resin primer 19.097
7. Cast metal post treated with resin primer 14.640
8. Cast metal post treated with resin primer 5.522
9. Cast metal post treated with resin primer 9.333
10. Cast metal post treated with resin primer 14.131
Table IX (Group 9)
Sl No. Name of the specimen Maximum load (kgf)
1. Cast metal post air abraded with alumina 20.096
2. Cast metal post air abraded with alumina 34.138
3. Cast metal post air abraded with alumina 41.291
4. Cast metal post air abraded with alumina 28.757
5. Cast metal post air abraded with alumina 25.188
6. Cast metal post air abraded with alumina 22.745
7. Cast metal post air abraded with alumina 30.890
8. Cast metal post air abraded with alumina 20.408
9. Cast metal post air abraded with alumina 23.333
33
Results
10. Cast metal post air abraded with alumina 21.478
Table X
Post Treatment Mean Std Dev
Abrasion 13.07 2.46
Alcohol 6.79 2.10 Carbon Fiber
Primer 6.25 1.71
Abrasion 28.97 7.00
Alcohol 14.32 4.28 Cast Metal
Primer 13.46 4.54
Abrasion 11.90 1.62
Alcohol 4.93 1.24 Glass Fiber
Primer 5.78 2.18
Table XI
Source DF Sum of Squares (SS) Mean SS F P-Value
Post 2 2234.19 1184.63 98.59 <0.001
Treatment 2 1830.86 957.90 79.72 <0.001
Post Treatment 4 349.32 87.33 7.27 <0.001
34
Results
Error 85 1021.32 12.02 --- ---
Total 93 5435.70 --- --- ---
Table XII
Multiple Comparisons
Dependent Variable: Tensile StrengthBonferroni
-9.59529* .874428 .000 -11.73089 -7.459691.58693 .867009 .212 -.53055 3.704419.59529* .874428 .000 7.45969 11.73089
11.18222* .887759 .000 9.01406 13.35038-1.58693 .867009 .212 -3.70441 .53055
-11.18222* .887759 .000 -13.35038 -9.01406
(J) PostCast MetalGlass FiberCarbon FiberGlass FiberCarbon FiberCast Metal
(I) PostCarbon Fiber
Cast Metal
Glass Fiber
MeanDifference
(I-J) Std. Error Sig. Lower Bound Upper Bound95% Confidence Interval
Based on observed means.The mean difference is significant at the .05 level.*.
35
Results
Table XIII
Multiple Comparisons Dependent Variable: Tensile Strength Bonferroni
95% Confidence Interval
(I)Treatment
Mean Difference (I-J)
Std. Error
Sig. Lower Bound Upper Bound
Abrasion Alcohol Primer
8.56414* 8.67751*
.887874 .847813
.000 .000
6.60692
10.73258 10.74811
Alcohol Abrasion Primer
-8.56414* .11337
.887874 .905818
.000 1.000
-10.73258 -2.09889
-6.39570 2.32563
Primer Abrasion Alcohol
-8.67751* -.11337
.847813 .905818
.000 1.000
-10.74811 -2.32563
-6.60692 2.09889
Based on observed means. * The mean difference is significant at the .05 level.
. Graph I
Mean Tensile Strength recorded in different posts and treatments
13.07
28.97
11.90
6.79
14.32
4.936.25
13.46
5.78
0
5
10
15
20
25
30
35
Carbon Fiber Cast Metal Glass Fiber
Post
Tens
ile S
treng
th
Abrasion
Alcohol
Primer
36
Results
Graph II M
ean
of T
ensi
le S
tren
gth
Glass FiberCast MetalCarbon Fiber
20
18
16
14
12
10
8
6PrimerAlcoholAbrasion
Post Treatment
Main Effects Plot (fitted means) for Tensile Strength
Graph III
Tr e a t me n t
Mea
n
P r im e rA lcoho lA b ra s ion
30
25
20
15
10
5
P o st
G lass F ib er
C ar b o n F ib erC ast M eta l
Inte r a c tio n P lo t ( f i tte d m e a ns ) fo r T e ns i le S tr e ngth
37
Discussion
Restorative methods for pulpless teeth with post–core systems have been
widely investigated with the aim of achieving long term promising prognosis. Use of
post is still regarded as the accepted method of core retention for restoration of
pulpless teeth which have suffered significant loss of the coronal structure.29
Extensive research has been carried out on the materials to be used to fabricate
the post and core. Cast metal posts and core foundations have a long history of
successful use due to their superior physical properties.2 However, their high elastic
modulus, corrosion and esthetic problems have led to development of other types of
post systems.
For fifteen years endodontic posts made of fiber reinforced composites (FRC)
have been described in the literature. Glass, silica and carbon fiber reinforced
materials especially, have been marketed and provided the dental profession with the
first true alternative to cast or pre-fabricated metal posts. 23
Certain properties, such as biocompatibility and corrosion resistance makes
the carbon fiber post a potential replacement for cast metal posts in many clinical
situations. Also, as with cast posts, the use of carbon posts has generally limited
esthetic expectations. Their dark underlying color can adversely influence the shade
of overlying gingival tissues and prosthetic restorations.1
Tooth colored posts such as glass fiber posts or zirconia posts are believed
to result in improved esthetics when used for anterior teeth to be restored with all-
38
Discussion
ceramic crowns. Glass-fiber posts are composed of glass fibers, inorganic filler, and a
resin matrix. They are usually luted with a resin cement to increase their retention and
improve the mechanical performance of the restored teeth.5 These posts have modulus
of elasticity values that approximate that of dentin and are believed to help prevent
root fracture.20 Another advantage is in endodontic retreatment, as most fiber posts
can be removed from a root canal with ease and predictability, when necessary.
Many in-vitro studies have investigated various factors that affect retention of
the post. These factors include length, design, diameter and the surface treatment of
the post. A study done by Ibrahim Nergis, Dr Med Dent and Peter Schamage5showed
that roughening the prepared dentinal surface also increased the retention of posts or
artificial crowns by increasing the surface area and enhancing the mechanical
interlocking between the dentin surface and the cement. Material used in fabrication
of the post can also influence the retentive strength of posts. John R. Gallo and Troy
Miller[4] in their study have reported that fiber-reinforced resin posts provided lower
retention when compared with metal posts.
In the present study single rooted teeth with a single root canal were
employed. Posts employed were of same length, diameter and taper. Post spaces were
prepared to 9mm in length for all the posts with the specific drill bit provided by the
manufacturer for the specific size of post. This was done to standardize the length and
diameter of posts. Posts were marked at 9mm length from apex with a permanent
marker to check whether the posts have seated properly or not. Posts were luted with
dual cure resin cement. However, dual cured cement was not light cured as the cast-
39
Discussion metal posts and carbon fiber posts were also employed in the study through which
light is not transmitted.
For the Retentive force test, a screw driven universal testing machine was
employed to apply tensile load to the post at a cross head speed of 2mm/min. The
force required to dislodge each post from prepared post space was recorded in
kilogram force (kgf). Then the readings were analysed using two-way ANOVA.
The results obtained in this study indicates that the air-borne alumina particle
abraded cast-metal posts had the highest retentive strength compared to all other
surface treated or untreated posts employed in the study. Resin primer treated and
ethyl alcohol treated cast metal posts had the next highest retentive strength. It was
followed by airborne alumina particle abraded glass fiber posts and carbon fiber posts.
Airborne alumina particle abrasion increased the retentive strength of all the
posts used in this study. Treating the surface of the posts with resin-primer and ethyl
alcohol produced no statistically significant difference in the retentive strength of all
the type of posts used in the study. Further, there was no significant difference in the
retentive strength observed between glass fiber posts and carbon fiber posts.
The above findings indicate that air borne alumina particle abrasion of the
surface increased the retention of all the posts. However, resin primer treatment of
the posts does not significantly affect the retentive strength. These findings are similar
to the findings of Ali Balbosh and Matthias Kern.5 The findings observed may be
40
Discussion
because the non-abraded posts had a relatively smooth surface area, which limited
mechanical interlocking between the post’s surface and the resin cement. A careful
visual observation with a magnifying lens of the dislodged posts revealed purely
adhesive failure mode at the resin cement/ post interface for all non-abraded posts.
The airborne alumina particle abraded posts were rougher and appeared to provide an
increased surface area which improved mechanical interlocking for the resin. Among
all the specimens tested, two teeth which were cemented with air borne-alumina
particle abraded cast metal posts, fractured during testing at 45 kgf and 46 kgf
respectively. However, none of the teeth of the test specimens cemented with glass
fiber posts and carbon fiber posts fractured during testing. The above finding also
supports that air borne alumina particle abrasion of the posts increases the retentive
strength.
The test for retention of different surface treated posts in this study was carried
out shortly after cementation. However, clinically the dislodgement of post-retained
restorations commonly occurs after several years of function. Long-term retention
may be influenced by various factors such as temperature changes and dynamic
mechanical loading. In this study artificial aging, which simulates to oral
conditions was not carried out. Further, other post systems like, threaded posts,
serrated posts, parallel posts and zirconia posts were not considered in the study. All
the posts used in this study were smooth, tapered and of same size. All the posts were
cemented with dual cured resin cement, which was not light cured. If dual cured
cement used in the study was light cured, then the glass fiber posts would have
probably given different retentive values during testing as light can transmit through
41
Discussion
it. Further, the surface details of the dislodged posts were also not analysed under
scanning electron microscope (SEM). Visualization under SEM can provide better
insight for the findings observed in the study.
42
Conclusion
The present study was done to evaluate the effect of surface treatment with ethyl
alcohol, resin primer and air-borne alumina particle abrasion on the retention of glass
fiber posts, carbon fiber posts and cast metal posts. The retentive strengths were
obtained using screw driven universal testing machine. The readings were subjected
to statistical analysis. The results indicate that
• Air-borne alumina particle abraded cast-metal posts had the highest retentive
strength compared to all other surface treated or untreated posts used in the
study followed by primer treated cast metal posts and ethyl alcohol treated
cast metal posts.
• Airborne alumina particle abraded glass fiber posts and carbon fiber posts had
the next highest retentive strengths.
• Airborne alumina particle abrasion increased the retentive strength of all the
type of posts used in this study.
• Treating the surface of the posts with resin-primer and ethyl alcohol produced
no statistically significant difference in the retentive strength of all the type of
posts used in the study.
• There was no significant difference in the retentive strength obtained between
Glass fiber posts and carbon fiber posts.
43
Summary
The retentive strength of the post depends on several factors like length,
design, diameter and the surface treatment of the post. Hence, all the factors must be
thoroughly understood in order to know their effect on the retentive strength of the
posts.
Type of surface treatment is one of the important factors influencing the
retentive strength of posts. The present in-vitro study was conducted to compare
effect of surface treatment with ethyl alcohol, resin primer and air-borne alumina
particle abrasion on retention of glass fiber post, carbon fiber post and cast metal
posts.
Ninety test specimens were made. Test specimens were divided into 9 groups,
each containing 10 specimens. Canals of all the test specimens were prepared with a
specific drill bit till a standard length. The surface treated posts subsequently were
luted with dual cure resin cement. For the Retentive force test, a screw driven
universal testing machine was used to apply tensile load to the post. The force
required to dislodge each post from prepared post space was recorded. The data was
analysed using two-way ANOVA test.
The results obtained in this study showed that air-borne alumina particle
abrasion increased the retentive strength of all the type of posts used in this study.
Treating the surface of the posts with resin-primer and ethyl alcohol produced no
statistically significant difference in the retentive strength.
44
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