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Contemporary Use of Bioactive Materials in Restorative Dentistry
Gerard Kugel, DMD, MS, PhD; and Steven Eisen, DMD
Abstract: While not a new concept in dentistry, bioactive restorative materials continue to show further potential, as new products appear to offer significant benefits for both clinicians and patients. Such materials can form a surface layer of an apatite-like substance in the presence of an inorganic phosphate solution. Their applications in dentistry include remineralization of dentin, maintenance of long-term bonded restorations, and repair of intrabony defects. This article reviews new developments in this expanding area of dentistry and highlights the still untapped promise that bioactive materials hold for practitioners.
The concept of a bioactive material was first recognized in 1969. Early on, bioactivity was defined as follows: “A bioactive material is one that elicits a specific biological response at the interface of the material which results in the formation of a bond between the tissues and the material.”1 Since then, the area of bioactive materials has expanded enormously in both medicine and dentistry.
Hench introduced the original criteria for the evaluation of bioactivity of a material. In 1994 he proposed a classification2 in which he divided bioactive materials into two groups: osteoproductive and osteoconductive. In osteoproductive materials, the bioactive surface is colonized by osteogenic stem cells. Bioactivity occurs when a material elicits both an intracellular and extracellular response at its interface (eg, bioglass materials are both osteoproductive and osteoconductive). Osteoconductive materials provide a biocompatible interface, along which bone migrates. Osteoconductive bioactivity occurs when a material elicits only an extracellular response at its interface (eg, synthetic hydroxyapatite [HA]).
The idea of bioactive restorative dental materials is not new. When one considers the concept of adhesion to tooth structure along with the release of fluoride, and more recently calcium and phosphate to help prevent recurrent decay, it is clear that “bioactive” restorative materials have been available in dentistry for many years in the form of fluoride-releasing materials. It now seems well accepted that a bioactive material is defined as one that forms a surface layer of an apatite-like material in the presence of an inorganic phosphate solution.3 Materials that are only fluoride-releasing such as resin-modified glass ionomers (RMGIs) are not truly bioactive and do not fall under either the osteoproductive or osteoconductive groups. Glass ionomers release fluoride ions in an effort to prevent secondary caries; however, the development of caries is still a major reason for clinical failure of glass-ionomer–cemented restorations.4 Glass ionomers are excellent materials for many situations and clinical indications, but their ability to prevent recurrent caries may be somewhat questionable and they do not form HA.