Opacity and color changes of tooth-colored restorative materials

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Aesthetic direct restorative materials are crucial in modern dentistry.
• Understanding their long-term stability, including color and opacity, is essential for clinical success.
• Previous research indicates potential degradation pathways affecting material properties.

Purpose of the Study:

• To evaluate the internal opacity and color changes in various esthetic direct restorative materials.
• To assess the impact of accelerated aging on material stability.
• To identify potential correlations between opacity changes and material discoloration.

Main Methods:

• An accelerated aging test was employed, based on Asmussen (1981).
• Materials tested included chemically cured composites, light-cured composites, and resin-modified glass-ionomer cements.
• Samples were stored in distilled water at 60°C for 4 weeks post-curing, with color change and contrast ratio (opacity) measured.

Main Results:

• Chemically cured composites showed significant darkening (dark yellow/brown) after 4 weeks.
• Two macrofilled composites experienced decreased opacity.
• Light-cured composites exhibited slight discoloration with negligible opacity changes.
• Resin-modified glass-ionomer cements demonstrated an initial abrupt opacity decrease and darkening.

Conclusions:

• Opacity decrease is a contributing factor to the discoloration observed in some tooth-colored restorative materials.
• The observed changes suggest potential alterations in the matrix phase, possibly related to refractive index shifts.
• Material selection and understanding degradation mechanisms are vital for predictable long-term esthetic outcomes.