An 11-year-old girl attends for a check-up. Her newly erupted lower left second premolar, now just reaching the occlusal plane, has a conical tubercle projecting from the centre of its occlusal surface, and the contralateral premolar is similar. Both teeth respond normally to cold and are symptom-free. The radiograph shows wide open apices and a pulp horn extending into each tubercle. What is the most appropriate management?