A Novel Method to Distinguish Old Composite from Enamel: Spectrophotometric Validation

Aim: To identify a dye for disclosing composite resin restoration margins using tooth shade spectrophotometry.

Materials and Methods:

Study Design: Experimental Study.

Forty sound, non-carious maxillary anterior teeth extracted for periodontal reasons were collected and standard box shaped class V cavities, 5 mm width, 2 mm height and 2 mm depth, were prepared and restored with composite resin. The samples were stored for 2 months in distilled water at 37°C and thermocycled for simulating ageing process (5°C-55°C/5000 cycles). Samples were then assigned into four groups according to the dyes used for staining: Coffee (5%), Carmoisine (0.1%), Erythrosine (1%) and Methylene blue (1%). A tooth shade spectrophotometer was used to assess the change in shade of enamel and composite resin before and after staining with four different dyes. The data was analyzed using one-way analysis of variance and Post Hoc LSD tests.

Results: The results of spectrophotometric analysis of enamel and composite staining showed that Methylene blue caused maximum composite staining (p<0.05). Erythrosine also showed a significant change in shade of composite, greater than enamel due to hydrophobic interaction between the resin and dye (p<0.05). The two hydrophobic food stains Coffee and Carmoisine showed no significant change in colour of composite and could not distinguish the boundary between composite resin and tooth enamel (p>0.05).

Conclusion: The exposure of specimens to colored solutions resulted in significant colour alteration. Composite resin is more stainable by hydrophobic dyes compared to tooth enamel.