The amalgam overhang dilemma: a review of causes and effects, prevention, and removal

Overhanging margins of restorations are common, and much iatrogenic periodontal disease is caused by plaque stagnation associated with overhangs. Greater awareness of the causes of overhangs--the clinical skills and judgment of the operator, the properties of the restorative materials, and the morphological features of the dentition--may help to reduce the number of overhangs placed and subsequently ignored. Thorough examination for overhangs, using both clinical and radiographic assessments, is the most reliable way of diagnosing overhanging margins. Neither clinical assessment nor radiographic examination alone is accurate. Failure to recognise and eliminate overhanging margins of restorations occur frequently and may constitute professional negligence. Once overhangs are recognised, they should not be ignored as they predispose to, and increase the severity of periodontal disease. Small overhangs are more easily removed than large ones, and the latter may necessitate replacement of the restoration. A variety of instruments may be used to remove overhanging margins, but such instruments need to be used carefully to avoid damaging adjacent dental tissues. Consequently, appropriate skills should be gained during the undergraduate course so that future generations of dentists are better able to cope with overhanging margins. The dental profession has an ethical obligation to recognise the need for improvement.