Background: Odontogenic fascial space infections originate from infected root canal(s) and can spread through the periapical area of a tooth to the surrounding bone and overlying soft tissues. Microbial causative agents of these lesions can be present in the form of an intraradicular or extraradicular infection and their treatment can be particularly problematic. Case presentation: A successful outcome of a therapy to treat a chronic apical abscess with mental space involvement and cutaneous sinus tract in a 20-year-old patient is presented in this case report. The treatment was performed by means of surgical decompression and ozone treatment. Twenty months after the end of treatment the patient was asymptomatic and the control radiographs revealed the healing of the periapical tissues. At the 4-year recall the periapical radiographs revealed the absence of the periapical lesion. Though the surgical intervention with complete enucleation of a periapical lesion may be the most expeditious treatment option, it can cause undesirable consequences. Conclusion: This article demonstrates how a conservative approach in therapy can offer a favourable outcome, allowing the practitioner to choose an alternative treatment option. Schlagwörter: ozone, periapical abscess, periapical periodontitis, root canal therapy, surgical decompression