Feasibility Study of Laser Photosensitization Treatment of Infected Dentin Tissue

Objectives: There is not yet a recognized method of confirming the presence or absence of bacteria in dentin tissue retained to avoid pulpal exposure during dental restoration. It is therefore appropriate to develop a method to ensure the sterility of the tissue prior to restoration. We utilized laser irradiation (543 nm) applied for 60 seconds as a photosensitizer to Tolonium Chloride (TC) dye (0.191 and 5 mg/ml) to explore the possibility of inhibiting the growth of Lactobacilli acidophilus(LA). Methods: Caries-like lesions were produced on dentin of 35 human teeth using acidified gel. Following sterilization, the teeth were assigned to seven experimental groups of 5 teeth as follows. (A) Sterile, (B) Infected with LA only (C) Infected/TC treatment (0.191mg/ml), (D) Infected/TC treatment (5 mg/ml), (E) Infected/laser treatment, (F) Infected/laser/ TC treatment (0.191mg/ml), and (G) Infected/laser/ TC treatment (5 mg/ml). After treatment, a biopsy of dentin tissue was taken from each lesion and incubated anaerobically in MRS broth at 37^oC and 5% CO₂ for 48 hours. Bacteria growth was measured by a count of colony forming unit per milliliter (cfu/ml) following plating and incubation in B12 culture agar under the same condition as above. Results: No growth was observed in groups A, D and G. Duncan’s multiple comparisons (n=5, a=0.05) indicated significant (p<0.001) growth inhibition in groups C (90%) and F (97%) when compared with B (positive control). No significant effect was observed with only laser treatment. Conclusions: We conclude that Tolonium Chloride alone at concentration currently used for cancer detection (5 mg/ml) or at low concentration in combination with low power laser beam, applied to infected dentin inhibited the growth of cariogenic bacteria, thus highlighting its potential usefulness for treatment of this tissue prior to dental restoration. Supported by CO*STAR, NIDCR Training Grant DE 14318.