TAIRA, ATSUTA, AND MATSUMURAINT CHIN J DENTInfluence of three carboxylic primers on bonding of an adhesive resin totitanium
Yohsuke Taira, DDS, PhD, Mitsuru Atsuta, DDS, PhD, and Hideo Matsumura, DDS,PhD
Division of Fixed Prosthodontics and Oral Rehabilitation, Nagasaki University
Graduate School of Biomedical Sciences, Nagasaki, Japan
Purpose: The purpose of this study was to evaluate the influence of three primers on bonding to titanium ofan adhesive luting agent.
Materials and Methods: The luting agent consisted of 4-methacryloyloxyethyl trimellitate anhydride(4-META), methyl methacrylate (MMA), and tri-n-butylborane (TBB) initiator.

Forty pairs of disk

specimens were prepared from 99.9% titanium metal, air-abraded with 50 µm grain size alumina, primed
with one of the three carboxylic primers (Acryl Bond, MR Bond, and Primer B), and bonded with the4-META/MMA-TBB resin along with an unprimed control. Shear bond strength was determined after 24hours of immersion in 37˚C water, and after 100,000 cycles of thermocycling at 4˚C and 60˚C.
Results: Bond strength was negatively affected by thermocycling and by the use of each of the threecarboxylic primers. After 100,000 thermocycles, the average bond strengths were categorized statisticallyinto three levels (p<0.05): a higher group (unprimed, 37.0 MPa), medium groups (Acryl Bond, 24.4 MPa;and MR Bond, 25.5 MPa), and a lower group (Primer B, 17.8 MPa).
Conclusion: Each of the three carboxylic primers reduced the bonding between 4-META/MMA-TBB resin
and titanium metal. (Int Chin J Dent 2002; 2: 116-120.)
Clinical Significance: There are some cases where primer should not be used. Clinicians need be informedof the longevity of resin-bonded titanium restorations.
Key words: bonding, carboxylic acid, thermocycling, titanium.

INTRODUCTION
Titanium is being used in the fabrication of resin-bonded fixed partial dentures,1 resin composite
veneered crowns,2 and implant supported fixed restorations.3 Durable bonding between the resin and thetitanium framework is required for these restorations to withstand the oral environment. Various functionalmonomers have recently been developed for use as primers or as adhesive luting agents.4,5Previous study has suggested that carboxylic monomers improve the durability of the bond between
resin-based luting material and 99.9% pure titanium metal.6,7 This bonding durability is improved further
when a phosphoric or a thiophosphoric primer is used, even when the luting agent contains carboxylic

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monomers.8,9 However, it is still unclear whether or not the carboxylic primers assist bonding when theluting agent contains another functional monomer. The relationships between different types of functionalmonomers have not been clarified with regard to titanium bonding.
The purpose of this study was to evaluate the effect of primers containing a carboxylic monomer on bondstrength between an adhesive luting agent containing 4-methacryloyloxyethyl trimellitate anhydride(4-META) and pure titanium metal, after thermocyclic stressing.

MATERIALS AND METHODS
The primers and the luting agent tested are summarized in Table 1. Two sizes of machine-milled disks(10 mm diameter x 2 mm thick, and 6 mm diameter x 2 mm thick) of 99.9% titanium metal (0.06% O,0.0075% Fe, and 0.0075% C; Furuuchi Chemical Ind., Tokyo, Japan) were used.
Table 1. Primers and luting agent used.
Trade name

Manufacturer

Lot number Component

Acryl Bond

Shofu Inc., Kyoto, Japan

019213

4-AET in solvent

MR Bond

Tokuyama Soda Co., Ltd., Tokyo, Japan002

MAC 10 in solvent

Primer B

Bisco Inc., Itasca IL, USA

129091

BPDM in solvent

Sun Medical Co., Moriyama, Japan

00501

4-META, MMA, PMMA, TBB

PrimerLuting agent
Super-Bond C&B

4-AET: 4-acryloyloxyethyl trimellitate, MAC 10: 11-methacryloyloxyundecan-1,1-dicarboxylic acid, BPDM: adductof 2-hydroxyethyl methacrylate and 3,4,4’,5’-biphenyl tetracarboxylic anhydride, 4-META: 4-methacryloyloxyethyl
trimellitate anhydride, MMA: methyl methacrylate, PMMA: poly(methyl methacrylate), TBB: tri-n-butylborane.

After each disk was ground using 600 grit silicon-carbide paper, the surfaces were sand-blasted with 50µm alumina under 0.5 MPa pressure for 10 s (Pen-Blaster; Shofu Inc., Kyoto, Japan).

A piece of50-µm-thick masking tape with a 5 mm diameter circular hole was placed on the 10 mm diameter disk todetermine the thickness of the adhesive resin and the adhesive area. One of the three primers was brushed
onto the titanium specimens, the luting agent was applied, and the 10 mm and 6 mm diameter specimens
were held together using finger pressure.
Following storage at room temperature for 1 hour after bonding, the specimens were immersed in waterat 37˚C for 24 hours (thermocycle 0).

The specimens were then immersed in 4˚C and 60˚C water

alternately for 1 minute periods for 100,000 cycles using a thermocycling machine (Rika Kogyo, Hachioji,Japan).

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Shear bond strength was determined by means of a universal testing device (AGS-10kNG; Shimadzu
Corp., Kyoto, Japan) with a cross-head speed of 0.5 mm/minute, following dental materials guidance on thetesting of adhesion to tooth structure (ISO/TR11405). The titanium surfaces of the debonded specimens
were examined with an optical microscope (x 4, SMZ-10; Nikon Corp., Tokyo, Japan) to evaluate theconditions of failure.
The mean and standard deviation of the bond strength for the five specimens were calculated for eachgroup. All data were analyzed by analysis of variance (ANOVA), and the mean values were comparedusing Duncan's new multiple range test, with p<0.05 considered significant.

RESULTS
Two factor ANOVA demonstrated that bond strength was significantly influenced (p<0.05) bythermocycling (F = 81.5), the type of primer used (F = 21.3), and thermocycling/primer interaction (F =9.7). Mean bond strength, standard deviation, and the results of the Duncan’s test are presented in Table 2.
Table 2. Shear bond strength results.
GroupThermocycle 0

100,000 cycles

MeanSD

Category

MeanSD

Category

Unprimed

39.3

1.5

d37.0

1.0

c dAcryl Bond

32.8

5.5

c24.4

2.9

bMR Bond

35.1

3.5

c d

25.5

3.9

b

Primer B

36.3

4.2

c d

17.8

2.2

Bond strength (MPa)aIdentical letters indicate that the values are not statistically different (n = 5, p>0.05). SD: Standard deviation calculated with
degree of freedom.

Table 3. Type of bond failure.
GroupThermocycle 0

100,000 cycles

ACAACAUnprimed

5041Acryl Bond

5023MR Bond

5005Primer B

5005Failure mode

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A: adhesive failure at resin-metal interface, AC: combined mode involving adhesive failure and cohesive failure within
resin.

After 100,000 cycles, the bond strengths were categorized into three levels, a higher group (unprimed),
medium groups (Acryl Bond and MR Bond), and a lower group (Primer B). The data of our previous
study8 was used as the positive control (unprimed). Bond strength ranged from 17.8 to 39.3 MPa. The
difference in bond strength between the unprimed group and the Acryl Bond group was significant, but nosignificant difference was found among the other groups at thermocycle 0. The bond strength of theunprimed group was maintained for up to 100,000 thermocycles. After thermocycling, the Acryl Bondgroup, the MR Bond group, and the Primer B group exhibited a significantly decreased bond strength.
As shown in Table 3, all of the specimen surfaces contained mixed adhesive and cohesive modes before
thermocycling.

One (unprimed), three (Acryl Bond) and five (MR Bond and Primer B) specimens

exhibited substantial adhesive failure after 100,000 thermocycles.

DISCUSSION
This study investigated the role of carboxylic functional monomers and their propriety in titanium bonddurability. The surface of pure titanium metal is coated with titanium oxide after sand-blasting, allowing
aluminum oxide particles to become partially embedded.10 The functional monomers used consist of acarboxylic group with a methacryloyl or an acryloyl group.

Carboxylic acid or the carboxylic acidanhydride group of 4-META is considered to interact with the metal oxides created on base metal alloys in
the atmospheric environment.11,12
The present findings suggest that bonding durability is affected by the primer that is applied to thetitanium surface. A hypothetical explanation is that no competitive relationship exists between 4-META
and the other carboxylic monomers. The carboxylic group of 4-META has a greater affinity with thetitanium surface than MAC 10, BPDM, and 4-AET. If a less effective carboxylic monomer is used to cover
the titanium surface, successful interaction between the 4-META and the original surface is less likely.
The durability may be related to the primer solvent or to the TBB initiator existing at the resin-metalinterface during the setting reaction.13 Further study is needed to confirm this hypothesis.
In contrast to these carboxylic primers, phosphoric and thiophosphoric primers significantly improve thedurability of 4-META/MMA-TBB resin bonds.5,8 Therefore, when selecting a primer in combination witha luting agent, the type of functional monomer to be used should be considered.

CONCLUSION
When titanium metal is bonded with 4-META/MMA-TBB resin, the Acryl Bond, MR Bond, and Primer
B carboxylic primers will not be needed.

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TAIRA, ATSUTA, AND MATSUMURAINT CHIN J DENTREFERENCES
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10. Kern M, Thompson VP. Effects of sandblasting and silica-coating procedures on pure titanium. J Dent 1994; 22: 300-6.
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Reprint request to:
Dr. Yohsuke Taira
Division of Fixed Prosthodontics and Oral Rehabilitation
Nagasaki University Graduate School of Biomedical Sciences
1-7-1, Sakamoto, Nagasaki 852-8588, Japan
Fax: +81-95-849-7689
E-mail: yohsuke@net.nagasaki-u.ac.jp
Received on August 12, 2002. Revised on September 12, 2002. Accepted on September 27, 2002.
Copyright ©2002 by the Editorial Council of the International Chinese Journal of Dentistry.

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