Human dental pulp cells (DPCs) were isolated and cultured in phenol-red-free α-MEM/10%-FCS at 37ºC in 5% CO₂. DPCs at passages 2-4 were seeded (150μL; 25,000 cell/ml) in black 96-microwell plates with transparent bases. 24h post-seeding, cultures were irradiated using a bespoke LED array consisting of 60 LEDs (3.5mW/cm²) of wavelengths from 400-900nm (10 wavelengths, n=6) for time intervals of up to 120s. Metabolic and mitochondrial activity was assessed via a modified MTT assay. Statistical differences were identified using multi-factorial analysis of variance and post-hoc Tukey tests (P=0.05). The biological responses were significantly dependent upon post-irradiation incubation period, wavelength and exposure time (P<0.05). At shorter wavelength irradiances (400nm), a reduction in mitochondrial activity was detected although not significant, whereas longer wavelength irradiances (at 633, 656, 781 and 799nm) significantly increased mitochondrial activity (P<0.05) in DPCs. At these wavelengths, mitochondrial activity was generally increased for exposures less than 90s with 30s exposures being most effective with 24h incubation. Increasing the post-irradiation incubation period increased the measured response and identified further significance (P<0.05). The biological responses of human DPCs were wavelength, exposure-time and incubation period dependent. The optimisation of irradiation parameters will be key to the successful application of LLLT in dentistry.

Date Published: 5 March 2015
PDF: 13 pages
Proc. SPIE 9309, Mechanisms for Low-Light Therapy X, 930906 (5 March 2015); doi: 10.1117/12.2077645

Published in SPIE Proceedings Vol. 9309:
Mechanisms for Low-Light Therapy X
Michael R. Hamblin; James D. Carroll; Praveen Arany, Editor(s)