Tsuge et al.

Int Chin J Dent 2008; 8: 49-52.

Radiopacity of anterior and posterior restorative composites
Takuma Tsuge, DDS,a Shoji Kawashima, DDS, PhD,b Kazuya Honda, DDS, PhD,bHiroyasu Koizumi, DDS, PhD,c Hideo Matsumura, DDS, PhD,c and Noriko Hisamatsu,DDS, PhDdab

Nihon University Graduate School of Dentistry, Department of Oral and Maxillofacial Radiology, andDivision of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry,cDepartment of Fixed Prosthodontics, and Division of Advanced Dental Treatment, Dental ResearchdCenter, Nihon University School of Dentistry, Tokyo, Japan, and Nagasaki University Hospital ofMedicine and Dentistry, Nagasaki, Japan
Purpose: The purpose of this study was to evaluate the difference in radiopacity of anterior and posterior
composites.
Materials and Methods: Four composites designed for anterior (Litefil II A and Solare A) or posterior
restorations (Litefil II P and Solare P) were evaluated. Two self-polymerizing acrylic resins (Unifast III andProvinice) were used as controls. Radiographs of the specimens were taken together with tooth slices andaluminum step wedges. The density of the specimens was determined with a transmission densitometer and wasexpressed in terms of the equivalent thickness of aluminum per 2.0 mm unit thickness of the specimen (mmAl/2.0 mm specimen).
Results The radiopacity values of composites ranged from 1.5 to 3.7, whereas the two acrylic resins wereradiolucent (less than 0.5).
Conclusion: The radiopacity of composite restorative materials varies considerably, and care must be taken in
the selection of materials. (Int Chin J Dent 2008; 8: 49-52.)
Key Words: aluminum, composite, densitometer, radiopacity.

Introduction
Dental composites are used as restorations, luting agents, base, core foundation, and in many otherapplications. Radiopacity is one of the prerequisites for dental materials, especially for composite restorations.
Advantages of radiopaque over radiolucent materials include easy detection of secondary dental caries as well as
observation of the radiographic interface between the materials and tooth structure.
A number of studies have evaluated the radiopacity of dental composites.1-8 Abou-Tabl et al.1 used analuminum step wedge as a radiographic reference for evaluating the radiopacity of dental materials. Most
investigators determined the radiopacity of composite on the basis of ISO 4049 standard.9 According to the ISO
4049 guidelines, the radiopacity of a radiopaque material should be equal to or greater than that of the same
thickness of aluminum.
An increasing number of posterior and anterior composite restorative materials have recently been introducedwith improved bonding and handling characteristics. However, only limited information is available about theradiographic properties of currently available composites. This study determined the radiopacity values ofanterior and posterior composites, and compared these values with those of unfilled acrylic resins.

Materials and Methods
Four restorative composites and two acrylic resins were assessed.

Characteristics of the materials are

summarized in Table 1. Step wedges made of 99.99% aluminum (2.0-20.0 mm in thickness, Seico Inc.,
Hiroshima, Japan) and extracted human molars were employed. This project was approved by the EthicalCommittee of the Nihon University School of Dentistry (2007-5).
Composite paste was poured into acrylic molds (10.0 mm in diameter and 2.3 mm in height) and light-cured

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Int Chin J Dent 2008; 8: 49-52.

between two glass plates at 25˚C.

Monomer liquid and powder of the MMA resins were mixed andself-polymerized according to the manufacturers' instructions, and 2.3-mm-thick specimens were prepared.
After 24 hours, the specimens were ground with #600 silicon-carbide paper to obtain a thickness of 2.0 mm.
Extracted human molar teeth were sectioned mesiodistally with a rotary cutting machine, wet-polished, and2.0-mm-thick specimens were prepared.
Table 1.

Materials assessed.

Materials

Manufacturer

Lot

Composition

Direct composite
Solare A
Solare P

GC Corp., Tokyo, JapanGC Corp.

06101310609152

UDMA, SiO2
UDMA, fluoro-alumino silicate, SiO2

Litefil II A
Litefil II P

Shofu Inc., Kyoto, Japan
Shofu Inc.

100640110658

UDMA, TEGDMA, alumino silicate, fused silica
UDMA, TEGDMA, alumino silicate, fused silica

0605291
0605292

Powder:Liquid:PMMA
MMA

060650100609Powder:Liquid:MMA-EMA copolymer
MMA

Self-polymerizing acrylic resin
Unifast III
GC Corp.
ProviniceShofu Inc.

UDMA, Urethane dimethacrylate; TEGDMA, Triethyleneglycol dimethacrylate;
PMMA, Poly(methyl methacrylate); MMA, Methyl methacrylate; EMA, Ethyl methacrylate

Each specimen was placed together with tooth slices and aluminum step wedges on a radiographic film
(Ultra-Speed Dental Film DF-50 Occlusal, Eastman Kodak Co., Rochester, NY, USA). Radiographs were takenwith a dental X-ray apparatus (DFW-20, Asahi Roentgen Ind., Kyoto, Japan) for 0.6 s at 60 kVp, 15 mA with atarget-film distance of 35 cm. The total filtration on the X-ray beam was 2 mm aluminum. The films wereprocessed in an automatic developing machine (Dent-X 9000, AFP Imaging Co., Elmsford, NY, USA) at 27˚Cfor 6 minutes. The radiographic density of the films was measured with a transmission densitometer (PDA-15,Konika-Minolta Inc., Tokyo, Japan). The radiopacity values of the specimens were expressed in terms of theequivalent thickness of aluminum per 2.0 mm unit thickness of material. For each condition, the mean value andstandard deviation of 10 replications were calculated. The radiopacity values of each group were compared byMann-Whitney U test with the value for statistical significance set at the P=0.01 level (SPSS software, Version
14.0.J for Windows, SPSS Japan Inc., Tokyo, Japan).

Results
The radiopacity values of the 2.0-mm-thick composite specimens are presented in Table 2.

A typical

radiograph of the specimens taken together with tooth slices and aluminum step wedges is shown in Fig. 1.
Statistical analysis results are also summarized in Table 2. The radiopacity values of composites were 1.5 forSolare A, 3.7 for Solare P, 1.8 for Litefil II A, and 2.2 for Litefil II P. The two acrylic resins were radiolucent,and the radiopacity values were less than 0.5. For each composite, the posterior material was more radiopaquethan the anterior material (P<0.001). The radiopacity values of human enamel and dentin were approximately
4.3 and 2.3 mm Al/2.0 mm specimen, respectively. Radiopacity values of the Litefil II composites were smaller
than that of dentin.

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Table 2.

Int Chin J Dent 2008; 8: 49-52.

Radiopacity values of direct composites (mm Al/2 mm specimen)

Material

Median Mean

SDMaterial

Median Mean

SDZ-value

P-value

Solare A
Litefil II A

1.5
1.8

0.1
0.1

Solare P
Litefil II P

3.8
2.2

0.2
0.1

-3.883-3.914

P<0.001
P<0.0011.5
1.8

Z-value=-3.933 P-value <0.001

3.7
2.2

Z-value=-3.865 P-value <0.001

Fig. 1.
A radiograph of Solare A, Solare P(top), Litefil II A, Litefil II P (middle),
Unifast III, and Provinice (bottom).
Two acrylic resins wereradiolucent, and were difficult todetect on the radiograph.

DiscussionPolymeric dental materials can be made radiopaque by incorporation of radiopaque elements into either thefiller particles or monomer liquids.

Zirconia, silica-zirconia, barium glass, barium sulfate and ytterbium

trifluoride are useful for enhancing the radiopacity of dental composites. They are usually added to inorganic
fillers before preparation of splintered filler particles. The results of the current study revealed that radiopacity
values of the Litefil II composites were not particularly high. This is probably derived from the fact that theamount of radiopaque elements added to the composite was not sufficient. The radiopacity values of the Solare
composites also were not high, and the values were smaller than that of enamel. As revealed in the current
investigation, the four composite materials showed radiopacity values below that of enamel, and two anterior
composites showed radiopacity values below that of dentin. The values may be sufficient to allow detection insome cavity preparations. However, the use of radiolucent materials may lead to an incorrect diagnosis. A
radiopacity value equal to or slightly greater than that of enamel is therefore desirable for restorative composites.
Acknowledgments
This work was supported in part by Sato Fund, Nihon University School of Dentistry (2008), Grant from Dental ResearchCenter (A and B), Nihon University School of Dentistry (2008), and Special Research Grant for the Development ofDistinctive Education from the Promotion and Mutual Aid Corporation for Private Schools of Japan (2008).

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6. Bouschlicher MR, Cobb DS, Boyer DB. Radiopacity of compomers, flowable and conventional resin composite for posterior
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Correspondence to:Dr. Hiroyasu Koizumi
Department of Fixed Prosthodontics, Nihon University School of Dentistry
1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
Fax: +81-3-3219-8351 E-mail: koizumi@dent.nihon-u.ac.jp
Received September 16, 2008. Accepted November 11, 2008.
Copyright ©2008 by the International Chinese Journal of Dentistry.

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