In the hierarchy of occupational hazard controls in dentistry, which approach is inexpensive to implement but expensive to maintain over time?

In the hierarchy of hazard controls (from most to least effective): elimination, substitution, engineering controls, administrative controls, and PPE. Administrative controls (such as scheduling, training, and protocols) and PPE (gloves, masks, gowns) are the least expensive to implement initially but become costly over time because of recurring expenditure on consumables (new gloves, masks, gowns for every patient), training updates, and compliance monitoring. Engineering controls and elimination/substitution require higher initial investment but are more cost-effective long-term. The original question and answer were inconsistent; the answer 'Virtual Appointment' did not correspond to any provided option.