An overhanging dental restoration (ODR) is defined as an excess of restorative material, extending beyond cavity preparation borders. Overhanging dental restorations are common causes of gingival inflammation and periodontal damage. Working in a very limited area in the mouth and having difficulties accessing certain teeth can lead to ODR, which is a particular problem in interproximal areas. In these regions, polishing procedures that reduce micro environments for bacteria are more challenging – particularly at the distoocclusal margins of maxillary molars.
The prevalence of ODRs is remarkably high. However, with careful treatment planning, and with the use of appropriate methodology, clinicians can reduce the impact, or completely avoid the formation of overhangs.
The prevalence and impact of overhanging restorations
Prevalence varies depending on the population and restorative material studied. Overhanging restorations have been identified in anything between 25-76 per cent of all restored surfaces. Overhanging dental restorations are often found in posterior teeth, particularly molars and premolars, and are more prevalent in the maxilla compared to the mandible. In one study, featuring the panoramic radiographs of 243 patients with one or more restoration, a total of 280 overhanging restorations were detected. More than half of the overhangs in this study were reported at the distal margins of class II restorations, which are located between the molars.
Overhangs can create crevices and micro-gaps that make it difficult for patients to maintain adequate oral hygiene. The accumulation of plaque in these regions leads to the development of destructive subgingival flora, causing inflammation of the gingiva. Over time, this can lead to periodontitis, characterised by alveolar bone loss and possible tooth mobility.
The anatomical shape of the tooth, the type of restorative material, and the location of the overhang all play a role in how easily plaque can accumulate. Particularly when the restoration is near the gumline, where the gingival sulcus is formed subgingivally, the gingiva can be directly irritated. This irritation can damage the epithelial tissue and subepithelial connective tissue, making it harder for the tissues to heal and maintain a healthy attachment to the tooth.
The role of technique and materials
While ODRs can be exacerbated by unusual tooth morphology or access problems, overhangs are predominantly iatrogenic. Poor cavity preparation, inappropriate matrix band selection, improper wedging, and excessive material placement can all lead to the formation of overhangs.
While both amalgam and composite restorations can be associated with ODRs, amalgam fillings tend to be more prone to marginal failure. In one study, overhanging margins in amalgam restorations had four times the prevalence of composite restorations. However, composites can also create overhanging margins if not placed carefully. Whether using amalgam or composite, dentists must be meticulous in their approach to avoid complications.
Prevention and treatment
Dentists must take care to place restorative material precisely, ensuring that it does not extend past the tooth’s natural contours. Choosing the correct matrix band is essential to achieving a properly contoured restoration. A well-adapted matrix ensures that the restorative material is contained within the preparation margins, preventing overhangs from forming.
Proper wedging stabilises the matrix band and helps to prevent excessive material from extruding beyond the preparation margins. This is especially important in class II restorations, where the contact point between adjacent teeth must be recreated accurately. Small overhangs can often be corrected or refined by smoothing out the margins of the restorative material. In cases where the overhang is severe or causing significant periodontal damage, the entire restoration may need to be removed and replaced.
Tools and techniques for effective treatment
In order to manage overhanging restorations, a high quality 1:1 handpiece will allow appropriate finishing and polishing without causing damage. The Synea Fusion handpiece from W&H offers an efficient, durable optic perfect for the job. If larger quantities of harder advanced ceramic materials, such as zirconia, require removal then you can benefit from specialised handpieces designed for the purpose such as the Synea Fusion Power Edition.
Taking into account the possible consequences of ODRs, dentists should take proactive steps to prevent their formation. Through careful restoration techniques, regular monitoring, and early intervention, it is possible to prevent or minimise the impact of overhanging restorations, protecting patients’ periodontal health.
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