Activity of chitosan antifungal denture adhesive against common Candida species and Candida albicans adherence on denture base acrylic resin

Abstract

Statement of problem: Candida adherence to the denture base is an important cause of denture stomatitis. In addition, infections with drug-resistant Candida have become more prevalent, especially among elderly and immunocompromised patients. Thus, alternative safe antifungal agents for oral applications are needed.

Purpose: The purpose of this in vitro study was to investigate the activity of chitosan, a natural biopolymer, against common oral Candida species and its efficacy in inhibiting C albicans adherence to denture-base acrylic resin.

Material and methods: The minimum fungicidal concentrations (MFCs) of 5 types of chitosan against 6 species of Candida and 10 C albicans clinical isolates were determined by broth and agar dilution, respectively. N-succinyl chitosan (NSC), low- and high-molecular-weight water-soluble chitosan (LMWC and HMWC), and oligomer and polymer shrimp-chitosan were examined. NSC and HMWC, as pure gel and as a mixture with carboxymethylcellulose (CMC), were applied to acrylic resin disks, incubated with C albicans for 24 hours, and washed, and adherent cells were collected for colony count. The effects of HMWC on human gingival fibroblasts after 1 and 24 hours of treatment were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The retention force of HMWC gel was measured by using a universal testing machine. The Kruskal-Wallis and Mann-Whitney U tests were used to compare the antiadherence activity (α=.05).

Results: HMWC had the highest antifungal activity against most Candida species tested and C albicans clinical isolates. HMWC gel completely inhibited C albicans adherence to denture base acrylic resin (P<.001). CMC denture adhesive significantly increased C albicans adherence (P<.001), but adding 2×MFC HMWC into CMC reduced the adherence, although this was not statistically significant (P=.06). HMWC at 1×MFC and 2×MFC showed no toxic effect on gingival fibroblast viability and proliferation. Moreover, the retention force provided by HMWC gel was sufficient for use as a denture adhesive (>5000 Pa).

Conclusions: High-molecular-weight, water-soluble chitosan is a biocompatible biopolymer that could inhibit C albicans adherence and that showed properties suitable for development into an antifungal denture adhesive.