Not every shadow or stain should be drilled and filled. Seeing a radiographic shadow under a restoration can make you doubt your own skills, or judge another dentist’s – depending on if the shadow belongs to a returning or new patient. Recurrent decay is a fact of life to be accounted for, as we are limited by our materials and our patients. Here we review, based on the latest scientific findings, how we can prepare for and manage secondary caries.
Characteristics of recurrent decay
Location: Almost 90% of recurrent decay happens at the gingival margin of a previous restoration. Margins that end on cementum show a higher incidence of recurrent decay, as compared to those on enamel. This is due to the lower resistance of cementum and dentin to decay progression. Also, restorations ending on cementum are usually deeper and more challenging.
Patient- caries risk: Patients with a higher caries risk show a higher chance of presenting with recurrent decay. This factor can be further broken down to poorer oral hygiene, lower compliance and fewer dental visits associated with a higher caries risk patient.
Clinician skill: It has been shown in a longitudinal study that the dentist’s experience has a significant negative correlation to formation of secondary carries. This is logical as secondary caries has a lot to do with the quality of the restoration placed, and the seal created. Various studies have shown that a 60 to 100 μm margin gap is the threshold for secondary caries to form.
Patient age: Lower age is usually linked to lower oral hygiene compliance, and more challenges for the practitioner in placing high quality restorations.
Materials: No significant difference was found between different restorative materials and secondary caries formation. However, amalgam restorations show lower secondary caries in high caries risk patients. Composite restorations show lower secondary caries in more extensive restorations. Glass ionomers show the same secondary caries risk as composites, however are more prone to fractures.
Detection methods
We have a variety of tools for caries detection, ranging from tactile sensation to near-infrared light trans-illumination. A review of studies was conducted comparing visual detection, tactile sensation, radiographic detection (in combination with visual detection and alone), laser fluorescence and light-induced fluorescence.
Visual, radiographic and laser fluorescence detection method all showed similar sensitivities and specificities. A combination of these three methods showed the best results. Tactile detection had the lowest accuracy. Finally, near-infrared light trans-illumination showed promise, with accuracy similar to that of radiographic detection – but the number of studies done on its performance is limited.
Treatment
Once secondary caries is detected, we have two main options: complete replacement of the restoration or repair of the restoration.
Repair or Replace
Repairing only the failed portion of the previous restoration can be a time-effective and cost effective treatment option. This is especially true if the previous restoration is extensive. Repairing an extensive restoration (instead of replacing) saves sound tooth structure and shows similar long-term stability (compared to replacing).
However, if the secondary caries is associated with a fracture of the restoration, repairing shows a significant increase in failure of the new restoration. Therefore, in the case of fracture, it is recommended that the entire restoration be replaced.