The Influence Of Light Parameters In The Effect Of Low Level Laser Therapy On Cutaneous Wound Healings

Objects:To study on the relationship between optical parameters involved in low-level laser therapy(LLLT) on cutaneous wound healings of Wistar rats and the therapeutic outcomes,which would necessarily contribute to not only the discovery of rules controlling LLLT and its mechanisms,but also setting directions for clinical applications.Methods:1.Four circular excisions were made on the dorsum of 32 healthy Wistar rats,and then wounds in treated groups were irradiated once a day for a consecutive 14 days.During the treatment,we recorded the outline of one of the four wounds in each rat every other day and calculated their areas to do statistical analysis.The other three wounds in each rat were biopsied seperately and specimens were observed after HE staining under microscope.2.Four identical circular full-thickness skin excisions were made symmetrically on the backs of 48 healthy Wistar rats that were divided randomly into 6 time-point groups(12,24,48,72,120,and 168 hours after injury). Three of the lesions were locally stimulated with a semiconductor laser(power density 10 mW/cm~2) each with respective daily doses of 1.2,2.4,and 3.6 J/cm~2, whereas the fourth one served as a control.At each time point,8 rats from the corresponding group were killed and samples were removed for histologcial evaluation.We also recorded margins of lesions in the rats of the 6th group using sterial films,by making use of ImageJ,an imaging processing software,we then calculated the areas and did ANOVA analysis to the acquired data.Results:1.There are significant differences in area reductions between the groups which used 630nm,alone or together with 808nm,and the groups which did not.The irradiation of 808nm alone seems to fail in improving wound healings in this experiment.2.No statistical differences exist among the control group and the other 3 different doses groups when the changes of wound areas were compared.However, evidently improved recovering of the LLLT groups were observed by histological examines,including the shorter period of inflammation,the greater development of granulations,collagens,and epithelialization.We could also see even better therapeutic outcomes in the groups with larger doses.Conclusions:Our experiments in this study proved the existence of the relationships between optical parameters and LLLT outcomes in promoting cutaneous wound healings,and this result would explain partly the controversial outcomes of former literatures.By predicting rules involved in LLLT,we may operate more appropriately in future experiments and clinical trails to gain steady therapeutic results,and what's more to provide theoretical basements for understanding mechanisms.