Abstract
Color modifiers can be mixed with resin composites to mimic the shade of severely discolored tooth. The aim of this study was to assess the effects of a color modifier on the physical and mechanical properties of a resin composite. The composite was mixed with a color modifier at 0 wt% (group 1), 1 wt% (group 2), 2.5 wt% (group 3), or 5 wt% (group 4). The degree of monomer conversion (DC) was examined after light curing for 20 or 40 s. Biaxial flexural strength (BFS)/modulus (BFM), surface microhardness (SH), and water sorption (Wsp)/solubility (Wsl) were also tested. The DC of group 1 was significantly higher than that of groups 3 and 4. The increase in curing time from 20 to 40 s increased the DC by ~10%. The BFS, BFM, Wsp, and Wsl of all the groups were comparable. A negative correlation was detected between the concentration of color modifier and the BFS and DC, while a positive correlation was observed with Wsp. In conclusion, the color modifier reduced the DC of composites, but the conversion was improved by extending the curing time. The increase in color modifier concentration also correlated with a reduction in strength and the increase in the water sorption of the composites.
Highlights
The systemic administration of tetracycline during skeletal and tooth development leads to the deposition of the drug into the tissues, causing irreversible intrinsic discoloration [1]
The current study showed that composites with an added color modifier of greater than 1 wt% exhibited Degree of Monomer Conversion (DC) values lower than 40%, even after being light-cured for 40 s
The results of the current study suggest that the DC of composites mixed with the color modifier was increased by ~10% after extending the light-curing time from 20 to 40 s
Summary
The systemic administration of tetracycline during skeletal and tooth development leads to the deposition of the drug into the tissues, causing irreversible intrinsic discoloration [1]. The application of light-cured characterizing materials or color modifiers under or between the incremental layers of composite may help to mask the discoloration and produce a natural appearance or desirable restoration shade [6]. A study showed that the placement of color modifiers between the composite layers reduced the cohesive strength of the composite, which may affect the longevity of the restoration [7]. Another minimally invasive and simplified method to restore a tetracycline-induced discolored tooth is the use of a composite-mixed color modifier to mimic the shade of the discolored tooth (Figure 1)
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