Staining protocols to improve the detection of composite restorations in human identification

The improvement of aesthetic properties of dental materials has hampered the work of forensic experts in cases of identification. Even in dental practice, the identification of the margins of restorations has become a challenge.

To establish protocols to improve the visual contrast between teeth and composites using dyes.

Anterior and premolar human teeth were chosen (n = 40) and class V cavities were made in the lingual/palatal and buccal surfaces. Ten commercially available dyes were dissolved in distilled water. Three protocols were proposed using phosphoric acid (Gphos) and hydrofluoric acid (Ghydro) for 60 s followed by application of the dye for 20 s. The control group (Gcontrol) was acid free, i.e. only distilled water was applied. Data was analysed using Kruskal-Wallis and Dunn´s tests.

Analyses showed that darker dyes, such as crystal violet, methylene blue, malachite green and neutral red, had better results (p < 0.001). The composite brand did not influence the results (p > 0.05). Both Gphos and Ghydro were effective in discriminating restorations when compared to Gcontrol (p > 0.001). No differences were detected between Gphos and Ghydro protocols (p > 0.05). In Gphos, the enamel surface was stained leaving the restoration without pigmentation. Oppositely, in Ghydro the composite filling was coloured, but not the enamel. In Gcontrol, both enamel and restoration were stained indistinctively.

Tooth etching with either phosphoric or hydrofluoric acids was suitable to discriminate the presence of aesthetic dental fillings.