Elsevier

Dental Materials

Volume 17, Issue 1, January 2001, Pages 87-94
Dental Materials

Color stability of highly filled composite resin materials for facings

https://doi.org/10.1016/S0109-5641(00)00065-8Get rights and content

Abstract

Objectives: The aim of the investigation was to examine the color stability of seven resin-based facing composites with a high content of inorganic filling material (Colombus, Artglass, Sinfony, Targis, Zeta LC, Zeta HC, BelleGlass HP/dentine, BelleGlass HP/enamel).

Methods: Changes in color of test samples were determined after UV irradiation in a fast-action UV instrument, Sunset CPS+, and after storage in a mouthrinse, tea, coffee, red wine and a 0.1% turmeric (curcuma) solution. Color differences were measured by using a Castor colorimeter and the total amount of color difference represented as ΔE.

Results: Red wine and the turmeric solution caused the most severe cases of discoloration (ΔE>10). Tea, coffee, the mouthrinse and UV irradiation caused invisible (ΔE<1) or visible (ΔE>1), and to some extent clinically unacceptable (ΔE>3.3), discoloration.

Significance: It is apparent from the results that it remains essential to improve the color stability of the composite resin materials used for facings.

Introduction

For over 50 years, resin-based composites have been used to make tooth-colored esthetic facings for prosthetic restorations. Despite continual improvements, facings made of these materials still display a number of inadequacies in clinical application. Apart from low resistance to abrasion [1], [2] and weak bond between the metal base and facings [1], [3], [4], the main disadvantages appear to stem from plaque retention and discoloration [1], [5], [6], [7], [8], [9], [10], [11]. During the last few years, several studies concerning the color stability of resin-based composites have shown that, for example, changes in color occur after UV irradiation [12], [13], [14]. In vitro discoloration due to coloring agents, filtered coffee and tea has also been observed [15], [16]. Recent clinical trials investigating the color stability of resin-based composite facings in telescopic partial dentures have shown that even after 1–2 years, verifiable and visible changes in color occurred [9], [10], [11]. Owing to these deficits, ceramic facings in permanent restorations have gained preference over the resin-based composites. On the other hand, resin-based composite facings in removable dentures have proved to have a greater degree of safety due to their higher elastic modulus and are, for instance, indicated for tapered crown and telescopic dentures. In recent years, composite resin materials have been on the market with improved mechanical properties due to new filling concepts and changes in the matrix. In particular, the so-called micro-filled hybrid composites with their high content of microfine inorganic particles have certainly been well received because of their superior strength and wear resistance [2], [17]. The aim of this investigation was to test the color stability of some of these highly filled resin-based composites after exposure to coloring agents and UV irradiation.

Section snippets

Materials and methods

The composites tested in the investigation are listed in Table 1. From each type of composite, 21 cylindrical test samples were made in a metal mold according to the manufacturer's instructions (diameter 6 mm, height 5 mm, color Vita-A 3.5). All light curable materials were layered and polymerized in several stages in order to guarantee complete polymerization. BelleGlass HP/dentine was first of all polymerized with light but the final stages of polymerization were completed in a nitrogen

UV irradiation in the suntest CPS+

The mean values and the standard deviations of the total color differences ΔE taken from each of the three samples of the tested composites after 24, 96 and 168 h of UV irradiation are recorded in Fig. 1. Discoloration in all the composites became more severe with increasing length of irradiation time. Only Sinfony displayed a reversal of discoloration after 96 h. Generally, the main increase was in the colormetric value b∗ for all the composites, i.e. the samples became yellowish.

Significant

Discussion

Set-up and mode of operation of the colorimeter, Castor, have already been described in detail in other publications [19], [20], [21]. Leibrock et al. [19] determined the good reproducibility of color measurement with this system for flat composite samples when certain conditions were observed. For this reason we used a tripod to position the measuring head when we took our color measurements, dried the test samples prior to measurement on the surface, and carried out white light balancing for

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