Biocompatiblity of resin-based materials: Bisphenol-A

Bisphenol-A is an organic compound with two phenol functional groups, commonly used in the production of many plastic products. Studies have shown that bisphenol-A may have adverse health effects such as hormonal, developmental, neurological as well as carcinogenic.

In spite of this, bisphenol-A may be part of dental resin-based materials as a direct ingredient, as a by-product of bio-degradation of other ingredients or as a trace material left-over from the manufacture of other ingredients. Though bisphenol-A is rarely used as a direct ingredient in dental composites, adhesives or sealants, it is a starting ingredient in the manufacture of the most commonly used resin - BisGMA. Also, some other, less frequently used resins, such as Bis-DMA, are also produced using bisphenol-A.

Concerns about bisphenol-A have been raised since studies have shown that various components of dental composites, adhesives and sealants may leach out and have potential local or systemic adverse effects. An in vivo study using an ELISA system showed that up to 100 ng/ml of bisphenol-A may be released into saliva from resin-based composites immediately after placement (Sasaki et al. 2005). Also, a more recent study showed that BisGMA, but also BisGA and BisDMA, all bisphenol-A - based monomers, may leach out from in vivo placed composite restorations (Uzunova et al. 2008). On the other hand, no traces of bisphenol-A were found from chemically and light-cured orthodontic adhesives after in vitro accelerated aging and elution (Eliades et al. 2007).

Over the past few years, both the FDA and ADA have supported research on biocompatibility and safety of resin-based materials containing bisphenol-A. Both organizations issued statements in 2007 (FDA) and 2008 (ADA) that the low-level of BPA exposure that may result from dental materials poses no known health threat. However, further research on this subject is encouraged by the ADA.

References:

• Sasaki N, Okuda K, Kato T. Salivary bisphenol-A levels detected by ELISA after restoration with composite resin. J Mater Sci: Mater in Med 2005;16:297-300.
• Uzunova Y, Lukanov L, Filipov I, Vladimirov S. High-performance liquid chromatographic determination of unreacted monomers and other residues contained in dental composites. J Biochem Biophys Methods 2008;70:883-888.
• Eliades T, Hiskia A, Eliades G, Athanasiou AE. Assessment of bisphenol-A release from orthodontic adhesives. Am J Orthod Dentofacial Orthol 2007;131:72-75.