 There is an intra-individual and inter-individual variability in the production of saliva. Various factors influence the production of saliva. Saliva flow tends to decrease with age, sleep, emotional state, and to increase after eating, and during pregnancy. Some drugs increase the salivary flow, others decrease it. Tobacco and alcohol tend to impair the quality of the saliva. Furthermore, 43 of 40-64 years and 61 over 65 take at least one antisialic medication. Lack of saliva can cause problems chewing, swallowing, speaking, and tasting perceptions. There is an increase in the number of oropharyngeal candidiasis that affects feeding behaviors and would be responsible for malnutrition in the elderly, and an increase in the number of caries for subjects still toothed. For edentulous or partially dentate subjects, salivary film plays two roles: the first is to allow adhesion of complete or almost complete dentures; the following is to protect the oral mucosa. In subjects suffering from mouth dryness the denture becomes difficult. In addition, saliva is essential for the first phase of digestion, for the creation of a correct bolus. There are several methods to measure the salivary flow. The most common include: 