Does the incorporation of zinc into calcium phosphate improve bone repair? A systematic review

Calcium phosphate (CP) has been used as biomaterial to regenerate bone defects. In order to improve its biological properties, substitutions in the calcium phosphate chemical structure have been investigated. Zinc has stimulatory effects on in vitro and in vivo bone formation and an inhibitory effect on in vitro osteoclastic bone resorption. The aim of this systematic review (SR) was to assess the effect of zinc incorporation into calcium phosphate on bone repair. This SR was performed in accordance with the PRISMA guidelines and Preclinical Systematic Review & Meta-analysis Facility. An electronic search was conducted using the MEDLINE/PubMed, Cochrane, Scopus, and Scielo databases. Eligibility criteria included only animal studies that compared the effect of zinc incorporation into CP-based materials on bone repair. The selection process yielded 18 studies among 335 retrieved. The ARRIVE guidelines checklist was used to assess the articles' quality. It was observed that zinc incorporation into CP did not affect its biocompatibility, tends to reduce the resorption rate and was considered to be osteoconductive. Most of the manuscripts suggested that zinc incorporation can enhance bone repair. The results indicate that zinc-doped CP has potential for increasing bone repair, being an interesting option for bone regeneration biomaterial.