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.
Highlights
Bisphenol A (BPA; 2,2-bis(4-hydroxyphenyl) propane) is an endocrine disruptor [1], affecting the hormonal system through the interaction of its phenolic structure with various receptors [2]
Compared to the values after 1 month, the average daily release of BPA after 3 months increased in all groups, significantly for prefabricated crowns and Tizian Blank Polycarbonate (TBP) in methanol and for Zirkonzahn Temp Premium Flexible shade A3-B3 (ZPF) in the artificial saliva
The release of BPA was initially highest from milled polycarbonates (TBP and ZPF) (p < 0.001), while 3D-printed polycarbonate crowns released the highest amounts of BPA at the remaining time points
Summary
Bisphenol A (BPA; 2,2-bis(4-hydroxyphenyl) propane) is an endocrine disruptor [1], affecting the hormonal system through the interaction of its phenolic structure with various receptors [2]. Since BPA may act either as a receptor agonist or antagonist under different circumstances, its dose–response relationship is nonmonotonic, and the effect on human health is difficult to predict [1,4]. The amounts of released BPA were inconsistent, but generally significantly below TDI, which led the European Commission’s independent Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) to conclude that long-term oral exposure to BPA via dental materials poses only a negligible risk to human health [11]
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