Background:Photobiomodulation therapy (PBMT) was suggested to support regenerative endodontic treatment by modulating cell growth, protein synthesis and secretion processes of several cell types like endothelial cells. Also, it was suggested to activate angiogenesis and affect the organization of endothelial cytoskeletons and creation of new capillary networks from endothelial progenitor cells.Aim: The aim of this study was to evaluate the effect of photobiomodulation therapy on endothelial cells count in regenerative endodontic procedures.Methods: 54 mature permanent roots of premolar teeth in dogs aged 10-12 months old were included in the current study and distributed into three equal groups (18 roots / each): Group I; REPs was followed using blood clot as scaffold (positive control group) and Group II, was treated with the same regenerative protocol as group I then subjected to photobiomodulation therapy (study group) and Group III (negative control group), no intervention. Each group was further divided into three subgroups (6 roots per subgroup) according to evaluation periods 3, 10, 15 weeks. In each group endothelial cells count was evaluated according to evaluation periods.Results: Data analysis revealed significant differences for endothelial cells count between studied groups at the different intervals (P< 0.001). Photobiomodulation therapy was significantly influence the endothelial cells count in regenerated tissue compared to traditional regeneration protocol that used blood clot as scaffold only.Conclusion: The results of this study revealed the positive effect of photobiomodulation on vascularity and characteristics of the regenerated tissue. It also supports the REPs in non-vital mature permanent teeth as another treatment method.

Endothelial cells. Mature dog teeth. Non-vital permanent teeth. Photobiomodulation. Regenerative endodontic procedures.