Polymerization efficiency and flexural strength of low-stress restorative composites

OBJECTIVES: To assess depth of cure (DOC), degree of conversion (DC), and flexural strength (FS) of several resin composites with low-stress behavior. METHODS: SonicFill (Kerr), SureFil(®) SDRTM (Dentsply), everX Posterior (GC), Kalore (GC), and Filtek Silorane (3M ESPE) were tested. DOC was measured with the Acetone Shake test. DC was assessed with Fourier Transform Infra-Red spectroscopy on top and at the bottom of 4mm-thick disk-shaped specimens. Bottom to top ratios of DC percentages were calculated. FS was evaluated with the Three-Point Bending test. DOC, DC, and FS data were statistically analyzed. RESULTS: SureFil(®) SDRTM and everX Posterior achieved significantly greater DOC than Kalore and Filtek Silorane. Also, SonicFill had significantly greater DOC than Filtek Silorane. Mean top DCs ranged between 71.46% and 52.44%. Kalore and everX Posterior had significantly lower top DCs than the other materials. Mean DC values at 4mm ranged largely from 57.95% to 6.82%. Kalore and Filtek Silorane had the lowest values of bottom DC and the difference was statistically significant. EverX Posterior and SonicFill recorded significantly higher FSs than the other materials. SIGNIFICANCE: SureFil(®) SDRTM and everX Posterior exhibited DOC over 4mm, the maximum thickness recommended for bulk placement, while SonicFill recorded DOC values very close to the 4mm threshold. SonicFill achieved the highest DC at the irradiated surface, as well as at 4mm depth. SureFil(®) SDRTM demonstrated similarly uniform curing through the bulk increment. All the tested composites complied with the requirements of FS established by ISO 4049/2009.