Investigating the Mechanisms of Discoloration in Modern Dental Materials: A Comprehensive Characterization Approach

Abstract

In general, patients' opinions on reaching ideal esthetics while restoring dental tissues is one of the most important part of the oral treatment. Unfortunately, discoloration of dental materials may occur due to intrinsic and extrinsic factors. The aim of the study was to evaluate the color stability of frequently used dental resin materials and determine the mechanism of their discoloration. The study used various characterization techniques (optical microscopy, Fourier-transform infrared spectroscopy, low-temperature N₂ adsorption, diffuse reflectance spectroscopy, and luminescence) to understand the effect of surface defects on discoloration. The adsorption of model liquids on the surface was confirmed to be related to the increase in BET surface area. The study found that the adsorption of discolorants, such as coffee, tea, and wine, on the surface of the dental material follows the multilayer BET model. When the surface is smooth, the discoloration is usually within acceptable limits, with a maximum of ∆E = 3.3. The discoloration made by tea and demineralized water was within acceptable limits even after 7 days of exposure.

Keywords: color parameters; dental composite; optical microscopy; surface defects.

Figure 1

Optical microscopy images of dental samples exposed to demineralized water, wine, coffee, and tea after 7 days.

Figure 2

Images of the surface of dental materials: (a) G-ænial A’chord (b) G-ænial Universal Injectable (c) G-ænial Anterior (d) Icon, and (e) Filtek™ Ultimate.

Figure 3

FTIR spectra for analyzed dental materials analyzed, control samples.

Figure 4

The proposed mechanism for the formation of discoloration on dental materials.

Figure 5

DRS (a,b) and luminescence (c,d) spectra for initial dental materials (a,c) and after 7 days of exposure to a red wine solution (b,d).