Systemic effects of low-power laser irradiation on the peripheral and central nervous system, cutaneous wounds, and burns

In this paper, we direct attention to the systemic effect of low-power helium-neon (HeNe) laser irradiation on the recovery of the injured peripheral and central nervous system, as well as healing of cutaneous wounds and burns. Laser irradiation on only the right side in bilaterally inflicted cutaneous wounds enhanced recovery in both sides compared to the nonirradiated control group (P less than .01). Similar results were obtained in bilateral burns: irradiating one of the burned sites also caused accelerated healing in the nonirradiated site (P less than .01). However, in the nonirradiated control group, all rats suffered advanced necrosis of the feet and bilateral gangrene. Low-power HeNe laser irradiation applied to a crushed injured sciatic nerve in the right leg in a bilaterally inflicted crush injury, significantly increased the compound action potential in the left nonirradiated leg as well. The statistical analysis shows a highly significant difference between the laser-treated group and the control nonirradiated group (P less than .001). Finally, the systemic effect was found in the spinal cord segments corresponding to the crushed sciatic nerves. The bilateral retrograde degeneration of the motor neurons of the spinal cord expected after the bilateral crush injury of the peripheral nerves was greatly reduced in the laser treated group. The systemic effects reported here are relevant in terms of the clinical application of low-power laser irradiation as well as for basic research into the possible mechanisms involved.     

Low-power laser biostimulation enhances nerve repair after end-to-side neurorrhaphy: a double-blind randomized study in the rat median nerve model

Previous studies have shown that low-power laser biostimulation (lasertherapy) promotes posttraumatic nerve regeneration. The objective of the present study was to investigate the effects of postoperative lasertherapy on nerve regeneration after end-to-side neurorrhaphy, an innovative technique for peripheral nerve repair. After complete transection, the left median nerve was repaired by end-to-side neurorrhaphy on the ulnar donor nerve. The animals were then divided into four groups: one placebo group, and three laser-treated groups that received lasertherapy three times a week for 3 weeks starting from postoperative day 1. Three different types of laser emission were used: continuous (808 nm), pulsed (905 nm), and a combination of the two. Functional testing was carried out every 2 weeks after surgery by means of the grasping test. At the time of withdrawal 16 weeks postoperatively, muscle mass recovery was assessed by weighing the muscles innervated by the median nerve. Finally, the repaired nerves were withdrawn, embedded in resin and analyzed by light and electron microscopy. Results showed that laser biostimulation induces: (1) a statistically significant faster recovery of the lesioned function; (2) a statistically significant faster recovery of muscle mass; (3) a statistically significant faster myelination of the regenerated nerve fibers. From comparison of the three different types of laser emissions, it turned out that the best functional outcome was obtained by means of pulsed-continuous-combined laser biostimulation. Taken together, the results of the present study confirm previous experimental data on the effectiveness of lasertherapy for the promotion of peripheral nerve regeneration and suggest that early postoperative lasertherapy should be considered as a very promising physiotherapeutic tool for rehabilitation after end-to-side neurorrhaphy.     

Effect of low-power pulsed laser on peripheral nerve regeneration in rats

The purpose of this study was to determine whether low-power pulsed laser irradiation could affect the regeneration of a 10-mm gap of rat sciatic nerve created between the proximal and distal nerve stumps, which were sutured into silicone rubber tubes. After 8 weeks of recovery, pulsed laser-irradiated groups at frequencies of 5 kHz and 20 kHz both had significantly lower success percentages of regeneration (50% and 44%, respectively) compared to sham-irradiated controls (100%). In addition, qualitative and quantitative histology of the regenerated nerves revealed a less mature ultrastructural organization with a smaller cross-sectional area and a lower number of myelinated axons in both pulsed laser-irradiated groups than in controls. These results suggest that pulsed laser irradiation could elicit suppressing effects on regenerating nerves.     

Double-blind randomized study evaluating regeneration of the rat transected sciatic nerve after suturing and postoperative low-power laser treatment

This double-blind randomized study evaluated the therapeutic effect of low-power laser irradiation (LPLI) on peripheral nerve regeneration, after complete transection and direct anastomosis of the rat sciatic nerve. After this procedure, 13 of 24 rats received postoperative LPLI, with a wavelength of 780 nm laser, applied transcutaneously, 30 min daily for 21 consecutive days, to corresponding segments of the spinal cord and to the injured sciatic nerve. Positive somatosensory evoked responses were found in 69.2 percent of the irradiated rats (p = 0.019), compared to 18.2 percent of the non-irradiated rats. Immunohistochemical staining in the laser-treated group showed an increased total number of axons (p = 0.026), and better quality of the regeneration process, due to an increased number of large-diameter axons (p = 0.021), compared to the non-irradiated control group. The study suggests that postoperative LPLI enhances the regenerative processes of peripheral nerves after complete transection and anastomosis.     

毫米波对周围神经部分损伤后神经修复的影响

目的探讨毫米波对周围神经部分损伤后神经修复的影响.方法SD雄性大鼠48只,制成左侧坐骨神经钳夹伤模型,随机分为治疗组和对照组.治疗组在神经损伤24 h后,将毫米波辐射损伤部位,每周5次,每次30 min.观察指标：从运动功能、电生理、组织学等方面观察其对大鼠坐骨神经部分损伤后神经修复的影响.结果治疗组在术后2、4、6周中运动神经传导速度均高于对照组,运动功能恢复时间明显短于对照组,有髓神经纤维横截面积均大于对照组.电镜观察,对照组在术后2周的神经变性程度比治疗组严重,治疗组在术后4、6周的神经再生数目和成熟度均优于对照组.结论毫米波能够促进周围神经损伤的修复和功能恢复.     

Effects of laser irradiation on the spinal cord for the regeneration of crushed peripheral nerve in rats

BACKGROUND AND OBJECTIVE: The purpose of the present study was to examine the recovery of the crushed sciatic nerve of rats after low-power laser irradiation applied to the corresponding segments of the spinal cord. STUDY DESIGN/MATERIALS AND METHODS: After a crush injury to the sciatic nerve in rats, low-power laser irradiation was applied transcutaneously to corresponding segments of the spinal cord immediately after closing the wound by using 16 mW, 632 nm He-Ne laser. The laser treatment was repeated 30 minutes daily for 21 consecutive days. RESULTS: The electrophysiologic activity of the injured nerves (compound muscle action potentials--CMAPs) was found to be approximately 90% of the normal precrush value and remained so for up to a long period of time. In the control nonirradiated group, electrophysiologic activity dropped to 20% of the normal precrush value at day 21 and showed the first signs of slow recovery 30 days after surgery. The two groups were found to be significantly different during follow-up period (P < 0.001). CONCLUSION: This study suggests that low-power laser irradiation applied directly to the spinal cord can improve recovery of the corresponding insured peripheral nerve.     

Effects of 830 nm continuous wave laser diode irradiation on median nerve function in normal subjects

The presence, magnitude, and nature of the effect that low intensity laser irradiation has on nerve function, growth, and repair constitute a contentious area of research. We have addressed one aspect of this controversy by systematically examining the influence of 830 nm laser radiation on median nerve function. In particular, we investigated median nerve motor and sensory distal latencies, action potential amplitudes, action potential areas, and conduction velocities as well as dorsal hand skin temperatures in 33 normal subjects in a double-blinded, randomized controlled study. All subjects received identical treatment: 30 seconds of “irradiation” at 10 points over the course of the right median nerve (five sites on the forearm and five sites distal to the wrist crease) with either an active (1.2 J/point) or inactive (0 J/point) 40 mW 830 nm continuous wave IR laser diode. Latencies, conduction velocities, amplitudes, areas, and skin temperatures were collected bilaterally at a baseline immediately prior to irradiation and at intervals of 1, 5, 10, 15, 20, and 30 minutes following treatment. Analysis of the results reveals that motor and sensory distal latencies were decreased in the treated limbs of the lasertreated group relative to the control group by 3–4% (P <.016 and.046, respectively, rank sum test). No significant differences in these quantities were found between the limbs within either group. Similarly, no alterations of action potential amplitudes, action potential areas, forearm conduction velocities, or skin temperatures were detected within or between the groups. Thus on the basis of this experiment, percutaneous 830 nm continuous wave laser irradiation can affect median nerve function, but the effects are quite limited and appear to be limited to the distal portion of the nerve. © 1993 Wiley-Liss, Inc.     

Response of peripheral nerve to He-Ne laser: experimental studies

Low-energy He-Ne laser irradiation (LELI) was found to affect the electric activity and morphology in both intact and severely injured peripheral nerves in rats. Action potential (AP) in the healthy nerve increased by 33% following a single transcutaneous irradiation. Similar irradiation in crushed nerves caused AP to increase significantly over the AP of nonirradiated crushed nerve. Morphological observations revealed that a laser-irradiated injured nerve had diminished scar tissue as compared to an injured but not an irradiated nerve.     

Comparative effects of wavelengths of low-power laser in regeneration of sciatic nerve in rats following crushing lesion

Peripheral nerves are structures that, when damaged, can result in significant motor and sensory disabilities. Several studies have used therapeutic resources with the aim of promoting early nerve regeneration, such as the use of low-power laser. However, this laser therapy does not represent a consensus regarding the methodology, thus yielding controversial conclusions. The objective of our study was to investigate, by functional evaluation, the comparative effects of low-power laser (660 nm and 830 nm) on sciatic nerve regeneration following crushing injuries. Twenty-seven Wistar rats subjected to sciatic nerve injury were divided into three groups: group sham, consisting of rats undergoing simulated irradiation; a group consisting of rats subjected to gallium–aluminum–arsenide (GaAlAs) laser at 660 nm (10 J/cm², 30 mW and 0.06 cm² beam), and another one consisting of rats subjected to GaAlAs laser at 830 nm (10 J/cm², 30 mW and 0.116 cm²). Laser was applied to the lesion for 21 days. A sciatic functional index (SFI) was used for functional evaluation prior to surgery and on days 7, 14, and 21 after surgery. Differences in SFI were found between group 660 nm and the other ones at the 14th day. One can observe that laser application at 660 nm with the parameters and methods utilised was effective in promoting early functional recovery, as indicated by the SFI, over the period evaluated.     

Central nervous system transplantation benefitted by low-power laser irradiation

The effect of low-power laser irradiation on mammalian central nervous system (CNS) transplantation is reported. Fetal brain allografts were transplanted into the brain (fornix region) of 20 adult rats and spinal cord allografts were transplanted into the spinal cord of eight dogs. For 21 days, the closed operated wounds of 10 rats and four dogs were exposed daily to transcutaneous low-power laser irradiation cw HeNe laser (16 mW, 632.8 nm, spot size 2 mm², energy density of 30 J cm⁻² for rats and 70 J cm⁻² for dogs). This study shows that the low-power laser irradiation prevents extensive glial scar formation (a limiting factor in CNS regeneration) between neural transplants and host brain or spinal cord. Abundant capillaries developed in the laser-irradiated transplants, this being of crucial importance for their survival. The results of the present study and our previous investigations suggest that low-power laser irradiation is a novel tool for treatment of CNS injuries and disorders.     

Muscle preservation by prolonged sensory protection

The functional recovery of a muscle target following nerve repair is inversely related to the denervation time: i.e., the longer the muscle denervation, the poorer the functional outcome following nerve reconstruction. The trophic and protective effects of sensory innervation to a motor nerve, following prolonged denervation (greater than 6 months), have been studied. Following proximal transection of the musculocutaneous nerve (MC) close to its C6 origin in 10 adult male Sprague-Dawley rats, the severed nerve was coapted to supraclavicular purely sensory nerves originating from C3 and C4 (sensory protection [SP] group). In another 10 Sprague-Dawley rats, the transected MC nerve was not protected by coaptation to sensory nerves (control group). After prolonged denervation or "sensory protection" (6 months), the MC nerve was then coapted in both groups to the purely motor medial pectoral nerve. Behavioral testing (grooming test) was performed on a weekly basis during the reinnervation time, which lasted 4 weeks. Statistically significant differences (p<0.05) favoring the SP group, were found at the second week of the reinnervation period, but not at the end of the experiment. Evaluation also included intraoperative electrical stimulation of the MC nerve, biceps muscle dry weights, motor endplate counts, and nerve axon counts of the MC nerve. The biceps muscle dry weights were statistically higher in the SP group, along with a trend for a higher number of motor endplates. No statistically significant difference was found in the nerve axon counts of the MC nerve between the two groups. Statistically better intraoperative electrical stimulation results were also encountered in the sensory protection group. An interpretation of the results favors the hypothesis that sensory reinnervation of a motor target may provide the necessary trophic environment to minimize muscle atrophy, until a motor donor nerve becomes available.     

A randomized placebo-blind study of the effect of low power laser on pain caused by irreversible pulpitis

This randomized placebo-blind study aimed to evaluate the effect of laser phototherapy (LPT) on pain caused by symptomatic irreversible pulpitis (SIP). Sixty patients diagnosed with SIP were randomly assigned to treatment groups (n?=?15): G1 (control), G2 (laser placebo—sham irradiation), G3 (laser irradiation at 780 nm, 40 mW, 4 J/cm²), and G4 (laser irradiation at 780 nm, 40 mW, 40 J/cm²). Spontaneous pain was recorded using a VAS score before (T0), immediately after (T1), and 15 min after treatment (T2). Local anesthetics failure during emergency endodontic treatment was also assessed. There was no pain difference in T1 and T2 between the experimental laser groups (G3 and G4) and the placebo group (G2). The 4-J/cm² (G3) irradiation resulted in significant increase in the local anesthetics failure in lower jar teeth. This effect could be suggested as consequence of the LPT improvement in local circulation and vasodilatation that would result in the increase of local anesthetic agent absorption. The application of 780-nm diode laser irradiation, at 4 and 40 J/cm², showed no effect in reducing the pain in SIP in comparison to the placebo group. The fluence of 4 J/cm² showed a negative effect in local anesthetics, resulting in significant increase of complimentary local anesthesia during emergency endodontic treatment. This work provides evidence of the consequence of LPT application on teeth with symptomatic irreversible pulpitis. LPT should be avoided in teeth with pain due to irreversible pulpitis.     

Effect of various surface treatments on the retention properties of titanium to implant restorative cement

There are conflicting results in the literature and divergent manufacturers' recommendations concerning the retention properties of implant restorative cements, and they can provide inadequate retention of implants, especially short or single implants. The objective of this study was to investigate the effects of sandblasting and different types of laser irradiation on the interfacial bond between titanium and resin cement through shear testing. A total of 60 samples (10?mm in length and 12?mm in diameter) were cut from titanium rods. The samples were divided into four equal groups according to the surface treatment: control, sandblasted, Nd:YAG laser-irradiated, and Er:YAG laser-irradiated. After surface treatment, the implant restorative cements were applied to the titanium samples which were stored in distilled water at 37°C for 24?h. The samples were then subjected to shear bond strength testing using a universal testing machine with a crosshead speed of 1?mm/min. The data were analysed with the Kruskal-Wallis and Mann-Whitney U tests (α?=?0.05). The highest mean bond strength was observed in the control group, followed by the sandblasted group. A statistically significant difference in shear bond strength was found between the sandblasted group and both the laser-irradiated groups (p?相似文献   

显微外科修复联合镜像治疗尺神经离断伤的疗效研究

背景:镜像治疗是一种由上而下的治疗模式,可以调节中枢神经系统,进而提高周围神经外伤后的治疗效果。目的:研究镜像治疗对尺神经离断伤显微外科修复术后临床疗效的影响。方法:2016年6月至2018年1月收治的26例尺神经离断伤患者为对照组,2018年2月至2019年7月收治的24例尺神经离断伤患者为研究组。两组患者均采用显微外科神经束膜吻合术修复尺神经,研究组在对照组基础上联合镜像治疗,应用轻触-深压觉检查、静态两点辨别觉检查及感觉分级方法评估感觉功能,应用明尼苏达手灵巧度测试(MMDT)及普度钉板测试(PPT)评估运动功能,比较两组患者术后的感觉运动功能。结果:治疗后,轻触-深压觉在两组间比较差异无统计学意义,研究组两点辨别觉的平均距离小于对照组(P=0.004),研究组感觉分级优于对照组(P=0.007)。与对照组相比,研究组治疗后单侧PPT测试(P=0.005)、双侧PPT测试(P=0.001)及装配PPT测试(P=0.001)结果均更高。与对照组相比,研究组治疗后MMDT测试的放置时间更短(P=0.001);翻转时间也更短(P=0.002)。结论:联合镜像治疗可以改善尺神经离断伤显微外科修复术后的临床疗效,提高患者术后手部感觉运动功能。     

ASIA脊髓损伤分类标准在颈髓损伤患者神经功能评定中的应用

目的：探讨ASIA标准在颈髓损伤患者神经功能评估中的意义。方法：应用ASIA标准对139例急性颈髓损伤患者的神经功能情况进行回顾性评估。结果：82例完全性脊髓损伤患者中5例逆转为不完全性损伤，77例无逆转者随访时ASIA感觉、运动评分有明显增加。57例不完全性颈髓损伤患者感觉、运动功能改善明显优于完全性损伤患者。结论：完全性颈髓损伤患者可能逆转为不完全性颈髓损伤，并且可有明显节段性神经功能恢复。在脊髓损伤神经功能评定中，ASIA感觉、运动评分具有重要意义。     

Spinal cord response to laser treatment of injured peripheral nerve

The authors describe the changes occurring in the spinal cord of rats subjected to crush injury of the sciatic nerve followed by low-power laser irradiation of the injured nerve. Such laser treatment of the crushed peripheral nerve has been found to mitigate the degenerative changes in the corresponding neurons of the spinal cord and induce proliferation of neuroglia both in astrocytes and oligodendrocytes. This suggests a higher metabolism in neurons and a better ability for myelin production under the influence of laser treatment.     

Lack of effect of pulsed low-intensity infrared (820 nm) laser irradiation on nerve conduction in the human superficial radial nerve

BACKGROUND AND OBJECTIVE: To investigate the effect of pulsed low-intensity laser irradiation on nerve conduction in the human superficial radial nerve and on temperature in the skin overlying the nerve. STUDY DESIGN/MATERIALS AND METHODS: Thirty-two healthy human volunteers were recruited and randomly assigned to either placebo, laser 1 (9.12 Hz), laser 2 (73 Hz), or control groups (n = 8 all groups). A GaAlAs laser diode (820 nm, 50 mW peak) was used to irradiate the skin overlying the right superficial radial nerve at three points (1.2 J per point; energy density, 9.55 J/cm(2)). Antidromic action potentials were recorded from the superficial radial nerve preirradiation and at 5, 10, and 15 minutes after irradiation. Skin temperature was monitored concomitantly by using two surface thermistor probes attached to the skin overlying the nerve. RESULTS: Repeated measures analysis of variance showed no significant differences between groups for negative peak latency nor skin temperature data after laser irradiation. CONCLUSION: This study has demonstrated that laser irradiation at the radiant exposure and pulsing parameters indicated did not produce any specific neurophysiologic effects in this model of nerve function.     

The clinical effect of LLLT in endodontic surgery: a prospective study on 72 cases.

OBJECTIVES: The purpose of this prospective study was to evaluate a possible clinical benefit of LLLT in endodontic surgery. STUDY DESIGN: Seventy-two endosurgery cases on incisors and premolars were included to the study and were split randomly into an LLLT test group, a placebo group, and a control group. In the LLLT group, irradiation was performed intraoperatively and postoperatively 1, 3, and 7 days after surgery. In the placebo group, irradiation was performed without laser activation. In the control group, neither LLLT nor placebo therapy was used. Swelling, wound healing, and pain were evaluated by a blinded investigator 1, 3, and 7 days postoperatively. RESULTS: No statistically relevant differences between the LLLT and the placebo groups were found. Patients in the control group reported on statistically relevant stronger pain. CONCLUSION: In routine endodontic surgery cases, LLLT does not achieve a significant clinical benefit. Further, the results indicate a prominent placebo effect of the soft laser therapy.     

Evidence of changes in sural nerve conduction mediated by light emitting diode irradiation

The introduction of light emitting diode (LED) devices as a novel treatment for pain relief in place of low-level laser warrants fundamental research on the effect of LED devices on one of the potential explanatory mechanisms: peripheral neurophysiology in vivo. A randomised controlled study was conducted by measuring antidromic nerve conduction on the peripheral sural nerve of healthy subjects (n=64). One baseline measurement and five post-irradiation recordings (2-min interval each) were performed of the nerve conduction velocity (NCV) and negative peak latency (NPL). Interventional set-up was identical for all subjects, but the experimental group (=32) received an irradiation (2 min at a continuous power output of 160 mW, resulting in a radiant exposure of 1.07 J/cm²) with an infrared LED device (BIO-DIO preprototype; MDB-Laser, Belgium), while the placebo group was treated by sham irradiation. Statistical analysis (general regression nodel for repeated measures) of NCV and NPL difference scores, revealed a significant interactive effect for both NCV (P=0.003) and NPL (P=0.006). Further post hoc LSD analysis showed a time-related statistical significant decreased NCV and an increased NPL in the experimental group and a statistical significant difference between placebo and experimental group at various points of time. Based on these results, it can be concluded that LED irradiation, applied to intact skin at the described irradiation parameters, produces an immediate and localized effect upon conduction characteristics in underlying nerves. Therefore, the outcome of this in vivo experiment yields a potential explanation for pain relief induced by LED.     

理化法快速鉴别周围神经束性质

目的 探索一种快速鉴别感觉与运动神经束的方法. 方法 纯种Wistar大鼠30只,处死后取整条脊柱.取脊神经节及背根纤维、腹根纤维及坐骨神经,采用免疫印迹实验观察Annexin V 和 Agrin特异性.其中15只大鼠作为实验组,取脊神经前根、后根、坐骨神经及其肌支、皮支行免疫组织化学染色;余15只用PBS代替一抗作为对照组.12月龄健康新西兰大白兔16只,采用喇曼光谱法对不同性质的神经束进行研究. 结果 Annexin V 和 Agrin 分别是感觉神经与运动神经中的特异物质.运动神经与感觉神经的喇曼光谱在 1088、1276、1439、1579 及 1659 cm-1等附近的喇曼振动峰相对强度存在明显差异,1276 cm-1 处的峰值与 1439 cm-1 处的峰值比Ⅰ1 276/Ⅰ1 439 分别为 0.95±0.06 和 1.17±0.08,提示运动神经与感觉神经间的微观结构差异(P<0.05). 结论 显微激光喇曼光谱法是一种鉴别神经束性质的有效的物理学方法,优于免疫组织化学法,具有临床应用的可行性.