Detection of tooth coloured restorative materials based on their optical properties

Objectives: The availability of aesthetic restorative materials and novel techniques such as layering and the use of tints and opaque stains has led to restorations which raises the challenge of detecting them reliably. This in vitro study compared the diagnostic reliability and validity of digital imaging fiber-optic transillumination (DiFOTI – using DIAGNOcam) Figure 1, and fluorescence-aided identification of restorations (FAIR) Figure 2, with routine visual and tactile examination for identifying tooth-coloured restorations. For FAIR the approached used was illumination with 405 nm wavelength violet light, accompanied by viewing the sample through a long pass filter with a cutoff of 520 nm.
Methods: Extracted human permanent teeth were mounted in anatomical order in typodonts. Three sets of models were made for both maxillary and mandibular arches. Cavity preparations in selected teeth were then restored with tooth coloured resin composites, ceramics and hybrid restorative materials such as ormocers, Vita Enamic and resin reinforced glass-ionomer types of cement. The models were then mounted in a phantom head dental mannequin.
Four examiners identified and charted tooth coloured restorations using the three different methods. Each examiner repeated the charting after 4 weeks.
The average sensitivity and specificity for identifying tooth coloured restorations were determined for each method.
Results: Both the sensitivity (95%) and specificity (97%) of the FAIR method were significantly higher than those for DiFOTI (82% and 82%) and conventional inspection (71% and 82%), Figure 3. Likewise, the positive and negative likelihood ratios for the FAIR method (32.66 and 0.08) were superior to DiFOTI (4.84 and 0.2) and conventional inspection (4.81 and 0.41).
Conclusions: FAIR using violet light is superior to both conventional examination under white light and to DiFOTI using near infrared light for identifying tooth coloured restorations. This method is simple to perform and time-efficient, making it well suited to use in both clinical and forensic situations.