Objectives: To determine the peroxide concentration at various time intervals on the teeth, the gingiva, in saliva and gel during use of a 10% w/w hydrogen peroxide gel predosed in a flexible tray (experimental product).
Methods: 16 healthy volunteers between the ages of 19 and 72 were randomised into this crossover, single-centre study. Subjects wore the predosed tray product at each study visit for a period of either 5, 30, 45 or 60 minutes based on a randomisation schedule. After the specified time period the tray was removed and the gel was sampled from the tray, teeth, and gingiva and a saliva sample was collected. These samples were then assayed using PeroXOquant Quantitative Peroxide Assay Kit. A washout period of 2 days took place between each of the visits.
Results: The median hydrogen peroxide concentrations are represented in the table.
| Time | Tray Gel | Tooth | Gingiva |
| 5 minutes | 5.73% | 3.93% | 2.50% |
| 30 minutes | 6.16% | 3.29% | 0.69% |
| 45 minutes | 5.33% | 2.97% | 1.15% |
| 60 minutes | 5.83% | 2.81% | 0.59% |
Salivary samples never exceeded a median concentration of 0.024% at any time point. Hydrogen peroxide concentrations were highest in the gel remaining in the tray and on the teeth and the lowest on the gingiva and in saliva. At all post-treatment time points, gingival peroxide concentrations were at least a third lower than the teeth peroxide concentrations.
Conclusion: The low salivary peroxide levels indicate minimal systemic exposure to hydrogen peroxide from saliva. Degradation of the hydrogen peroxide on the gingiva and teeth decreased over time but not as quickly as in the saliva. After 60 minutes, significant peroxide remained in the tray gel sustaining a higher concentration which could be delivered to the teeth.