An Investigation of Yellow Fluorescent Lines Observed in Human Dentinal Hard Tissues

Abstract

Orally administered tetracycline antibiotics have been known to deposit in mineralized tissues. Tetracycline is readily identified as yellow bands under light microscopy and as fluorescent lines in bone or dentin under the ultraviolet light of fluorescent microscopy. In addition, inhibition by tetracycline of hard tissues formation and calcification has also been demonstrated.
In observations of ground sections of human deciduous teeth in the present study, numerous yellow lines that were deposited along the incremental lines of dentin were detected. All teeth examined were free of remarkable dental caries, dental structural defects, or macroscopic discoloration.
The frequency of appearance of yellow fluorescent lines in the deciduous teeth in the present study was only 27% under light microscopic observation, but was as high as 52% in the deciduous incisors,62% in the deciduous canines, and 66% in the deciduous molars (an average of 61%), when examined under fluorescent microscopy, indicating a significantly higher frequency of tetracycline deposition than originally evident under light microscopy.
In the present study, in order to clarify nature of the yellow line within the dentin, absorption spectra were measured using a microspectrophotometer in order to measure the characteristics of the wave-length of absorbency. The wave-length characteristics of absorbency of the material deposited in the dentin were found to be identical with those of the tetracycline antibiotics (Vibramycin syrup). The former demonstrated a peak at 260-280 nm, whereas the latter peaked at 370-390 nm. Accordingly, the evidence strongly suggests that the yellow fluorescent lines identified in human dentin in the present study were due to tetracycline.
Moreover, the relationship between the fluorescent and incremental lines largely reflects the observation that tetracycline deposition appears most distinctly in the dentin. When tetracycline is incorporated into the developing dentin, a yellow fluorescent deposition line appears not only in the dentin, but also in the dentin-predentin junction. From an embryological viewpoint, the fluorescent line coincides with the fluorescent line in the enamel as well as the fluorescent line within the cementum at the junction.
These findings illustrate the synchronicity between periodic calcification and tetracycline deposition.
These findings were based primarily upon studies of deciduous teeth, similar finding have been obtained for permanent teeth (upper first premolar and lower third molars).