Quantifying Leakage of Dental Composites in Model Cavities

Objective: The objectives of this study were to 1) introduce a new method for quantifying microleakage using 3D imaging and image analysis, and 2) explore relationships between the chemical/physical properties of a composite and its leakage area in model cavities. Method: A series of composites was formulated based on BisGMA:TEGDMA (50:50 by mass) resin and varied filler content, ranging from 55 % to 75 % (by mass) at 5 % intervals. The polymerization shrinkage and the corresponding leakage pattern in optically clear PMMA model cavities were determined using X-ray microcomputed tomography (μCT) and image analysis. MATLAB codes were written to process series of 2D images collected using μCT, and to identify the location of volume changes upon polymerization at the composites-cavities interface. The leakage area was defined as the debonded area from the wall of the cavity. Results were illustrated in both 2D and 3D maps and were compared with those visualized by dye penetration methods. Stress development upon photopolymerization of these composites was monitored through tensometer, and the results were used to understand the phenomena observed in the leakage experiments. Results: Leakage patterns at the interface determined by μCT and image analysis were in agreement with those obtained by dye penetration. The largest leakage area was observed from the composite with the highest filler content, which also had the lowest degree of conversion and the lowest shrinkage value. The fastest rate of stress build-up and reduced wetting of this composite to the cavity wall likely resulted in this increased interface leakage. Conclusion: This is the first demonstration of quantitative leakage area measurements, which provide a clearer picture of the true interface phenomenon after photopolymerization. We also demonstrate that the leakage pattern developed in a given cavity geometry is affected by multiple materials properties. Support: NIDCR/NIST Interagency Agreement Y1-DE-7005-01.