Fig. 1

Experimental design. Step 1: Bovine mandibles were pre-incubated in a bioreactor designed and characterized by us¹⁶ for 7 days before the experiments took place to re-condition the teeth. The oral cavity simulator bioreactor consists of a thermostatic bath (A), filled with distilled water. The bath contains a cubic glass tank (B) immersed. The mandible is fixed to a stub support on the tank bottom (C). Salivary substitute solution (D) is maintained at 37.5 °C in a thermostatic bath (E) and shaken at 20 rpm (F) to allow the oscillating artificial saliva to contact the tooth surfaces of the samples. The pH (7.0), temperature (37.5 °C), and humidity (93 kg/m³) are monitored through a pH Meter, a thermocouple, and a digital thermo-hygrometer, respectively. Before treatment, the tooth surface is cleaned with an airflow, erythritol powder, and water (G). Step 2: The brightness is analyzed with a special spectrophotometer (H) before the treatment. The bleaching is performed through (a) Blanc and (b) Opale, (c) Pola, or (d) Zoom. Step 3: Custom trays (I) were created for all mandibles holding home-bleaching products. Tests are performed through a split-mouth experimental set-up, where 18 mandibles are analyzed, six mandibles for each comparative experiment (L). The treatments were performed over 10 days, each lasting 8 h (the average time for an overnight exposure). Step 4: Post-reconditioning was achieved by keeping the mandibles in the bioreactor during non-whitening treatment hours. Step 5: The brightness is measured with the spectrophotometer 48 h after the last treatment.