Abstract: A curette or like instrument for use by a dental practitioner in removing plaque and calculus from tooth surfaces within periodontal pockets comprises a tip having a debridement portion. The debridement portion is provided with a marking in the form of mutually contrasting bands to give the practitioner a visual indication of the extent to which the instrument has in use penetrated a periodontal pocket, so that its end (which is sharp) does not cause pain or injury to the patient. The bands are formed, eg by etching or by differently coloured materials, to accord with markings already used on periodontal probes. The invention is applicable to ultrasonic, sonic and piezo-electric scaling instruments as well as to manual instruments.