RELEASE PROFILE OF BISPHENOL-A FROM DENTAL RESINS IN WATER ASSESSED BY LC-MS/MS

Abstract

Dental resins have been designed to replace amalgam restorations due to their more favorable physical, chemical, and biological properties. However, depending on its composition, the efficiency of its polymerization, and the degradation of the polymer matrix, Bisphenol-A can be present and therefore released from this material to the human body. It has been reported that residues of additives and minority by-products of polymer reactions, such as Bisphenol-A, can be released from plastics into aqueous media through polymer hydration, water-polymer diffusion, residue dissolution, and equilibrium between dissolved residues in water and polymer. Over time, this could lead to a polymer material with an external layer practically free of Bisphenol-A. However, the newly formed layer could be removed by brushing during oral cleaning, similar to toothbrushing, exposing the new layer containing Bisphenol-A to the aqueous media. Due to the toxic effects of this compound, an increasing number of plastics labeled as BPA-free have been introduced to the dental market, including tooth coating, dental sealants, and resins. Nevertheless, more specific studies on analytical chemistry have revealed a trace of Bisphenol-A in dental resins labeled as BPA-free and pointed out the need for even more sensitive and accurate detection methods to help manufacturers evaluate the presence of background contaminations in their products and to avoid false-negative results. In this way, liquid chromatography-tandem mass spectrometry has been considered one of the most suitable methods for confirming Bisphenol-A even at low concentrations, in high complex matrices, due to its high select sensitivity. In the present work, we developed a sensitive, reliable, and efficient approach to trace the release profile of Bisphenol-A by LC-MS/MS in dental resin samples purchased in the Brazilian dental market. With the analysis of five different brands of resin composites performed in eight days of exposition to water, four of them released Bisphenol-A from 3.4 pg/mm2 to 10.1 ng/mm2. The brand labeled as BPA-free released BPA at concentrations of 1.1 ng/mm2. However, one sample reached the maximum of released BPA in only 3 days, one in 4 days, and two virtually did not reach a maximum of BPA released into the water in the window time assessed. Limits of detection and quantification of the LC-MS/MS method were 40 pg/mm2 and 100 pg/mm2, respectively, and allowed the quantification of BPA released from a composite labeled as BPA-free. For future analysis, we will conduct a more comprehensive study on the release profile of BPA from resin composites into the water using a tooth brushing simulator to determine if the obtained profiles might have clinical implications.