In vitro evaluation of the oxidation efficacy of transgingival photodynamic therapy

OBJECTIVE: To evaluate the capability of soft laser light to penetrate blood, serum, gingival connective tissue and pure collagen type I. MATERIALS AND METHODS: A 1:1 mixture of methylene blue (MB) and diphenylisobenzofuran (DPBF) was irradiated for 60 s with a diode laser (670 nm, 0.3 W) through blood, serum, gingival connective tissue and collagen type I (2 mm transillumination thickness). The oxidation of DPBF by MB was determined spectrophotometrically by measuring the optical density (oD) at 410 nm. The absorption spectra of DPBF/MB irradiated through MB (1%) and strawberry red solution (3%) served as control. RESULTS: The mean oD of non-irradiated DPBF/MB was 1.98 ± 0.04. Irradiation through MB showed no oxidation of DPBF (1.98 ± 0.02; p > 0.05), while interposition of strawberry red and serum resulted in almost complete oxidation of DPBF (0.13 ± 0.09, 0.06 ± 0.03; p ≤ 0.0001). Irradiation through gingiva and collagen reduced the oxidation of DPBF significantly (1.0 ± 0.04, 0.7 ± 0.04; p ≤ 0.0001), accounting for 50% to 35% of the non-irradiated DPBF/MB solution. CONCLUSION: Red light from a diode laser can penetrate blood and gingival tissues. However, light absorption for collagen and connective tissue can hamper the oxidation process

Influence of light-curing mode on the cytotoxicity of resin-based surface sealants

Background Surface sealants have been successfully used in the prevention of erosive tooth wear. However, when multiple tooth surfaces should be sealed, the light-curing procedure is very time-consuming. Therefore, the aim of this study was to investigate whether reduced light-curing time (while maintaining similar energy density) has an influence on resin-based surface sealant cytotoxicity. Methods Bovine dentine discs were treated as follows: group 1: untreated, groups 2–5: Seal&Protect and groups 6–9: experimental sealer. Groups 2 and 6 were light-cured (VALO LED light-curing device) for 40 s (1000 mW/cm2), groups 3 and 7 for 10 s (1000 mW/cm2), groups 4 and 8 for 7 s (1400 mW/cm2) and groups 5 and 9 for 3 s (3200 mW/cm2). Later, materials were extracted in culture medium for 24 h, and released lactate dehydrogenase (LDH) activity as a measure of cytotoxicity was determined photometrically after cells (dental pulp cells and gingival fibroblasts) were exposed to the extracts for 24 h. Three independent experiments, for both sample preparation and cytotoxicity testing, were performed. Results Overall, lowest cytotoxicity was observed for the unsealed control group. No significant influence of light-curing settings on the cytotoxicity was observed (p = 0.537 and 0.838 for pulp cells and gingival fibroblasts, respectively). No significant difference in the cytotoxicity of the two sealants was observed after light-curing with same light-curing settings (group 2 vs. 6, 3 vs. 7, 4 vs. 8 and 5 vs. 9: p > 0.05, respectively). Conclusions Shortening the light-curing time, while maintaining constant energy density, resulted in no higher cytotoxicity of the investigated sealants