Physico-chemical analysis of eight pre-mixed hydraulic silicate sealers

Introduction Pre-mixed root canal sealers containing hydraulic silicate cements are marketed under the “bioceramic” umbrella term. Eight such sealers were investigated to get a comprehensive overview. Materials and methods Disclosure of composition was assessed in safety data sheets and instructions for use. Elemental analysis was conducted using energy-dispersive x-ray spectroscopy (EDS). Flowability, radiopacity, and setting time were tested according to ISO norm 6876 (2012). Knoop hardness was tested after 7 d. Samples were immersed in phosphate-buffered saline for up to 28 d and assessed for continued pH induction and release of calcium ions (Ca), which was measured using atomic absorption spectroscopy (AAS). Cumulative aluminum (Al) leaching after 28 d was quantified using AAS. Results Dispersing agents were not disclosed in 5 of the 8 sealers, and cement components not specified in 4. As assessed by EDS, 4 of the sealers under investigation were Portland cement-related, and 4 were Al-free silicates. The ISO-requested flowability and radiopacity were met by all the sealers. Radiopacity ranged from 3.4 ± 0.1 to 7.4 ± 0.3 mm Al. Setting time ranged from 122 ± 4 min to 4,258 ± 14 min. The sealers containing Al tended to set quicker and reached a considerably higher 7-d hardness than their Al-free counterparts. All sealers maintained an alkaline pH induction over 28 d, but differed in Ca release. Al leaching was observed with 2 of the 4 Portland cement-related sealers, but to a different degree. Conclusion The materials under investigation differed considerably in their basic properties and their propensity to leach elements.