An Erosion Test Method for Determining Tooth Whitener Safety

Objective: Develop a model to determine the safety of OTC whitening agents for ISO Standard 28399.  Methods: Bovine enamel and dentin specimens were mounted in methacrylate blocks then ground and polished to be plano-parallel and flat as possible.  Baseline surface roughness (Ra) was determined using a Mitutoyo SV-3100 contact profilometer.  The original surface was preserved by taping over opposite sides of the specimen leaving a 2mm window.  The specimens (6 of each per group) were treated with either a water negative control, one of three dose response citrate positive controls or one of 5 commercial whitening agents.  Treatments were designed to approximate actual usage.  Following treatments, the tape was removed and the specimen surface profiles were once again determined going from the original sound surface on one side, across the treated window and onto the protected sound surface on the other side of the specimen.  The roughness and tissue loss (drop from original surface) was determined at 3 predetermined areas of each specimen.  The 3 point specimen average and then the 6 specimen group average were determined to get a group average roughness change and microns tissue loss.  Analyses within groups was t-test and across groups SNK.  Results: The negative control specimens had no change.  The positive control dose response showed a distinct relationship with tissue loss and a marginal relationship with Ra.  The whitening agents were dispersed between the negative and positive controls.  The least severe positive control caused significantly more tissue loss than the most aggressive whitening agent.   Conclusions: A model is presented that significantly distinguishes a negative control from all three positive controls.  The positive controls separate significantly from each other.  Tissue loss is a much more discriminating measurement than Ra.  None of the 5 whitening agents tested indicated any significant tissue loss from enamel or dentin.