Which condition could suggest the need for sealant application?

The application of sealants is primarily indicated for deep pits and fissures on molars. This is because these areas are more susceptible to decay due to their complexity and the increased likelihood of food particles and plaque accumulation within them. Sealants provide a protective coating that fills in these grooves, thereby reducing the risk of cavity formation by preventing bacteria and food debris from settling in the hard-to-clean areas.

While visible cavities on the buccal surfaces would indicate existing decay and not a preventive measure like sealation, teeth that have undergone endodontic treatment have already been addressed for decay or damage, making sealants unnecessary in such cases. Flat surfaces without occlusal grooves typically do not require sealants since they are less prone to caries due to the absence of deep fissures that need protection. Thus, the focus on deep pits and fissures makes it clear why this option is the most appropriate.