In-vitro Bleaching Effectiveness of Sodium Percabonate from Non-Aqueous Medium

Objective:  Deliver a hydrophilic bleach from a non-aqueous medium, enabling the bleach to remain at the tooth surface to induce significant whitening.  It is well known that peroxide compounds applied to teeth in the form of a gel via a tray, or coated as a thin film on a flexible strip, provide significant bleaching of extrinsic and intrinsic stains because they maintain the bleach at the tooth surface for a sufficient length of time.  The hydrophilic nature of recently introduced aqueous paint-on formulations limits the retention of those gels on teeth, reducing bleach efficacy. We investigated a hydrophobic, barrier-less matrix for its ability to remain on the tooth surface and effectively deliver Sodium Percarbonate (NaPC, 19%) to achieve a bleaching benefit. Method: Extracted molars with visible extrinsic stain were imaged, and baseline color was obtained in CIEL*a*b* color space using a Fuji HC1000 digital camera and Giant software.  Specimens were randomly assigned to treatment groups containing 19% NaPC or placebo.  Treatments were applied using a small cosmetic brush.  After incubation in a humid environment at 37°C for 1hr, any film residue was removed, and specimens were re-imaged.  This procedure was repeated 13x for a total exposure time of 14 hours.  Areas of only extrinsic or intrinsic stain were analyzed along with overall tooth color.  Results: The non-aqueous medium remained on the specimens during treatment, and the NaPC group had positive changes in L*, indicating a bleaching benefit for each area measured.  The table lists results after 14 treatments.

Conclusion: A barrier-less non-aqueous matrix is capable of retaining sodium percarbonate at the tooth surface for a sufficient length of time to provide intrinsic and extrinsic stain bleaching.