Purpose: The aim of the study is to observe the bone healing process of a guided periradicular surgery, performed in the endodontics postgraduate course of the University of Santo Tomas, in which an osteotomy was performed for a bone window with erbium, chromium: yttrium, scandium, gallium, garnet (Erbium,Chromium:YSGG) laser, and the healing process was evaluated by cone beam computed tomography (CBCT) during the first four months after surgery. Materials and Methods: After completing the clinical history and studying the CBCT scans, a patient was selected with a diagnosis of symptomatic apical periodontitis, periapical lesion less than 5mm with intact vestibular cortex that required periradicular surgery due to the presence of an adapted fixed prosthesis and the proximity of the mental foramen to the apex of the tooth to be treated. The treatment plan was established, the surgical guide was designed and the osteotomy was performed with Erbium,Chromium:YSGG laser. The size of the periradicular lesion and the bone density of the surgical area were measured at three points in time: pre-surgical (T0) and post-surgical at 24 hours (T1), at 4 months (T2) and at one year. Results: Bone density measured in Hounsfield units (HU) on CBCT in the axial section showed preoperative values in the vestibular apex of 1478 and 1435 HU, at 24 hours after surgery -95 and -210 HU, and in the control at 4 months of 992 and 860 HU. In the coronal slice in the mid vestibular area at the apex level, a preoperative value (T0) of 1335 HU was reported, at 24 hours (T1) -18 HU and at 4 months 1269 HU. At one year of evolution, greater bone density was evidenced comparing between month 4 and month 12. Conclusions: By performing a surgical procedure with guided technique and Erbium,Chromium:YSGG laser for the osteotomy, the adverse effects of the surgical procedures are reduced, achieving results with greater accuracy and better prognosis.