Introduction. It is an example of tendon to bone healing of rotator cuff tears. Low Level Laser Therapy (LLLT) is used in pain literature, pain palliation, tendinopathies, osteoarthritis treatment, implant osteointegration in jaw surgery, wound healing, fracture healing, tendon healing, nerve healing. But; there is not a study on tendon-bone healing. It is aimed to investigate the effects of tendon to bone healing with the rotator cuff experimental tear model. Material and Methods. 60 Wistor Albino Rat right shoulders were used in our project in four groups. Effectiveness of the study in each study group to increase and use the minimum number of animals that would be significant it was planned to use 15 (6 histology + 9 biomechanical) subjects. In our study, there are 4 groups in total. 1. Group 4. Week sacrified control group 2. Group 4. Week sacrificed LLLT group 3. Group 8. Week sacrified control group 4. Group is postoperative LLLT group. The 4 round SSP tendons have been cut with a full course. A total of eight sessions of biostimulation were performed with 24 j energy per session. Biomechanical tensile test and histopathological examination were performed on rats sacrificed at 4 and 8 weeks. In histological examination, cellularity at the repair site with hemotoxylin-eosin staining, extracellular matrix localization with Masson trichrome staining and fibrosis, TRAP (Tartrate Resistance Acid Phosphatase) and osteoclast activity, collagen fibril organization with picrochucine were evaluated. In immunohistological examination, proliferation activity was evaluated by CD-31 (Abcam, Cambridge, MA, USA) through vascular endothelial cells, Ki-67 (Tucson, AZ) and tendon proliferation index. Failure load for comparison of biomechanical stability between groups drawing will be done. Biomechanical pulling applications Linear pulling force over tendon It will be realized by applying. Last failure load (Newton), elongation (mm) and hardness values was recorded. Results. Two rats died in the postoperative first group and one rat died in the other groups. Six animals from each group were examined histopathologically. While the mean of stifness was higher in the patient who underwent LLLT at the 4th week biomechanically compared to the control group, there was no difference in the 8th week between the control group LLLT biomechanically. Histologically, the group with LLLT at 4 weeks showed increased fibroblastic activity and osteoclastic activity, but at 8 weeks there was no significant difference. Discussion. There are studies on the benefits of biostimulation with LLLT in fracture healing, implant integration, wound healing, tendon healing. Biostimulation experiments with LLLT for tendon healing were evaluated in
