The present invention is directed to a process for electrochemically whitening a tooth, the process comprising: a) contacting the tooth with a whitening gel that is located in a dental device, the dental device comprising a positive electrode and a negative electrode; b) flowing a current between the positive electrode and the negative electrode through the whitening gel to whiten the tooth; wherein the whitening gel comprises: water; a bleaching agent; a thickener composition comprising a non-ionic compound; a surfactant; and an electrolyte source comprising a first conductive salt.