mCT for measuring polymerization shrinkage of dental composites


Jirun SUN and Sheng LIN-GIBSON


Photopolymerizable dimethacrylate based composites are used extensively as dental restorative (for filling tooth decays) because of their superior adhesion to the target and their attractive aesthetic properties. On the other hand, the polymerization shrinkage of these resins generates tension, which may damage the interface integrity between the restorative and tooth. Volumetric shrinkage as low as 2 % is enough to produce gaps and channels at the tooth/composite interface, which leads to premature failures. Current methods for determining the shrinkage, such as dilatometers, are laborious, time-consuming, and are burdened with data dispersion when used in the high viscosity region. Moreover, these tests cannot be used to examine shrinkage and dimensional changes such as those found in the clinical settings. X-ray microcomputed tomography (mCT) is a non-destructive 3D imaging technique that can be used to inspect the internal structures of small objects with high spatial resolution and unprecedented speed. mCT measures the content at each pixel which can be used to evaluate the volume of composites aided by the presence of X-ray radio opaque fillers. mCT can also be used to determine the void content and quantify changes in dimensionality. Theoretically, the volumetric polymerization shrinkage can be calculated according to the volume changes between cured and uncured composites, Results from the tested dimethacrylate resins based composites and commercial composites validate this hypothesis.


Author information:

Jirun Sun

Mentor: Sheng Lin-Gibson

Polymers Division

Biomaterials Group 
Building 224, Room A111

Mail stop: 8543

Tel: (301)975-5439
Fax: (301)975-4977


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Category: Material