Development of novel citrate-based dental tissue conditioners

Abstract

Dental tissue conditioners are compliant, viscoelastic gels used primarily to form a soft cushion between the oral mucosa and the hard denture base. Their uses include the treatment of inflamed mucosa resulting from ill-fitting dentures and in treatment of denture related stomatitis. They are presented in powder/liquid format where the powder is usually poly(ethyl methacrylate) (PEMA) and the liquid is a mix of an aromatic ester (plasticiser, usually a phthalate) with ethanol. In use, the ethanol and plasticiser leach out with time causing the material to harden. In recent years there has been concern about possible toxic effects of the leached phthalate. Preliminary work has shown citrate plasticisers to be acceptable replacements for phthalates. Another disadvantage of the powder/liquid format is the porosity produced on mixing which can lead to microbial ingress and contamination. One possible solution would be to use a pre-gelled material which would have the advantages of easy application and reduced porosity. Candidal infections are a common etiological factor in denture related stomatitis. Earlier studies have shown it possible to release chlorhexidine diacetate (a broad spectrum antibacterial/antifungal agent) from powder/liquid tissue conditioners to treat these infections The aim of this study is to develop citrate-based pre-gelled and powder/liquid tissue conditioners and explore its use as potential drug delivery vehicle for chlorhexidine diacetate. The experimental pre-gelled system (EPGS) containing PEMA and acetyl tributyl citrate (ATBC) only showed stable Shore A hardness values over an 18 month time Abstract 5 period when stored at 7oC. The Shore A hardness and creep compliance ratio (flow) of EPGS indicated that it could be used as both a tissue conditioner and a temporary denture lining material, whereas experimental powder liquid system (EPLS), which contained 16 hours ball-milled PEMA powder and ATBC plus 5% ethanol, had more suitable properties for use as a tissue conditioner. Addition of chlorhexidine diacetate alone or with sodium fluoride did have an effect on the hardness and creep compliance ratio of the materials but these were within acceptable range. Both EPGS and EPLS containing 1% chlorhexidine had a higher percent release than those containing 9% chlorhexidine. The addition of sodium fluoride increased the release of chlorhexidine in all formulations.