Oral tissues are exposed to optical radiation during e.g. dental treatments. Therefore, it is of interest to investigate if optically induced tissue changes occur. In this pilot study, optical spectroscopy was used to non-invasively monitor oedema after optical exposure. Pigmented rats (Long-Evans) were exposed to blue light or UV on three oral mucosal sites and four abdominal skin sites for control. Blue light treatment was performed with a dental halogen polymerisation lamp (380-515 nm; λpeak: 494 nm) with irradiance 566 mW/cm2 for 40 s per site (radiant exposure: 23 J/cm2). UV-treatment was performed with a sunbed fluorescent tube with CIE-weighted irradiance of 0.05 mW/cm2 (unweighted irradiance 16 mW/cm2) for approx. 500 s (weighted radiant exposure: 25 mJ/cm2; 2.5 SED). Spectral reflectance was assessed by near-infrared reflection spectroscopy at water absorption peaks: 971, 980, 1200 and 1451 nm. The values obtained were used to evaluate changes in reflectance immediately after exposure and one day later. All changes were calculated relative to baseline values measured immediately before treatment. Preliminary results showed that reflectance decreased immediately after UV exposure of skin and mucosa followed by an increase during the next 24 h. Blue light did not cause any reflectance changes in the skin. However, reflectance obtained from the oral mucosa increased during 24 h. These results indicate that oral mucosa may be more sensitive than skin to blue light.

Effects of UV radiation and visible light on oral mucosa characterised by reflection spectroscopy.
Randeberg LL, Dahl JE, Bruzell EM.
13th Congress of the European Society for Photobiology, Wroclaw, Poland, September 5/10, 2009