Background: Osteoporosis can make bone repair difficult. Low‐level laser therapy (LLLT) has been shown to be a promising tool for bone neoformation. This study aimed to analyze the effect of LLLT on calvaria bone defects of ovariectomized rats using stereology. Methods: Fifty‐four Wistar rats were subjected to bilateral ovariectomy, and bone defects were created in calvaria after 150 days. The animals were divided into nine groups (n =  6 per group), and 24 hours after the bone defects were created they received three, six or 12 sessions of LLLT at 0, 20 or 30 J/cm2 , using a 780‐nm low‐intensity GaAlAs laser. One‐way ANOVA followed by Tukey's post hoc test was used for data processing. A difference of P < 0.05 was considered statistically significant. The parameters evaluated were osteocyte density (Nvost), total osteocyte number (Ntoost), trabecular surface density (Svt ), and trabecular surface area (Sat ). Results: Data obtained showed that Ntoost, Svt , and Sat in group G2 rats were significantly different from G1 (0 J/cm2 ) (P < 0.05). Compared to group G4, G5 presented higher values for the parameters Svt and Sat , and G6 presented significantly higher values for almost all the analyzed parameters (Nvost, Ntoost, Svt , and Sat ) (P < 0.05). Compared to group G7, G8 showed a higher value only for the parameter Sat , and G9 showed significantly higher values for parameters Nvost, Ntoost, Svt , and Sat . Conclusion: We conclude that LLLT stimulated bone neoformation and contributed to an increase in the total number of osteocytes, especially with a laser energy density of 30 J/cm2 given for six and 12 sessions.

Background: The purpose of the study was to analyze the effect of cell therapy on the repair process in calvaria defects in rats subjected to irradiation. Methods: Bone marrow mesenchymal cells were characterized for osteoblastic phenotype. Calvariae of male Wistar rats were irradiated (20 Gy) and, after 4 weeks, osteoblastic cells were placed in surgically created defects in irradiated (IRC) and control animals (CC), paired with untreated irradiated (IR) and control (C) animals. After 30 days, histological and microtomographic evaluation was performed to establish significant (P < 0.05) differences among the groups. Results: Higher alkaline phosphatase detection and activity, along with an increase in mineralized nodules, in the IRC, C and CC groups compared to the IR group, confirmed an osteoblastic phenotype. Histology showed impaired bone neoformation following irradiation, affecting bone marrow composition. Cell therapy in the IRC group improved bone neoformation compared to the IR group. Microtomography revealed increased bone volume, bone surface and trabecular number in IRC group compared to the IR group. Conclusion: Cell therapy may improve bone neoformation in defects created after irradiation.