Abstract
Polycarbonates are polymers of bisphenol A (BPA), a well-known endocrine disruptor. This study evaluated the release of BPA from polycarbonate crowns that were (1) milled from Temp Premium Flexible (ZPF, Zirkonzahn, Italy) or Tizian Blank Polycarbonate (TBP, Schütz Dental, Germany), or (2) 3D-printed (Makrolon 2805, Covestro, Germany). Commercial prefabricated polycarbonate crowns (3M, USA) and milled poly(methyl methacrylate) (PMMA) crowns (Temp Basic, Zirkonzahn, Italy) were included for comparison. The crowns were stored at 37 °C in artificial saliva (AS) or methanol, which represented the worst-case scenario of BPA release. Extracts were collected after 1 day, 1 week, 1 month and 3 months. BPA concentrations were measured using liquid chromatography-tandem mass spectrometry. The amounts of released BPA were expressed in micrograms per gram of material (μg/g). After 1 day, the highest amounts of BPA were measured from milled polycarbonates, TBP (methanol: 32.2 ± 3.8 μg/g, AS: 7.1 ± 0.9 μg/g) and ZPF (methanol 22.8 ± 7.7 μg/g, AS: 0.3 ± 0.03 μg/g), followed by 3D-printed crowns (methanol: 11.1 ± 2.3 μg/g, AS: 0.1 ± 0.1 μg/g) and prefabricated crowns (methanol: 8.0 ± 1.6 μg/g, AS: 0.07 ± 0.02 μg/g). Between 1 week and 3 months, the average daily release of BPA in methanol and AS decreased below 2 μg/g and 0.6 μg/g, respectively. No BPA was released from PMMA in AS, and the cumulative amount released in methanol was 0.2 ± 0.06 μg/g. In conclusion, polycarbonates could be a relevant source of BPA, but the current tolerable daily intake of BPA (4 μg/kg body weight) should not be exceeded.