Characterisation of Microparticle Waste from Dental Resin-Based Composites

Steven Mulligan; Jesús J Ojeda; Gabriella Kakonyi; Steven F Thornton; Keyvan Moharamzadeh; Nicolas Martin

doi:10.3390/ma14164440

Characterisation of Microparticle Waste from Dental Resin-Based Composites

Materials (Basel). 2021 Aug 8;14(16):4440. doi: 10.3390/ma14164440.

Authors

Steven Mulligan¹, Jesús J Ojeda², Gabriella Kakonyi³, Steven F Thornton³, Keyvan Moharamzadeh⁴, Nicolas Martin¹

Affiliations

¹ Academic Unit of Restorative Dentistry, School of Clinical Dentistry, Claremont Crescent, The University of Sheffield, Sheffield S10 2TA, UK.
² Systems and Process Engineering Centre, College of Engineering, Swansea University, Swansea SA1 8EN, UK.
³ Groundwater Protection and Restoration Group, Department of Civil and Structural Engineering, Sir Frederick Mappin Building, Mappin Street, The University of Sheffield, Sheffield S1 3JD, UK.
⁴ Hamdan Bin Mohammed College of Dental Medicine (HBMCDM), Mohammed Bin Rashid University of Medicine and Health Sciences (MBRU), Dubai P.O. Box 505055, United Arab Emirates.

Abstract

Clinical applications of resin-based composite (RBC) generate environmental pollution in the form of microparticulate waste.

Methods: SEM, particle size and specific surface area analysis, FT-IR and potentiometric titrations were used to characterise microparticles arising from grinding commercial and control RBCs as a function of time, at time of generation and after 12 months ageing in water. The RBCs were tested in two states: (i) direct-placement materials polymerised to simulate routine clinical use and (ii) pre-polymerised CAD/CAM ingots milled using CAD/CAM technology.

Results: The maximum specific surface area of the direct-placement commercial RBC was seen after 360 s of agitation and was 1290 m²/kg compared with 1017 m²/kg for the control material. The median diameter of the direct-placement commercial RBC was 6.39 μm at 360 s agitation and 9.55 μm for the control material. FTIR analysis confirmed that microparticles were sufficiently unique to be identified after 12 months ageing and consistent alteration of the outermost surfaces of particles was observed. Protonation-deprotonation behaviour and the pH of zero proton charge (pH_zpc) ≈ 5-6 indicated that the particles are negatively charged at neutral pH7.

Conclusion: The large surface area of RBC microparticles allows elution of constituent monomers with potential environmental impacts. Characterisation of this waste is key to understanding potential mitigation strategies.

Keywords: FTIR; microparticle; microplastic; particles size analysis; pollution; potentiometric titration; resin-based composite.

Grants and funding

REF: 002-2013/Shirley Glasstone Hughes Research Grant