Instrument used to measure the relative mobility of teeth and dental implants. Device utilizes a tapping piston to percuss a tooth or an implant four times per second. Rate of deceleration recorded at the point of contact is measured as the relative stiffness of the tooth or implant. Periotest values range from ‐08 to +50, with the ‐08 to +09 range indicating no discernible movement, +10 to +19 just discernible movement, +20 to +29 obvious movement, and +30 to +50 mobile on pressure.