Characterization of Extractables from Dental Bite Guards Using GC-TOFMS

Significance of the topic

Non-targeted chemical characterization of extractables and leachables (E&L) from medical devices is a critical component of ISO 10993 risk assessment workflows. Identifying volatile and semi-volatile compounds that can migrate from materials into patients or consumers enables toxicological evaluation and helps ensure device safety and regulatory compliance. Gas chromatography coupled with time-of-flight mass spectrometry (GC-TOFMS), and in particular high-resolution TOFMS, provides the sensitivity, spectral fidelity and deconvolution capability necessary for comprehensive E&L screening of polymeric medical items such as dental bite guards.

Objectives and overview of the study

• Demonstrate a practical ISO 10993 analytical screening workflow for over‑the‑counter dental bite guards using GC-TOFMS.
• Use Pegasus BTX for initial non-target screening of isopropyl alcohol extracts and determine analytical evaluation threshold (AET).
• Apply Pegasus HRT+ high-resolution accurate mass data to characterize unknowns above the AET that could not be library-identified.
• Confirm tentative structural assignments by comparison with purchased standards.

Methodology

• Sample preparation: Commercial over‑the‑counter dental bite guards (silicone, ethyl vinyl acetate and similar materials) were extracted following an exaggerated ISO 10993 guidance: 1 g sample in 5 mL solvent, 50 °C for 72 h with agitation.
• Solvents: Both hexane and isopropyl alcohol (IPA) were tested; hexane dissolved the devices so subsequent work used IPA extracts only.
• Post-extraction handling: Samples were centrifuged 20 min at ~4000 rpm and supernatants analyzed.
• Screening and data processing: Pegasus BTX GC-TOFMS provided full-scan EI data; ChromaTOF software performed non-target peak finding, deconvolution and library (spectral + retention index) matching.
• AET determination: A subset of FDA CLAP extractables standards was analyzed at 10 ppm to translate the ISO 10993 AET concentration into an instrument intensity threshold (average peak height ~0.62e8 used as cutoff).
• Follow-up identification: Features above AET lacking confident library matches were reanalyzed on Pegasus HRT+ to acquire high-resolution EI and chemical ionization (CI) data using a multi-mode ion source for elemental formula determination and structure proposals.
• Verification: Proposed structures were confirmed by analysis of authentic standards where available.

Used instrumentation

• Pegasus BTX GC-TOFMS — initial full-scan EI screening with ChromaTOF deconvolution and RI calculations.
• Pegasus HRT+ GC-TOFMS — high-resolution accurate-mass EI and CI using the multi-mode ion source (MMS) for formula confirmation and improved spectral interpretation.

Main results and discussion

• Chromatographic landscape: Extracts were dominated by an intense late-eluting peak (~1000 s) with many lower-intensity coeluting features across samples. Deconvolution revealed both major and trace constituents.
• Identifications via BTX and ChromaTOF: The dominant peak in all samples was identified as butylated hydroxytoluene (BHT) with high spectral similarity and RI agreement (observed RI 1516 vs library 1513). Other library-identifiable compounds included pentadecane, siloxanes (background), erucamide (slip agent), and Irganox 1076 (antioxidant).
• Blank and background screening: Some features (e.g., siloxanes) were also present in method blanks and therefore excluded from device-origin reporting.
• AET application: The calculated AET for the testing scenario was 10 ppm. Using instrument response from CLAP standards at 10 ppm, features above the intensity cutoff were flagged for toxicological follow-up.
• Unknowns resolved by high-resolution MS: Sample D contained five peaks above AET; two of these lacked library matches on BTX. Pegasus HRT+ provided accurate-mass EI and CI data enabling elemental formula assignment and structural proposals. Tentative identifications were oleyl palmitamide (a lubricant/slip agent) and N,N'-ethylenedioleamide (a bisamide wax/anti-fogging agent). Both assignments were confirmed by analysis of authentic standards.
• Value of deconvolution and RI: Mathematical deconvolution improved spectral quality for coeluted and low-intensity peaks, while retention index comparison provided orthogonal confirmation to library spectral matches.

Contributions and practical applications

• Demonstrates a practical, ISO 10993‑aligned workflow for device E&L screening combining non-target GC-TOFMS, deconvolution, RI verification and targeted high-resolution follow-up.
• Highlights importance of blank controls and intensity-based AET application to prioritize analytes for toxicological assessment.
• Shows that combining EI and CI high-resolution data facilitates formula determination and identification of additives not present in commercial libraries.
• Provides an approach adaptable to routine QC, preclinical safety assessment, and regulatory submissions for polymeric medical devices and consumer products.

Future trends and potential applications

• Expansion of high-resolution spectral libraries and incorporation of CI/soft-ionization spectra will reduce the number of unidentifiable features in non-target E&L studies.
• Greater automation in peak finding, deconvolution and AET mapping will improve throughput and reproducibility for laboratory workflows.
• Integration of orthogonal techniques (LC-HRMS for non-volatile extractables, surface analysis, and direct-infusion HRMS) will provide more comprehensive E&L coverage.
• Lower instrumental detection limits and improved sample preparation protocols will refine exposure estimates and support tighter regulatory thresholds.
• Harmonization of AET calculation approaches and reporting formats across regulatory bodies will simplify risk assessment and streamline device approval.

Conclusion

GC-TOFMS screening with targeted high-resolution follow-up provides a robust, practical workflow for characterization of volatile and semi-volatile extractables from dental bite guards in the context of ISO 10993. The combined use of non-target deconvolution, retention index matching, and accurate-mass EI/CI acquisition enabled confident identifications of common antioxidants, slip agents and previously unreported additives. Applying an instrument-calibrated AET effectively prioritized analytes for toxicological review, and confirmation with authentic standards validated the workflow for safety-relevant device assessment.

Reference

1. LECO Corporation (2025). Characterization of Extractables from Dental Bite Guards Using GC-TOFMS. Application Note, Pegasus BTX and Pegasus HRT+. Form No. 203-821-708. St. Joseph, MI: LECO Corporation.