Little has been published in the dental literature on the combination of distinct variables in the design of oral health scales. Particular interest in the idea of representing the oral health status in a single numerical value arose with the development of “Periodontal Medicine”, which aims to establish correlations between infectious/inflammatory disorders of the oral cavity and the appearance of certain systemic diseases. In this thesis, we propose a new global oral health scale that establishes a single value for the infectious potential of the oral cavity, which has its clinical expression in the form of local and focal infections. The scale incorporates dental and periodontal variables organised according to objective and tested indices that reflect to a certain degree the presence of the principal infectious disorders of the oral cavity, caries and periodontal disease. The different grades of the scale have been correlated with the presence and concentration of various bacterial species of the salivary flora.