Technique for Darkening of Extracted Teeth Simulating Pulpal Necrosis Discoloration

Background: The use of discolored teeth is required to test whitening products, and it is difficult to obtain them, given their scarcity.

Objective: To present a technique for in vitro darkening of extracted teeth simulating pulpal necrosis discoloration.

Materials and methods: Hemolysates I and II from human blood were subjected or not to laser irradiation (442 nm) for 1 h. The concentration of oxyhemoglobin (O₂Hb) was analyzed by ultraviolet/visible spectroscopy, and the conversion of O₂Hb to methemoglobin (MetHb) by transmission spectroscopy was assessed immediately and after 3 and 40 days. For darkening evaluation, bovine incisors were divided into two groups (n = 25), and their pulp chambers were filled with hemolysate solution II (HSII) and hemolysate II solution + laser (HSII+L). After storage in artificial saliva for 40 days at 37°C, color changes were measured by a colorimeter and ΔE was compared with the NBS parameters. Data were analyzed using a mixed linear model (α=5%).

Results: HSII+L presented the lowest O₂Hb and higher MetHb. The conversion of O₂Hb to MetHb in HSII+L was 42% higher than in HSII. Both groups were effective in darkening the teeth, according to the NBS. Darkening stabilized from day 35. HSII promoted a marked color difference.

Conclusion: The proposed technique was effective in darkening the extracted teeth simulating necrosis discoloration for in vitro models.