Method: 24 human-dentin-blocks, 4.0x4.0x0.4mm, were worn with 600-grain-abrasive-paper and treated with the following dyes: 10 μL of Methylene Blue (MB), Toluidine Blue-O (TBO) or Malachite Green (MG), at 0.1mg/mL and 0.01mg/mL concentrations for 1, 5 or 30-minutes. All blocks were submitted to PAS to quantify dentin-permeability. Readouts were taken of occlusal and pulp surfaces of each sample before PS application as control for comparison of spectra later obtained. Complementary evaluations were performed by electron scanning microscopy and optical microscopy.
Result: The PAS data showed that the 3 PS presented similar penetration behavior in 5 and 30-min periods, with value for TMB 0.1mg/mL for 5min being the highest (0.240 mm) and MG 0.1mg/mL for 5min was the lowest (0.180mm). For 1min-period the three PS at 0.1mg/mL had similar and lower permeation (0.150 mm). For 0.01mg/mL, there was no detection of penetration in 5min. Using the PAS experimental data, it was possible to propose a semi-quantitative-model predicting the penetration depth profile, along the dentin thickness, of both PS concentration and light intensity. The model provided guidelines for appropriate choice of PS concentration and light intensity to be used in PDT clinical protocols.
Conclusion: MB, TBO and MG showed properties of penetration into human dentin which may enable their use in PDT for dental caries treatment. No chemical bonds between PS and dentin were found.