Internal bleaching with calcium oxalate and laser irradiation for managing discolorations induced by mineral trioxide aggregate.

Aim: This in vitro study investigated the effects of incorporating 1%, 3%, and 5% calcium oxalate into 15% hydrogen peroxide (HO), with and without laser activation, on the whitening of teeth discolored by mineral trioxide aggregate (MTA).

Methods: The pulp tissue of 80 bovine incisors was removed, and an MTA plug was placed at 2 mm below the cementoenamel junction. After nine months, the samples were randomly divided into eight groups (n = 10). Groups 1 to 4 were treated with 15% HO gel containing 0, 1, 3, or 5% calcium oxalate, respectively. The same gels were applied in groups 5 to 8 but activated with an 810 nm diode laser (2 W, continuous wave). The teeth were incubated for five days, followed by the second gel application. Tooth color was evaluated at baseline (T1), after MTA discoloration (T2), and after the first (T3) and second (T4) gel applications, using the CIELAB system to measure color changes (ΔE).

Results: The mean ΔE and ΔE differed significantly between groups (P = 0.002 and P = 0.040, respectively). After the first and second gel applications, ΔE values were significantly higher in groups 2 (HO + 1% calcium oxalate) and 6 (HO + 1% calcium oxalate + laser) than in groups 1 (HO), 5 (HO + laser), and 8 (HO + 5% calcium oxalate + laser) (P < 0.05).

Conclusions: Incorporating 1% calcium oxalate into 15% HO can enhance the whitening of teeth discolored by white MTA. Laser activation did not further improve the outcome of internal bleaching in teeth with MTA discoloration.