Ion Release and Shear Bond Strength of Activa™ – Bioactive Cement™ and RelyX™ Unicem 2

Objectives: Recently, bioactive cements have attracted attention due to their capability to release remineralizing ions such as calcium and fluoride as stated by the manufacturers. However, it is still unclear how ion release impacts other material properties such as bond strength. Therefore, we compared Activa™ - Bioactive Cement™ (ABC) with the well-established self-adhesive resin cement RelyX™ Unicem™ 2 Automix (RU2) in terms of their ion release and shear bond strength.
Methods: RU2 (3M™ ESPE™) and ABC (Pulpdent®) were tested. All materials were applied according to the manufacturers’ instructions. Cylindrical specimens (height=1.5mm; diameter=15mm) were prepared either by self-curing (sc) or light-curing (lc) and stored in deionized water for 27 days (d). Calcium and fluoride release was determined using an inductively coupled plasma optical spectrometer (Optima™ 8000, Perkin Elmer®) or a fluoride-selective electrode (Titrando™, Metrohm™), respectively. Bovine teeth were ground flat to expose enamel or dentin, polished (grit 320 sandpaper) and water-rinsed. Stainless steel rods (diameter=4mm) were sandpapered, sandblasted, silanized (ESPE Sil, 3M ESPE) and subsequently cemented under standardized pressure (20g/mm²). For self-curing, glycerine gel (Airblock™, Dentsply™) was applied and the specimens were stored for 1h (36°C). For light-curing, the cement was irradiated from 4 sides (10s each; Elipar™ S10, 3M ESPE). All specimens were stored for 24h (36°C; 100% relative humidity) before shear bond strength (SBS) testing (Zwick Z010; n=6; crosshead speed=0.75mm/min). Data analysis was performed using One-Way ANOVA (Fisher; p<0.05).
Results: See table.
Conclusions: Both cements showed no significantly different SBS on enamel in both curing modes. However, on dentin ABC demonstrated a poor SBS and values were significantly lower than those of RU2. The investigation of the ion release revealed that self-cured specimens resulted in higher ion release than the light-cured ones. ABC showed higher fluoride release whereas RU2 released higher amounts of calcium. Further research is needed to determine long-term ion release and SBS of aged specimens.