Monomer Release from Dental Resins: The Current Status on Study Setup, Detection and Quantification for In Vitro Testing

Abstract

Improvements in mechanical properties and a shift of focus towards esthetic dentistry led to the application of dental resins in various areas of dentistry. However, dental resins are not inert in the oral environment and may release monomers and other substances such as Bisphenol-A (BPA) due to incomplete polymerization and intraoral degradation. Current research shows that various monomers present cytotoxic, genotoxic, proinflammatory, and even mutagenic effects. Of these eluting substances, the elution of BPA in the oral environment is of particular interest due to its role as an endocrine disruptor. For this reason, the release of residual monomers and especially BPA from dental resins has been a cause for public concern. The assessment of patient exposure and potential health risks of dental monomers require a reliable experimental and analytical setup. However, the heterogeneous study design applied in current research hinders biocompatibility testing by impeding comparative analysis of different studies and transfer to the clinical situation. Therefore, this review aims to provide information on each step of a robust experimental and analytical in vitro setup that allows the collection of clinically relevant data and future meta-analytical evaluations.

Keywords: biocompatibility; bisphenol A; elution; leaching; materials testing; monomer; resin based dental materials.

Figure 1

HPLC-MS Chromatogram of a Luxatemp Automix Plus (DMG Chemisch-Pharmazeutische Fabrik, Hamburg, Germany) sample immersed in HPLC grade water with diethyl phthalate (DEP) as an internal standard. At the top, the chromatogram and then, from top to bottom, the extracted ion chromatograms of TEGDMA, UDMA, and the internal standard DEP, respectively. Definitive peak identification is accomplished by the relative abundance of the corresponding molecular mass. This chromatogram was prepared for a study on the monomer elution from resin-based temporary crown and bridge materials [120].

Figure 2

Tandem mass spectrometry fragmentation spectra of derivatized isotope-labeled BPA (top), derivatized unlabeled BPA (middle), and underivatized BPA (bottom). The spectra were obtained by HPLC-MS/MS with negative ionization for native BPA and positive ionization for BPA derivatized with pyridine-3-sulfonyl chloride. The unique and most abundant product ion is highlighted by a blue square. This mass spectrum was prepared for a study on the monomer elution from resin-based temporary crown and bridge materials [120].

Figure 3

Calibration curve of TEGDMA in relation to the internal standard diethyl phthalate (DEP) including the plot of residuals. The data are fitted by a linear regression model and assessed by the determination coefficient r2. This calibration curve was prepared for a study on the monomer elution from resin-based temporary crown and bridge materials [120].

Figure 4

(a) HPLC-MS Chromatogram of an ExperTemp sample (Ultradent, South Jordan, USA) immersed in HPLC grade water and Gibco Antibiotic-Antimycotic solution. Due to the overlapping peaks of the antibiotic-antimycotic solution, the peaks corresponding to the masses of TEGDMA and UDMA are not identifiable. (b) Chromatogram of an ExperTemp sample (Ultradent, South Jordan, USA) immersed in pure HPLC grade water. The peaks corresponding to TEGDMA and UDMA are highlighted. This figure was taken from preliminary tests made by our working group for a study on the elution of monomers from resin-based temporary crown and bridge materials [120].