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In vitro wear rates of tooth-colored direct restoratives
Koichi Shinkai, DDS, PhD,a Shiro Suzuki, DDS, PhD,b and Yoshiroh Katoh, DDS,PhDaa

Department of Operative Dentistry, School of Dentistry at Niigata, The Nippon
Dental University, Niigata, Japan, and bDepartment of Prosthodontics andBiomaterials, School of Dentistry, University of Alabama at Birmingham,
Birmingham, AL, USA
Purpose: To evaluate the wear resistance of resin-modified glass-ionomer cements and compomers forlight loading using an in vitro wear simulation machine.
Materials and Methods: Materials tested included Vitremer, Fuji II LC, Advance, Dyract, and Spectrum
TPH resin composite (control). Cylindrical Class I cavities were prepared on occlusally flattened humanmolars, and the cavities were restored with the respective materials according to the manufacturers'
instructions. Six specimens for each material were used for an in vitro three-body wear testing, and thewear depth was measured with a profilometer on epoxy replicas after 60,000, 120,000, 180,000, and
240,000 cycles. The data were statistically analyzed by ANOVA and Scheffe's test.
Results: The wear rates of all materials gradually decreased after 60,000 cycles. Advance exhibited thehighest wear value at every testing interval, and the TPH control showed the lowest value. The wear valuesof Vitremer and Fuji II LC were nearly twice that of Dyract at each testing interval. There were significant
differences in wear values among all materials, except between Vitremer and Fuji II LC at the 180,000 and
240,000 intervals.
Conclusion: Based upon the results within the range of respective materials tested, it can be concluded thatthe compomer is significantly more wear resistant than the resin-modified glass-ionomer cements but lesswear resistant than the resin composite. (Int Chin J Dent 2003; 3: 82-90.)
Clinical Significance: The wear resistance of the resin-modified glass-ionomer cements and compomer
seem to be insufficient even for the stress bearing area of anterior teeth.
Key Words: tooth-colored filling material, wear resistance, wear simulator.

Introduction
As restorative materials, conventional glass polyalkenoate (ionomer) cements have many desirable
properties such as fluoride release, similar thermal expansion to dentin, and chemical adhesion to tooth
substrates. On the other hand, they also have several disadvantages including moisture sensitivity and low
mechanical properties. They are considered unsuitable restorative materials for stress-bearing areas, suchas occlusal surfaces due to their low wear resistance. They are mainly indicated for restoring cervical82

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lesions, class III cavities, and primary teeth. Resin-modified glass-ionomer cements and polyacid-modified
resin composites (compomers) have been developed to improve the handling property and to overcome
problems of the conventional glass-ionomer cements including moisture sensitivity and low mechanicalstrength, while maintaining some of their clinical advantages. They have become popular alternative
materials for the conventional glass-ionomer cements among clinicians.
Several in vitro studies have reported that the physical properties of resin-modified glass-ionomer
cements and compomers are better than those of conventional glass-ionomer cements,1-3 but they provide
little information concerning the wear resistance of these materials. Other studies have reported that
resin-modified glass-ionomer cements and compomers have lower wear resistance than resin composite
materials.4-7

Some clinical studies have reported satisfactory clinical performance of compomers inanterior restorations.8-11

Thus, resin-modified glass-ionomer cements and compomers are suitable

restorative materials for permanent anterior teeth.

However, these previous studies provide little

information concerning the use of these materials for class III and IV restorations. It is necessary toinvestigate the wear of these materials during loading, since lingual or incisal surfaces of anterior teeth areconsiderably stressed by antagonist teeth.
This study evaluated the wear rates of three kinds of resin-modified glass-ionomer cements, a compomer,
and a resin composite by using an in vitro three-body wear testing machine under the loading.

Materials and Methods
The materials used in this study are presented in Table 1. The resin-modified glass ionomer cements
used were Vitremer (3M/ESPE, St. Paul, MN, USA), Fuji II LC Capsule (GC Corp., Tokyo, Japan), andAdvance (Dentsply/Caulk, Milford, DE, USA). Vitremer is a hand mixing and tri-cure type. Fuji II LC
Capsule is a mechanical mixing and dual-cure type. Advance is a chemical-cure type. The compomer used
was Dyract (Dentsply/DeTrey, Konstanz, Germany), and Spectrum TPH resin composite (Dentsply/Caulk)
was used as a control.
Table 1. Materials used.
Material

Trade name

Manufacturer

Lot number

Main composition

RMGI

Vitremer

3M/ESPE
St. Paul, MN, USA

Powder: 455
Liquid: 429

Fluoro-alumino-silicate glass
Polycarboxylic acid, HEMA, Water

RMGI

Fuji II LC
CapsuleGC Corp.
Tokyo, Japan

250141

Fluoro-alumino-silicate glass,
Polycarboxylic acid, HEMA, Water

RMGI

Advance

Dentsply/Caulk
Milford, DE, USA

Powder: 9504201 Fluoro-alumino-silicate glass
Liquid: 9505221 Polycarboxylic acid, HEMA, Water,

Compomer Dyract

Dentsply/DeTrey
Konstanz, Germany

C9408103

UDMA, TCB,
Strontium-fluoro-silicate glass

Composite

Dentsply/Caulk
Milford, DE, USA

9505032

Bis-GMA, Colloidal silica,
Barium-alumino-borosilicate glass

Spectrum TPH

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Caries-free extracted human molars were used in this study. First, tooth cusps were removed by wet
grinding with 600-grit silicon carbide paper to obtain a flat occlusal enamel surface. A cylindrical Class I
cavity (4 mm diameter and 2 mm depth) was prepared on the occlusal surface of each tooth, and thecavities were restored with the respective materials according to manufacturers' instructions (Table 2).
After storage in 37˚C distilled water for 48 hours, the restored surface was finished and polished by
wet-grinding with 800-grit silicon carbide paper. Six specimens were prepared for each material, and eachcompleted specimen was fixed onto a stainless cup with acrylic resin.
Table 2. Restoration procedures for each material.
Material

Restoration procedures

Vitremer

Apply Vitremer Primer (30 s), Dry (15 s), Light cure (20 s),
Mix powder and liquid (30 s), Fill the mixture of Vitremer, Light cure (40 s)

Fuji II LC Capsule

Apply Dentin Conditioner (20 s), Dry (10 s), Mix powder and liquid using GC capsule mixer
CX-I (8 s), Fill the mixture of Fuji II LC, Light cure (40 s)

AdvanceMix powder and liquid (15 s), Fill the mixture of Advance

DyractApply De Trey Conditioner 36 (15 s), Water spray (5 s), Blot dry, Apply Prime&Bond (20 s),
Gently air dry, Light cure (10 s), Apply second layer of Prime&Bond, Gently air dry,
Light cure (10 s), Fill Dyract paste, Light cure (40 s)

Spectrum TPH

Apply De Trey Conditioner 36 (15 s), Water spray (5 s), Blot dry, Apply Prime&Bond (20 s),
Gently air dry, Light cure (10 s), Apply second layer of Prime&Bond, Gently air dry,
Light cure (10 s), Fill Spectrum TPH paste, Light cure (40 s)

The mounting was completed so as the flat occlusal surface was parallel to the plane of the flat
polyacetal stylus. A three-body wear test was employed on the surface of the restorations using an in vitro
wear simulator developed by our department (Fig. 1). The cylindrical stylus (20 mm diameter) slides 10
mm horizontally against the flat occlusal and rises 45 degree at the end of each stroke (Fig. 2). It moves
back to the original position and repeats the stroke. This stroke simulates the movement of mastication.
The specimens were covered with a slurry of poly(methyl methacrylate beads) (Ostron II, GC Corp.) andpoppy seeds (1:1 volume ratio), and relatively light load (4.9 N) was continuously applied at a rate of 120
contacts per minute for up to 240,000 cycles. After every 60,000 cycle, a replica of the worn surface wasprepared with a polyvinylsiloxane impression material (Exafine, GC Corp.) and an epoxy resin (Stycast
1266/A, Aplestik Co., Atsugi, Japan). The worn surface of each restoration was then scanned by aprofilometer (Surfcom 470A, Tokyo Seimitsu Co., Tokyo, Japan) along two planes perpendicular to eachother. The wear depth of the restoration was determined by measuring the deviation between enamel andworn material (Fig. 3). The mean depth of wear for each material was measured on the respective
profilometric tracings and recorded as the wear value. The data were statistically analyzed by analysis ofvariance (ANOVA) and Scheffe's test. After determining the wear values of the restorations, some replicas
were randomly selected for scanning electron microscopic examination. They were mounted on aluminum
stubs and sputter coated with platinum/palladium (Hitachi E 101, Hitachi Co., Tokyo, Japan). Surface

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texture and filler/matrix interface of worn surfaces were evaluated with a scanning electron microscope(SEM, Hitachi S-800, Hitachi Co.)

StylusSlurryFig. 1. In vitro wear simulator.

Fig. 2. Schematic diagram of the
movement of the stylus.

50.0
(µｍ)

0.0

Specimen

E
D1

D2

D4

D3

D5

R

-50.0

Fig. 3. Typical profilometric tracing of a specimen after three-body wear. E: Enamel surface,
R: Resin composite surface, D1-5: Five different wear depth measurements.

Results
The wear rates of all materials are presented in Fig. 4. All of them exhibited gradual decreases after
60,000 cycles. Advance demonstrated the largest, and the Spectrum TPH resin composite showed thesmallest wear value at every testing interval. The wear values of Vitremer and Fuji II LC were nearly twiceof that for Dyract at each testing interval. The wear value of Vitremer was similar to that of Fuji II LC.
The mean wear depths of all materials are presented in Table 3. There were no significant differencesamong the wear values of Vitremer, Fuji II LC, and Dyract at 60,000 cycles, but the wear value of Dyract
became significantly lower than those of Vitremer and Fuji II LC after 120,000 cycles. There were no
significant differences between the wear values of two resin-modified glass ionomer cements, Vitremer andFuji II LC, at any testing interval. Spectrum TPH resin composite exhibited significantly higher wear
resistance compared to the other materials at 180,000 and 240,000 cycles, while Advance demonstrated
significantly lower wear resistance than the other materials for all time intervals.
Typical SEM photographs of the respective materials after 240,000 cycles are presented in Fig. 5. Theview of entire restoration was presented at low magnification, and the surface texture was visualized at high85

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Int Chin J Dent 2003; 3: 82-90.

magnification. SEMs of Vitremer showed that the enamel walls were fairly exposed at the cavity margin
due to loss of material. Protruding core particles and small defects due to the exfoliation or plucking-out ofthe particles were confirmed. Air voids could also be observed on the worn surface of Vitremer.
The loss of Fuji II LC increased progressively with the number of wear cycles. Protruding large core
particles and small defects was seen on its worn surface. SEMs of Advance showed substantial loss ofmaterial after 240,000 cycles. The worn surface texture of Advance at low magnification was rougher thanthat of Fuji II LC. Under high magnification, the worn surface texture of Advance was similar to that of
Fuji II LC, except for the presence of air voids.
The surface texture of worn Dyract was smoother than that of Vitremer, Fuji II LC, and Advance. It wasquite different from those of the resin-modified glass-ionomers but very similar to that of Spectrum TPH
resin composite.
The SEMs of Spectrum TPH demonstrated less material loss and smoother surface texture compared tothe other materials. However, this material also showed protruded small-sized particles and small defects
caused by the exfoliation of filler particles.
Wear 10(µm)

Advance08Fuji II LC

0

LC

6

Vitremer0
40

Dyract200Spectrum TPH

0

60,00
0

120,000

180,000240,000Wear cycles

Fig. 4. Comparison of the wear rates for the materials tested.
Table 3. Wear testing results in µm.
Cycles60,000Mean SD

Spectrum
DyractVitremer
Fuji II LC
Advance

2.9
16.2
31.8
35.2
68.5

0.7
5.5
9.6
12.6
27.1

120,000
Mean SD
a
a, b
b
b

5.5
23.8
48.2
50.6
82.5

2.0
7.9
6.5
6.5
24.5

c
c
d
d

180,000
Mean SD

240,000
Mean SD

6.8
28.3
52.5
62.4
87.7

8.0
31.7
56.1
67.7
92.9

Groups identified by the same letters are not statistically different (p>0.05).

86

2.7
6.2
8.0 e
6.1 e
22.8

2.6
6.0
8.6 f
7.0 f
21.1

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Fig. 5. Typical scanning electron micrographs of the respective materials
tested at 240,000 cycles.
(a), (f): Fuji II LC, (b), (g): Spectrum TPH, (c), (h): Vitremer(d), (I): Advance, (e), (j): Dyract
a-d: overall view, x20. e-h: magnified view, x500.

Discussion
Glass-ionomer cements have several advantages including fluoride release, chemical adhesion to tooth
substances, ease of use, and good biocompatibility. The physical properties of glass-ionomer cements,
however, are not as good as those of resin composites.1 Recently, resin-modified glass-ionomers have beendeveloped by adding resin monomer components to the composition of the conventional glass-ionomer.
The composition of compomers more closely resembles resin composites than glass-ionomer cements. The
physical properties of these restorative materials have been improved by the resin component. Somestudies have reported the physical properties of resin-modified glass-ionomers and compomers.1-3 Kimura
et al. reported that the compressive strength and the flexural strength of the compomer tested weresignificantly higher than those of resin-modified glass-ionomers, but significantly lower than those of resin
composites.3

Attin et al. reported that the physical properties of resin-modified glass-ionomers andcompomers were inferior to those of hybrid resin composites.2 It is speculated that the wear resistance of
these restorative materials is also improved by adding resin monomer components. The results of this study
revealed that the wear value of Dyract was nearly half of those for Vitremer and Fuji II LC, but the wear
resistance of Dyract was significantly lower compared to Spectrum TPH resin composite. Based upon the
results, the compomer tested seemed to have superior wear resistance than resin-modified glass-ionomer
but inferior wear resistance than resin composite.
Several studies have investigated the wear resistance of resin-modified glass-ionomers and87

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Int Chin J Dent 2003; 3: 82-90.

compomers.4,5 de Gee et al. evaluated in vitro wear rates of occlusal contact-free areas for conventional
glass-ionomers, metal-reinforced glass-ionomers, and resin-modified glass-ionomers and reported that theresin-modified glass-ionomers had significantly smaller wear rates than the conventional glass-ionomers at
every stage.4 The results of their study are similar to the results of our study. Pelka et al. compared
two-body and three-body wear of glass-ionomers, visible light cured glass-ionomers, and resin composites.5
The results of these in vitro wear tests showed that the visible-light-cured glass-ionomer had lower wear
resistance than the resin composite.

Momoi et al. examined the in vitro toothbrush abrasion ofresin-modified glass-ionomers and reported that the wear resistance of resin-modified glass-ionomers wasinferior to that of the conventional acid-base glass-ionomers.12 Their studies showed counter findings toother studies in that the resin-modified glass-ionomers exhibited superior wear resistance than theconventional glass-ionomer cements.

Several clinical studies have reported findings that the wear

resistance of resin-modified glass-ionomers and compomers was inferior to that of resin composites.6,7Duke et al. examined the clinical performance of a representative resin-modified glass ionomer in cervicalabrasions and root caries in adults, and the results of their clinical trial showed the resin-modified
glass-ionomer to be inferior to conventional resin composite in terms of color stability and loss of anatomic
form or wear.6 Folwaczny et al. used an optical three-dimensional laser scanning device to investigate thesubstance loss of cervical restorations of four tooth-colored restoration materials including a resin
composite, a compomer, and two resin-modified glass-ionomers in vivo.7

They concluded that theresin-modified glass-ionomers and the compomer demonstrated a distinctly higher wear rate over time incomparison to the resin composite. The results of these clinical studies were much the same as the resultsof this study.
In vitro wear values of resin composites subjected to 400,000 cycles with Leinfelder’s three body wear
simulator are comparable to the clinical wear data of resin composite restorations evaluated after a two-year
study13 and a three-year study.14 In Leinfelder’s wear simulator, a flat-planed polyacetal stylus is verticallyloaded onto the restored surface under a load of 75 N.15 In the wear simulator used in this study, 4.9 N load
was vertically applied onto the restored surface. There are several differences in vertical loading and stylus
movement between Leinfelder’s and our machine, but the concept for the simulation is quite similar.
A number of studies have suggested that the wear resistance of resin composites is affected by filler size
and amount.16-22 Microfilled resin composites generally exhibit excellent resistance to generalized wear or
three-body wear,18,19 whereas, resin composites containing large-sized fillers offer low resistance togeneralized wear.16 The SEM examinations of the worn surfaces of the materials tested in the present study
showed that Vitremer, Fuji II LC, and Advance protruded large alumino-silicate glass cores. The worn
surface texture of Dyract, on the other hand, was quite different from that of the resin-modified
glass-ionomers but similar to that of Spectrum TPH resin composite, which was smoother than the othermaterials. Thus, the large-sized core particles may be responsible for the lower wear resistance of theresin-modified glass-ionomers.
The property of the matrix is also an influencing factor for the wear resistance. The differences in the88

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matrix components among the materials tested might have a large effect on wear resistance.

Conclusion
Based upon the results within the range of respective materials tested, it can be concluded that thecompomer is significantly more wear resistant than the resin-modified glass-ionomer cements but less wear
resistant than the resin composite.

Therefore, it is suggested that the compomer and resin-modified

glass-ionomers tested are not recommended for anterior restorations when the materials used for stressbearing areas including lingual and incisal surfaces.

References
1. Momoi Y, Hirosaki K, Kohno A, McCabe JF. Flexural properties of resin-modified "hybrid" glass-ionomers in comparison
with conventional acid-base glass-ionomers. Dent Mater 1995; 14: 109-19.
2. Attin T, Vataschki M, Hellwig E. Properties of resin-modified glass-ionomer restorative materials and two
polyacid-modified resin composite materials. Quintessence Int 1996; 27: 203-9.
3. Kimura T, Tanaka N, Ino M, Onozawa T, Tokuda K, Katoh Y. Study on the light-cured restorative glass ionomer cement.
Physical properties of Dyract. Jpn J Conserv Dent 1996; 39: 1075-83.
4. de Gee AJ, van Duinen RN, Werner A, Davidson CL. Early and long-term wear of conventional and resin-modified glassionomers. J Dent Res 1996; 75: 1613-9.
5. Pelka M, Ebert J, Schneider H, Kramer N, Petschelt A. Comparison of two- and three-body wear of glass-ionomers andcomposites. Eur J Oral Sci 1996; 104: 132-7.
6. Duke ES, Trevino DF. A resin-modified glass ionomer restorative: three-year clinical results. J Indiana Dent Assoc 1998;
77: 13-25.
7. Folwaczny M, Mehl A, Kunzelmann KH, Hickel R. Determination of changes on tooth-colored cervical restorations invivo using a three-dimensional laser scanning device. Eur J Oral Sci 2000; 108: 233-8.
8. Frazier KB, Rueggeberg FA, Mettenburg DJ. Comparison of wear-resistance of Class V restorative materials. J Esthet
Dent 1998; 10: 309-14.
9. Luo Y, Lo EC, Fang DT, Wei SH. Clinical evaluation of polyacid-modified resin composite posterior restorations:
one-year results. Quintessence Int 2000; 31: 630-6.
10. Crisp RJ, Burke FJ. One-year clinical evaluation of compomer restorations placed in general practice. Quintessence Int
2000; 31: 181-6.
11. Papagiannoulis L, Kakaboura A, Pantaleon F, Kavvadia K. Clinical evaluation of a polyacid-modified resin composite(compomer) in Class II restorations of primary teeth: a two-year follow-up study. Pediatr Dent 1999; 21: 231-4.
12. Momoi Y, Hirosaki K, Kohno A, McCabe JF. In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers.
Dent Mater 1997; 13: 82-8.
13. Leinfelder KF, Broome JC. In vitro and in vivo evaluation of a new universal composite resin. J Esthet Dent 1994; 6:
177-83.
14. Leinfelder KF, Suzuki S. In vitro wear device for determining posterior composite wear. J Am Dent Assoc 1999; 130:1347-53.
15. Leinfelder KF, Beaudreau RW, Mazer RB. An in vitro device for predicting clinical wear. Quintessence Int 1989; 20:755-61.
16. Leinfelder KF, Sluder TB, Sockwell CL, Strickland WD, Wall JT. Clinical evaluation of composite resins as anterior andposterior restorative materials. J Prosthet Dent 1975; 33: 406-17.
17. Leinfelder KF, Wilder AD, Teixeira LC. Wear rates of posterior composite resins. J Am Dent Assoc 1986; 112: 829-33.
18. Mazer RB, Leinfelder KF, Russell CM. Degradation of microfilled posterior composite. Dent Mater 1992; 8: 185-9.

89Shinkai et al.

Int Chin J Dent 2003; 3: 82-90.

19. Mazer RB, Leinfelder KF. Evaluating a microfill posterior composite resin. A five year study. J Am Dent Assoc 1992;
123: 333-8.
20. Lambrechts P, Vanherle G, Vuylsteke M, Davidson CL. Quantitative evaluation of the wear resistance of posterior
dental restorations: a new three-dimensional measuring technique. J Dent 1984; 12: 252-67.
21. Lutz F, Phillips RW, Roulet JF, Setcos JC. In vivo and in vitro wear of potential posterior composites. J Dent Res 1984;
63: 914-20.
22. Lambrechts P, Braem M, Vanherle G. Evaluation of clinical performance for posterior composite resins and dentin
adhesives. Oper Dent 1987; 12: 53-78.

Reprint request to:Dr. Koichi Shinkai
Department of Operative Dentistry, School of Dentistry at Niigata, The Nippon Dental University
1-8, Hamaura-cho, Niigata 951-8580, Japan
Fax: +81-25-265-7259 E-mail: shinkaik@ngt.ndu.ac.jp
Received on May 19, 2003. Revised on June 19, 2003. Accepted on July 7, 2003.
Copyright ©2003 by the Editorial Council of the International Chinese Journal of Dentistry.

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