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Controlling of tooth bleaching process in real time

Objective: Bleaching outcomes are generally unpredictable due to the varying bleaching setups and tooth characteristics. To prevent over- bleaching and other side-effects, this study presents an experimental device that could simultaneously perform and monitor the bleaching process. It was developed at the Institute of Physics, Zagreb. Method: The setup consists of light emitting diodes, multitrack optical fibers, camera and controller. Bleaching was performed with 30% hydrogen peroxide (Dash, Philips, USA) activated by ultraviolet light emitting diodes with center wavelength of 405 nm. The light for monitoring was emitted by white light emitting diodes. A K-type thermocouple was used to measure the temperature increase on the tooth surface. The performance of developed setup was demonstrated on extracted human teeth bleached for 20 minutes. The RGB color space was used for monitoring the changes. The bleaching outcomes were compared to A1 color (Chromascop, Ivoclar Vivadent, Liechtenstein) that was specified as desired result of the bleaching process and measured as the sum of RGB components. Result: The reflected light intensity of RGB components at the end of bleaching process increased up to 28% of the baseline intensity. Optimal bleaching time substantially varied among different teeth. To reach reference color (A1), bleaching time ranged from 3.5 to more than 20 minutes. Surface temperature increased for 4.0 °C. Conclusion: Contrary to the so far known bleaching procedures, this experimental setup enables real-time monitoring of the bleaching process. It provides essential information when to stop the bleaching process to achieve the desired results and prevent over-bleaching or overheating. Bleaching intensity could be adjusted by a specific segment, leading to a more uniform bleaching. Presented experimental model might have large impact on the future bleaching process and development of future apparatus and chemicals for tooth bleaching. This study was supported by the Croatian Science Foundation and BICRO.