Strategies for enhancing biocompatibility, bioactivity, and resistance to biodegradation in dental resin composites: A narrative review.

Dental resin composites (DRCs), while indispensable in restorative dentistry for addressing tooth defects, are constrained by several inherent limitations. Conventional DRCs not only have cytotoxic potential but also undergo accelerated biodegradation mediated by host-derived enzymes and oral microbiota. Additionally, conventional DRCs are inherently bioinert-lacking the bioactivity required to inhibit the initiation and progression of secondary caries. Existing studies have found that degradation byproducts of DRCs may enhance the virulence of cariogenic pathogens. Concurrently, microleakage at resin-dentin interfaces causes salivary permeation and biofilm colonization, collectively establishing a pathogenic 'degradation-infection' feedback cycle. Furthermore, residual monomer release during biodegradation exacerbates cytotoxic responses, thereby generating synergistic "degradation-toxicity" compounding effects. These compounding effects severely compromise the clinical longevity and functional stability of DRC-based restorations. Therefore, this review comprehensively examines the factors and mechanisms underlying the cytotoxicity and biodegradation of conventional DRCs in oral environments from both bacterial and host perspectives. It also discusses their early-stage application profile characterized by "mere structural repair"-reflecting bioinertness. In addition, this review places particular focus on design strategies for novel DRCs intended to overcome these limitations and to impart improved biological performance. This review provides a theoretical framework for the biological optimization of DRCs and offers new ideas for developing next-generation DRCs with both biological safety and clinical durability.