Purpose: The objective of this study was to investigate the physical properties of a model dental compound formulated to autonomically heal cracks. Methods: A visible light cured model resin consisting of TEGMA:UDMA:BisGMA (1:1:1) at 45% w/w with 0.7 µ silanated glass was formulated with a self-healing system consisting of encapsulated dicyclopentadiene spheres and Grubb's metathesis catalyst. The base resin was also formulated with the spheres and Grubb's catalyst alone. Fracture toughness (KIc) was assessed using a single edge notch specimen (2.5mm (B) x 5 mm (W) x 25 mm; a/w=0.5) in 3-point bend (n=12). Data was analyzed with ANOVA/Tukey's at p ≤ 0.05. Dynamic mechanical analysis (DMA) was performed from -150 ºC to 250 ºC at 1 degree/min and 1 Hz. Storage and loss modulus, glass transition temperature and tangent of delta was recorded for each material.
Results:
Sample | E' 109 | E” 108 | Tg | Tan Delta | K1c |
Control | 6.7 | 3.5 | 137 | 0.2342 | 1.21 ± 0.09 |
Spheres | 5.1 | 3.1 | 125 | 0.2493 | 1.30 ± 0.07 |
Grubbs | 7.7 | 4.2 | 131 | 0.2289 | 1.53 ± 0.17 |
Spheres+Grubbs | 4.1 | 2.5 | 126 | 0.2460 | 1.10 ± 0.06 |
The self-healing material was loaded to failure for 24 hours and loaded a second time to failure. These specimens had a K1c of 0.68± 0.07 for a 65% recovery rate or the original fracture toughness. The modulus and fracture toughness of the self healing material statistically similar (p>0.05) to the control and the tan delta suggests no real loss of the material's ability to absorb energy by damping.
Conclusion: The self healing capability of a dental material was explored. Autonomic healing was demonstrated with a model dental composite and DMA data suggest favorable properties compared to a control material. This study was supported by the Health Future Foundation. All materials were provided by Esstech, Kennsington PA.