Several different biomaterials are being introduced for clinical application. However, no systematic studies could define a parameter to evaluate these materials from a clinical point of view to assess material-specific application fields. The aim of the present study was to provide clinicians with a tool to assess the regeneration pattern of biomaterials. The present study histologically evaluated 13 polymeric biomaterials and 19 bone substitute materials (BSMs) of different compositions and origins after their implantation in a standardized subcutaneous model. Semiquantitative analysis was performed according to a standardized score for the induction of multinucleated giant cells (MNGCs), a frequently observed cell type in the implantation bed of biomaterials. The results allowed the introduction of a novel classification system for polymeric biomaterials and bone substitute materials independent of their origin. Polymeric biomaterials were classified based on the MNGC score and represented biomaterial groups that induced no MNGCs at any time point (class I), a constant number of MNGCs (class II) and an increasing number of MNGCS (class III) over 30 days. All BSMs induced MNGCs to different extents. Thereby, the classification of BSMs included materials that induce MNGCs with decreasing tendency (class I), constant tendency (class II) and increasing tendency (class III) over 30 days. The absence or presence of MNGCs in a decreasing number (class I) was associated with biomaterial integration and structure stability, whereas the induction of MGNCs in an increasing number (class II and III) resulted in disintegration, rapid material degradation and enhanced pathologic vascularization. Interestingly, the induction of MNGCs was dependent on biomaterial-specific physicochemical properties (surface, size, porosity and others) and independent of biomaterial origin (synthetic vs. natural). This novel classification provides clinicians a tool to assess the capacity and suitability of biomaterials in the intended clinical indication for bone and soft tissue implantations.

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