Beyond the Microscale: Early Nanoscale Changes in Experimental Resin Composites Exposed to Acidic and Alkaline Environments
- 1Department of Conservative Dentistry, Faculty of Dentistry, University of Benghazi, Benghazi P.O. Box 1308, Libya
- 2School of Dental Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne NE2 4BW, UK
- 3Department of Clinical Dental Sciences, College of Dentistry, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
Abstract
The study investigates the effects of acidic, neutral, and alkaline environments on the micro- and nanoscale properties of experimental BisGMA/TEGDMA resin composites with varied filler loading. Experimental composites based on BisGMA:TEGDMA at 75:25 wt% with three silica-glass filler loadings (75, 40, and 0 wt%) were stored at 37 °C in phosphate-buffered saline (PBS; pH 7.2), citric acid (pH 3.8), or sodium hydroxide (NaOH; pH 11) for up to 28 days. Microscale changes were assessed using sorption, Vickers hardness, and scanning electron microscopy (SEM), while atomic force microscopy (AFM) was used to evaluate nanoscale surface roughness and Young’s modulus. Storage medium did not significantly affect percentage mass increase (p = 0.092) or Vickers hardness (p = 0.098). Higher filler loading was associated with lower mass increase (ρ = −0.902, p < 0.001) and greater hardness (r = 0.660, p < 0.0001). SEM revealed surface degradation, particularly at the filler–matrix interface following NaOH exposure. Nanoscale surface roughness was negatively associated with filler loading (ρ = −0.368, p = 0.001), with changes observed predominantly in unfilled materials after 28 days. AFM measurements demonstrated a shift towards lower Young’s modulus values after only one day of exposure to citric acid and NaOH, whereas the reduction in PBS occurred later. Acidic and alkaline exposure produced limited alterations in conventional microscale measures but more changes in surface morphology and nanoscale properties. These exploratory findings suggest that AFM-derived Young’s modulus may detect early softening following acidic and alkaline exposure, suggesting its potential utility for characterizing early changes associated with chemical ageing than conventional microscale measurements.
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BibTeX
@article{elfakhri2026beyond,
title = {{Beyond the Microscale: Early Nanoscale Changes in Experimental Resin Composites Exposed to Acidic and Alkaline Environments}},
author = {Farah Elfakhri and Giles McCracken and Matthew German and Rawan N. AlKahtani},
journal = {Polymers},
year = {2026},
month = nov,
doi = {10.3390/polym18212755},
url = {https://www.mdpi.com/2073-4360/18/21/2755},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Beyond the Microscale: Early Nanoscale Changes in Experimental Resin Composites Exposed to Acidic and Alkaline Environments
AU - Farah Elfakhri
AU - Giles McCracken
AU - Matthew German
AU - Rawan N. AlKahtani
PY - 2026
DA - 2026/11/05
JO - Polymers
DO - 10.3390/polym18212755
UR - https://www.mdpi.com/2073-4360/18/21/2755
AB - The study investigates the effects of acidic, neutral, and alkaline environments on the micro- and nanoscale properties of experimental BisGMA/TEGDMA resin composites with varied filler loading. Experimental composites based on BisGMA:TEGDMA at 75:25 wt% with three silica-glass filler loadings (75, 40, and 0 wt%) were stored at 37 °C in phosphate-buffered saline (PBS; pH 7.2), citric acid (pH 3.8), or sodium hydroxide (NaOH; pH 11) for up to 28 days. Microscale changes were assessed using sorption, Vickers hardness, and scanning electron microscopy (SEM), while atomic force microscopy (AFM) was used to evaluate nanoscale surface roughness and Young’s modulus. Storage medium did not significantly affect percentage mass increase (p = 0.092) or Vickers hardness (p = 0.098). Higher filler loading was associated with lower mass increase (ρ = −0.902, p < 0.001) and greater hardness (r = 0.660, p < 0.0001). SEM revealed surface degradation, particularly at the filler–matrix interface following NaOH exposure. Nanoscale surface roughness was negatively associated with filler loading (ρ = −0.368, p = 0.001), with changes observed predominantly in unfilled materials after 28 days. AFM measurements demonstrated a shift towards lower Young’s modulus values after only one day of exposure to citric acid and NaOH, whereas the reduction in PBS occurred later. Acidic and alkaline exposure produced limited alterations in conventional microscale measures but more changes in surface morphology and nanoscale properties. These exploratory findings suggest that AFM-derived Young’s modulus may detect early softening following acidic and alkaline exposure, suggesting its potential utility for characterizing early changes associated with chemical ageing than conventional microscale measurements.
SN - 2073-4360
ER -