Circular saw blades with a number of teeth less than 25 are suitable for cutting wood very often, while those with a greater number of teeth are used for thin thicknesses.  The type of material to be cut also affects the number of teeth that the blade must have to ensure optimal results and a good finish of the cut.  Plastic and aluminum, for example, require blades with a high number of teeth, from 40 to 80 or even more depending on the specific cases.