Radiopacity for Contemporary Luting Cements Using Digital Radiography under Various Exposure Conditions Seo-Young An, DDS, MS,1 Du-Hyeong Lee, DDS, MS,2 & Kyu-Bok Lee, DDS, PhD2 1

Department of Oral and Maxillofacial Radiology, School of Dentistry, Kyungpook National University, Daegu, Korea Department of Prosthodontics, School of Dentistry and Advanced Dental Device Development Institute, Kyungpook National University, Daegu, Korea

2

Keywords Dental cements; radiography; dental; digital; radiopacity. Correspondence Kyu-bok Lee, Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea. E-mail: [email protected] This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (2008–0062282). The authors deny any conflicts of interest. Seo-Young An and Du-Hyeong Lee contributed equally to this work. Accepted September 15, 2014 doi: 10.1111/jopr.12288

Abstract Purpose: This study examined the radiopacity of contemporary luting cements using direct digital radiography under a range of exposure conditions. Materials and Methods: Disc specimens (N = 80, n = 10 per group, ø5 mm × 1 mm) were prepared from 8 resin-based luting cements (BisCem Clearfil SA Luting, Duolink, Maxcem Elite Multilink Speed, Panavia F 2.0, RelyX Unicem Clicker, Vlink). The specimens were radiographed using a charge-coupled device sensor along with an 11-step aluminum step wedge (1.5-mm incremental steps) and 1-mm-thick tooth cut using five tube voltage/exposure time setups (60 kVp, 0.10/0.08 seconds; 70 kVp, 0.10/0.08/0.06 seconds) at 4 mA and 30 cm. The radiopacity of the specimens was compared with that of the aluminum step wedge and human enamel and dentin using NIH ImageJ software (available at http://rsb.info.nih.gov/ij/). A linear regression model for the aluminum step wedge was constructed, and the data were analyzed by ANOVA and Duncan post hoc test. Results: Maxcem Elite (5.142 to 5.441) showed the highest radiopacity of all materials, followed in order by Multilink Speed (3.731 to 3.396) and V-link (2.763 to 3.103). The radiopacity of Panavia F 2.0 (2.025 to 2.429), BisCem (1.825 to 2.218), Clearfil SA Luting (1.692 to 2.145), Duolink (1.707 to 1.993), and RelyX Unicem Clicker (1.586 to 1.979) were between enamel (2.117 to 2.330) and dentin (1.302 to 1.685). The radiopacity of 70 kVp conditions was higher than that of the 60 kVp conditions. Conclusions: The radiopacities of the tested luting materials were greater than those of dentin or aluminum, satisfying the criteria of the International Organization for Standardization, and they differed significantly from each other in the exposure setups.

Luting materials fill the minute void between an indirect restoration and tooth (or implant abutment), and mechanically lock the restoration in place to prevent its dislodgement during function.1 Since several luting cements were first introduced, it has been important to evaluate their physical, chemical, and radiographic properties. Radiopacity is an essential requirement of luting materials because it should provide proper contrast between the tooth substrate and materials.2-5 Sufficient radiopacity improves the radiographic diagnosis of recurrent caries, faulty proximal contour, marginal adaptation, and excess cement.4,6-9 The International Organization for Standardization (ISO)5 and American National Standards Institute/American Dental Association (ANSI/ADA)3 have published standardized procedures

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for quantifying the radiopacity of several types of dental materials. A pure aluminum (purity ࣙ98%) step wedge is used as a reference. The radiopacity of the materials should be equal to or greater than that of the same thickness of aluminum. Some studies have examined the radiopacity of dental materials, comparing not only enamel and dentin with the same thickness but also with an aluminum step wedge as an internal standard.10-12 Most studies use direct digital radiography to assess the radiopacity of dental materials instead of the conventional film method.9,13-16 However, the radiopacity of contemporary luting cements has not been fully reported. Moreover, most studies did not examine the effects of the exposure parameters, such as the tube voltage and exposure time, on the radiopacity of dental materials in digital radiography.15,17

C 2015 by the American College of Prosthodontists Journal of Prosthodontics 24 (2015) 642–646 

An et al

Radiopacity for Contemporary Luting Cements

Table 1 Luting cements tested Product BisCem (BC) Clearfil SA Luting (CSL) Duolink (D) Maxcem Elite (ME) Multilink Speed (MS) Panavia F 2.0 (PF) RelyX Unicem Clicker (RUC) V-link (V)

Manufacturer

Lot number

Shade

Bisco Inc., Schaumberg, IL Kuraray Medical Inc., Okayama, Japan Bisco Inc., Schaumberg, IL Kerr Corp., Orange, CA Ivoclar Vivadent, Schaan, Liechtenstein Kuraray Medical Inc., Okayama, Japan 3M ESPE AG, Seefeld, Germany Ivoclar Vivadent, Schaan, Liechtenstein

1100009289 00251A 1100006102 3673633 P62316 00571A, 00110B 451230 P18601, N01551

Translucent Universal Translucent Clear Transparent Light TR Transparent

Exposure time and tube current do not change the mean and maximum energy of each electron, whereas tube voltage effects them.18 Therefore, exposure condition may result in a difference of radiopacity. The purpose of this study was to examine the radiopacity of eight contemporary luting cements using a charge-coupled device (CCD) sensor and to clarify the effects of the exposure condition on the radiopacity.

Materials and methods Specimen preparation

Table 1 lists the luting cements used in this in vitro study. Disc specimens were prepared (N = 40, n = 10 per group; diameter: 5 mm, thickness: 1 mm). The materials were mixed according to the instructions of each manufacturer, compressed between two glass slides in the mold, and light cured using a curing light source (Elipar TriLight; 3M ESPE, Seefeld, Germany; standard mode). The output intensity of 750 mW/cm2 was monitored constantly during the experiment using a built-in radiometer. The thickness of the light-cured specimens was measured using a digital micrometer (293-821 LCD Digimatic Micrometer; Mitutoyo, Kawasaki, Japan) with a critical tolerance of 1 ± 0.01 mm. Human enamel and dentin specimens with a thickness of 1 mm were also prepared by the longitudinal sectioning of a freshly extracted premolar using a slow-speed diamond saw (Isomet, Buehler, IL). The patients were informed that their teeth were to be extracted for orthodontic reasons, and written informed consent was obtained. The study was approved by the School of Dentistry, Kyungpook National University, ethics committee. Digital imaging

An aluminum step wedge was used as an internal standard for measuring the equivalent radiopacity of different materials compared to its thickness. An 11-step wedge (1.5-mm incremental steps) was machined from a 99.5% pure aluminum block (Alu-Keil; PEHA Medikal Ger¨ate GmbH, Sulzbach, Germany). The images were taken using a CCD sensor (Kodak RVG 6100; Carestream Health, Inc., Rochester, NY) and a dental X-ray machine (Kodak 2200 Intraoral X-ray System; Carestream Health, Inc.) operating at 4 mA, 30 cm, and with a total filtration equivalent to 2.5 mm of aluminum. Each specimen was radiographed using five different combinations of the

tube voltage and exposure time (i.e., 60 kVp, 0.10/0.08 seconds; 70 kVp, 0.10/0.08/0.06 seconds). Each material along with the aluminum step wedge and a tooth specimen were positioned over the sensor. The raw images, free of any imaging processing, were saved in 8-bit TIFF format for later radiopacity analysis. The gray values of the specimen were analyzed using NIH ImageJ software (available at http://rsb.info.nih.gov/ij/). Four regions of interest with a size of 10 × 10 pixels for each specimen were measured. The gray value of each specimen was recorded from the mean of the four readings. Special care was taken to analyze only those regions free of air bubbles, gaps or similar defects. In a similar procedure, the enamel and dentin slices were also measured in four different regions. Subsequently, the gray value was converted to an absorbance using the following equation: A = –log (T) = –log (1 – G/255), where A is the absorbance, T is the transmission, and G is the gray value (0 to 255).16 In five radiographs, each of the 11 steps of the aluminum step wedge was measured for the gray value and converted to the absorbance. The absorbance of the aluminum steps was plotted as a function of the corresponding thickness. The equivalent thickness of aluminum for each material was calculated from the calibration curve. Statistical analysis

The absorbance of the luting cements, enamel, and dentin was reported as the mean ± standard deviation. SPSS for Windows v18.0 (SPSS Inc., Chicago, IL) was used for data analysis. A linear regression model for the aluminum step wedge was constructed for each specific condition. The model is described by the equation “Y = a × X + b” and the corresponding R2 , and the standard error of the estimate was obtained. To compare the radiopacity of the luting cements under different conditions, one-way ANOVA with a Duncan’s post hoc test was performed to calculate the significant differences. A p value of

Radiopacity for Contemporary Luting Cements Using Digital Radiography under Various Exposure Conditions.

This study examined the radiopacity of contemporary luting cements using direct digital radiography under a range of exposure conditions...
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