Effects of Continuous and Pulsed Infrared Laser Application on Bone Repair Using Different Energy Doses. Study in Rats
The Laser Therapy effects on the cellular proliferation are extensively searched and widely known. However, there are controversies on the best out put power used in the applications, the ideal fluency and irradiance, better emission mode and the adequate number of sessions in order to obtain the best results. The aim of this paper was to search for the best application fluency and emission mode, using an infrared laser in the repair of bone defects in the rat tibia. Thus, the histological quality of the neo-formed bone was evaluated by analysis using common optic microscopy and polarized light. Application Parameters: 100 mW, 830 nm, spot diameter = 0,06 nm, CW and 10 Hz, 3 sessions with 72 h of interval, energies and respective fluencies: 2 J =70 J/cm 2, 4 J =140 J/cm 2 , 6 J =210 J/cm 2 , 8 J =160 J/cm 2 , 10 J =200 J/cm 2 . Conclusions: Laser Therapy has increased and accelerated the time bone repairing process (in the initial period of 10 days). This laser effect showed to be dose-dependent with the presence of an effective therapeutic window presenting biostimulation of the bone tissue between 4J and 8 J of total energy for both emission mode. The use of the laser with 10 J of energy generated, characterized by the bioinhibition of the tissues (in the initial pe-riod of 10 days). This inhibition took place at the exact irradiation spot).
Biomodulatory effects of LLLT on bone regeneration
Tissue healing is a complex process that involves local and systemic responses. The use of Low Level Laser Therapy (LLLT) for wound healing has been shown to be effective in modulating both local and systemic response. Usually the healing process of bone is slower than that of soft tissues. The effects of LLLT on bone are still controversial as previous reports show different results. This paper reports recent observations on the effect of LLLT on bone healing. The amount of newly formed bone after 830nm laser irradiation of surgical wounds created in the femur of rats was evaluated morphometricaly. Forty Wistar rats were divided into four groups: group A (12 sessions, 4.8J/cm2 per session, 28 days); group C (three sessions, 4.8J/cm2 per session, seven days). Groups B and D acted as non-irradiated controls. Forty eight hours after the surgery, the defects of the laser groups were irradiated transcutaneously with a CW 40mW 830nm diode laser, (f∼1mm) with a total dose of 4.8J/cm2. Irradiation was performed three times a week. Computerized morphometry showed a statistically significant difference between the areas of mineralized bone in groups C and D (p=0.017). There was no significant difference between groups A and B (28 days) (p=0.383). In a second investigation, we determined the effects of LLLT on bone healing after the insertion of implants. It is known that dental implants need four and six months period for fixation on the maxillae and on the mandible before receiving loading. Ten male and female dogs were divided into two groups of five animals that received the implant. Two animals of each group acted as controls. The animals were sacrificed 45 and 60 days after surgery. The animals were irradiated three times a week for two weeks in a contact mode with a CW 40mW 830nm diode laser, (f ∼1mm) with a total dose per session of 4.8J/cm2 and a dose per point of 1.2J/cm2. The results of the SEM study showed better bone healing after irradiation with the 830nm diode laser. These findings suggest that, under the experimental conditions of the investigation, the use of LLLT at 830nm significantly improves bone healing at early stages. It is concluded that LLLT may increase bone repair at early stages of healing.
Low-level laser therapy induces differential expression of osteogenic genes during bone repair in rats.
Objectives: The aim of this study was to measure the temporal pattern of the expression of osteogenic genes after low-level laser therapy during the process of bone healing. We used quantitative real-time polymerase chain reaction (qPCR) along with histology to assess gene expression following laser irradiation on created bone defects in tibias of rats.
Material and methods: The animals were randomly distributed into two groups: control or laser-irradiated group. Noncritical size bone defects were surgically created at the upper third of the tibia. Laser irradiation started 24 h post-surgery and was performed for 3, 6, and 12 sessions, with an interval of 48 h. A 830 nm laser, 50 J/cm(2), 30 mW, was used. On days 7, 13, and 25 post-injury, rats were sacrificed individually by carbon dioxide asphyxia. The tibias were removed for analysis.
Results: The histological results revealed intense new bone formation surrounded by highly vascularized connective tissue presenting slight osteogenic activity, with primary bone deposition in the group exposed to laser in the intermediary (13 days) and late stages of repair (25 days). The quantitative real-time PCR showed that laser irradiation produced an upregulation of BMP-4 at day 13 post-surgery and an upregulation of BMP4, ALP, and Runx 2 at day 25 after surgery.
Conclusion: Our results indicate that laser therapy improves bone repair in rats as depicted by differential histopathological and osteogenic genes expression, mainly at the late stages of recovery
The effects of infrared-830 nm laser on exercised osteopenic rats
The aim of this study was to investigate the effects of low-level laser therapy (LLLT), 830 nm, on femora of exercised osteopenic rats. Sixty female rats were used, which were divided into six groups: sham-operated control, osteopenic control, sham-operated trained, osteopenic trained, sham-operated trained and irradiated, and osteopenic trained and irradiated. The exercise program and the laser irradiation were performed 48 h over an 8-week period. The exercise program was made in a container, filled with warm water, and consisted of jumps (four series, with ten jumps). The laser irradiation was performed with a Ga-Al-As laser, 830 nm, 100 W/cm2, 120 J/cm2. Femora were submitted to a physical and geometrical properties evaluation, a biomechanical test, and calcium and phosphorus evaluation. Exercised animals showed higher bone strength and physical properties values. However, the LLLT did not improve the stimulatory effects of the exercise on the osteopenic rats. The exercise program was able to increase femora strength and physical properties of osteopenic rats. However, concurrent treatments did not produce a more pronounced effect on femora.
Effects of 830-nm laser, used in two doses, on biomechanical properties of osteopenic rat femora
Objective: The aim of this study was to investigate the effects of photoradiation–infrared at 830 nm–used in two doses, on femora of osteopenic rats.
Background data: Osteoporosis has recently been recognized as a major public health problem. Based on stimulatory effects of photoradiation on the proliferation of bone cells, we hypothesized that photoradiation would be efficient in improving bone mass in osteopenic rats.
Methods: Sixty female animals, divided into six groups, were used: sham-operated control (SC), osteopenic control (OC), sham-operated irradiated with the dose of 120 J/cm(2) (I120), osteopenic irradiated with the dose of 120 J/cm(2) (O120), sham-operated irradiated with the dose of 60 J/cm(2) (I60), and osteopenic irradiated with the dose of 60 J/cm(2) (O60) Animals were 90 days old when operated. Laser irradiation was initiated 8 weeks after operation, and it was performed 3 times a week for 2 months. Femora were submitted to a biomechanical test and to a physical properties evaluation.
Results: Maximal load of O120 did not show any difference when compared with SC and I120, but it was higher than the O60 group. Wet weight, dry weight, and bone volume of O60 and O120 did not show any difference when compared with SC.
Conclusion: The results of the present study indicate that photoradiation had stimulatory effects on femora of osteopenic rats, mainly at the dose of 120 J/cm.(2) However, further studies are needed to investigate the effects of different parameters, wavelengths, and sessions of applications on ovariectomized rats.
Effects of 830-nm laser light on preventing bone loss after ovariectomy
Objective: The aim of this study was to investigate the effects of low-level laser therapy (LLLT; infrared, 830 nm) on the bone properties and bone strength of rat femora after ovariectomy (OVX).
Background data: Osteoporosis affects 30% of postmenopausal women, and it has been recognized as a major public health problem. Based on the stimulatory effects of LLLT on proliferation of bone cells, we hypothesized that LLLT would be efficient in preventing bone mass loss in OVX rats.
Methods: Forty female rats were divided into four groups: sham-operated control (SC), OVX control (OC), sham-operated irradiated at a dose of 120 J/cm(2) (I120), and OVX irradiated at a dose of 120 J/cm(2) (O120). Animals were operated at the age of 90 days. Laser irradiation was initiated 1 day after the operation and was performed three times a week, for 2 months. Femora were submitted to a biomechanical test and a physical properties evaluation.
Results: Maximal load of O120 was higher than in control groups. Wet weight, dry weight, and bone volume of O120 did not show any difference when compared with SC.
Conclusion: The results of the present study indicate that LLLT was able to prevent bone loss after OVX in rats. However, further studies are needed to investigate the effects of different parameters, wavelengths, and sessions of applications on OVX rats.