In vitro evaluation of complex carbohydrate denture adhesive formulations

Objective: Acemannan, a complex mannose carbohydrate dervied from the aloe vera plant, has an inherent stickiness/viscosity. Prototype Acemannan denture adhesive for mulations were evaluated for pH changes, cytotoxicity to human gingival fibroblasts and adhesive strength in both dry and wet conditions. Method and materials: The denture adhesive formulations consisted of five combinations of Acemannan with varying concentrations of preservtives and two other formulations without preservatives. The pH of each formulation was measured over 24 hours. Assessment of cytotoxicity was accomplished using the in vitro, tetrazolium-based colorimetri c assay on cultures of human gingival fibroblasts after exposure to the adhesive formulations for up to 24 hours. The adhesive strength was evaluated with a universal testing machine under intial dry conditions and after immersion in a constant-temperature water bath for up to 20 minutes. Results: Formulations 1 and 2 acheived and maintained pH values above 6.0 (the critical pH for hydroxyapatite dissolution) approximately 6 hours into the study. None of the prototypes demonstrated an initial pH above the critical pH. Formulations 1, 2, 3, and 5 exhibited significant cytotoxicity to human gingival fibroblasts over 24 hours. Formulations 4, 20:1, and 150:1 demonstrated minimal cytotoxicity. Formulation 1 exhibited the poorest adhesive strength, while the most viscous formulation (prototype 150:1) was by far the best performer. Generally, adhesive bond strengths for all prototypes were quite high and relatively stable over time in a wet environment. Conclusion: To achieve the ideal adhesive in terms of strength, pH, and cytotoxicity. Acemannan formulation 150:1 should be adjusted to contain the preservative concentration of formulation 4 and have an initial pH value of 6.0 or higher.