Viscosity and wettability of animal mucin solutions and human saliva

OBJECTIVE: The purpose of this study was to compare viscosity and wettability between animal mucin solutions and human saliva. MATERIALS AND METHODS: Human whole and glandular saliva, porcine gastric mucin, bovine submaxillary mucin, and a mucin-based saliva substitute were used. Viscosity was measured with a cone-and-plate digital viscometer, while wettability on acrylic resin and Co-Cr alloy was determined by the contact angle. RESULTS: The viscosity of animal mucin solutions was proportional to mucin concentration, with the animal mucin solution of concentration 5.0 mg ml(-1) displaying similar viscosity to stimulated whole saliva. A decrease in contact angle was found with increasing animal mucin concentration. For the saliva samples tested, viscosity increased in the following order: stimulated parotid saliva, stimulated whole saliva, unstimulated whole saliva, stimulated submandibular-sublingual saliva. Contact angles of human saliva on the tested solid phases were inversely correlated with viscosity. Contact angles of human saliva on acrylic resin were much lower than those of animal mucin solutions and of those on Co-Cr alloy (P < 0.01). CONCLUSIONS: The effectiveness of animal mucin solutions in terms of their rheological properties was objectively confirmed, indicating a vital role for mucin in proper oral function as well as the development of effective salivary substitutes.