Laser fluorescence measurements of residual dentin in excavated cavities

Objective: It has been suggested that laser fluorescence close to the dental pulp shows different values than more distant measurements. The aim of the present study was to compare fluorescence assessed with a device for fluorescence aided caries excavation (FACE) on the cavity floor of medium and deep depth dentin cavities after conventional caries excavation.

Method: 41 carious lesions (22 front teeth, 19 premolars/molars) were excavated with a bur in vivo. The endpoint of caries removal was determined by visual, tactile and auditory means. After excavation, 19 cavities were classified as deep, 22 as medium depth cavities. Fluorescence was induced employing a FACE device with an irradiation wavelength of 405 nm. Cavities were observed through a 515-nm high-pass filter.  

Result: Comparing conventionally excavated medium and deep depth cavities, a statistically significant difference in fluorescence could be observed (p<0.05). Medium depth cavities showed a predominantly green fluorescence. In contrast, all deep depth cavities showed distinct brownish/greyish appearing areas.

Conclusion: Green fluorescence of an excavated medium depth carious lesion can be used as criterion for complete caries excavation. However, using the same criterion for FACE guided caries removal of deep caries lesions might possibly lead to over-excavation into sound hard tissues.