Somatosensory Trigeminal Evoked Potential Amplitudes Following Low Level Laser and Sham Irradiation Over Time

Abstract

The effect on somatosensory trigeminal evoked potentials (STEP) and latencies by intraoral low level laser irradiation of the maxillary nerve was evaluated. After electrical input at the left infraorbital foramen on 24 experimentally blinded pain-free subjects, He-Ne laser irradiation (1.7mW, 632.5nm, 50Hz) was performed for two minutes on 12 of these subjects, and sham irradiation on the other 12, at the left maxillary third molar apical area. Far-field STEP latencies and amplitudes were recorded: at base-line, immediately after intervention, and ten and twenty minutes after intervention. In the irradiated group, an immediate (average) STEP amplitude decrease from base-line of 60 per cent occurred, with further reduction to 65 and 72 per cent, at the ten and twenty minute intervals (p > .0001). No significant change occurred in the sham irradiation group (p > .05), and no change in latencies occurred in either group (p > .997). Low level laser treatment is commonly used in musculoskeletal and neurologic conditions, with mixed results. This experiment demonstrates that intraoral laser application to the maxillary nerve, where covered only by mucous membrane, results in significantly reduced STEP amplitudes. This findings suggests that intraoral laser therapy may be an effective pain control treatment.

Inhibitory Effects of Laser Irradiation on Peripheral Mammalian Nerves and Relevance to Analgesic Effects: A Systematic Review

“…Nine studies 22,29,36,[39][40][41][42]44,45 used standardized protocols for assessment of electrophysiology. [46][47][48][49][50][51][52][53][54][55] Ten studies used maximal or supramaximal electrical stimuli, to ensure all axons were stimulated prior to LI and to establish consistent baseline responses for each participant.…”

“…[46][47][48][49][50][51][52][53][54][55] Ten studies used maximal or supramaximal electrical stimuli, to ensure all axons were stimulated prior to LI and to establish consistent baseline responses for each participant. 22,29,[33][34][35][36][37][38][39]42 CAP response to LI was recorded in six studies, [29][30][31]40,43,44 of which four studies recorded CV and CAP simultaneously. 29,40,43,44 Cambier used ''mild discomfort'' as the upper limit of intensity of electrical stimulation (ES).…”

“…Five studies reported recruitment of ''healthy'' or ''normal'' participants, 28,[30][31][32]44 and 12 studies excluded participants with underlying neurological problems. 22,29,[33][34][35][36][37][38][39][40][41][42] Both male and female participants were selected in seven studies; 22,29,[37][38][39][40][41] one study recruited only female subjects, 36 and another only males.…”

“…41,43 In three studies, LI was applied to a single point or area of skin overlying a nerve, specifically: the median nerve at the wrist or forearm; 40 one point on the skin of the palm, supplied by the median nerve; 32 and the apex of a tooth, supplied by the trigeminal nerve. 44 Electrophysiological responses were recorded for up to 30 min, 1-5 min intervals.…”

“…Eighteen human studies included a total of 630 participants, with the number in individual trials ranging from 9 to 90 22,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] (Table 1).…”