From bioactivity to biofunctional restorative materials: reappraising terminology and evidence

To critically appraise use of the term bioactivity in restorative dentistry and to propose a framework that aligns terminology with biological context, demonstrated mechanism, evidence level, and clinical relevance.

This narrative review examined conceptual papers, policy statements, standards, review articles, laboratory evidence, and clinical syntheses on restorative materials carrying bioactive claims. The Hench definition, the Fédération Dentaire Internationale (FDI) Policy Statement, and the scope of International Organization for Standardization (ISO) 23,317 were compared with conditions at enamel, dentine, and pulp interfaces. Claimed mechanisms and validation methods were organised within a five-tier framework.

In the Hench formulation, bioactivity is an interfacial outcome in which a specific host response culminates in a stable bond between a material and living tissue. Ion exchange and apatite precipitation can be mechanistic precursors, but they do not establish that endpoint. Most direct restorative materials act at enamel, dentine, or oral-fluid interfaces and should be described by their demonstrated functions. Biofunctional restorative material is proposed as an umbrella designation for intentional, mechanism-specific chemical or biological functions beyond structural restoration. Evidence is dominated by laboratory studies, and consistent clinical superiority over conventional materials has not been demonstrated. The five-tier framework separates restorative performance, defined mechanism, functional challenge testing, biological validation, and clinical translation.

Bioactivity should be reserved for applications in which Hench-type tissue bonding or integration is demonstrated, not inferred from ion release or apatite precipitation in simulated body fluid. Biofunctionality more accurately describes the wider restorative domain and permits claims to be matched to mechanism and evidence.

The FDI Policy Statement places conditions on use of the term bioactive but does not require that ion-releasing or mineral-precipitating restorative materials carry that label. ISO 23,317 is an initial screening method for bone-contacting implant materials, not a nomenclature standard for dentine-targeted restoratives. Application-qualified biofunctional terminology may improve claim accuracy, product evaluation, and clinical communication.