Introduction
Biocompatibility and cytotoxicity of denture base materials which are in contact with oral mucosa are still contradictory.1 When used, these materials are in direct contact with oral tissues for a prolonged period of time; the biologic factors unique to the oral environment such as pH and thermal changes, moisture, microorganisms and enzymes can change the chemical and physical properties of these materials.2
Denture-base alloys usually have a multiphase structure containing several metals. Corrosion causes the release of elements from these alloys that may have a cytoxic effect in the oral environment.3 On the other hand, the biologic characteristics of denture-base resins are influenced by the monomer to polymer conversion. Despite the various methods used to initiate the polymerization of acrylic resin, the conversion of monomers to polymers is incomplete leaving residual monomer in the denture base that can leach into the saliva. The unreacted monomer can cause adverse reactions in the oral mucosa in contact with the denture.4 On the other hand, acrylic resin has a low thermal conductivity compared with denture-base metal alloys. Studies have shown thermal diffusivity to be an important material property in determining the gustatory response. Other studies experimented with increasing the thermal conductivity of acrylic resin by adding metal5 or ceramic filler.6,7
Adding ceramic filler can improve some physical properties of acrylic resins.8 Therefore, a study of the biologic properties of a mixture of acrylic resin and ceramic filler is essential. Biocompatibility testing can be conducted using in vitro tests (using cell cultures), in vivo tests (animal studies), or clinical trials (human testing).9 The aim of the present work was to study the biologic reaction of cobalt chromium (Co-Cr) alloy, a heat-cure acrylic resin denture-base material, and a mixture of heat-cure acrylic resin and ceramic filler (aluminum oxide) (Al2O3) which was implanted in the vestibular mucosa of dog mouths using the histopathologic method.
