Effect of adhesives on bond strength of porcelain veneer to
5
Prosthodontics Effect of adhesives on bond strength of porcelain veneer to base metal alloy Reza Goharian, DDS, MSVFatemeh Maleknejad, DDS^/Taghi Saiari,DDS3/ Marjaneh Ghavamnasiri, DDS-^/Mohammad Derhami, Objective: The purpose of this in vitro study was to evaluate the bond strength of porcelain veneer to base metal alloy using different adhesive systems. Method and materials: Eighty cylindrical models were cast in a nlckel-chromium-beryIlium base metal alloy. After they were mounted in self-cured acrylic resin, the surfaces of the specimens were air abraded. Specimens were divided into four groups of 20, Control porcelain disks were baked on the base metal. For the experimental groups, 60 porcelain disks were made. After öO-pm aluminum oxide sandblasting, a silane coupling agent was applied to the surface of the porcelain. The experimental groups were based on the type of adhesive used to bond porcelain to metal: Scotchbond Multipurpose and Duo Cement; One Coat Bond and Duo Cement; or Panavia 21 Ex, After 500 thermal cycles, the bonded porcelain specimens were placed under a continuous shear load of 2 mm/min until fracture occun-ed. Results: Mean values for bond strength were 25,39 (control), 19.10 ¡Panavia 21 Ex), 15,81 (Scotchbond Multipurpose), and 13,69 MPa (One Coat Bond], Statistically significant differ- ences in bond strength were noted between tfie control group and all the experimental groups, A statisti- cally significant difference was observed between Panavia 21 Ex specimens and One Coat Bond speci- mens. Conclusion: Panavia 21 Ex provided an effective bond strength between a porcelain veneer and a base metal alloy, the closest of all the experimental groups to that of the control group, (Quintessence int 2002:33:595-599) Key words: adhesive, base metal alloy, bond strength, porcelain veneer CLINICAL RELEVANCE: The repair of a fractured metal- ceramic crown with a porcelain veneer cemented to the base metal substructure is a possible treatment alterna- tive, Panavia 21 Ex may be a suitable resin cement for bonding the porcelain veneer to the base metal. M etal-ceramic crowns are the most widely used type of complete veneer restoration. Considering the large difference in modulus of elasticity hetween 'Associate Professor, Departmenl ol Prostlioöondcs, Faoulty of Dentistry, Mashhad Unrversity, Mashrtad, Iran. 'Assistant Professor, Department of Operative Dentistry, Faculty of [lentstry, Mashhad University, Mashhad, Iran, ^Assistant Professor, Department of Piosthodonlcs, Faculty of Dentistry, Mashhad Univeisify, Mashhad, Iran. 'Associate Professor, Department of Operative Dentistry, Faculty of Dentistry, Mashhad Univeisity, Mashhad, Iran, Reprint requests: Or M. Ghavamnasiri, Associate Professor, Department ol Operative Dentistry, Mashhad University, Mashhad, Iran. E-maii; dr_Marjaneh @yahoo,com metal and porcelain, it is not surprising that mechani- cal faiiures of the metal-ceramic bond can occur. Causes of metal-ceramic faiiure include unsuitable de- sign of metal coping, tecbnical errors, contamination, physical trauma, and premature occlusal contact. Porcelain fracture does not necessarily mean failure of the restoration. It may pose only an esthetic and/or a functional dilemma for the patient and dentist. If the restoration is to be repaired, the bond strength of the repair must be strong and dtirable.' Types of failure in metal-ceramic cro«Tis include fracture only in porce- lain without metal exposure, fracture with partial metal exposure, and fracture with complete metal exposure.- Various methods have been introduced for repair- ing fractured porcelain with resin composite. Sandblasting with aluminum oxide is one method of surface roughening.^ The porcelain can also be etched with hydrofluoric acid to facilitate mlcromechanical retention of resin composite,'"^ Use of an intraoral sandblaster is an alternative way to provide microme- chanical retention, although the roughening of the ce- ramic surface by the sandblaster may be less than that produced by hydrofluoric acid,' Quintessenc 595
Effect of adhesives on bond strength of porcelain veneer to
Prosthodontics
Effect of adhesives on bond strength of porcelain veneer to base
metal alloy
Reza Goharian, DDS, MSVFatemeh Maleknejad, DDS /Taghi Saiari,DDS3/
Marjaneh Ghavamnasiri, DDS- /Mohammad Derhami,
Objective: The purpose of this in vitro study was to evaluate the
bond strength of porcelain veneer to base metal alloy using
different adhesive systems. Method and materials: Eighty
cylindrical models were cast in a nlckel-chromium-beryIlium base
metal alloy. After they were mounted in self-cured acrylic resin,
the surfaces of the specimens were air abraded. Specimens were
divided into four groups of 20, Control porcelain disks were baked
on the base metal. For the experimental groups, 60 porcelain disks
were made. After öO-pm aluminum oxide sandblasting, a silane
coupling agent was applied to the surface of the porcelain. The
experimental groups were based on the type of adhesive used to bond
porcelain to metal: Scotchbond Multipurpose and Duo Cement; One
Coat Bond and Duo Cement; or Panavia 21 Ex, After 500 thermal
cycles, the bonded porcelain specimens were placed under a
continuous shear load of 2 mm/min until fracture occun-ed. Results:
Mean values for bond strength were 25,39 (control), 19.10 ¡Panavia
21 Ex), 15,81 (Scotchbond Multipurpose), and 13,69 MPa (One Coat
Bond], Statistically significant differ- ences in bond strength
were noted between tfie control group and all the experimental
groups, A statisti- cally significant difference was observed
between Panavia 21 Ex specimens and One Coat Bond speci- mens.
Conclusion: Panavia 21 Ex provided an effective bond strength
between a porcelain veneer and a base metal alloy, the closest of
all the experimental groups to that of the control group,
(Quintessence int 2002:33:595-599)
Key words: adhesive, base metal alloy, bond strength, porcelain
veneer
CLINICAL RELEVANCE: The repair of a fractured metal- ceramic crown
with a porcelain veneer cemented to the base metal substructure is
a possible treatment alterna- tive, Panavia 21 Ex may be a suitable
resin cement for bonding the porcelain veneer to the base
metal.
Metal-ceramic crowns are the most widely used type of complete
veneer restoration. Considering
the large difference in modulus of elasticity hetween
'Associate Professor, Departmenl ol Prostlioöondcs, Faoulty of
Dentistry,
Mashhad Unrversity, Mashrtad, Iran.
^Assistant Professor, Department of Piosthodonlcs, Faculty of
Dentistry,
Mashhad Univeisify, Mashhad, Iran.
Reprint requests: Or M. Ghavamnasiri, Associate Professor,
Department ol Operative Dentistry, Mashhad University, Mashhad,
Iran. E-maii; dr_Marjaneh @yahoo,com
metal and porcelain, it is not surprising that mechani- cal
faiiures of the metal-ceramic bond can occur. Causes of
metal-ceramic faiiure include unsuitable de- sign of metal coping,
tecbnical errors, contamination, physical trauma, and premature
occlusal contact.
Porcelain fracture does not necessarily mean failure of the
restoration. It may pose only an esthetic and/or a functional
dilemma for the patient and dentist. If the restoration is to be
repaired, the bond strength of the repair must be strong and
dtirable.' Types of failure in metal-ceramic cro«Tis include
fracture only in porce- lain without metal exposure, fracture with
partial metal exposure, and fracture with complete metal
exposure.-
Various methods have been introduced for repair- ing fractured
porcelain with resin composite. Sandblasting with aluminum oxide is
one method of surface roughening.^ The porcelain can also be etched
with hydrofluoric acid to facilitate mlcromechanical retention of
resin composite,'"^ Use of an intraoral sandblaster is an
alternative way to provide microme- chanical retention, although
the roughening of the ce- ramic surface by the sandblaster may be
less than that produced by hydrofluoric acid,'
Quintessenc 595
• Goharian et ai
Mechanical roughening of the fractured surface fol- lowed by
application of a silane coupling agent can enhance the
resin-to-porcelain bond,' Phosphoric acid etching does nol increase
the porcelain-resin compos- ite bond strength,' It was recognized
that roughening and etching of porcelain are more important for me-
chanical retention than are silane coupling agent and chemical
retention.^ Appeldoorn et al"* found the bond strength of resin
composite to porcelain was 23.5 MPa; after thermocycling, the bond
strength de- creased. Chung and Hwang' showed that aluminum oxide
sandblasting and hydrofiuoric acid treatment followed by
application of Scotchbond can result in a porcelain repair bond
strength of 14.7 MPa.
Surface treatment of base metal alloys with alu- minum oxide
sandblasting is a valuable procedure for increasing roughness."-'^
A previous study reported that tbe aluminum oxide content of base
metal alloys increases up to 30 vt Vo after sandblasting.
Ultrasonic cleaning resulted in only minor removal of the embed-
ded aluminum oxide, which can create chemical bonds with adhesives
and enhance bond strength.'^
Further improvements in adhesion of resin compos- ite to base
metals have recently been reported by the following
1. Multipurpose resins such as Scotchbond Multi- purpose (3M
Dental), for which a bond strength of 30 MPa to Rexillium cast
metal alloy (feneric/ Pentron) has been quoted by the manufacturer.
""
2. All-Bond 2 {Bisco Dental), for which a bond strength of 21.8 MPa
to Rexillium III cast metal alloy has been reported.^
3. Panavia Ex (Kuraray), a dimethacrylate in wbich phosphate ester
groups are incorporated in a bis- GMA resin. Aboush and Jenkins'**
have reported bond strengths of up to 28 MPa between Panavia Ex and
sandblasted nickel-chromium alloy,
A number of studies on porcelain repair by resin composite have
been published,^'^-^' but, when metal is completely exposed, tbere
seem to be two ways to solve the problem: (1) bonding a resin
composite ve- neer to base metal (2) bonding a porcelain veneer to
base metal. Only two clinical reports have been pub- lished ahout
bonding of a porcelain veneer to exposed metal. ' ^ Therefore, the
aim of the present study was to evaluate the effect of adhesives on
tbe bond strength of a porcelain veneer to a base metal
alloy.
METHOD AND MATERIALS
Eighty cast specimens were made in a nickel- chromium-beryllium
alloy (Super Cast MP, Therma-
bond Alloy). All the manufacturer's re ¡.cndations for the burnout
and casting proced ^ • were fol- lowed. The specimens consisted of
twi. 'lisiiS, one (11 mm in diameter and 3 mm thick) for porcelain
veneer application and the other (8 mm in ditimeter and 3 mm thick)
for mounting in a self-cured acrylic resin mold (Formatray,
Kerr/Sybron). The surfaces of all specimens were air abraded with
50-[¡m aluminum oxide (Micro-etcher, Model ERC, Danville Engin-
eering) used with a pressure of 50 kg/cm^ at a dis- tance of 5
mm.
Specimens were divided into four groups of 20. In the control group
(C), 20 specimens were selected for firing of porcelain (Vita Omega
A-2 Metalkeramic, Vita Zahnfabrik). A piece of platinum foil was
pre- pared, with a hole (4 mm in diameter) punched ap- proximately
at its center, and adapted on the cast- metal disk to create a
standardized area for porcelain application. Porcelain firing was
carried out in a porcelain oven (Vita Vacumat 300, Vita
Zahnfabrik). After 24 hours, specimens underwent 500 thermal cy-
cles from 500"C to 55''C,
In the experimental groups, 60 cast specimens were maintained at
96O''C for 5 minutes, which was similar to the firing cycle for the
metal-ceramic specimens. The base metal surtaces were then
roughened with a coarse diamond bur, rinsed in tap water, and
subjected to 50-ijm aluminum oxide sandblasting. Holes were created
in a piece of platinum foil (4 mm in diameter), which was then
adapted to a piece of mica. In this way, the porcelain disks were
fired in a porcelain oven.
After the bonding surface of the porcelain disks was sandblasted, a
9.50/0 hydrofiuoric acid gel (Ultradent) was applied to this
surface for 4 minutes. A frosted ap- pearance was observed after
the surface was rinsed with water and dried. The ceramic primer was
applied to the bonding surface of the porcelain disks. The
manufacturer's directions for each system were fol- lowed when the
porcelain was bonded to the base metal. Tbc experimental groups of
specimens were di- vided into three groups of 20, based on tbe type
of ad- hesive. Scotchbond Multipurpose {group S) is a dentin
bonding agent. After application of activator on the metal surface,
Scotchbond primer was applied and dried after 5 seconds until a
glossy appearance was observed. The catalyst was applied to the
primed sur- face. Duo Cement (Coltene/Whaledent) was used as a
luting cement. Duo Cement was applied first to the porcelain
bonding surface and then to the metal sur- face and light cured
with the Coltene light-curing unit (Coltene/Whaledent) from each
side for 60 seconds.
One Coat Bond (group O) is a dentin bonding agent
{Coltene/Whaledent). One drop of the adhesive was applied to the
bonding surface of porcelain and light cured for 20 seconds with
the Coltene light-ciiring
596 Volume 33, Number 8, 2002
• Gotiarian et al
unit. The rest of the procedure was similar to that de- scribed for
group S.
Panavia 21 Ex (group P) is a resin cement. The base and catalyst
were mixed and applied to the porcelain disk. The disk was
Immediately placed on the bonding surface of metal and mild finger
pressure was main- tained until the cement set.
Thermocycîing was performed for the experimental groups in a manner
similar to that used for the control group. An Instron testing
machine (Model 8500. Instron Engineering) was equipped with a
chisel- shaped rod with a shearing force along the interface
between metal and porcelain. The bonded porcelain cylinders were
placed under sustained, continuous loading at 2 mm/min until
fracture occurred (Fig 1). Sbear bond strengths were calculated and
recorded in megapascals.
Statistical analysis of data was accomplished by analysis of
variance. The Duncan multiple range test and / test were used for
all post hoc pairwise compari- sons at the QS /o confidence
level.
DISCUSSION
Previous studies have indicated that, for repair of porce- lain,
etching with hydrofluoric acid and application of a süane coupling
agent in combination with an unfilled resin could create a suitable
bond strength.-*- The pre- sent smdy evaluated the effect of
adhesives on the bond strengths of porcelain veneers to base metal
alloys.
It was not surprising that the metal-ceramic speci- mens (controi)
displayed tbe higbest bond strength. Miller et al--' found that
metal-ceramic bond strength was 720 psi in axial loading. The most
important causes of higher bond strengths in metaj-ceramic
are:
1. The surface roughness of the ailoy. which is filled and wetted
by porcelain during sintering.
2. Tbe creation of a chemical bond between porcelain and metal
oxides.
3. Tbe compact bond between the ceramic and the base metal. =
RESULTS
The mean bond strength values for each group are listed in Table 1.
The bond strength values ranged from 13.69 ± 6.62 MPa to 25.39 ±
6.68 MPa. One-way analysis of variance for the experimental groups
re- vealed a stadstically significant difference among them (P <
.05). Duncan's mulfiple range test revealed a sta- tistically
significant difference (P < .05) between groups P and O. Tbere
was no statistically significant difference between the bond
strengths of Scotchbond Multipurpose and Panavia 21 Ex. The t test
reveaied a statistically significant difference (P < .01)
between the mean bond strengtb of group C and tbe mean bond
strengths of all three experimental groups (Fig 2).
— Shea nng device
-Embedded material
Fig 1 Positioning of test specimer>s in the tesling
apparatus.
TABLE 1 Shear bond strength (MPa)
Group Mean SD
Scotchbond Muftipurpose (S) 15.81 7.50 Panavta 21 Ex (P) 19.10 8.90
One Coat Bond (0) 13.69 6.62 Control (C) 25 39 6.68
'S Q-
H•—•—^M c
Fig 2 Sheaf txind strengths ot experimental groups and control; (S)
Scotchbond Multipurpose; (P) Panavia 21 Ex; (O) One Coat Bond; (C)
controE.
Quintess 597
• Goharian et al
Among experimental groups, the highest bond strengtb was observed
in group P altbougb it was not significantly different from group
S, Panavia 21 Ex re- portedly adheres to sandblasted base metal
alloy,"'' '"* The manufacturer also has recommended this proce-
dure, Williams et al" found that, after 1,080 thermal cycles,
Panavia demonstrated higher bond strengths to sandblasted metal
than did Super-Bond B&C, Omura et al ^ found tbe best base
metal surface treatment for Panavia was aluminum oxide
sandblasting, which re- sulted in minor roughness and embedding of
the alu- minum oxide in metal surface. ' Phosphate groups in
Panavia could react with metal oxides and create both mechanical
and chemical bonds,"
Tbe mean bond strength of group S was not signifi- cantly different
tban tbat of Panavia, but its bond strengtb was lower tban enamel
to resin composite bond strength,- ' ^ Tbe ceramic primer in this
adbesive could act as adhesion promoter on the metal sur- face,^^^
However, when paired with Duo Cement dual-cured resin cement,
Scotchbond Multipurpose did not achieve a high bond strength.
Film tbickness of tbe luting cement is a very impor- tant factor in
bond strengtb; the lower the thickness, the greater the bond
strengtb, "' i Tbe film tbickness of adhesive resins such as
Panavia is in the range of 13 to 20 pm,'^ It is thought that tbe
lower bond strengtb of Duo Cement could be attributed to the
greater film thickness of this resin cement (about lOf) ]im}.'^^
This may be the reason that the eombination of Scotcb- bond
Multipurpose and Duo Cement achieved a lower mean bond strength
tban Panavia,
Chung and Hwang' found that Liner M repair sys- tem sbowed
significantly greater bond strength tban did resin composite to
metal surfaces, with or without sandblasting. Their suggestion for
treatment of ex- posed metal before bonding of resin composite was
only sandblasting of alloy, Tbey showed that, after sandblasting
and application of Seotchbond Multi- purpose, bond strength with
resin composite was 10.2 MPa, lower than tbe finding in the present
study.
One Coat Bond accompanied by Duo Cetitent achieved a mean bond
strengtb of 13.6 MPa, wbieh was the lowest of the four groups. This
adhesive did not have an adhesion promoter for metal surfaces. In
addition, the combination with Duo Cement did not create a suitable
bond.
Long-term studies are not available to evaluate ail tbe factors
contributing to success or failure of porce- lain veneer-base metal
bonds. Further clinical studies are indicated.
CONCLUSION
1, The mean bond strengths of groups C, P, S, and 0 were 25,39,
19,10, 15,81 and 13,69 MPa, respec- tively,
2, The metal-ceramic control specimens showed the greatest bond
strength,
3, Among the experimental groups, Panavia 21 Ex achieved tbe
greatest bond strength, whieh was sig- nificantly greater than that
of One Coat Bond,
ACKNOWLEDGMENTS
Tiiis study was supported by a grant from the Research Council of
Mashhad Universily of Medical Science, Mashhad, Iran,
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Quintessen
HoUiston L. Riviere
128 pp (spii3Í binding) 2 )5 color illustrations ISBN 0-86715-386-5
US 534
This lab manual of color oral histo]oa\ photographs is designed to
aid dental and dental hygiene students in identifying tho salient
feauires of microscopic anatomv of oral tissLies. It presents
large, clear, identi- fiable photos af normal oral tissues and
developing teeth accompanied by brief descriptions highlighting the
special fea- tures of each.
Contents
Chapter I Iboth Development Chapter 2 Enamel Chapter 3 Dendn
Chapter 4 Pulp Chapter 5 Cementum Chapter 6 Periodontal Ligament
and
Den togiiigival Junction Clinpler 7 .\lveolar Bone Chapter S Tooth
Emption and Shedding Chapter 9 Mticosa Chapter 10 Salivary Glands
Chapter 1! Temporomandibuiar Joint
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