Biomodulatory Effects of LLLT on Bone Regeneration

Abstract

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/cm 2 per session, 28 days); group C (three sessions, 4.8J/cm 2 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/cm 2 . 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/cm 2 and a dose per point of 1.2J/cm 2 . 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.

Comparação dos efeitos do laser de baixa potência e do ultrassom de baixa intensidade associado ao Biosilicato® no processo de reparo ósseo em tíbias de ratos

“…It is known that Biosilicate® is a highly bioactive glass ceramic (5) and that both LLLT and US have high osteogenic potential (11,18) . One hypothesis may be that associating these types of treatment might have caused excessive stimulation to the lesion site.…”

Low-level laser therapy improves bone formation: stereology findings for osteoporosis in rat model

“…The number of osteocytes and Havers channels is also higher when the laser is applied [13]. In addition to promoting the proliferation of osteoblasts, the laser also increases the activity of these cells as well as chondrocytes and fibroblasts [14].…”

A preliminary study of hardness and modulus of elasticity in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy

“…These findings may suggest that the application of LLLT during the activation period in fact provokes a delay in bone healing, a hypothesis that is reinforced by the marked presence of cartilage tissue and endochondral ossification observed in specimens irradiated with LLLT during the activation period, as proposed by Cerqueira et al (18). Although the use of distraction osteogenesis has become increasingly common, it can cause significant discomfort to the patient, especially when external devices are used, possibly leading to infections, paresthesia, hypertrophic scars and social difficulties (14). Therefore, when this clinical and surgical approach is used to treat humans, early device removal becomes especially important.…”

“…Moreover, several previous studies had already adopted the same period of 60 days to assess bone healing, e.g. Friesen et al (13) and Pinheiro et al (14). Distraction osteogenesis involves metabolic activities that are potentially biomodulated by the use of laser.…”