A filling can look perfectly ordinary while decay is forming at its edge. This study asks whether a three-dimensional dental scan can help find that hidden trouble—without replacing the dentist’s judgment. Decay around an existing restoration is one of the main reasons a restoration is repaired or replaced, regardless of the material used.

These lesions develop around an existing restoration when marginal failures allow bacteria to penetrate and initiate demineralization of the tooth structure. If they go unnoticed and remain untreated, these lesions may progress over time and lead to further damage of the tooth structure.

These close-up scans capture how restored back teeth can look very different from one another, from smooth, tooth-coloured surfaces to darkened or visibly worn areas. That variety is why judging disease around a restoration from images alone is not straightforward.

Finding decay around a restoration is difficult because the restoration itself can hide what is happening at its edge. The usual approach combines a hands-on examination with an x-ray. The hands-on examination checks visible surfaces, while an x-ray can show decay between teeth, how deep it is, and how close it is to the tooth’s nerve.

The study tested whether a three-dimensional intraoral scanner could detect decay around restorations, using image-based severity categories and comparing its results with a visual-tactile clinical examination. The expectation was that the scans might perform about as well as a hands-on examination, while their performance could change depending on how severe the decay was.

The scanner used ordinary white light to create three-dimensional models that matched the natural color of the teeth, with the teeth kept moist during scanning. A scan counted as adequate when the software captured enough detail of the teeth being examined.

The participants were adults between eighteen and sixty years old; in total, the sample included thirty-four women and seven men. The restorations included both front and back teeth, with forty-six located in anterior teeth and two hundred fifty-three in posterior teeth.

Most of the restorations examined were in back teeth, rather than front teeth. The scan found seventy-five percent of the earliest lesions, but only forty percent of moderate lesions and fifty-seven point one percent of severe lesions.

Its ability to correctly identify restorations without lesions stayed high: eighty-four point one percent for the earliest threshold, ninety-seven point four percent for moderate lesions, and ninety-nine point seven percent for severe lesions. Overall, the scan performed better when the earliest and severe lesion thresholds were considered.

Its ability to rule out lesions stayed high across severity levels, while its positive predictive value was highest for severe lesions. Because severe lesions often lead to repair or replacement, the scan may be useful as an extra way to assess restored teeth, alongside clinical judgment and, when needed, an x-ray.

The scan was good at ruling out serious decay around restorations, but less reliable for catching every lesion, especially moderate ones. It is best used as an extra view alongside examination and, when needed, radiography.