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ePaper created 2017-04-20, 12:10:03 | version 1.38.0
laser_industry Fig. 13: Fracture of an implant and missing teeth from 12 to 22. Figs. 14–17: A regenerative procedure with bone substitute. Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 laser 34 3+4_2016 34 within a tissue mass, in a uniform and predictable manner, has been lacking. Several problems complicate the adoption of a standardised protocol. While the biostimulatory ef- fect of laser energy is experienced on a cellular level, the energy is applied macroscopically to large vol- umes of tissue in a non-uniform manner. As energy passes through tissue, part of it is absorbed so each successive depth of cells is irradiated differently. Beers law is usually used to define this relationship. However, this is inadequate since the dominant form of interaction at wavelengths between 600 nm and 1,400 nm is scattering.22 Thus, as energy enters tissue, its density decreases rapidly. The output of most clinical lasers is Gaussian in spa- tial profile. Therefore, cells directly in the centre of the beam are irradiated at a very high fluence, while those on the periphery of the incident beam receive a very low dose. As a result, cells at the beam centre may be overstimulated far above the scientifically recom- mended range of 3–10 J/cm2 and inhibited while those on the periphery receive insufficient cellular energy to produce any effect. Further complicating standardisation is the issue of beam divergence. Fibre-delivered laser energy exits the fibre with a significant divergence, usually on the order of 8 degrees. The applied energy is, therefore, distributed over an increasing area as the tip-to- tissue distance increases, dramatically affecting en- ergy density at the cellular level. At currently reported beam divergences, energy density can be diminished by 90 per cent with only 3 millimetres of tip-to-tissue distance. This makes the repeatable application of an appropriate energy density extremely technique- sensitive and operator-sensitive. As a result of these problems, a handpiece was de- veloped that provides homogeneous irradiation over a 1 cm2 surface with a constant irradiation area (spot size) irrespective of the tip-to-tissue distance (from 10 to 100 mm) from the target tissue. With the intro- duction of this new flat-top handpiece,14 it is now pos- sible to irradiate a target surface with a homogenous energy density, using relatively high-power densities, in less time and without risk of significant thermal damage. This would make the application repeatable and not operator-sensitive,14, 23 a significant step for- ward in standardisation of treatment parameters. The aim of this study is to present, through a series of clinical cases, a preliminary report on the dental and medical applications of a new flat-top handpiece used in conjunction with an Nd:YAG laser according to the therapeutic protocols described in Benedicen- ti’s textbook.24