Bioactivity of zinc-doped dental adhesives

Design of restorative materials should be focused on promoting not only adhesion but also dentine self-repair processes.

To ascertain if ZnO and ZnCl2-doped resins are materials able to induce calcium (Ca) and phosphate (P) deposition.

48 resin disks were prepared with the following materials: (1) single bond -3M/ESPE-, (2) single bond+ZnO particles 20wt% and (3) single bond+ZnCl2 2wt%. Specimens were polymerised and polished. Bioactivity was tested through a simulated body fluid solution (SBFS) immersion test. At time 24h, 7 d and 21 d surfaces were analyzed by stereomicroscope, high resolution scanning electron microscope (HRSEM), energy-dispersive analysis (EDX), confocal laser Raman, and X-ray diffraction (XRD) for morphological and chemical composition.

Under the stereomicroscope, crystal formations were encountered in both zinc-doped resin adhesives after 7 d of immersion. It was, detected by EDX, that the ZnO-doped resin produced Zn, Ca and P deposition (globular formations were observed by HRSEM) after 7 d. Zn and P crystals were detected by HRSEM and EDX in the experimental ZnCl2-doped resin after 7 d and 21 d. Hopeite formation was identified by Raman on both Zn-doped resins. Single bond did not produce mineral or crystal precipitation.

ZnO-doped resin induced Ca and P deposition after SBFS immersion. On ZnCl2-doped resin hopeite formation was detected, if this hopeite may be further converted into apatite, after SBFS immersion, remains to be ascertained.

Bonding with ZnO-doped resin may facilitate incorporation of Ca and P at the interfacial bonding zone.