Biocompatibility of resin-modified filling materials

Increasing numbers of resin-based dental restorations have been placed over the past decade. During this same period, the public interest in the local and especially systemic adverse effects caused by dental materials has increased significantly. It has been found that each resin-based material releases several components into the oral environment. In particular, the comonomer, triethyleneglycol di-methacrylate (TEGDMA), and the 'hydrophilic' monomer, 2-hydroxy-ethyl-methacrylate (HEMA), are leached out from various composite resins and 'adhesive' materials (e.g., resin-modified glass-ionomer cements [GICs] and dentin adhesives) in considerable amounts during the first 24 hours after polymerization. Numerous unbound resin components may leach into saliva during the initial phase after polymerization, and later, due to degradation or erosion of the resinous restoration. Those substances may be systemically distributed and could potentially cause adverse systemic effects in patients. In addition, absorption of organic substances from unpolymerized material, through unprotected skin, due to manual contact may pose a special risk for dental personnel. This is borne out by the increasing numbers of dental nurses, technicians, and dentists who present with allergic reactions to one or more resin components, like HEMA, glutaraldehyde, ethyleneglycol di-methacrylate (EGDMA), and dibenzoyl peroxide (DPO). However, it must be emphasized that, except for conventional composite resins, data reported on the release of substances from resin-based materials are scarce. There is very little reliable information with respect to the biological interactions between resin components and various tissues. Those interactions may be either protective, like absorption to dentin, or detrimental, e.g., inflammatory reactions of soft tissues. Microbial effects have also been observed which may contribute indirectly to caries and irritation of the pulp. Therefore, it is critical, both for our patients and for the profession, that the biological effects of resin-based filling materials be clarified in the near future.