Jing-zhi Ma, Franklin Tay
BACKGROUND: Head and neck radiotherapy creates a high-consequence dental environment in which tooth loss may precipitate osteoradionecrosis, particularly after extraction in high-dose mandibular regions. Tooth preservation through nonsurgical root canal treatment is therefore a risk reduction strategy. However, evidence relevant to endodontic decision-making remains dispersed among clinical series, laboratory research, pulp testing studies and oncology dental guidance. OBJECTIVE: To synthesise contemporary evidence relevant to endodontic management before, during and after head and neck radiotherapy, and to present a clinically applicable, dose-informed framework for diagnosis, treatment planning, technical modification and follow-up. METHODS: A narrative review with integrative synthesis was undertaken using evidence from clinical outcome studies, dosimetric and planning studies, pulp sensibility and vascular assessment studies, laboratory investigations of irradiated dental tissues and materials and guideline-based oncology dental literature. Evidence was organised by radiotherapy phase as before treatment, during treatment, early after radiotherapy and late after radiotherapy, and interpreted using three tooth-level dose tiers: below 30 Gray, 30-60 Gray and at least 60 Gray. RESULTS: Radiotherapy depresses neural sensibility responses, yielding false-negative cold and electric pulp testing results that do not reliably indicate pulp necrosis. Vascular-oriented assessments suggest that pulpal blood flow may be partly preserved or recover later in some teeth. Hyposalivation and radiation-related caries accelerate structural breakdown and often trigger pulpal disease through restorative destabilisation. Laboratory evidence indicates dose-dependent alterations in dentine structure and mechanics that may complicate adhesion, fracture resistance and retreatment. Direct clinical outcome data remain limited, yet available series in irradiated patients report symptom control and tooth retention after primary root canal treatment, with no osteoradionecrosis events attributed to nonsurgical endodontics. Technical priorities include conservative working length control, minimisation of apical extrusion of debris, irrigants, intracanal medicaments, filling materials and rapid establishment of a durable coronal seal. Evidence gaps include prospective dose-annotated cohorts, retreatment-specific data and outcome reporting in proton-based radiotherapy populations. CONCLUSION: Endodontic care before, during and after radiotherapy should be dose-informed, phase-matched and centred on tooth preservation in high-dose regions, with cautious interpretation of sensibility testing and explicit linkage of prognosis to restorability and coronal integrity.