Date Published: May 27, 2018
Publisher: Taylor & Francis
Author(s): Rune Becher, Hanne Wellendorf, Amrit Kaur Sakhi, Jan Tore Samuelsen, Cathrine Thomsen, Anette Kocbach Bølling, Hilde Molvig Kopperud.
BPA has been reported to leach from some resin based dental restorative materials and materials used for orthodontic treatment. To confirm and update previous findings, especially in light of the new temporary lower threshold value for tolerable daily BPA intake, we have investigated the leaching of BPA from 4 composite filling materials, 3 sealants and 2 orthodontic bonding materials. The materials were either uncured and dissolved in methanol or cured. The cured materials were kept in deionized water for 24 hours or 2 weeks. Samples were subsequently analyzed by ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS-MS). The composite filling material Tetric EvoFlow® and the fissure sealant DELTON® showed significantly higher levels of BPA leaching compared to control samples for all test conditions (uncured, 24 h leaching and 2 weeks leaching). There were no significant differences in amount of leached BPA for any of the tested materials after 24 hours compared to 2 weeks. These results show that BPA is still released from some dental materials despite the general concern about potential adverse effects of BPA. However, the amounts of BPA were relatively low and most likely represent a very small contribution to the total BPA exposure.
Bisphenol A (BPA) is a high production volume chemical mainly used for manufacturing polycarbonate plastics, epoxy resins and methacrylate resins used in dentistry. In animal studies, a number of adverse health effects have been associated with BPA including effects on hormonal activity, asthma, diabetes, obesity, behavioral changes, cancer, infertility and genital malformations [1–6]. The largest source for human exposure is food packed in BPA-containing materials. A recent review by EFSA (the European Organization for Food Safety) concluded that rats and mice exposed to BPA are likely to experience effects on the general health of liver and kidneys as well as on breast tissue in terms of increased cell growth . Since the most serious effect at the lowest BPA concentration was observed in kidneys, increased focus on the kidneys of mice was used as the basis for a new threshold value for tolerable daily intake (TDI). In mice, adverse effects on kidney are observed at about 600 micrograms per kg body weight per day. The new TDI value was lowered from 50 to 4 µg per kg body weight per day, using an uncertainty factor of 150 . Due to uncertainty about possible effects on breast, reproductive, neurological and metabolic systems, as well as the immune system in laboratory animals, the new TDI value is temporary and a new evaluation of BPA will be performed by EFSA in near future.
Dental materials containing monomers bis-GMA or bis-EMA as potential source of BPA were selected for the study. All test materials were from the manufacturers (see supplemental data, Table S1). These materials included four composite restorative materials, three fissure-sealants and two bonding agents used in orthodontic treatment (Table 1). Both BPA and its C-13 labeled internal standard were bought from Cambridge Isotope Laboratories Inc. (Andover, MA, USA).
Bisphenol A is found in a wide variety of different consumer products including some dental materials. Here we present data from two sets of analyses of various composites, fissure sealants and bonding agents used in both Norwegian and international dental practices. Initially, we conducted a pilot study (study 1) where fewer numbers of parallels were analyzed. Here hydroquinone was added to all samples, including controls, as a mean to stabilize leached material. From a clinical perspective it is relevant to convert the amount of BPA leaching to the surface area of the material, as this would give a measure of how much of the material that is exposed to the oral environment in a patient. Thus, all leached amounts are given both as amount per ml and amount per surface area.