Dental hygiene therapy–led pre-radiotherapy oral assessment and osteoradionecrosis incidence in Nigerian oncology centres: a target-trial emulation of assessment-to-treatment intervals

Osteoradionecrosis of the jaw remains a severe complication of head and neck radiotherapy, and pre-radiotherapy oral assessment is widely recommended to reduce its incidence. In Nigerian oncology centres, dental hygiene therapists increasingly conduct this assessment, yet the interval between assessment and radiotherapy initiation varies substantially and its relationship to osteoradionecrosis risk is poorly characterised. The framework specifies the causal estimand, defines eligibility criteria, and proposes a before-after-control-impact design with clustering at the centre level. A design-based power analysis was conducted across 2000 replications per cell, with between-cluster standard deviation of 6.0, residual standard deviation of 4.5, and intraclass correlation of 0.64. The analysis identified that 52 clusters are required to detect a 5 percentage-point difference at 80% power. The framework distinguishes dental hygiene therapy–led assessment from dentist-led assessment and specifies how assessment-to-treatment interval should be measured, classified, and modelled. The contribution is a methodologically explicit template for causal inference in a context where randomisation is infeasible, together with design parameters that can guide future multicentre studies of pre-radiotherapy oral care in Nigeria.