The effect of dosage on the efficiency of LLLT in new bone formation at the expanded suture in rats

Abstract

The aim of this study was to investigate the effect that dosage has on the efficiency of low-level laser therapy (LLLT) in bone formation in a rat study model. Twenty-eight rats were divided into four groups as only expansion (OE), expansion + low dose (0.15 J) (LD), expansion + medium dose (0.65 J) (MD), and expansion + high dose (198 J) (HD) laser therapy groups. The midpalatal suture was expanded during 5 days. Afterwards, irradiations were started and performed with an 820 nm, continuous wave, Ga-Al-As diode laser (Doris, CTL-1106MX, Warsaw, Poland). At the end of experiment, the premaxillae of the animals were dissected. The sections were transferred into PC environment and analyzed by using Image Analysis program. Number of osteoblasts, osteoclasts, fibroblasts, vessels, transforming growth factor beta (TGF-β) expression, and new bone formation were evaluated with this program. Amount of expansion did not show any difference among the groups. All parameters except the number of osteoclasts were increased in all lased groups while that parameter was significantly decreased. Vessels, TGF-β expression, and new bone formation were mostly increased in LD group followed by HD group. Among the lased groups, a significant difference was observed only for the amount of new bone formation, which was between the LD and the MD groups. On the other hand, the difference in this parameter was insignificant between OE and MD groups. Low-level laser therapy with both 5 and 6,300 J/cm(2) doses was found to be significantly effective, while the 20 J/cm(2) dose did not show a significant effect in increasing new bone formation. This finding reveals that the efficiency of the therapy is affected by the dosage.

Effects of low-level laser therapy on the expression of osteogenic genes during the initial stages of bone healing in rats: a microarray analysis

“…In this context, several studies demonstrated that LLLT had a positive effect in the process of bone consolidation in experimental models in rats [9,23,24]. These findings are in line with the results of the current study, which revealed that LLLT was able to modulate the inflammatory process in the area of the bone defect and to produce an earlier deposition of granulation tissue and newly formed bone.…”

“…In addition, it is important to emphasize that the energy of the laser 2.8 J used in this study had a positive result on bone metabolism at the site of the injury. It is possible to find in literature a wide range of fluencies and energy of laser irradiation used by different authors on bone healing and fractures [9,23,24,40]. In a recent study, Batista et al, [46] used 830 nm laser irradiation, at 6 J, and presented a positive local biostimulative effect in the early stage of bone healing.…”

The effects of low-level laser therapy on orthodontically induced root resorption

“…With the molecular absorption of laser light, different cellular organelles are affected and several cellular responses are triggered creating anti-inflammatory or regenerative changes [9,10]. There are several studies in literature that reported the positive outcomes of 800-830-nm LLLT applied in various fields [11]. Osteoblast and osteoclast differentiation, the expression of receptor activator of nuclear factor kappa ligand (RANKL)-and RANK-positive cells, and bone remodeling [12] were increased during orthodontic tooth movement, and collagen synthesis was stimulated [12,13] via the therapy.…”

Avaliação da irradiação com laser infravermelho (808nm) na cicatrização de feridas cutâneas de ratos

“…Estudos confirmam que o protocolo infravermelho atua biomodulando positivamente a cicatrização óssea em animais e pode ser empregado em casos de implantodontia 17 , distração osteogênica 18 , expansão maxilares 19 e fraturas ósseas 20 . Enquanto isso, o protocolo vermelho apresenta resultados positivos de reparação de feridas em tecidos moles [10][11][12][13][14] .…”

“…A terapia é afetada pelo comprimento de onda, potência e dose 19 . Estudos in vitro em culturas celulares de fibroblastos demonstram que densidades de energia baixas (2J/cm²) são estimulantes, enquanto maiores (16J/cm²) podem ser prejudiciais 22 .…”