Objectives: This immunohistochemical study was performed to assess the different immunohistochemical activities in dentin-pulp organs in the pulp of mongrel dogs after stimulation with low-level laser (LLL), mineral trioxide aggregate (MTA), and TheraCal light-cured (LC) as pulp therapy and compare their effect with the conventional calcium hydroxide (Ca(OH)) cement material. Materials and Methods: A total of 8 male mongrel dogs 12-18 months old and weighing 10-15 kg were selected to be enrolled in this study. Animal choice, administration, surgical protocol, and provision were completed according to regular techniques standards by the Faculty of Veterinary, Cairo University, Egypt. All surgical techniques were accomplished under general anesthesia (GA) in a sterile operating room under aseptic circumstances with restricted isolation. The pulp exposure procedure was carried out through the preparation of a Class V cavity on the buccal surfaces of the animal premolar teeth. In each animal four premolar teeth were involved and allocated to four different groups grounded on the pulp therapy procedure (group I: LLL; group II: MTA; group III: TheraCal LC; and group IV; Ca(OH). The final cavity restoration was glass ionomer cement (GIC). The immunohistochemical analysis was completed following the established methods.