A whitening smart pen apparatus (10) for automatically dispensing a teeth whitening substance onto one or more teeth of a user comprises a fluid reservoir (16), a nozzle (18) having an output port (26), a fluid dispenser (20), a sensor (22) and a controller (24). The fluid dispenser dispenses the teeth whitening substance from the fluid reservoir to the nozzle and is output via the output port. The sensor, positioned in an advance dispensing direction of the nozzle, senses a target surface that comprises either (i) a tooth surface (12) or (ii) other surface (14). The controller (24) is configured for (i) controlling a gating of the fluid dispenser (20) to dispense the teeth whitening substance from the fluid reservoir (16) in response to the sensor (22) detecting the tooth surface (12), and (ii) stopping or disabling the gating of the fluid dispenser to stop or disable a dispensing of the teeth whitening substance from the fluid reservoir in response to the sensor (22) detecting the other surface (14).
