An in vitro evaluation of the effect of sealant characteristics on laser fluorescence for caries detection.

Purpose: The purposes of this study were to: (1) evaluate the ability of a laser fluorescence (LF) unit to detect simulated caries under pit and fissure sealants; (2) determine the effect of an opacifying agent in sealants on LF values; and (3) determine interexaminer reproducibility values of the unit in a highly controlled, laboratory setting. Sealant characteristics specifically considered were: (1) filler content; (2) opacity; and (3) intrinsic fluorescence.

Methods: Three sealants were used in this study: 2 unfilled and 1 filled. To evaluate the effect of an opacifying agent, titanium dioxide powder was added to both filled and unfilled sealants. 0.5-mm thick sealant discs were prepared for all samples. The sealant discs were individually placed on top of 3 wells filled with varying amounts of protoporphyrin IX, a fluorescent material that mimicked dental caries. A total of 270 readings were made through the different sealant discs to evaluate signal attenuation of the laser fluorescence unit.

Results: Clear sealants, without an added opacifying agent, attenuated LF readings. At baseline protoporphyrin IX levels yielding DIAGNOdent readouts of 20 and 60, there was a significant difference in the LF readings between the baseline protoporphyrin (uncovered) and with sealant disc covered in all 3 sealant types (P<.001). Furthermore, the filled sealant attenuated LF signals significantly more than the unfilled sealant (P<.001). Sealants with titanium dioxide added had variable levels of intrinsic fluorescence. Titanium dioxide added to the sealants also had a profound effect on fluorescence transmission of the underlying simulated caries. As the concentration of titanium dioxide approached 0.5%, the fluorescence signal was almost fully attenuated.

Conclusion: Clinical detection of caries under dental sealants with the use of laser fluorescence units is unreliable and not recommended due to a high likelihood of inaccurate readings caused by: (1) intrinsic fluorescence of sealant material; and (2) attenuation of fluorescence signals by the sealant.