Figure 9. (a) Main metabolic processes associated with the pH vectors that characterize dental plaque acid-base metabolism. Vectors 1 and 4 produce base; Vectors 2 and 3 produce acid. Dashed line represents neutrality, and SCCA is the abbreviation for short-chain carboxylic acids. (b) Diagrams 1 and 2 characterize plaque with balanced acid-base metabolisms; 1 is for thicker and 2 is for thinner plaque (Imfeld, 1983). Diagram 3 characterizes plaque where alkali formation is more dominant, whereas in 4, acid formation dominates (modified from Kleinberg and Westbay, 1992).