EX VIVO STUDY: ABSORPTION OF A 645nm DIODE LASER ON SWINE HARD TISSUES SAMPLES

Mesenchymal derived stem cells have emerged as a popular and versatile tool in the field of regenerative medicine and a growing interest has been shown for their use in tissues engineering during the last decades. Despite the fact that most of published articles highlight positive effects of LLLT on tissues, to the best of our knowledge, no studies have been conducted upon how deep the light beam is able to reach cells’ layers inside the irradiated tissue. The present preliminary ex vivo study aims to assess the possible interaction between complex biological systems and laser light, through irradiation of different hard tissue’s samples. A 645nm wavelength diode laser was adopted to perform the present evaluation (Raffaello, Dental Medical Technologies, DMT srl. Lissone -MB, Italy), allowing further comparison with the most used wavelength in published studies found in literature. Due to known similarities to human tissues, swine tissue samples were used. Samples were harvested 24 hours before the beginning of the experiment. Tissue samples were taken from a swine mandible preserved in 500 mL of Medium 199 with Earle’s salts plus sodium azide 0.05% at a temperature between 2° and 8°C. Chosen power output value was set as 220 mW, measurements were performed with a powermeter located underneath the irradiated tissue. Emission was performed perpendicularly to the power-meter at approximately 2 cm of distance. An actual power output of 168 mW was detected. Irradiation was performed for 113 seconds, no support system was used; the chosen laser tip measured 0.337 cm2 of area. Two samples of spongious bone of 4.45 mm and 2.9 mm of thickness, and two samples of cortical bone measuring 4.4 mm and 4.7 mm were used for as soft target tissues. Before performing the laser irradiation on swine tissues, irradiation was performed with and without plastic protection devices around the laser tip and surrounding the power meter. After 10 cycles of irradiation, data-log were converted into graphics: laser light was never completely absorbed by bone samples. For each sample values of mean absorption and standard deviation were calculated. Calculated values of mean absorption showed how higher thicknesses coincide with lower transmissions. No differences were highlighted between detected measurements when laser was used with or without plastic protection devices. Red-light laser with 645nm wavelength has the ability to reach cells in each layer of measured tissues. This ex vivo experiment conducted on soft swine tissues established with the use of a powermeter that every tissue layer was reached by the laser beam. Since thickness of swine samples are comparable to human tissues, protocols based on such laser features can allow to reach deeper targets and lead to possible interactions (photobiomodulation) of human cells. Also sterile and non-sterile devices can be used to isolate the laser tip from operative fields during procedures without interfering with delivered laser energy.