Although it has been reported that low level laser irradiation (LLLI) appears to stimulate bone formation, little is known in detail about its possible role in osteoblast function. The present study examines the effect of LLLI on the function of rat calvarial osteoblast cells (ROB) and rat osteoblast cell lines (ROS 17/2.8) in terms of cell proliferation, alkaline phosphatase (ALP) activity, and calcified nodule formation. To determine the effects of LLLI on the osteoblast cell function, the ROB and ROS 17/2.8 cells were cultured and were treated with LLLI. An unirradiated group served as the control. LLLI irradiated cells demonstrated a slight increase in proliferation and slight decrease in the number of dead cells compared with the control,, but the differences were not statistically significant. LLLI increased the ALP activity in culture of ROBs and ROS 17/2.8 cells with a statistically significant difference (ANOVA and multiple comparison tests) compared with the unirradiated controls (p ‹ 0.0001 in both groups). LLLI irradiated cells also showed a statistically significantly greater increase in bone nodule formation for both ROBs (p = 0.0421) and ROS 17/28 cells (p = 0.0119) using an unpaired t-test. These results offer the possibility that LLLI could promote osteoblast-modulated bone formation by stimulating osteoblast function in addition to bone mineralization.

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In the last decade the applications of the laser in surgery and medicine have increased dramatically. With the increase of indications has come a concomitant increase in possible classification of laser reactions. The author presents a classification which is based on the laser/tissue reaction rather than on the hardware used to produce the laser beam. Laser/tissue reactions fall into two broad groups. When the tissue reaction to absorption of the incident laser energy results in photodestruction of, or an irreversible photomodulated change to the tissue architecture, then the level of reaction is higher than the survival threshold of the target cells. The author refers to this as high reactive-level laser treatment (HLLT), or more generally as laser surgery. On the other hand, the level of tissue reactivity to very low incident power and energy densities is well below the cells' survival threshold so that instead of being damaged the cells are directly activated by the low incident photon density. In this case the changes in the irradiated tissue are photoactivative and reversible: the author refers to this group of reactions as low reactive-level laser therapy (LLLT), or more generally as laser therapy. Both of these groups can be classed under the general heading of laser treatment (LT). LT is further subdivided into three main types: mono-type LT (Mo-LT, single laser treatment; multi-type LT (Mu-LT, multi-laser treatment); and concomitant LT (Cc-LT), in which any of the above LT types can be used in combination with conventional treatment methods. Mo-LT in turn contains pure LT (Pu-LT) single laser, single reaction; and auto-simultaneous LT (ASi-LT), single laser with a range of reaction types, each of which has its own abbreviation. Mu-LT contains two main sub-types, combined LT (Cb-LT) and compound LT (Cp-LT). Cb-LT concerns the same disease whereas Cp-LT is used to describe 2 or more diseases treated with the same or different lasers. Both Cb-LT and Cp-LT are further subclassified into the homogeneous and xenogeneous types, referring to the use of the same or different types of laser, respectively. If the lasers are applied at the same time, that is homo- or xeno-simultaneous laser treatment (HoSi-LT, XoSi-LT), and if at different times the term is homo- or xeno-succesive laser treatment (HoSu-LT, XeSu-LT). The various sub-sets of Mono-type and Multi-type laser treatment are further expanded, to give an accurate, treatment-based categorization of laser treatment. In addition to the above classification, the author has devised a graphical representation of laser surgical and therapeutic beams whereby the laser type, parameters, penetration depth, and tissue reaction can all be shown in a single illustration, which the author has termed the ‘Laser Apple’, due to the typical pattern generated when a laser beam is incident on tissue. Apple types fall into two main subdivisions, destructive or D-Apples (HLLT) which include the C-Apple (carbonization), V-Apple (vaporization) and so on, and the activative or A-Apple type (LLLT). When the above classification is combined and illustrated with the appropriate laser apple type or types, the author feels this offers an accurate and simple method of classifying laser/tissue reactions by the reaction, rather than by the laser used to produce the reaction.

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A laser speckle flowmetry technique has been developed to enable visualization of the distribution of skin blood flow and has been used to measure the microcirculation in various angiopathies as well as to monitor blood flow changes and other haemodynamics in skin flaps. The principal author's institute has recently acquired such a laser speckle flowmetry system. The present preliminary study was designed to test the efficacy of the gallium aluminium arsenide (GaAlAs) diode laser on flap survival in the rat model using laser speckle flowmetry. Caudal-based random pattern flaps were raised on the back of two groups of Wistar rats, 10 rats in each group. The first group served as the control and underwent sham irradiation, otherwise they were handled in exactly the same way as the second group. The blood flow in all flaps was measured with laser blood flowmetry using the laser speckle method. Blood flow was measured in the flaps of the experimental animals and the unirradiated controls preirradiation, and the flaps were sutured back in place. The experimental group received laser irradiation from a GaAlAs diode laser (60 mW, 830 nm, continuous wave) for one minute on a point at the centre of the flap base (energy density ≅ 36 J/cm²). Laser speckle flowmetry was then performed on all animals immediately postirradiation and 30 minutes postirradiation. The following points were noted. There was no significant change in the flow rate of the flaps in the unirradiated animals. Immediately following the one minute irradiation in the experimental animals a decrease in the blood flow rate was seen compared with the unirradiated controls, but at 30 minutes postirradiation the blood flow rate in the flaps increased in the irradiated animals compared with controls. Five days postirradiation the survival area of the diode laser irradiated flaps was greater than the control flaps (≅1.12 : 1). It was concluded that GaAlAs diode LLLT increased early perfusion of the experimental flaps, thereby possibly accelerating early stage wound repair while at the same time controlling the inflammatory response, thus giving the irradiated flaps a better and earlier ‘take’.

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Neurogenic facial pain has been one of the more difficult conditions to treat, but the introduction of laser therapy now permits a residual group of patients hitherto untreatable to achieve a life free from or with less pain. The present investigation was designed as a double-blind, placebo controlled study to determine whether low reactive-level laser therapy (LLLT) is effective for the treatment of trigeminal neuralgia. Two groups of patients (14 and 16) were treated with two probes. Neither the patients nor the dental surgeon were aware of which was the laser probe until the investigation had been completed. Each patient was treated weekly for five weeks. The results demonstrate that of 16 patients treated with the laser probe, 10 were free from pain after completing treatment and 2 had noticeably less pain, while in 4 there was little or no change. After a one year follow-up, 6 patients were still entirely free from pain. In the group treated with the placebo system, i.e. the non-laser probe, one was free from pain, 4 had less pain, and the remaining 9 patients had little or no recovery. After one year only one patient was still completely free from pain. The use of analgesics was recorded and the figures confirmed the fact that LLLT is effective in the treatment of trigeminal neuralgia. It is concluded that the present study clearly shows that LLLT treatment, given as described, is an effective method and an excellent supplement to conventional therapies used in the treatment of trigeminal neuralgia.

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