## 5 Discussion
From Table 1, many biochemical mediators have been shown to be influenced through applied PBM therapy; although several areas of activity may be a consequence of an inflammatory response as a precursor to tissue repair, the influences of PBM may be judged as wide ranging. The choice of three areas of treatment allows some analysis of the applied light doses to be conducted relative to the surgical site. Indeed, as has been researched extensively, the inherent Gaussian distribution of the majority of photonic emission beams, together with the anisotropic nature of oral and dental soft and hard tissue, has considerable effect on the potential attenuation of the surface applied dose, resulting in variable degrees of beam scattering, non-target absorption at depth and a consequently reduced fluence at sub-surface surgical sites [10; 17]. The clinical objectives of biostimulation and/or pain mitigation relative to the three anatomically heterogenous treatment areas pose consequently differing dose delivery challenges to the clinician. Key to effective PBM at depth is the employment of an optimal surface fluence in order to accommodate the beam density reduction as it passes through tissue layers. The influence of varying (non-PBM) treatment protocols, such as surgical access preferences or (orthodontic) appliance therapy, has been demonstrated to have influence on the outcomes [84; 85; 86; 87; 88; 89; 90]. Across the three groups, the variation in clinical outcome, as a measure of the effective PBM application, however, appears to be related to the laser operating parameters. This may be related to and draws upon the inherent nature of the laser being used (wavelength, emission mode, delivery mechanism, output power range). Consequent to this, operator-applied permutations of an overall light dose ('spot' size, fluence, irradiation, average power) together with the dose regimen (frequency of application, repetition, total energy) may significantly influence the therapeutic benefits offered by PBM. A third area of influence may be seen in terms of the nature of the clinical condition (pathology, wound trauma, otherwise 'normal' tissue modulation), along with the anatomical site in terms of a possible three-dimensional irradiation, and the effects of photon absorption and scattering. However, with the exception of outcomes relating to oral surgical molar removal, no statistical significance was found. The influences of variable elements may be considered as follows [91]:  
_Group structure--test/control/placebo_: Many positive outcomes were reported in the included studies, albeit with little statistical significance. Within the orthodontic movement group, the majority of studies utilised a split-mouth design as a control; within the TMJ group, an element of significance related to the influence of a placebo photonic delivery. Hence, it appears that within third molar oral surgery studies, adjunctive PBM effects were measured against a pure surgical treatment, albeit with some variation in the applied light dose and intra-oral verses extra-oral differences. _Wavelength/emission mode_: Across all groups, there appears no significance. Even allowing for the extensive emergence of PBM and PBM-type effects with short visible wavelengths, as well as mid- and far-IR, the choice of predominantly visible diode red and NIR wavelengths constitutes a logical choice. However, in view of the wide variation in applied fluences relative to tissue type and surgical site, there has been no opportunity to analyse differences in outcomes across the wavelength range chosen. _Power meter:_ According to recent primary research [92], the significant variation in the optic fibre delivery fluence arising from impurities may exert considerable influence. That only very few (in number) of the studies analysed cited the use of a power meter or calibration must be seen as a source of error in the results and outcomes of such studies.