Journal of Oral Rehabilitation, 1990, Volume 17, pages 245-248

The radiopacity of glass ionomer dental materials J.A. WILLIAMS and R.W. BILLINGTON University College and Middlessex School of Dentistry, University of London, London, U.K. r.

Summary

Although some glass ionomer dental materials are described as radiopaque by the manufacturer, it is rare for the actual degree of radiopacity to be specified. Using a technique previously described for measurement of the radiopacity of enamel, dentine and composite resin dental materials, the radiopacity of a number of glass ionomer materials, including restorative, lining and luting cements, was determined. Introduction

A technique for measuring the radiopacity of dental materials has previously been described by Williams and Billington (1987). The composite resin materials measured using this method all had radiopacities equivalent to or greater than that of enamel (2-2mm Al/lmm enamel) and dentine (1-0mm Al/lmm dentine). Although radiopacity is not a requirement for materials used in anterior restorations, it is essential that materials used for posterior restoration techniques and for lining purposes are sufficiently radiopaque to be detected on a dental X-ray. The number of glass ionomer materials available has increased recently, but in several cases precise data concerning their radiopacity is lacking. Measurements were therefore made on these materials using the same technique. Materials and methods

The materials used are listed in Table 1 and the available data for radiopacity are shown in Table 2. The technique requires 1-mm-thick discs of mixed material and a step-wedge of pure aluminium interposed between the beam of a conventional dental X-ray machine and a sheet of dental X-ray film. The visual opacity of the developed film is subsequently measured at 550 nm with a spectrophotometer, both for the material under investigation and for the step-wedge of known thickness, the latter acting as an internal standard. In general, 10mm diameter discs were made, which enabled at least three measurements of radiopacity to be made on each disc of material. ITie radiopacity is expressed in terms of the number of mm Al/lmm dental cement. Obviously measurements in areas containing imperfections, such as air bubbles, in the cements should be avoided. Results

The results are shown in Table 3, and it can be seen that there is considerable variation in the degree of radiopacity considered necessary for different applications. Correspondence: Mrs J. A. Williams, Department of Biomatedals Scietice, Institute of Dental Surgery, 256 Gray's Inn Road, London WCl XUD, U.K.

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J.A. Williams and R.W. Billington

Table 1. Details of materials used Material

Type

Batch

Manufacturer

AlphaBond

Powder/liquid base

P D 028804 LA 098814

Billericay Dental Supply Co., Perry Way, Witham, Essex, U.K.

AlphaCore

Powder/hquid Core build up Build up

P A 108824 L A 098814

BaseLine

Anhydrous hner and base

880827

De Trey, Dentsply AG, CH-8037, Zurich, Switzerland

Ceramcore (3

Anhydrous core Build up Anhydrous base

028610

PSP Dental Manufacturing Co. Ltd, Belvedere, Kent, U.K.

Powder/liquid Lining Powder/hquid Luting Powder/liquid Restorative

P 250461 L 210461 P 041271 L 271171 P 290381 L 29038

G-C Dental Industrial Corp. 76-1 Hasunuma-cho Habashi-Ku, Tokyo 174, Japan

Powder/liquid capsule Powder/liquid Liner

N 300 P 021 0013 L 021 0013

ESPE Fabdk Pharmazeutisher, Praparate GMBH, D-8031, Seefeld/Oberbay, W. Germany

Powder/liquid Base Powder/liquid Core build up

P L P L

Rexodent Ltd. 25/27 Merrick Rd, Southall, Middlesex, U.K.

Powder/liquid Base Powder/liquid Lining

P 048701 L 128701 P 028612 L 018610

Ceramlin p Liv Lining Fuji I Radiopaque Fuji II Radiopaque KetacSilver KetaeBond

RGI Bond RGI CoreBuildUp

Shofu Base Shofu Lining

48606

A D D B

078801 088803 068808 048806

Shofu Inc., 11 Kamitakamtsucho, Fukuine, Higashiyamaku, Kyoto 605, Japan

Table 2. Available data for radiopacity of materials Material

Powder/hquid ratio

Enamel Dentine BaseLine RGI Bond RGI CoreBuildUp

Radiopacity (mm Al/lmm cement) 2-2 1-0

6-4/1 5-4/1 6-0/1

2-1 2-0 3-0

Glass ionomer dental materials

247

Table 3. Results of determination of radiopacity of a number of glass ionomer materials Material

Powder/liquid ratio

Radiopaeity (mm Al/lmm eement)

Standard deviation

Luting cements • Fuji I Radiopaque

1-8

Lining materials BaseLine KetacBond Liv Lining Shofu Lining

3-2 34 1-2 1-6

1-8 2-1 1-8 4-5

0-15 0-16 0-10 0-18

Base materials AlphaBond BaseLine Ceramlin P RGI Bond Shofu Base

54 64 34 54 2-6

2-6 2-0 1-6 2-6 1-5

0-17 0-14 0-09 0-15 0-07

6-0 capsule 6-0

2-8 5-5 3-1

0-26 0-60 0-11

2-7

2-1

0-08

Core build up materials AlphaCore KetaeSilver RGI CoreBuildUp Restorative material Fuji II Radiopaque

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The rationale for a radiopaque luting cement is unclear when this type of dental material is normally used in thin layer applications and must have a film thickness of

The radiopacity of glass ionomer dental materials.

Although some glass ionomer dental materials are described as radiopaque by the manufacturer, it is rare for the actual degree of radiopacity to be sp...
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