Effect of Over‐the‐Counter Tooth Whitening Consumer Products of Release of Collagen and Protein from Teeth

Abstract

While tooth whitening used to consist of either whitening strips or professional treatments: there are now a variety of products available to consumers in the United States. While most involve either hydrogen peroxide or its precursor, carbamide peroxide, as the active ingredients, there are alternatives. Carbamide peroxide can be administered in gel form in a tray with or without an LED light. Instead of a strip, hydrogen peroxide can now by applied directly to the teeth in form of pen and remains overnight. The goal of this project was to examine the effect of whitening agents on the release of both collagen and other proteins. Extracted molars from patients who signed informed consent forms were placed in artificial saliva and treated with activated charcoal, carbamide peroxide with (35%) or without (44%) an LED light, or a whitening pen with 14% hydrogen peroxide according to manufacturer’s instructions. Artificial saliva was changed daily, and all teeth received six days of no treatment and four rounds of 6 treatments with a break between the second and third. The fluid surrounding the teeth underwent a trichloroacetic acid precipitation to remove the non‐ collagen protein. The supernatant was adjusted to the proper pH and collagen was measured using a modified version of the Lowry assay. In addition, the proteins were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). Molars that received no treatment, as well as prior to treatment, show no protein. All treated teeth showed collagen and non‐collagen protein released whenever treatments were applied as well as in between rounds of treatment. The amount of collagen released from activated charcoal, 35% carbamide peroxide with LED, 44% carbamide peroxide and 14% hydrogen peroxide pen in mg/ml were 1.048, 1.994, 1.530, and 0.9034 respectively. For non‐collagen, the average amount of protein released for activated charcoal, 35% carbamide peroxide with LED, and 44% carbamide peroxide in mg/ml respectively were: 0.5714, 0.4155, and 0.6363. Both collagen and non‐collagen were released from all treated teeth in between rounds of treatments. The size of the proteins released was characterized using SDS PAGE. Consistent with the TCA and modified Lowry results, no bands were observed in artificial saliva prior to treatment but all treatments resulted in bands at molecular weight (MW) of 129 and 75 kDa among others. The MW of former band matches the expected subunit MW of collagen which is found in the dentin of teeth. These results demonstrate that treatment of teeth with hydrogen peroxide, carbamide peroxide with or without LED light or activated charcoal results in release of various proteins from dentin and enamel. In addition, these proteins continued to be released after treatments were applied. Hydrogen peroxide was measured using a colorimetric test. The amounts of peroxide in other samples was consistent with manufacturer’s claims.