Toothbrush and system

A toothbrush comprising:

• a main body including a head portion having a bristle raising surface on which bristles are provided in a standing manner;
• a light emitting diode that emits light through a specific region of the bristle raising surface to a tooth surface, and an optical filter member that receives radiated light from the tooth surface resulting from the light through the specific region, the light emitting diode and the optical filter member being provided in the main body;
• and
• a processor that collectively detects whether or not dental plaque or dental calculus is present on the tooth surface based on an output from the optical filter member,
• wherein the processor determines that dental calculus is present on the tooth surface when a state in which the processor detects the presence of dental plaque or dental calculus continues for a predetermined period from a start of brushing of the tooth surface.