Article_6_1_2
DENTAL MATERIALS
THE EFFECT OF CLEANING PROCEDURES ON THE BOND STRENGTH OF CERAMIC
Original Article
SURFACES CONTAMINATED WITH SALIVA AND TRY-IN PASTE
Luiz H. Gonzaga1a*, Himanshu Arora1,2b, William C. Martin1c
1Center for Implant Dentistry, College of Dentistry, University of Florida, Gainesville, FL, USA
2School of Dentistry and Oral Health, Griffith University, Gold Coast, Australia
a
DDS, MS
b
BDS, MDS, PhD
c
DDS, MS, FACP
ABSTRACT DOI: https://doi.org/10.25241/stomaeduj.2019.6(1).art.2
Purpose of the study: To evaluate the effectiveness of different cleaning procedures on
removing the saliva and try-in paste remnants from contaminated zirconia and lithium OPEN ACCESS This is an
Open Access article under the CC
disilicate surfaces. BY-NC 4.0 license.
Material and Methods: Fifty samples of zirconia (IPS e.max ZirCAD) and 50 samples of
Peer-Reviewed Article
lithium disilicate (IPS e.max CAD) were divided into 5 groups: Group 1 – No contamination
with saliva and try-in paste (control); Group 2 – Contamination followed by rinsing with Citation: Gonzaga LH, Arora H, Martin
WC. The effect of cleaning procedures on
water; Group 3 – Contamination followed by cleaning with NaOCL 7% for 30 seconds; the bond strength of ceramic surfaces
Group 4 – Contamination followed by cleaning with H3PO4 35% for 30 seconds; Group contaminated with saliva and try-in
paste. Stoma Edu J. 2019;6(1):18-23
5 – Contamination followed by cleaning with Ivoclean for 30 seconds. Zirconium oxide Received: February 12, 2019
cylinders were luted to the samples using Multilink Implant cement. After being stored for Revised: February 22, 2019
Accepted: March 13, 2019
24 hours in a deionized water bath at 370C, the samples were subjected to shear forces at a Published: March 14, 2019
crosshead speed of 0.5 mm/min. ANOVA and Tukey’s post-hoc test were used for statistical *Corresponding author:
analysis. Luiz H. Gonzaga, DDS, MS
Results: No significant differences were observed between various groups for zirconia Clinical Assistant Professor, Department
of Oral & Maxillofacial Surgery, Center for
samples with all cleaning protocols showing shear bond strengths similar to the control Implant Dentistry, College of Dentistry,
groups. Group 4 showed significant improvement in shear bond strength when compared University of Florida, 1395 Center Drive,
Rm D7-6, Gainesville, FL 32610, USA
to control (p < 0.05) for lithium disilicate samples. Tel/Fax: +1 (352) 273-6715,
Conclusions: Within the limitations of this study it could be said that the application of e-mail: lgonzaga@dental.ufl.edu
phosphoric acid for 30 seconds is effective to clean lithium disilicate samples contaminated Copyright: © 2019 the Editorial
with saliva and try-in paste. Council for the Stomatology Edu
Journal.
Keywords: Bond strength; contamination; saliva; zirconia; lithium disilicate.
1. Introduction mechanical retention and chemical bonding of
The pursuit for restorations that mimic nature is luting cement to the ceramic substrate [4]. Zirconia’s
more evident than ever. Ceramics are widely used acid resistance makes it unresponsive to common
in dentistry due to their ability to mimic the optical etching and silanization procedures, which makes
characteristics of enamel and dentine as well as for establishing a strong and stable bond to resin
their biocompatibility and chemical durability [1]. luting agents a clinically challenging protocol [6].
The development of all-ceramic restorations and The risk of bond failure further intensifies with any
evolution of luting agents are making cementation contamination on the cementation surfaces and
of dental restorations stronger and more predictable insufficient removal of the contaminants following
[2]. At the same time a myriad of combinations intraoral try-in procedures [7-9]. Once a restoration
between material and cement options make a is received from the laboratory, it undergoes an
simple task more complex, with diverse steps. The initial inspection by the dentist which is followed by
achievement of good bonding is sometimes essential a series of events including, removal of temporary
for the survival and an all-ceramic restoration restoration, cleaning of the cavity/prepared tooth,
because high retention, better marginal adaptation. try-in of the restoration (usually pretreated in
The achievement of proper bonding is essential for the lab), cleaning the restoration after try-in and
the survival of an all-ceramic restoration, as a result bonding of the restoration. While the majority of the
of a precise marginal adaptation associated with bonding process is controlled by the practitioner,
adequate bonding cementation, which prevents laboratory technicians perform some of the steps,
microleakage, and increase fracture resistance of the like etching or abrasive particles blasting, which are
restored tooth and the restoration [3,4]. described as pretreatment of the restoration. Those
Superior physical properties, biocompatibility, and restorations with enhanced surface for bonding
esthetics have made zirconium oxide ceramics will then be tried in and sometimes adjusted by the
(zirconia) a popular high-strength ceramic coping clinician. During the try-in phase, the restoration
and framework material [5]. Reliable bonding comes in contact with saliva, blood, and/or try-in
of zirconia ceramic was reportedly obtained by pastes. This process can lead to contamination of
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THE EFFECT OF CLEANING PROCEDURES ON THE BOND STRENGTH OF CERAMIC SURFACES CONTAMINATED
WITH SALIVA AND TRY-IN PASTE
Original Article
Figure 1. Experimental design.
the internal surface of the restoration which could blocks were sectioned to create 10x15x3mm samples
eventually compromise the bonding process during IsoMet 1000 Buehler) at 150 RPM with Cool 3 cutting
the seating of the restoration [6,7,9-11]. Some of fluid lubricant (Buehler, Lake Bluff, IL, USA). The
the commonly used decontamination methods for samples were later sintered using a Sintramat (Ivoclar
restoration surfaces include scrubbing the surface Vivadent AG, Schaan, Liechtenstein) sintering oven.
with acetone, application of 37% phosphoric acid, The samples were placed in the firing saggar with
immersing in 96% isopropanol, cleaning with 70% sintering beads. The saggar was loaded to the firing
ethanol, airborne-particle abrasion, application of 2% chamber at room temperature. The P1 program was
chlorhexidine, or 5% sodium hypochlorite and water used and the sintering was done automatically for 8
rinsing [10,12,13]. In addition to these products, a hours with a maximum temperature of 1500°C. The
universal cleaning agent (Ivoclean; Ivoclar Vivadent furnace could only be opened after the temperature
AG, Schaan, Liechtenstein) is also available for the dropped below 97°C. After removal the saggar was
extraoral cleaning of ceramic and metal restorations. allowed to cool to room temperature. IPS e.max
It is a non-toxic cleaning agent consisting of an CAD lithium metasilicate blocks (Ivoclar Vivadent
alkaline suspension of zirconium dioxide particles, AG, Schaan, Liechtenstein) were sectioned to create
which tend to absorb and bond to phosphate 10x15x3mm samples. The samples were crystalized
contaminants and helps in surface decontamination according to the manufacture instructions using
[7,12,14]. Although, the effect of various cleaning the Programat P500 furnace (Ivoclar Vivadent AG,
agents/solutions on decontamination of saliva Schaan, Liechtenstein). The samples were placed in
affected all ceramic restorations has been evaluated the furnace using a firing plate without any glaze
[7,9,10,14-21], there is no clear protocol on the use application since the idea was to simulate the intaglio
of these agents. Also, the available literature is still of the restoration. For crystallization, Sintramat’s
inconclusive on the decontamination protocol for preloaded program for e.max CAD was used without
all ceramic restorations contaminated by both saliva altering any parameters. After crystallization, all
and try-in pastes [11]. Therefore, the purpose of this samples were embedded in auto-polymerized
bench study was to evaluate the bond strength of acrylic resin (Acratray Blue, Zahn Dental, NY, USA)
a resin-based cement to two commercial materials using an Ultradent 15-hole mold leaving one of the
used for all ceramic restorations, IPS e.max ZirCAD surfaces exposed. The exposed surface was ground
and IPS e.max CAD after the contamination with with a silicon carbide paper in a polishing station
saliva and try in paste and subsequent cleaning with with abundant water cooling to 240 grit size. For
35% phosphoric acid or universal cleaning agent, or the zirconium oxide ceramic, the test surfaces were
7% Sodium Hypochlorite or simple water rinse. The blasted with aluminum oxide 50 microns at 1 bar.
null hypothesis was that there will be no difference The lithium disilicate ceramic samples were etched
in the bond strength between the resin cement and for 20 seconds with a 5% hydrofluoric acid gel (IPS
the ceramic materials after decontamination of the ceramic Etching Gel, Ivoclar Vivadent AG, Schaan,
ceramic materials with the four methods used. Liechtenstein), rinsed with a water spray for 20
seconds and thoroughly dried with compressed air.
One group with 10 samples for each material was not
2. Materials and Methods contaminated before bonding. Unstimulated human
The experimental design is shown in Fig. 1. Ten saliva was collected from one of the researchers that
samples for each group were fabricated as follows. had withdrawn for eating or drinking one-hour prior
IPS e.max ZirCAD (yttrium-stabilized zirconium the collection. Saliva and try-in paste (Variolink II try-
oxide, Ivoclar Vivadent AG, Schaan, Liechtenstein) in paste, Ivoclar Vivadent AG, Schaan, Liechtenstein)
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THE EFFECT OF CLEANING PROCEDURES ON THE BOND STRENGTH OF CERAMIC SURFACES CONTAMINATED
WITH SALIVA AND TRY-IN PASTE
Original Article
Figure 2. Test set-up for evaluation of shear bond strength.
were applied to the samples. A plastic disc was used Table 1. Shear bond strengths (MPa) for a max. ZirCAD (EMZ) samples.
to apply pressure over the samples to simulate a
Mean Standard Deviation
crown try-in. After the contamination with saliva and
try-in paste all test samples were rinsed with water Control 7.36 6.48
for 20 seconds and air-dried. EMZ-W 9.96 6.62
The samples were divided in 5 groups with 10 EMZ-HC 8.14 5.31
samples each for both materials, e.max ZirCAD (EMZ) EMZ-PA 12.95 7.96
and e.max CAD (EMC):
EMZ-IC 9.10 5.30
Group 1 (control group) – No contamination before
bonding
Test groups - Saliva/try-in paste contamination with
different cleaning methods:
Group 2: Water rinse
Group 3: Water rinse + Cleaning with NaOCL 7% for
30 seconds followed by air-water rinse
Group 4: Water rinse + Cleaning with H3PO4 35% for
30 seconds followed by air-water rinse
Group 5: Water rinse + Cleaning with Ivoclean for 30
seconds followed by air-water rinse
Zirconium oxide cylinders (Ultradent, UT, USA)
designed with four 50 μm pegs (Fig. 2) that defined
the thickness of the cement layer were cemented Figure 3. Shear bond strength values for IPS e.max ZirCAD samples for
to the samples. The Zirconium oxide cylinders were test and control groups.
blasted with aluminum oxide 50 microns at 1 bar and Table 2. Shear bond strengths (MPa) for EMC samples.
a primer was applied (Zirconia Bond I, Signum). All
the samples were treated with an all-purpose primer Mean Standard Deviation
for 60 seconds (Monobond Plus, Ivoclar Vivadent Control 4.65 3.72
AG, Schaan, Liechtenstein) prior to the cementation
with Multilink Implant cement (Ivoclar Vivadent AG, EMC-W 6.78 5.30
Schaan, Liechtenstein) without light activation. EMC-HC 7.99 5.60
After cementation, the samples were placed in a EMC-PA 12.28 7.22
deionized water bath at 37°C for 24 h hours after
which they were subjected to shear forces using an EMC-IC 9.45 5.96
Ultradent jig at a crosshead speed of 0.5mm/min with
a universal testing machine (Instron, Norwood, MA,
USA) to test for bond strength (Fig. 2). The mode of
failure (cohesive, adhesive, or mixed) was examined
under an optical microscope with 100x and 300x
magnification (Keyence VHX-700F series). For the
statistical analysis, ANOVA and Tukey’s post hoc tests
were used to find differences between the cleaning
methods with the help of SAS software. The statistical
significance was set at p < 0.05.
3. Results
The shear bond strengths for the EMZ samples are
shown in Table 1 and Fig. 3. The difference between Figure 4. Shear bond strength values for IPS e.max CAD samples for
various groups was not statistically significant (p = test and control groups.
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THE EFFECT OF CLEANING PROCEDURES ON THE BOND STRENGTH OF CERAMIC SURFACES CONTAMINATED
WITH SALIVA AND TRY-IN PASTE
Original Article
a) b)
Figure 5. Microscopic evaluation of failure modes:
a) Failure at test ceramic surface;
b) Adhesive failure;
c) Failure at the peg interface. c)
0.419). The shear bond strengths for the EMC samples proteins can be absorbed on the tooth surface as well
are shown in Table 2 and Fig. 4. as the restorative materials [12]. It has been reported
Group 4 showed the highest shear bond strength. previously that the elimination of this saliva or try-in
The initial analysis showed statical differences in paste contamination is essential to improve the long-
between the treatment groups (p = 0.028). term durable ceramic bonding [8,9,18].
The Tukey’s test confirmed that only the difference All the cleaning methods used in the current study
between the control and the H3PO4 means were were able to eliminate the negative effects of saliva
significantly different (p < 0.05). and try-in paste contamination on zirconia as
The microscopic analysis failed to find any cohesive measured with shear bond strengths. Ivoclean and
failures in the test ceramic or the pegs (Fig. 5). sodium hypochlorite have been shown to be effective
Mixed failures in the tested ceramic interface in removing the effects of salivary contamination
(63%); mixed failures with adhesive failures in both on zirconia in previous studies [7,16,18,20]. Zirconia
side (34%); mixed failures predominant in the peg has a strong adsorption potential to the salivary
interface (3%). phosphoproteins which leads to contamination
when it comes in contact with saliva [16]. Ivoclean
consists of zirconia particles, which, when brought
4. Discussion in contact with contaminated zirconia, help absorb
The present study evaluated the shear bond the phosphoproteins from its surface, which are then
strengths of saliva and try-in paste contaminated washed away during subsequent rinsing [20,22].
lithium disilicate and zirconia samples subjected Interestingly, cleaning the zirconia surface with
to different cleaning regimes. All the cleaning phosphoric acid showed not higher bond strength
regimens employed in this study showed positive than control uncontaminated surfaces in this study.
effects on the shear bond strength values. The It has been reported previously that phosphoric acid
treatment with phosphoric acid showed the highest successfully removes carbon-based contaminants but
values which were significantly better than control may leave a residue of phosphor-based contaminants
for the lithium disilicate samples (p < 0.05). The on the zirconia surface [23]. These phosphor-based
advancement in bonding technology is probably contaminants compete with the binding sites on the
the great contributor for the high success of ceramic primer and lead to reduce bond strengths for saliva
restorations, but the technique can be very sensitive. contaminated samples [16]. On the other hand,
Salivary contamination comes into play when the phosphoric acid proved to be an effective cleaning
restorations are tried-in for fit intraorally. The saliva agent for zirconia samples contaminated with a
Stomatology Edu Journal 21
THE EFFECT OF CLEANING PROCEDURES ON THE BOND STRENGTH OF CERAMIC SURFACES CONTAMINATED
WITH SALIVA AND TRY-IN PASTE
Original Article combination of saliva and dental stone or saliva current study are comparatively lower when
alone [23]. The values observed with phosphoric acid compared to some studies [7,16,21,23] and
in our study could be due to the duration of time of comparable to others [18]. Some of the differences
its application, which was 30 seconds as compared in the numbers could be accounted due to different
to 60 seconds in the previous study [16], which could materials used for bonding the ceramic surfaces.
have minimized the phosphor-based contaminant Another reason could be the slight diameter
residue on the zirconia surface. Nonetheless, this mismatch between the pegs which were bonded to
finding needs further exploration in future studies. the ceramic samples and the notch inside the head
Cleaning with phosphoric acid showed a significant of the shear tool on the testing machine as shown in
improvement in shear bond strength when compared Fig. 2. This could have led to excessive forces on the
to uncontaminated control lithium disilicate samples. pegs during the shear test resulting in the observed
This finding is similar to the results from previous lower values.
studies [11,14]. Klosa et al. tested the effect of
various cleaning agents of lithium disilicate samples
contaminated with saliva and silicone disclosing 5. Conclusion
paste [14]. The authors found that both hydrofluoric Within the limitations of the study the following
acid and phosphoric acid were significantly better in inference could be made:
improving bond strengths for saliva contaminated The cleaning methods used in the current study were
samples, although only hydrofluoric acid was able able to improve the bond strengths of saliva and
to achieve significantly higher bond strengths with try-in paste contaminated zirconia samples to be
saliva and silicone paste contamination. Interestingly, comparable to the samples without contamination.
the samples were only visually inspected after silicone Treatment with phosphoric acid was able to
paste contamination and not cleaned with air/water, significantly increase the bond strength of lithium
which might have led to the abovementioned results. disilicate samples contaminated with saliva and try-
Nonetheless, the significantly higher bond strengths in paste.
observed with phosphoric acid in our study shows
that it is an effective way to clean lithium disilicate
samples contaminated with saliva and try-in paste. Author Contributions
No cohesive failures were observed in this study. LG: Idea, experimental design, performed the experiment,
All the failures were mixed with a majority of them wrote initial manuscript. HA: wrote final manuscript,
being either on the test ceramic interface or mixed proofread manuscript, WM: contribution with literature
adhesive failures on both sides suggesting that shear review, discussion and proofread manuscript.
stresses were applied on the adhesive interface.
More detailed results could have been observed with
the use scanning electron microscopy at a higher Acknowledgement
magnification as compared to the low magnification The authors thank Ivoclar Vivadent for donating the
of optical microscopy used in this study. materials.
This study used shear bond strength as a measure of
effectiveness of various cleaning agents on ceramic
samples contaminated with saliva and try-in paste. References
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Luiz H. GONZAGA
DDS, MS, Clinical Assistant Professor
Department of Oral & Maxillofacial Surgery, Center for Implant Dentistry
College of Dentistry, University of Florida
Gainesville, FL, USA
CV
Dr. Luiz H. Gonzaga, DDS, MS graduated from the Catholic University of Brasilia College of Dentistry in 2004. After working in
private practice and taking perio/implants CE courses for one year he was accepted for the Implant/Periodontic specialty training,
graduating in 2009. Dr. Gonzaga was awarded with the ITI scholarship in 2009 and completed his OMFS fellowship the next
year. He completed a residency program and Masters in Prosthodontics from the University of Florida in 2014. Currently he is a
Clinical Assistant Professor at the University of Florida Center for Implant Dentistry. Dr. Gonzaga is an ITI speaker and Fellow of the
International Team for Implantology, a member of the American College of Prosthodontics, and the Academy of Osseointegration.
Questions
1. What percentage of Hydrofluoric 3. How long was Ivoclean applied for?
acid was used to etch Lithium Disilicate qa. 30 seconds;
samples? qb. 20 seconds;
qc. 15 seconds;
qa. 3.5%;
qd. 10 seconds.
qb. 5%;
qc. 7%;
qc. 9.5%; 4. How long were samples placed in
deionized bath?
2. Which try-in paste was used? qa. 6 hours;
qa. Duolink; qb. 12 hours;
qb. Variolink; qc. 24 hours;
qc. Panavia; qd. 1 week.
qd. Multilink.
Stomatology Edu Journal 23