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.