Objectives: To evaluate the 3D-marginal adaptation of low shrinking composites placed in dentin cavities and compare it to their shrinkage strain rate.
Methods: The materials tested were Ceram-X Mono/CX (Dentsply), Premise/PR (Kerr), Clearfil Majesty/CM (Kuraray), ELS/EL (Saremco) and Filtek Silorane/FS (3M/Espe) all of A2 shade. Dentin cavities (n:4, h:1mm, dia:2mm) were prepared and filled with a single layer of resin composite without any adhesive cavity pre-treatment and light-cured (40s, 750W/cm2, halogen unit). The specimens were imaged by computerized X-ray microtomography with horizontal sections taken at 100kV and 5.66 pixel size and the micro-void volume fraction (%VF) was calculated via the software. Shrinkage strain rate (%SR) was calculated using the bonded-disk method (n:5) at 100s acquisition time and the same irradiation conditions. Statistical analysis of the %VF and %SR was performed by one-way ANOVA and Tukey's post-hoc test (a=0.05) and Pearson's correlation coefficient.
Results: The results of %VF were: CX 7.5±0.4a,b, PR 4.1±1.1a, CM 5.9±0.9c, EL 3.1±1.6b,c, FS 5.5±1.3 (same letters show mean values with statistically significant differences). The maximum strain rate (%/s) for each material was: CX 0.151±0.014, PR 0.113±0.01a, CM 0.093±0.004a, EL 0.103±0.02a, FS 0.067±0.003 (same letters show mean values with no statistically significant differences). No correlation was found between %VF and %SR.
Conclusion: The results imply that %SR does not directly affect %VF. Other factors, like handling characteristics (packing, viscosity etc) may contribute to interfacial porosity.